EXHIBITS

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WPX ENERGY, INC.

30,000,000 Shares of Common Stock

($0.01 Par Value Per Share)

UNDERWRITING AGREEMENT

July 16, 2015

Barclays Capital Inc.

As Representative of the several Underwriters

c/o Barclays Capital Inc.

745 Seventh Avenue

New York, New York 10019

Ladies and Gentlemen:

WPX Energy, Inc., a Delaware corporation (the “Company”), confirms its agreement with Barclays Capital Inc. (“Barclays”) and each of the other Underwriters named in Exhibit A hereto (collectively, the “Underwriters,” which term shall also include any underwriter substituted as hereinafter provided in Section 10 hereof), for whom Barclays is acting as representative (in such capacity, the “Representative”), with respect to the issue and sale by the Company and the purchase by the Underwriters, acting severally and not jointly, as set forth in said Exhibit A hereto, of (i) an aggregate of 30,000,000 shares of the Company’s common stock, $0.01 par value per share (“Common Stock”) and (ii) at the option of the Underwriters, up to an additional 4,500,000 shares of Common Stock. The aforesaid 30,000,000 shares of Common Stock (the “Initial Securities”) to be purchased by the Underwriters and all or any part of the 4,500,000 shares of Common Stock subject to the option described in Section 2(b) hereof (the “Option Securities”) are hereinafter called, collectively, the “Securities.”

The Company understands that the Underwriters propose to make a public offering of the Securities as soon as the Representative deems advisable after this Agreement has been executed and delivered.

The Securities are being issued in connection with the proposed merger of Thunder Merger Sub, LLC, a Delaware limited liability company (“Merger Sub”) and subsidiary of the Company into RKI Exploration & Production, LLC, a Delaware limited liability company (“Thunder”, and together with its subsidiaries, the “Thunder Entities”)), pursuant to that certain Agreement and Plan of Merger, dated July 13, 2015, among the Company, Merger Sub and Thunder (together with all exhibits, schedules and other disclosure letters thereto, collectively, as may be amended, the “Acquisition Agreement”). Prior to the consummation of the merger, Thunder will dispose of its Powder River Basin assets and certain non-core assets in accordance with the Acquisition Agreement. These transactions (including the proposed merger) are herein collectively referred to as the “Acquisition.” The date of the consummation of the Acquisition is referred to herein as the “Acquisition Closing Date.”

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In connection with the Acquisition, the Company is seeking an amendment to its Amended and Restated Credit Agreement, dated as of October 28, 2014, by and among the Company, the lenders party thereto, and Citibank, N.A., as Administrative Agent and Swingline Lender (the “Existing Facility”).

The Company has prepared and previously delivered to you a preliminary prospectus supplement dated July 14, 2015 relating to the Securities and pursuant to the Registration Statement, an automatic shelf registration statement as defined in Rule 405, as amended by a post-effective amendment filed on July 14, 2015, which includes the base prospectus dated September 3, 2014 (the “Base Prospectus”). Such preliminary prospectus supplement and Base Prospectus, including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, are hereinafter called, collectively, the “Pre-Pricing Prospectus.” Promptly after the execution and delivery of this Agreement, the Company will prepare a prospectus supplement dated July 16, 2015 (the “Prospectus Supplement”) and will file the Prospectus Supplement and the Base Prospectus with the Commission, all in accordance with the provisions of Rule 430B and Rule 424(b), and the Company has previously advised you of all information (financial and other) that will be set forth therein. The Prospectus Supplement and the Base Prospectus, in the form first furnished to the Underwriters for use in connection with the offering of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), are herein called, collectively, the “Prospectus.” Any reference in this Agreement to the Registration Statement, any Pre-Pricing Prospectus or the Prospectus shall be deemed to refer to and include the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, as of the effective date of the Registration Statement or the date of such Pre-Pricing Prospectus or the Prospectus, as the case may be and any reference to “amend”, “amendment” or “supplement” with respect to the Registration Statement, any Pre-Pricing Prospectus or the Prospectus shall be deemed to refer to and include any documents filed after such date under the 1934 Act that are deemed to be incorporated by reference therein.

SECTION 1. Representations and Warranties .

(a) Representations and Warranties by the Company . The Company represents and warrants to each Underwriter as of the date hereof, as of the Applicable Time, and as of the Closing Date referred to in Section 2(b) hereof, and agrees with each Underwriter, as follows:

(1) Status as a Well-Known Seasoned Issuer . (A) At the respective times the Registration Statement or any amendments thereto were filed with the Commission, (B) at the time of the most recent amendment to the Registration Statement for the purposes of complying with Section 10(a)(3) of the 1933 Act (whether such amendment was by post-effective amendment, incorporated report filed pursuant to Section 13 or 15(d) of the 1934 Act or form of prospectus), (C) at any time the Company or any person acting on its behalf (within the meaning, for this clause only, of Rule 163(c)) made any offer relating to the Securities in reliance on the exemption of Rule 163 and (D) at the date hereof, the Company was and is a “well-known seasoned issuer” as defined in Rule 405. The Registration Statement is an “automatic shelf registration statement,” as defined in Rule 405 and the Securities, since their registration on the Registration Statement, have been and remain eligible for registration by the Company on such an

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“automatic shelf registration statement.” The Company has not received from the Commission any notice pursuant to Rule 401(g)(2) objecting to the use of an automatic shelf registration statement. Any written communication that was an offer relating to the Securities made by the Company or any person acting on its behalf (within the meaning, for this sentence only, of Rule 163(c)) prior to the filing of the Registration Statement has been filed with the Commission in accordance with Rule 163 and otherwise complied with the requirements of Rule 163, including without limitation the legending requirement, to qualify such offer for the exemption from Section 5(c) of the 1933 Act provided by Rule 163.

(2) Compliance with Registration Requirements . The Company meets the requirements for use of Form S-3 under the 1933 Act and the Securities have been duly registered under the 1933 Act pursuant to the Registration Statement. The Registration Statement and any post-effective amendments thereto have become effective under the 1933 Act and no stop order suspending the effectiveness of the Registration Statement has been issued under the 1933 Act and no proceedings for that purpose or pursuant to Section 8A of the 1933 Act against the Company or related to the issuance and sale by the Company of the Securities have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission, and any request on the part of the Commission for additional information has been complied with. The Registration Statement was filed with the Commission on July 14, 2015.

(3) Registration Statement, Prospectus and Disclosure at Time of Sale . At the respective times that the Registration Statement and any amendments thereto became effective, at each time subsequent to the filing of the Registration Statement that the Company filed an Annual Report on Form 10-K (or any amendment thereto) with the Commission, at each deemed effective date with respect to the Underwriters pursuant to Rule 430B(f)(2), and at the Closing Date (and, if any Option Securities are purchased, at the Date of Delivery (as defined in Section 2(b))), the Registration Statement and any amendments to any of the foregoing complied and will comply in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations and did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

As of its date, at the respective times the Prospectus or any amendment or supplement thereto was filed pursuant to Rule 424(b), at the Closing Date (and, if any Option Securities are purchased, at the Date of Delivery), and at any time when a prospectus is required (or, but for the provisions of Rule 172, would be required) by applicable law to be delivered in connection with sales of Securities (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise), neither the Prospectus nor any amendments or supplements thereto included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

As of the Applicable Time and as of each time prior to the Closing Date that an investor agrees (orally or in writing) to purchase any Securities from the Underwriters,

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neither (x) the Pricing Term Sheet (as defined in Section 3(m) below), any other Issuer General Use Free Writing Prospectuses, if any, issued at or prior to the Applicable Time and the Pre-Pricing Prospectus as of the Applicable Time, all considered together (collectively, the “General Disclosure Package”), nor (y) any individual Issuer Limited Use Free Writing Prospectus, when considered together with the General Disclosure Package, included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

Each preliminary prospectus and the Prospectus and any amendments or supplements to any of the foregoing filed as part of the Registration Statement or any amendment thereto, filed pursuant to Rule 424 under the 1933 Act, or delivered to the Underwriters for use in connection with the offering of the Securities, complied when so filed or when so delivered, as the case may be, in all material respects with the 1933 Act and the 1933 Act Regulations.

The representations and warranties in the preceding paragraphs of this Section 1(a)(3) do not apply to statements in or omissions from the Registration Statement, any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative expressly for use therein, it being understood and agreed that the only such information furnished by the Underwriters as aforesaid consists of the information described as such in Section 6(b) hereof.

At the respective times that the Registration Statement or any amendment thereto was filed, as of the earliest time after the filing of the Registration Statement that the Company or any other offering participant made a bona fide offer of the Securities within the meaning of Rule 164(h)(2), and at the date hereof, the Company was not and is not an “ineligible issuer” as defined in Rule 405, in each case without taking into account any determination made by the Commission pursuant to paragraph (2) of the definition of such term in Rule 405; and without limitation to the foregoing, the Company has at all relevant times met, meets and will at all relevant times meet the requirements of Rule 164 for the use of a free writing prospectus (as defined in Rule 405) in connection with the offering contemplated hereby.

The copies of the Registration Statement and any amendments thereto and the copies of each preliminary prospectus, each Issuer Free Writing Prospectus that is required to be filed with the Commission pursuant to Rule 433 and the Prospectus and any amendments or supplements to any of the foregoing, that have been or subsequently are delivered to the Underwriters in connection with the offering of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise) were and will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T of the Commission. For purposes of this Agreement, references to the “delivery” or “furnishing” of any of the foregoing documents to the Underwriters, and any similar terms, include, without limitation, electronic delivery.

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Each Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the completion of the public offering and sale of the Securities did not, does not and will not include any information that conflicted, conflicts or will conflict with the information contained in the Registration Statement, any preliminary prospectus or the Prospectus that has not been superseded or modified.

(4) Incorporated Documents . The documents incorporated or deemed to be incorporated by reference in the Registration Statement, any preliminary prospectus and the Prospectus, at the respective times they were or hereafter are filed with the Commission, complied and will comply in all material respects with the requirements of the 1934 Act and the 1934 Act Regulations and did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

(5) Independent Accountants . Ernst & Young LLP, who have reported upon the audited financial statements and any supporting schedules included in the Registration Statement, the General Disclosure Package and the Prospectus are independent public accountants with respect to the Company as required by the 1933 Act, the 1933 Act Regulations, the 1934 Act, the 1934 Act Regulations and the PCAOB.

(6) Financial Statements . The historical financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus comply as to form in all material respects with the applicable requirements of Regulation S-X under the 1933 Act and present fairly in all material respects the financial condition, results of operations and cash flows of the consolidated businesses purported to be shown thereby at the dates and for the periods indicated, all in conformity with GAAP applied on a consistent basis throughout the periods involved (except as otherwise noted therein).

To the knowledge of the Company, the historical financial statements of the Thunder Entities included in the Registration Statement, the General Disclosure Package and the Prospectus present fairly in all material respects the financial condition, results of operations and cash flows of the consolidated businesses purported to be shown thereby at the dates and for the periods indicated, and except as described in the Registration Statement, the General Disclosure Package and the Prospectus, in conformity with GAAP applied on a consistent basis throughout the periods involved (except as otherwise noted therein).

The unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus include assumptions that provide a reasonable basis for presenting the significant effects directly attributable to the transactions and events described therein, the related pro forma adjustments give appropriate effect to those assumptions, and the pro forma adjustments reflect the proper application of those adjustments to the historical financial statement amounts in the unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus. The aforementioned unaudited pro forma financial statements included in the Registration Statement, the General Disclosure

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Package and the Prospectus comply as to form in all material respects with the applicable requirements of Regulation S-X under the 1933 Act.

The Company’s ratios of earnings to fixed charges included in the Registration Statement, the General Disclosure Package and the Prospectus comply with Item 503(d) of Regulation S-K of the Commission. All “non-GAAP financial measures” (as such term is defined in the rules and regulations of the Commission), if any, contained in the Registration Statement, the General Disclosure Package and the Prospectus comply with Item 10 of Regulation S-K of the Commission, to the extent applicable.

(7) No Material Adverse Change in Business . Since the date of the latest audited financial statements included in the General Disclosure Package, none of the Company, its Significant Subsidiaries (as defined below) or, to the knowledge of the Company, the Thunder Entities have sustained any loss or interference with its business from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree, or incurred any material liability or obligation, direct or contingent, other than liabilities and obligations that were incurred in the ordinary course of business, which would be reasonably likely to result in any Material Adverse Effect (as defined below), nor has there been any development involving a material adverse change in or affecting the financial condition, results of operations, business or prospects of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, otherwise than as disclosed in the General Disclosure Package and the Prospectus. Since the respective dates as of which information is given in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) or since the date of the General Disclosure Package, after giving effect to the Acquisition, there has not been (i) any material change in the capital stock or long-term debt of the Company or its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities, (ii) any material adverse change in or affecting the financial condition, results of operations, business or prospects of the Company or its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities, or (iii) any transaction entered into by any of the Company or its Significant Subsidiaries, other than in the ordinary course of business, that is material to the Company and its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities other than as disclosed, in the case of each of (i), (ii) or (iii) above, in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto).

(8) Good Standing of the Company and Significant Subsidiaries . Each of the Company, its “significant subsidiaries,” as defined in Rule 1-02(w) of Regulation S-X under the 1934 Act (each, a “ Significant Subsidiary ”) and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, has been duly organized, is validly existing and in good standing as a corporation or other business entity under the laws of its jurisdiction of organization and is duly qualified to do business and in good standing as a foreign corporation or other business entity in each jurisdiction in which its ownership or lease of property or the conduct of its businesses requires such

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qualification, except where the failure to be so qualified or in good standing would not have a material adverse effect on the financial condition, results of operations, business or prospects of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition (a “ Material Adverse Effect ”). Each of the Company, its Significant Subsidiaries and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition has all power and authority necessary to own or hold its properties and to conduct its business as described in the General Disclosure Package and the Prospectus. The subsidiaries listed on Exhibit B hereto are (a) the only Significant Subsidiaries of the Company as of the date hereof and (b) the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition.

(9) Capitalization . The Company has the capitalization as set forth in each of the General Disclosure Package and the Prospectus; all the issued shares of capital stock of the Company have been duly authorized and validly issued, are fully paid and non-assessable; all of the issued shares of capital stock or other equity interests, as applicable, of each Significant Subsidiary of the Company that are owned directly or indirectly by the Company have been duly authorized and validly issued and are fully paid (to the extent required under such entities’ Organizational Documents) and non-assessable (except as such non-assessability may be affected by Sections 18-607 and 18-804 of the Delaware Limited Liability Company Act or Sections 17-303, 17-607 and 17-804 of the Delaware Revised Uniform Limited Partnership Act) and are owned directly or indirectly by the Company free and clear of all liens, encumbrances, security interests, equities charges or claims (collectively, “ Liens ”) except (i) as disclosed in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) or (ii) to the extent any such Liens would not have a Material Adverse Effect.

(10) Due Authorization; Authorization of Agreement . The Company has all requisite corporate power and authority to execute, deliver and perform its obligations under this Agreement. This Agreement has been duly authorized, executed and delivered by the Company and, assuming due authorization, execution and delivery by the Representative, constitutes the valid and binding agreement of the Company, enforceable against the Company in accordance with its terms, subject to (i) the effects of bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other similar laws relating to or affecting creditors’ rights generally, (ii) general equitable principles (whether considered in a proceeding in equity or at law), and (iii) except as rights to indemnity and contribution hereunder may be limited by federal or state securities laws or principles of public policy.

(11) Listing . The Securities have been approved for quotation on the NYSE upon official notice of issuance.

(12) The Securities . The Securities to be purchased by the Underwriters from the Company have been duly authorized for issuance and sale to the Underwriters pursuant to this Agreement and, when issued and delivered by the Company pursuant to this Agreement against payment of the consideration set forth herein, will be validly

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issued and fully paid and non-assessable; and the issuance of the Securities is not subject to the preemptive or other similar rights of any securityholder of the Company.

(13) Description of the Securities . The Securities conform and will conform in all material respects to the statements relating thereto contained in the Registration Statement, the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) and are and will be in substantially the respective forms filed or incorporated by reference, as the case may be, as exhibits to the Registration Statement.

(14) Absence of Defaults and Conflicts . None of the Company, its Significant Subsidiaries or, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is (i) in violation of its Organizational Documents, (ii) in default, and no event has occurred which, with notice or lapse of time or both, would constitute such a default, in the due performance or observance of any term, obligation, agreement, covenant or condition contained in any material contract, indenture, mortgage, deed of trust, loan agreement, lease or other agreement or instrument to which it is a party or by which it is bound or which any of its properties or assets may be subject or (iii) in violation of any law, ordinance, governmental rule, regulation or court decree to which it or its property or assets may be subject, except, with respect to (ii) or (iii), for any such violations or defaults that would not be reasonably likely, singly or in the aggregate, to have a Material Adverse Effect. The execution and delivery of this Agreement by the Company, the consummation of the transactions contemplated hereby, the application of the proceeds from the sale of the Securities as described under “Use of Proceeds” in the General Disclosure Package and the Prospectus will not (i) conflict with or result in a breach or violation of any of the terms or provisions of, impose any Lien, charge or encumbrance upon any property or assets of the Company, its Significant Subsidiaries and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition under, or constitute a default under, any indenture, mortgage, deed of trust, loan agreement, license, lease or other agreement or instrument to which the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is a party or by which the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is bound or to which any of the property or assets of the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is subject; (ii) result in any violation of the provisions of the Organizational Documents of the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition; or (iii) result in any violation of any statute or any judgment, order, decree, rule or regulation of any court or governmental agency or body having jurisdiction over the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon

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giving effect to the Acquisition, or any of their respective properties or assets, except with respect to clauses (i) and (iii), conflicts, breaches, violations or defaults that would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.

(15) Absence of Labor Dispute . No labor disturbance by or dispute with the employees of the Company or any of its affiliates that are dedicated to the Company’s business or, to the knowledge of the Company, any of the Thunder Entities, exists or, to the knowledge of the Company, is imminent that would reasonably be expected to have a Material Adverse Effect.

(16) Absence of Proceedings . Except as described in the General Disclosure Package and the Prospectus, there are no legal or governmental proceedings pending to which the Company or any of its subsidiaries or, to the knowledge of the Company, any of the Thunder Entities, is a party or of which any property or assets of the Company or any of its subsidiaries or, to the knowledge of the Company, any of the Thunder Entities, is the subject that would, in the aggregate, reasonably be expected to have a Material Adverse Effect or would, in the aggregate, reasonably be expected to have a material adverse effect on the performance by the Company of its obligations under this Agreement or the consummation of the transactions contemplated hereby; and to the Company’s knowledge, no such proceedings are threatened or contemplated by governmental authorities or others.

(17) Accuracy of Descriptions and Exhibits . The information in the Pre-Pricing Prospectus and the Prospectus under the captions “Description of Capital Stock” and “Material U.S. Federal Tax Considerations for Non-U.S. Holders” and the information in the Company’s Annual Report on Form 10-K for the fiscal year ended 2014 under the captions “Business—Regulatory Matters,” “Business—Environmental Matters” and “Legal Proceedings,” insofar as they purport to constitute summaries of the terms of statutes, rules or regulations, legal or governmental proceedings or contracts and other documents, constitute accurate summaries of the terms of such statutes, rules and regulations, legal and governmental proceedings and contracts and other documents in all material respects; and there are no franchises, contracts, indentures, mortgages, deeds of trust, loan or credit agreements, bonds, notes, debentures, evidences of indebtedness, leases or other instruments, agreements or documents required to be described or referred to in the Registration Statement, the Pre-Pricing Prospectus or the Prospectus or the documents incorporated or deemed to be incorporated by reference therein or to be filed as exhibits thereto which have not been so described and filed as required.

(18) Absence of Further Requirements . No filing with, or authorization, approval, consent, license, order, registration, qualification or decree of, any court or governmental authority or agency, domestic or foreign is necessary or required for the execution, delivery or performance by the Company of its obligations under this Agreement, for the offering, issuance, sale or delivery of the Securities hereunder, or for the consummation of any of the other transactions contemplated by this Agreement, in each case on the terms contemplated by the Registration Statement, the General Disclosure Package and the Prospectus, except such as have been obtained under the

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1933 Act or the 1933 Act Regulations, except for the filing of the Prospectus and the Pricing Term Sheet pursuant to Rules 424(b) and 433, respectively, except as have been obtained prior to the execution hereof and except that no representation is made as to such as may be required under state or foreign securities laws.

(19) Possession of Licenses and Permits . The Company and each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, have such permits, licenses, franchises, certificates of need and other approvals or authorizations of governmental or regulatory authorities (“ Permits ”) as are necessary under applicable law to own, hold or lease, as the case may be, and to operate their properties and conduct their businesses in the manner described in the Registration Statement, the General Disclosure Package or the Prospectus, except where the failure to possess such Permits would not reasonably be expected to have a Material Adverse Effect. None of the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, has received notice of any revocation or modification of any such Permits except to the extent that any such revocation or modification would not have a Material Adverse Effect.

(20) Title to Property . Except as described in the Registration Statement, the General Disclosure Package or the Prospectus, the Company has, directly or indirectly through its subsidiaries, and, to the knowledge of the Company, Thunder, directly or indirectly through its subsidiaries, has, good and marketable title to all real property and good title to all personal property described in the Registration Statement, the General Disclosure Package or the Prospectus as being owned by it and valid, legal and defensible title to the interests in oil and gas properties underlying the estimates of the Company’s proved reserves described in the Registration Statement, the General Disclosure Package or the Prospectus, in each case free and clear of all liens, encumbrances and defects except (i) as are described in the Registration Statement, the General Disclosure Package or the Prospectus, (ii) as do not materially interfere with the use made in the aggregate of such properties, as described in the Registration Statement, the General Disclosure Package or the Prospectus, (iii) as are permitted under the Existing Facility, or (iv) as would not reasonably be expected to have a Material Adverse Effect; and the working interests derived from oil, gas and mineral leases or mineral interests which constitute a portion of the real property held or leased by the Company, its subsidiaries and the Thunder Entities reflect in all material respects the right of the Company and its subsidiaries and, to the knowledge of the Company, each of the Thunder Entities, to explore, develop or produce hydrocarbons from such real property, and the care taken by the Company and its subsidiaries and, to the knowledge of the Company, each of the Thunder Entities, with respect to acquiring or otherwise procuring such leases or mineral interests was generally consistent with standard industry practices in the areas in which the Company and its subsidiaries operate for acquiring or procuring leases and interests therein to explore, develop or produce hydrocarbons.

(21) Investment Company Act . The Company is not, and after giving effect to the offer and sale of the Securities and the application of the proceeds therefrom as

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described in the General Disclosure Package and the Prospectus, will not be, an “investment company” as defined in the 1940 Act.

(22) Reserve Engineers . Netherland, Sewell & Associates Inc., who issued a report with respect to certain of the Company’s oil and natural gas reserves and who has delivered or will deliver the letters referred to in Sections 5(j) and 5(k) hereof, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Company.

To the knowledge of the Company, LaRoche Petroleum Consultants, Ltd., who issued a report with respect to certain of the Thunder Entities’ oil and natural gas reserves and who has delivered or will deliver the letters referred to in Sections 5(l) and 5(m) hereof, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Thunder Entities.

(23) Reserve Data . The factual information underlying the estimates of reserves of the Company and, to the knowledge of the Company, Thunder, which was supplied to the independent petroleum engineers referenced in Section 1(a)(22) for the purposes of preparing the audit reports of the estimates of proved reserves included in the Registration Statement, the General Disclosure Package and the Prospectus, including, without limitation, production, costs of operation and development, current prices for production, agreements relating to current and future operations and sales of production, was true and correct in all material respects on the dates such estimates were made and such information was supplied and was prepared in accordance with customary industry practices; other than normal production of the reserves, intervening market commodity price fluctuations, fluctuations in demand for such products, adverse weather conditions, unavailability or increased costs of rigs, equipment, supplies or personnel, the timing of third party operations and other factors, in each case in the ordinary course of business, the Company is not aware of any facts or circumstances that would result in a material adverse change in the aggregate net reserves, or the present value of future net cash flows therefrom, as described in the Registration Statement, the General Disclosure Package and the Prospectus; estimates of such reserves and present values as described in the Registration Statement, the General Disclosure Package and the Prospectus comply in all material respects with the applicable requirements of Regulation S-X and Subpart 1200 of Regulation S-K under the Act.

(24) Environmental Laws . The Company, each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, (i) is in compliance with all laws, regulations, ordinances, rules, orders, judgments, decrees, permits or other legal requirements of any governmental authority, including without limitation any international, foreign, national, state, provincial, regional, or local authority, relating to pollution, the protection of human health or safety, the environment, or natural resources, or to the use, handling, storage, manufacturing, transportation, treatment, discharge, disposal or release of hazardous or toxic substances or wastes, pollutants or contaminants (“ Environmental Laws ”) applicable to such entity, which compliance includes, without limitation, obtaining, maintaining and complying

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with all permits, authorizations and approvals required by Environmental Laws to conduct its respective business, and (ii) has not received notice or otherwise has knowledge of any actual or alleged violation of Environmental Laws, or of any actual or potential liability for or other obligation concerning the presence, disposal or release of hazardous or toxic substances or wastes, pollutants or contaminants, except, with respect to (i) and (ii), as may be disclosed in the Registration Statement, the General Disclosure Package and the Prospectus and except where such noncompliance with Environmental Laws, failure to obtain or maintain required permits, authorizations or approvals or failure to comply with the terms and conditions of such permits, authorizations or approvals would not be reasonably likely to have a Material Adverse Effect.

(25) Absence of Registration Rights . There are no persons with registration rights or other similar rights to have any securities (debt or equity) registered pursuant to the Registration Statement or included in the offering contemplated by this Agreement.

(26) FINRA Matters . All of the information provided to the Representative or to counsel for the Underwriters in connection with any letters, filings or other supplemental information provided to FINRA pursuant to FINRA Rule 5110 or 5121 is true, complete and correct.

(27) Tax Returns . The Company, all of its subsidiaries and, to the knowledge of the Company, all of the Thunder Entities, have filed all federal, state, local and foreign income and franchise tax returns which are required to be filed by them and have paid all taxes due, other than those which, if not filed or paid, would not be reasonably expected to have a Material Adverse Effect, or which are being contested in good faith by appropriate proceedings. Except as would not be reasonably expected to have a Material Adverse Effect, no tax deficiency has been determined adversely to the Company, any of its subsidiaries or, to the knowledge of the Company, the Thunder Entities, and the Company has no knowledge of any tax deficiencies that have been, or would reasonably be expected to be asserted.

(28) Insurance . The Company, each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition carry, or are covered by, insurance in such amounts and covering such risks as is reasonable in accordance with customary practices for companies engaged in similar businesses in similar industries for the conduct of their respective businesses and the value of their respective properties.

(29) Accounting and Disclosure Controls . The Company maintains a system of internal control over financial reporting (as such term is defined in Rule 13a-15(f) of the 1934 Act) that complies with the requirements of the 1934 Act and that has been designed by, or under the supervision of, the Company’s principal executive and principal financial officers, or persons performing similar functions, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles in the United States. The Company maintains internal accounting

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controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorization, (ii) transactions are recorded as necessary to permit preparation of the Company’s financial statements in conformity with accounting principles generally accepted in the United States and to maintain accountability for its assets, (iii) access to the Company’s assets is permitted only in accordance with management’s general or specific authorization, (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences, and (v) the interactive data in eXtensible Business Reporting Language included or incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus is prepared in accordance with the Commission’s rules and guidelines applicable thereto. As of the date of the most recent balance sheet of the Company reviewed or audited by Ernst & Young LLP and the audit committee of the board of directors of the Company, there were no material weaknesses in the Company’s internal controls, except as may be disclosed in the Registration Statement, the General Disclosure Package and the Prospectus.

The Company maintains disclosure controls and procedures (as such term is defined in Rules 13a-15(e) and 15d-15(e) under the 1934 Act); and such disclosure controls and procedures (i) are designed to ensure that information required to be disclosed by the Company in the reports it files or submits under the 1934 Act is accumulated and communicated to the Company’s management, including the Company’s principal executive officer and principal financial officer, as appropriate, to allow timely decisions regarding required disclosure and (ii) except with respect to the material weaknesses in internal controls disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, such disclosure controls and procedures are effective at a reasonable assurance level to perform the functions for which they were established.

Except as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, since the date of the most recent balance sheet of the Company reviewed or audited by Ernst & Young LLP and the audit committee of the board of directors of the Company, (i) the Company has not been advised of or become aware of (A) any significant deficiencies in the design or operation of internal controls that could adversely affect the ability of the Company or any of its subsidiaries to record, process, summarize and report financial data, or any material weaknesses in internal controls, or (B) any fraud, whether or not material, that involves management or other employees who have a significant role in the internal controls of the Company and each of its subsidiaries; and (ii) there have been no significant changes in internal controls or in other factors that could significantly affect internal controls, including any corrective actions with regard to significant deficiencies and material weaknesses.

(30) Compliance with the Sarbanes-Oxley Act . The Company is in compliance in all material respects with the applicable provisions of the Sarbanes-Oxley Act and the rules and regulations promulgated in connection therewith.

(31) Pending Proceedings and Examinations; Comment Letters . The Registration Statement is not the subject of a pending proceeding or examination under

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Section 8(d) or 8(e) of the 1933 Act, and the Company is not the subject of a pending proceeding under Section 8A of the 1933 Act. The Company has provided the Representative with true, complete and correct copies of any written comments received from the Commission by the Company or its legal counsel or accountants, and of any transcripts made by the Company, its legal counsel or accountants of any oral comments received from the Commission, with respect to the Registration Statement, any preliminary prospectus, the Prospectus, any Issuer Free Writing Prospectus or any document incorporated or deemed to be incorporated by reference therein or any amendments or supplements to any of the foregoing and of all written responses thereto (in each case other than comment letters or written responses that are publicly available on EDGAR).

(32) Absence of Manipulation . The Company and its affiliates (as defined in Rule 501(b) of Regulation D under the 1933 Act) have not taken, directly or indirectly, any action designed to or that might reasonably be expected to cause or result, under the 1934 Act or otherwise, in stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities. The Securities are an “actively-traded security” exempted from the requirements of Rule 101 of Regulation M under the Exchange Act by subsection (c)(1) of such rule.

(33) Statistical and Market-Related Data . The statistical and market-related data included in the Registration Statement, the General Disclosure Package or the Prospectus is based on or derived from sources that the Company believes to be reliable in all material respects.

(34) No Unlawful Payments . Neither the Company nor any of its subsidiaries nor, to the knowledge of the Company, any of the Thunder Entities, or any director, officer, agent, employee or affiliate of the Company or any of its subsidiaries is aware of or has taken any action, directly or indirectly, that could result in a violation or a sanction for violation by such persons of the Foreign Corrupt Practices Act of 1977 or the U.K. Bribery Act 2010, each as may be amended, or similar law of any other relevant jurisdiction, or the rules or regulations thereunder; and the Company and its subsidiaries and, to the knowledge of the Company, the Thunder Entities, have instituted and maintain policies and procedures to ensure compliance therewith. No part of the proceeds of the offering will be used, directly or indirectly, in violation of the Foreign Corrupt Practices Act of 1977 or the U.K. Bribery Act 2010, each as may be amended, or similar law of any other relevant jurisdiction, or the rules or regulations thereunder.

(35) Money Laundering Laws . The operations of the Company and its subsidiaries and, to the knowledge of the Company, the Thunder Entities, are and have been conducted at all times in compliance with applicable financial recordkeeping and reporting requirements and the money laundering statutes and the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “Money Laundering Laws”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries or, to

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the knowledge of the Company, any of the Thunder Entities, with respect to the Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(36) No Conflicts with Sanctions Laws . None of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities and, to the knowledge of the Company, none of the Company’s or its subsidiaries’ directors, officers, agents, employees or affiliates (i) is, or is controlled or 50% or more owned by or is acting on behalf of, an individual or entity that is currently subject to any sanctions administered or enforced by the United States (including any administered or enforced by the Office of Foreign Assets Control of the U.S. Treasury Department, the U.S. Department of State, or the Bureau of Industry and Security of the U.S. Department of Commerce), the United Nations Security Council, the European Union, the United Kingdom (including sanctions administered or enforced by Her Majesty’s Treasury) or other relevant sanctions authority (collectively, “Sanctions” and such persons, “Sanctioned Persons”), (ii) is located, organized or resident in a country or territory that is, or whose government is, the subject of Sanctions that broadly prohibit dealings with that country or territory (collectively, “Sanctioned Countries” and each, a “Sanctioned Country”) or (iii) will, directly or indirectly, use the proceeds of this offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other individual or entity in any manner that would result in a violation of any Sanctions by, or could result in the imposition of Sanctions against, any individual or entity (including any individual or entity participating in the offering, whether as underwriter, advisor, investor or otherwise). Except as has been disclosed to the Underwriters or is not material to the analysis under any Sanctions, none of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities has engaged in any dealings or transactions with or for the benefit of a Sanctioned Person, or with or in a Sanctioned Country, in the preceding 3 years, and none of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities have any plans to increase its dealings or transactions with or for the benefit of Sanctioned Persons, or with or in Sanctioned Countries.

(37) Offering Materials . Without limitation to the provisions of Section 17 hereof, the Company has not distributed and will not distribute, directly or indirectly (other than through the Underwriters), any “written communication” (as defined Rule 405 under the 1933 Act) or other offering materials in connection with the offering or sale of the Securities, other than the Pre-Pricing Prospectus, the Prospectus, any amendment or supplements to any of the foregoing that are filed with the SEC and any Permitted Free Writing Prospectuses (as defined in Section 17).

(38) Brokers . The Company has not paid or agreed to pay to any person any compensation for soliciting another to purchase the Securities (except as contemplated in this Agreement).

(b) Certificates . Any certificate signed by any officer of the Company or any of its subsidiaries (whether signed on behalf of such officer, the Company or such subsidiary) and delivered to the Representative or to counsel for the Underwriters shall be deemed a representation and warranty by the Company to each Underwriter as to the matters covered thereby.

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SECTION 2. Sale and Delivery to Underwriters; Closing .

(a) The Initial Securities . On the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Company agrees to sell to each Underwriter, severally and not jointly, and each Underwriter, severally and not jointly, agrees to purchase from the Company, at a price per share of $9.7465, the number of Initial Securities set forth in Exhibit A opposite the name of such Underwriter.

(b) The Option Securities . In addition, on the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Company hereby grants an option to the several Underwriters to purchase up to an additional 4,500,000 shares of Common Stock, as set forth in Exhibit A, at the price per share of $9.7465, less an amount per share equal to any dividends or distributions declared by the Company and payable on the Initial Securities but not payable on the Option Securities.

If any Option Securities are to be purchased, the number of Option Securities to be purchased by each Underwriter shall be the number of Option Securities which bears the same ratio to the aggregate number of Option Securities being purchased as the number of Initial Securities set forth opposite the name of such Underwriter in Exhibit A (or such number increased as set forth in Section 10 hereof) bears to the aggregate number of Initial Securities being purchased from the Company by the several Underwriters, subject, however, to such adjustments to eliminate any fractional Securities as the Representative in its discretion shall make.

The option hereby granted will expire 30 days after the date hereof and may be exercised in whole or in part from time to time upon notice by the Representative to the Company setting forth the number of Option Securities as to which the Underwriters are then exercising the option and the time and date of payment and delivery for such Option Securities. Any such time and date of delivery (a “Date of Delivery”) shall be determined by the Representative, but shall not be later than seven full business days after the exercise of said option, nor in any event prior to the Closing Date.

(c) Payment . Payment of the purchase price for, and delivery of, the Initial Securities shall be made at the offices of Simpson Thacher & Bartlett LLP, 425 Lexington Avenue, New York, New York 10017, or at such other place as shall be agreed upon by the Representative and the Company, at 10:00 A.M. (New York City time) on July 22, 2015 (unless postponed in accordance with the provisions of Section 10), or such other time not later than five business days after such date as shall be agreed upon by the Representative and the Company (such time and date of payment and delivery being herein called “Closing Date”).

In addition, in the event that any or all of the Option Securities are purchased by the Underwriters, payment of the purchase price for, and delivery of certificates for, such Option Securities shall be made at the above-mentioned offices, or at such other place as shall be agreed upon by the Representative and the Company on each Date of Delivery as specified in the notice from the Representative to the Company.

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Payment shall be made to the Company by wire transfer of immediately available funds to a single bank account designated by the Company against delivery to the Representative for the respective accounts of the Underwriters of the Securities to be purchased by them. It is understood that each Underwriter has authorized the Representative, for its account, to accept delivery of, receipt for, and make payment of the purchase price for, the Securities which it has agreed to purchase. Barclays, individually and not as representative of the Underwriters, may (but shall not be obligated to) make payment of the purchase price for the Securities to be purchased by any Underwriter whose funds have not been received by the Closing Date, but such payment shall not relieve such Underwriter from its obligations hereunder. Delivery of the Securities shall be made through the facilities of The Depository Trust Company (“DTC”) unless the Representative shall otherwise instruct.

(d) Registration . The Initial Securities and the Option Securities, if any, shall be registered in such names as the Representative may request in writing at least one full business day before the Closing Date or the relevant Date of Delivery, as the case may be.

SECTION 3. Covenants of the Company . The Company covenants with each Underwriter as follows:

(a) Compliance with Securities Regulations and Commission Requests . The Company, subject to Section 3(b), will comply with the requirements of Rule 430B and Rule 433 and will notify the Representative immediately, and confirm the notice in writing from the Applicable Time through the Closing Date or the relevant Date of Delivery, as the case may be (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)), (i) when the Registration Statement or any post-effective amendment to the Registration Statement shall become effective, or when any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing shall have been filed, (ii) of the receipt of any comments from the Commission (and shall promptly furnish the Representative with a copy of any comment letters and any transcript of oral comments, and shall furnish the Representative with copies of any written responses thereto a reasonable amount of time prior to the proposed filing thereof with the Commission and will not file any such response to which the Representative or counsel for the Underwriters shall reasonably object), (iii) of any request by the Commission for any amendment to the Registration Statement or any amendment or supplement to any preliminary prospectus or the Prospectus or any Issuer Free Writing Prospectus or for additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any order preventing or suspending the use of any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing or any notice from the Commission objecting to the use of the form of the Registration Statement or any post-effective amendment thereto, or of the suspension of the qualification of the Securities for offering or sale in any jurisdiction or of the loss or suspension of any exemption from any such qualification, or of the initiation or threatening of any proceedings for any of such purposes, or of any examination pursuant to Section 8(e) of the 1933 Act concerning the

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Registration Statement and (v) of the initiation or threatening of any proceeding under Section 8A of the 1933 Act in connection with the offering of the Securities. The Company will make every reasonable effort to prevent the issuance of any stop order and the suspension or loss of any qualification of the Securities for offering or sale and any loss or suspension of any exemption from any such qualification, and if any such stop order is issued, or any such suspension or loss occurs, to obtain the lifting thereof at the earliest possible moment. The Company shall pay the required Commission filing fees relating to the Securities within the time required by Rule 456(b)(1)(i) of the 1933 Act Regulations without regard to the proviso therein and otherwise in accordance with Rules 456(b) and 457(r) of the 1993 Act Regulations, except to the extent such filing fees have been paid prior to the date hereof.

(b) Filing of Amendments . From the Applicable Time through the Closing Date or the relevant Date of Delivery, as the case may be (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)), the Company will give the Representative notice of its intention to file or prepare any amendment to the Registration Statement, any Issuer Free Writing Prospectus or any amendment, supplement or revision to any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus, whether pursuant to the 1933 Act or otherwise, and the Company will furnish the Representative with copies of any such documents within a reasonable amount of time prior to such proposed filing or use, as the case may be, and will not file or use any such document to which the Representative or counsel for the Underwriters shall reasonably object. The Company has given the Representative notice of any filings made pursuant to the 1934 Act or the 1934 Act Regulations within 48 hours prior to the Applicable Time; the Company will give the Representative notice of its intention to make any such filing from the Applicable Time through the Closing Date or the relevant Date of Delivery, as the case may be (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)) and will furnish the Representative with copies of any such documents a reasonable amount of time prior to such proposed filing, as the case may be, and will not file or use any such document to which the Representative or counsel for the Underwriters shall reasonably object.

(c) Delivery of Registration Statements . If requested, the Company has furnished or will deliver to the Representative and counsel for the Underwriters, without charge, copies of the Registration Statement and of each amendment thereto (including exhibits filed therewith or incorporated by reference therein and documents incorporated or deemed to be incorporated by reference therein or otherwise deemed to be a part thereof) and copies of all consents and certificates of experts. The copies of the Registration Statement and each amendment thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

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(d) Delivery of Prospectuses . The Company has delivered to each Underwriter, without charge, as many copies of each preliminary prospectus and any amendments or supplements thereto as such Underwriter reasonably requested, and the Company hereby consents to the use of such copies for purposes permitted by the 1933 Act. The Company will furnish to each Underwriter, without charge, during the period when the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), such number of copies of the Pre-Pricing Prospectus, the Prospectus and any Issuer Free Writing Prospectus and any amendments or supplements to any of the foregoing as such Underwriter may reasonably request. Each preliminary prospectus, the Prospectus, each Issuer Free Writing Prospectus and any amendments or supplements to any of the foregoing furnished to the Underwriters were and will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(e) Continued Compliance with Securities Laws . The Company will comply with the 1933 Act, the 1933 Act Regulations, the 1934 Act and the 1934 Act Regulations so as to permit the completion of the distribution of the Securities as contemplated by this Agreement, the General Disclosure Package and the Prospectus. If at any time when a prospectus is required (or, but for the provisions of Rule 172, would be required) by the applicable law to be delivered in connection with sales of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), any event shall occur or condition shall exist as a result of which it is necessary to amend the Registration Statement or amend or supplement the General Disclosure Package or the Prospectus (or, in each case, any documents incorporated or deemed to be incorporated by reference therein) so that the Registration Statement, the General Disclosure Package or the Prospectus, as the case may be, will not include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made or then prevailing, not misleading or if it is necessary to amend the Registration Statement or amend or supplement the General Disclosure Package or the Prospectus (or, in each case, any documents incorporated or deemed to be incorporated by reference therein) in order to comply with the requirements of the 1933 Act, the 1933 Act Regulations, the 1934 Act or the 1934 Act Regulations, the Company will promptly notify the Representative of such event or condition and of its intention to file such amendment or supplement and will promptly prepare and file with the Commission, subject to Section 3(b) hereof, such amendment or supplement as may be necessary to correct such untrue statement or omission or to comply with such requirements, and, in the case of an amendment or post-effective amendment to the Registration Statement, the Company will use its commercially reasonable efforts to have such amendment declared or become effective as soon as practicable and the Company, if requested, will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request. If at any time an Issuer Free Writing Prospectus conflicts with the information contained in the Registration Statement or if an event shall occur or condition shall exist as a result of which it is necessary to amend or supplement such Issuer Free Writing Prospectus so that it will not include an untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were

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made or then prevailing, not misleading, or if it is necessary to amend or supplement such Issuer Free Writing Prospectus in order to comply with the requirements of the 1933 Act or the 1933 Act Regulations, the Company will promptly notify the Representative of such event or condition and of its intention to file such amendment or supplement and will promptly prepare and, if required by the 1933 Act or the 1933 Act Regulations, file with the Commission, subject to Section 3(b) hereof, such amendment or supplement as may be necessary to eliminate or correct such conflict, untrue statement or omission or to comply with such requirements, and the Company will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request.

(f) Blue Sky and Other Qualifications . The Company will furnish such information as may be required and otherwise cooperate with the Underwriters to qualify the Securities for offering and sale, or to obtain an exemption for the Securities to be offered and sold, under the applicable securities laws of such states and other jurisdictions (domestic or foreign) as the Representative may reasonably designate and to maintain such qualifications and exemptions in effect for so long as required for the distribution of the Securities (but in no event for a period of not less than one year from the date of this Agreement); provided, however, that the Company shall not be obligated to file any general consent to service of process or to qualify as a foreign corporation or as a dealer in securities in any jurisdiction in which it is not so qualified or to subject itself to taxation in respect of doing business in any jurisdiction in which it is not otherwise so subject. In each jurisdiction in which the Securities have been so qualified or exempt, the Company will file such statements and reports as may be required by the laws of such jurisdiction to continue such qualification or exemption, as the case may be, in effect for so long as required for the distribution of the Securities (but in no event for a period of not less than one year from the date of this Agreement).

(g) Rule 158 . The Company will make generally available to its securityholders and the Underwriters as soon as practicable an earnings statement that satisfies the last paragraph of Section 11(a) of the 1933 Act and Rule 158 promulgated thereunder.

(h) Use of Proceeds . The Company will use the net proceeds received by it from the sale of the Securities in the manner specified in the Pre-Pricing Prospectus and the Prospectus under “Use of Proceeds.”

(i) Restriction on Sale of Securities . For a period commencing on the date hereof and ending on the 90th day after the date of the Prospectus (the “Lock-Up Period”), not to, directly or indirectly, (A) offer for sale, sell, pledge, or otherwise dispose of (or enter into any transaction or device that is designed to, or could be expected to, result in the disposition by any person at any time in the future of) any shares of Common Stock or securities convertible into or exercisable or exchangeable for Common Stock (other than shares issued pursuant to employee benefit plans, qualified stock option plans or other employee compensation plans existing on the date hereof or pursuant to currently outstanding options, warrants or rights not issued under one of those plans), or sell or grant options, rights or warrants with respect to any shares of Common Stock or

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securities convertible into or exchangeable for Common Stock (other than the grant of options pursuant to option plans existing on the date hereof), (B) enter into any swap or other derivatives transaction that transfers to another, in whole or in part, any of the economic benefits or risks of ownership of such shares of Common Stock, whether any such transaction described in clause (A) or (B) above is to be settled by delivery of Common Stock or other securities, in cash or otherwise, (C) file or cause to be filed a registration statement, including any amendments thereto, with respect to the registration of any shares of Common Stock or securities convertible, exercisable or exchangeable into Common Stock or any other securities of the Company (other than any registration statement on Form S-8), or (D) publicly disclose the intention to do any of the foregoing, in each case without the prior written consent of the Representative, on behalf of the Underwriters; provided that this Section 3(i) shall not apply to (i) the concurrent offering by the Company of 7,000,000 shares of its 6.25% series A mandatory convertible preferred stock (or 8,050,000 shares if the underwriters exercise their option to purchase additional shares in full) or any conversion of such 6.25% series A mandatory convertible preferred stock, (ii) the issuance to Thunder of 40,000,000 shares of Common Stock in connection with the Acquisition and the granting of registration rights to Thunder with respect to such shares and (iii) the filing of registration statements, including any amendments thereto, with respect to the registration of the securities described in clauses (i) and (ii) of this proviso. Additionally, the Company shall cause each executive officer and director of the Company set forth on Exhibit G-1 hereto to furnish to the Representative, on or prior to the date hereof, a letter or letters, substantially in the form of Exhibit G-2 hereto (the “Lock-Up Agreements”).

(j) Reporting Requirements . The Company, during the period when the Prospectus is required (or, but for the provisions of Rule 172, would be required) by applicable law to be delivered (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), will file all documents required to be filed with the Commission pursuant to the 1934 Act and the 1934 Act Regulations within the time periods required by the 1934 Act and the 1934 Act Regulations.

(k) Preparation of Prospectus . Immediately following the execution of this Agreement, the Company will, subject to Section 3(b) hereof, prepare the Prospectus, which shall contain the public offering price and terms of the Securities, the plan of distribution thereof and such other information as may be required by the 1933 Act or the 1933 Act Regulations or as the Representative and the Company may deem appropriate, and will file or transmit for filing with the Commission, in accordance with the provisions of Rule 430B and in the manner and within the time period required by Rule 424(b) (without reliance on Rule 424(b)(8)), the Prospectus.

(l) DTC . The Company will use their best efforts to permit the Securities to be eligible for clearance and settlement through DTC.

(m) Pricing Term Sheet . The Company will prepare a pricing term sheet (the “ Pricing Term Sheet ”) in substantially the form attached hereto as Exhibit C and otherwise in form and substance satisfactory to the Representative, and shall file such Pricing Term Sheet as an “issuer free writing prospectus” pursuant to Rule 433 prior to

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the close of business on the business day following the date hereof; provided that the Company shall furnish the Representative with copies of any such Pricing Term Sheet a reasonable amount of time prior to such proposed filing and will not use or file any such document to which the Representative or counsel to the Underwriters shall reasonably object.

(n) No Stabilization . The Company will not take, directly or indirectly, any action designed to or that could reasonably be expected to cause or result in any stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities and will not take any action prohibited by Regulation M under the Exchange Act in connection with the distribution of the Securities contemplated hereby.

SECTION 4. Payment of Expenses .

(a) Expenses . The Company will pay all expenses incident to the performance of its obligations under this Agreement, including (i) the preparation, printing and filing of the Registration Statement and each amendment thereto (in each case including exhibits) and any costs associated with electronic delivery of any of the foregoing, (ii) the printing (or reproduction) and delivery to the Underwriters of this Agreement and such other documents as may be required in connection with the offering, purchase, sale, issuance or delivery of the Securities, (iii) the preparation, issuance and delivery of the certificates for the Securities and the issuance and delivery of the Securities to the Underwriters, including any issue or other transfer taxes and any stamp or other taxes or duties payable in connection with the sale, issuance or delivery of the Securities to the Underwriters, (iv) the fees and disbursements of the counsel, accountants and other advisors to the Company and Thunder, (v) the qualification or exemption of the Securities under securities laws in accordance with the provisions of Section 3(f) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters in connection therewith and in connection with the preparation of the Blue Sky Survey and any supplements thereto, (vi) the preparation, printing and delivery to the Underwriters of copies of each preliminary prospectus, any Permitted Free Writing Prospectus and the Prospectus and any amendments or supplements to any of the foregoing and any costs associated with electronic delivery of any of the foregoing, (vii) the preparation, printing and delivery to the Underwriters of copies of the Blue Sky Survey and any supplements thereto and any costs associated with electronic delivery of any of the foregoing, (viii) fees and expenses of the transfer agent and any registrar, including the fees and disbursements of counsel for the transfer agent, (ix) the filing fees incident to, and the reasonable fees and disbursements of counsel to the Underwriters in connection with, the review, if any, by FINRA of the terms of the sale of the Securities, (x) the costs and expenses of the Company and any of its officers, directors, counsel or other representatives in connection with presentations or meetings undertaken in connection with the offering of the Securities, including, without limitation, expenses associated with the production of road show slides and graphics and the production and hosting of any electronic road shows, fees and expenses of any consultants engaged in connection with road show presentations, travel, lodging, transportation, and other expenses of the officers, directors, counsel or other representatives of the Company incurred in connection with any such presentations or meetings and (xi) the fees and expenses incurred in connection with the inclusion of the Securities on the

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NYSE. Notwithstanding the foregoing, except as otherwise expressly provided in this Section 4(a) and Sections 4(b), 6 and 7 hereof, the Underwriters shall bear their own costs and expenses related to the issuance and sale by the Company of the Securities, including transfer taxes on resale of any Securities by them, and any advertising expenses in connection with any offers they make.

(b) Termination of Agreement . If this Agreement is terminated by the Representative in accordance with the provisions of Section 5 or Section 9 hereof, the Company shall reimburse the Underwriters for all of their out-of-pocket expenses, including the reasonable fees and disbursements of counsel for the Underwriters.

SECTION 5. Conditions of Underwriters’ Obligations . The obligations of the several Underwriters hereunder to purchase the Initial Securities on the Closing Date or the Option Securities on the Date of Delivery, as the case may be, are subject to the accuracy of the representations and warranties of the Company contained in this Agreement, or in certificates signed by any officer of the Company or any subsidiary of the Company (whether signed on behalf of such officer, the Company or such subsidiary) delivered to the Representative or counsel for the Underwriters, to the performance by the Company of its covenants and other obligations hereunder, and to the following further conditions:

(a) Effectiveness of Registration Statement . The Registration Statement shall have become effective, and no stop order suspending the effectiveness of the Registration Statement shall have been issued under the 1933 Act or proceedings therefor, pursuant to Rule 401(g)(2) or Section 8A of the 1933 Act, initiated or, to the knowledge of the Company, threatened by the Commission, and any request on the part of the Commission for additional information shall have been complied with to the reasonable satisfaction of the Representative and the Commission shall not have notified the Company of any objection to the use of the form of the Registration Statement. The Prospectus shall have been filed with the Commission in the manner and within the time period required by Rule 424(b) (without reliance upon Rule 424(b)(8)) and each Issuer Free Writing Prospectus required to be filed with the Commission shall have been filed in the manner and within the time period required by Rule 433, and, prior to the Closing Date or the Date of Delivery, as the case may be, the Company shall have provided evidence satisfactory to the Representative of such timely filings.

(b) Opinion and 10b-5 Statement of Counsel for Company . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received the favorable opinion and 10b-5 statement, dated as of Closing Date or the Date of Delivery, as the case may be, of Weil, Gotshal & Manges LLP, counsel for the Company (“ Company Counsel ”), in form and substance satisfactory to the Representative, together with signed or reproduced copies of such opinion and 10b-5 statement for each of the other Underwriters, to the effect set forth in Exhibit E hereto and to such further effect as the Representative may reasonably request.

(c) Opinion of Company’s General Counsel . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received the favorable opinion, dated as of the Closing Date or the Date of Delivery, as the case may be, of

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Dennis C. Cameron, Senior Vice President and General Counsel of the Company, in form and substance satisfactory to the Representative, together with signed or reproduced copies of such opinion for each of the other Underwriters, to the effect set forth in Exhibit F hereto and to such further effect as the Representative may reasonably request.

(d) Opinion and 10b-5 Statement of Counsel for Underwriters . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received the favorable opinion and 10b-5 statement, dated as of Closing Date or the Date of Delivery, as the case may be, of Simpson Thacher & Bartlett LLP, counsel for the Underwriters, together with signed or reproduced copies of such opinion and 10b-5 statement for each of the other Underwriters, with respect to the Securities to be sold by the Company pursuant to this Agreement, the Registration Statement, the General Disclosure Package and the Prospectus and any amendments or supplements thereto and such other matters as the Representative may reasonably request.

(e) Officers’ Certificate . At the Closing Date or the Date of Delivery, as the case may be, there shall not have been, since the date hereof or since the respective dates as of which information is given in the Registration Statement, the General Disclosure Package and the Prospectus (in each case exclusive of any amendments or supplements thereto subsequent to the date of this Agreement), any material adverse change or any development that would reasonably be expected to result in a prospective material adverse change, in the financial condition, earnings, business or operations of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, from that set forth or contemplated in the General Disclosure Package and the Prospectus (in each case exclusive of any amendments or supplements thereto subsequent to the date of this Agreement), and, at the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received a certificate of the Company, signed by an executive officer of the Company, dated as of Closing Date or the Date of Delivery, as the case may be, (a) making representations and warranties with respect to the written comments received from the Commission and (b) to the effect that (i) there has been no such material adverse change, (ii) the representations and warranties of the Company in this Agreement are true and correct at and as of the Closing Date or the Date of Delivery, as the case may be, with the same force and effect as though expressly made at and as of Closing Date or the Date of Delivery, as the case may be, (iii) the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied at or prior to Closing Date or the Date of Delivery, as the case may be, under or pursuant to this Agreement, and (iv) no stop order suspending the effectiveness of the Registration Statement has been issued and no proceedings for that purpose, pursuant to Rule 401(g)(2) or Section 8A under the 1933 Act, have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission and the Commission has not notified the Company of any objection to the use of the form of the Registration Statement, and to the effect set forth in Section 5(n) below.

(f) Accountant’s Comfort Letter . At the time of the execution of this Agreement, the Representative shall have received from Ernst & Young LLP a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the

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other Underwriters, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information of the Company contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(g) Bring-down Comfort Letter . At Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from Ernst & Young LLP a letter, dated as of Closing Date or the Date of Delivery, as the case may be, and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (f) of this Section, except that the specified date referred to shall be a date not more than three business days prior to Closing Date or the Date of Delivery, as the case may be.

(h) Thunder Comfort Letter . At the time of the execution of this Agreement, the Representative shall have received from Grant Thornton LLP a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information of the Thunder Entities contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(i) Thunder Bring-Down Comfort Letter . At Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from Grant Thornton LLP a letter, dated as of Closing Date or the Date of Delivery, as the case may be, and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (h) of this Section, except that the specified date referred to shall be a date not more than three business days prior to Closing Date or the Date of Delivery, as the case may be.

(j) Reserve Engineer’s Letter . At the time of the execution of this Agreement, the Representative shall have received from Netherland, Sewell & Associates, Inc. a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, covering certain matters relating to information about the reserves of the Company contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(k) Bring-Down Reserve Engineer’s Letter . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from Netherland, Sewell & Associates, Inc. a letter, dated as of the Closing Date or the Date of Delivery, as the case may be, and in form and substance satisfactory to the Representative, to the

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effect that they reaffirm the statements made in the letter furnished pursuant to subsection (j) of this Section.

(l) Thunder Engineer’s Letter . At the time of the execution of this Agreement, the Representative shall have received from LaRoche Petroleum Consultants, Ltd. a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, covering certain matters relating to information about the reserves of the Thunder Entities contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(m) Thunder Bring-Down Reserve Engineer’s Letter . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from LaRoche Petroleum Consultants, Ltd. a letter, dated as of the Closing Date or the Date of Delivery, as the case may be, and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (l) of this Section.

(n) No Downgrade . There shall not have occurred, on or after the date of this Agreement, any downgrading in the rating of any debt securities of or guaranteed by the Company or any preferred securities of the Company by any “nationally recognized statistical rating organization” (as defined by the Commission in Section 3(a)(62) of the 1934 Act) or any public announcement that any such organization has placed its rating on the Company or any such debt or preferred securities under surveillance or review or on a so-called “watch list” (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement by any such organization that the Company or any such debt or preferred securities has been placed on negative outlook.

(o) No Objection . Prior to the date of this Agreement, FINRA shall have confirmed in writing that it has no objection with respect to the fairness and reasonableness of the underwriting terms and arrangements.

(p) No Material Adverse Change . Since the date of the most recent financial statements included in the General Disclosure Package (exclusive of any amendment or supplement thereto) and the Prospectus (exclusive of any amendment or supplement thereto), there shall not have been any change, or any development that would reasonably be expected to result in a prospective change, in the financial condition, earnings, business or operations of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, from that set forth in the Pre-Pricing Prospectus, the effect of which is, in the sole judgment of the Representative, so material and adverse as to make it impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto).

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(q) Additional Documents . At the Closing Date or the Date of Delivery, as the case may be, counsel for the Underwriters shall have been furnished with such documents and opinions as they may reasonably require for the purpose of enabling them to pass upon the issuance and sale of the Securities as herein contemplated, or in order to evidence the accuracy of any of the representations or warranties, or the fulfillment of any of the conditions, contained in this Agreement, or as the Representative or counsel for the Underwriters may otherwise reasonably request; and all proceedings taken by the Company in connection with the issuance and sale of the Securities as herein contemplated and in connection with the other transactions contemplated by this Agreement shall be satisfactory in form and substance to the Representative.

(r) Lock-up Agreements . The Lock-Up Agreements between the Representative and the executive officers and directors of the Company set forth on Exhibit G-1, delivered to the Representative on or before the date of this Agreement, shall be in full force and effect on the Closing Date or the Date of Delivery, as the case may be.

(s) Approval of Listing . At the Closing Date or the Date of Delivery, as the case may be, the Securities shall have been approved for inclusion on the NYSE subject to official notice of issuance.

(t) Termination of Agreement . If any condition specified in this Section 5 shall not have been fulfilled when and as required to be fulfilled, this Agreement, or, in the case of any condition to the purchase of Option Securities on a Date of Delivery which is after the Closing Date, the obligations of the Underwriters to purchase the relevant Option Securities, may be terminated by the Representative by notice to the Company at any time on or prior to the Closing Date or such Date of Delivery, as the case may be, and such termination shall be without liability of any party to any other party except as provided in Section 4 hereof and except that Sections 1, 6, 7, 8, 11, 12, 13, 14, 15, 16, 18, 19 and 20 and hereof shall survive any such termination of this Agreement and remain in full force and effect.

SECTION 6. Indemnification .

(a) Indemnification by the Company . The Company agrees to indemnify and hold harmless each Underwriter, its affiliates, and its and their officers, directors, employees, partners and members and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act as follows:

(i) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, arising out of any untrue statement or alleged untrue statement of a material fact in the Registration Statement (or any amendment thereto), or the omission or alleged omission therefrom of a material fact required to be stated therein or necessary to make the statements therein not misleading, or arising out of any untrue statement or alleged untrue statement of a material fact in any preliminary prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package or the Prospectus (or any amendment or supplement to any of the foregoing), or in any “issuer information” (as defined in

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Rule 433) or “road show” (as defined in Rule 433) that does not constitute an Issuer Free Writing Prospectus, or the omission or alleged omission therefrom of a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading and agrees to reimburse each such indemnified party, as incurred, for any legal or other expenses reasonably incurred by them in connection with defending any such loss, liability, claim, damage or action;

provided , however , that this indemnity agreement shall not apply to any loss, liability, claim, damage or expense to the extent arising out of any untrue statement or omission or alleged untrue statement or omission made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative expressly for use in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package or the Prospectus (or in any amendment or supplement to any of the foregoing), it being understood and agreed that the only such information furnished by the Underwriters as aforesaid consists of the information described as such in Section 6(b) hereof.

(b) Indemnification by the Underwriters . Each Underwriter agrees, severally and not jointly, to indemnify and hold harmless the Company, its directors, each of its officers who signed the Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act against any and all loss, liability, claim, damage and expense described in the indemnity contained in subsection (a)(1) of this Section 6, as incurred, but only with respect to untrue statements or omissions, or alleged untrue statements or omissions, made in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement to any of the foregoing), in reliance upon and in conformity with written information furnished to the Company by such Underwriter through the Representative expressly for use therein. The Company hereby acknowledges and agrees that the information furnished to the Company by the Underwriters through the Representative expressly for use in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement to any of the foregoing), consists exclusively of the information appearing under the caption “Underwriting” in the Pre-Pricing Prospectus and the Prospectus regarding stabilization, syndicate covering transactions, penalty bids and discretionary sales appearing in the 15th, 16th and 17th paragraphs under such caption (but only insofar as such information concerns the Underwriters).

(c) Actions Against Parties; Notification . Each indemnified party shall give notice as promptly as reasonably practicable to each indemnifying party of any action commenced against it in respect of which indemnity may be sought hereunder, but failure to so notify an indemnifying party shall not relieve such indemnifying party from any liability hereunder unless and to the extent it did not otherwise learn of such action and such failure results in the forfeiture by the indemnifying party of substantial rights and defenses. The indemnifying party shall be entitled to appoint counsel of the indemnifying party’s choice at the indemnifying party’s expense to represent the indemnified party in any action for which indemnification is sought (in which case the indemnifying party shall not thereafter be responsible for the fees and expenses of any separate counsel retained by the indemnified party or parties except as set forth below); provided , however , that such counsel shall be reasonably satisfactory to the indemnified

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party. Notwithstanding the indemnifying party’s election to appoint counsel to represent the indemnified party in an action, the indemnified party shall have the right to employ separate counsel (including local counsel), and the indemnifying party shall bear the reasonable fees, costs and expenses of such separate counsel if (i) the use of counsel chosen by the indemnifying party to represent the indemnified party would present such counsel with a conflict of interest, (ii) the actual or potential defendants in, or targets of, any such action include both the indemnified party and the indemnifying party and the indemnified party shall have reasonably concluded that there may be legal defenses available to it and/or other indemnified parties which are different from or additional to those available to the indemnifying party, (iii) the indemnifying party shall not have employed counsel reasonably satisfactory to the indemnified party to represent the indemnified party within a reasonable time after notice of the institution of such action or (iv) the indemnifying party shall authorize the indemnified party to employ separate counsel at the expense of the indemnifying party. In no event shall the indemnifying party be liable for the fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for the Underwriters and the other indemnified parties referred to in Section 6(a)(1) above; and the fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for the Company, its directors, each of its officers who signed the Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act, in each case in connection with any one action or separate but similar or related actions in the same jurisdiction arising out of the same general allegations or circumstances. No indemnifying party shall, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever in respect of which indemnification or contribution could be sought under this Section 6 or Section 7 hereof (whether or not the indemnified parties are actual or potential parties thereto), unless such settlement, compromise or consent (i) includes an unconditional release of each indemnified party from all liability arising out of such litigation, investigation, proceeding or claim and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party.

SECTION 7. Contribution . If the indemnification provided for in Section 6 hereof is for any reason unavailable to or insufficient to hold harmless an indemnified party in respect of any losses, liabilities, claims, damages or expenses referred to therein, then each indemnifying party shall contribute to the aggregate amount of such losses, liabilities, claims, damages and expenses incurred by such indemnified party, as incurred, (i) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other hand from the offering of the Securities pursuant to this Agreement or (ii) if the allocation provided by clause (i) is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause (i) above but also the relative fault of the Company on the one hand and of the Underwriters on the other hand in connection with the statements or omissions which resulted in such losses, liabilities, claims, damages or expenses, as well as any other relevant equitable considerations.

The relative benefits received by the Company on the one hand and the Underwriters on the other hand in connection with the offering of the Securities pursuant to this Agreement shall be deemed to be in the same respective proportions as the total net proceeds from the offering of

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the Securities pursuant to this Agreement (before deducting expenses) received by the Company and the total underwriting discounts and commissions received by the Underwriters, in each case as set forth on the cover of the Prospectus, bear to the aggregate initial public offering price of the Securities as set forth on such cover.

The relative fault of the Company on the one hand and the Underwriters on the other hand shall be determined by reference to, among other things, whether any such untrue or alleged untrue statement of a material fact or omission or alleged omission to state a material fact relates to information supplied by the Company on the one hand or by the Underwriters on the other hand and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission.

The Company and the Underwriters agree that it would not be just and equitable if contribution pursuant to this Section 7 were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to above in this Section 7. The aggregate amount of losses, liabilities, claims, damages and expenses incurred by an indemnified party and referred to above in this Section 7 shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue or alleged untrue statement or omission or alleged omission.

Notwithstanding the provisions of this Section 7, no Underwriter shall be required to contribute any amount in excess of the amount by which the total price at which the Securities underwritten by it and distributed to the public were offered to the public exceeds the amount of any damages which such Underwriter has otherwise been required to pay by reason of any such untrue or alleged untrue statement or omission or alleged omission.

No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the 1933 Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

For purposes of this Section 7, each affiliate, officer, director, employee, partner and member of each Underwriter and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as such Underwriter, and each director of the Company, each officer of the Company who signed the Registration Statement, and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as the Company. The Underwriters’ respective obligations to contribute pursuant to this Section 7 are several in proportion to the principal amount of Securities set forth opposite their respective names in Exhibit A hereto and not joint.

SECTION 8. Representations, Warranties and Agreements to Survive Delivery . All representations, warranties and agreements contained in this Agreement or in certificates signed by any officer of the Company or any of its subsidiaries (whether signed on behalf of such officer, the Company or such subsidiary) and delivered to the Representative or counsel to the

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Underwriters, shall remain operative and in full force and effect, regardless of any investigation made by or on behalf of any Underwriter, any officer, director, employee, partner, member or agent of any Underwriter or any person controlling any Underwriter, or by or on behalf of the Company, any officer, director or employee of the Company or any person controlling the Company.

SECTION 9. Termination of Agreement .

(a) Termination; General . This Agreement shall be subject to termination in the absolute discretion of the Representative, by notice given to the Company prior to delivery of and payment for the Securities, if at any time prior to such time (i) trading in the Company’s shares shall have been suspended by the Commission or the NYSE or trading in securities generally on the NYSE shall have been suspended or limited or minimum prices shall have been established on such exchange, (ii) a banking moratorium shall have been declared either by federal or New York State authorities or (iii) there shall have occurred any outbreak or escalation of hostilities, declaration by the United States of a national emergency or war, or other calamity or crisis the effect of which on financial markets is such as to make it, in the sole judgment of the Representative, impractical or inadvisable to proceed with the offering, sale or delivery of the Securities as contemplated by any Pre-Pricing Prospectus or the Prospectus (exclusive of any amendment or supplement thereto).

(b) Liabilities . If this Agreement is terminated pursuant to this Section 9, such termination shall be without liability of any party to any other party except as provided in Section 4 hereof, and except that Sections 1, 6, 7, 8, 11, 12, 13, 14, 15, 16, 18, 19 and 20 hereof shall survive such termination and remain in full force and effect.

SECTION 10. Default by One or More of the Underwriters . (a) If one or more of the Underwriters shall fail at the Closing Date to purchase the amount of Securities which it or they are obligated to purchase under this Agreement (the “ Defaulted Securities ”), the Representative shall have the right, within 24 hours thereafter, to make arrangements for one or more of the non-defaulting Underwriters, or any other underwriters, to purchase all, but not less than all, of the Defaulted Securities in such amounts as may be agreed upon and upon the terms herein set forth; if, however, the Representative shall not have completed such arrangements within such 24-hour period, then:

(i) if the amount of Defaulted Securities does not exceed 10% of the aggregate amount of Securities, each of the non-defaulting Underwriters shall be obligated, severally and not jointly, to purchase the full amount of such Defaulted Securities in the proportions that their respective underwriting obligations hereunder bear to the underwriting obligations of all non-defaulting Underwriters; or

(ii) if the number of Defaulted Securities exceeds 10% of the aggregate amount of Securities, this Agreement shall terminate without liability on the part of any non-defaulting Underwriter.

(b) No action taken pursuant to this Section 10 shall relieve any defaulting Underwriter from liability in respect of its default.

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In the event of any such default which does not result in a termination of this Agreement, the Representative shall have the right to postpone the Closing Date for a period not exceeding seven days in order to effect any required changes in the Registration Statement, the General Disclosure Package or Prospectus or in any other documents or arrangements. As used herein, the term “Underwriter” includes any person substituted for an Underwriter under this Section 10.

SECTION 11. Notices . All notices and other communications hereunder shall be in writing, shall be effective only upon receipt and shall be mailed, delivered by hand or overnight courier, or transmitted by fax (with the receipt of any such fax to be confirmed by telephone). Notices to the Underwriters shall be directed to the Representative at Barclays Capital Inc.

745 Seventh Avenue, New York, New York 10019, Attention: Syndicate Registration; and notices to the Company shall be directed to it at WPX Energy, Inc., 3500 One Williams Center, Tulsa, Oklahoma 74172, Attention: Chief Financial Officer (Fax: (539) 573-0026), Attention: Treasurer (Fax: (539) 573-0026) and Attention: General Counsel (Fax: (539) 573-5608), with a copy mailed, delivered or telefaxed to Weil, Gotshal & Manges LLP, Attention: Todd R. Chandler, Esq. (Fax: (212) 310-8007 and confirmed at (212) 310-8000).

SECTION 12. Parties . This Agreement shall each inure to the benefit of and be binding upon the Underwriters and the Company and their respective successors. Nothing expressed or mentioned in this Agreement is intended or shall be construed to give any person, firm or corporation, other than the Underwriters and the Company and their respective successors and the controlling persons and other indemnified parties referred to in Sections 6 and 7 and their successors, heirs and legal representatives, any legal or equitable right, remedy or claim under or in respect of this Agreement or any provision herein contained. This Agreement and all conditions and provisions hereof are intended to be for the sole and exclusive benefit of the Underwriters and the Company and their respective successors, and said controlling persons and other indemnified parties and their successors, heirs and legal representatives, and for the benefit of no other person or entity. No purchaser of Securities from any Underwriter shall be deemed to be a successor by reason merely of such purchase.

SECTION 13. Governing Law and Time . THIS AGREEMENT AND ANY CLAIM, CONTROVERSY OR DISPUTE ARISING UNDER OR RELATED TO THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK. EXCEPT AS OTHERWISE EXPRESSLY SET FORTH HEREIN, SPECIFIED TIMES OF DAY REFER TO NEW YORK CITY TIME.

SECTION 14. Waiver of Jury Trial . The Company and the Underwriters hereby irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.

SECTION 15. Effect of Headings . The Section and Exhibit headings herein are for convenience only and shall not affect the construction hereof.

SECTION 16. Definitions . As used in this Agreement, the following terms have the respective meanings set forth below:

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“ Applicable Time ” means 5:25 p.m. (New York City time) on July 16, 2015 or such other time as agreed by the Company and the Representative.

“ Commission ” means the Securities and Exchange Commission.

“ DTC ” means The Depository Trust Company.

“ GAAP ” means generally accepted accounting principles.

“ Issuer Free Writing Prospectus ” means any “issuer free writing prospectus,” as defined in Rule 433, relating to the Securities that (i) is required to be filed with the Commission by the Company, (ii) is a “road show” that is a “written communication” within the meaning of Rule 433(d)(8)(i), whether or not required to be filed with the Commission, or (iii) is exempt from filing pursuant to Rule 433(d)(5)(i) because it contains a description of the Securities or of the offering that does not reflect the final terms, and all free writing prospectuses that are listed in Exhibit D hereto, in each case in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g).

“ Issuer General Use Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being specified in Exhibit D hereto.

“ Issuer Limited Use Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is not an Issuer General Use Free Writing Prospectus.

“ NYSE ” means the New York Stock Exchange.

“ Organizational Documents ” means (a) in the case of a corporation, its charter and by-laws; (b) in the case of a limited or general partnership, its partnership certificate, certificate of formation or similar organizational document and its partnership agreement; (c) in the case of a limited liability company, its articles of organization, certificate of formation or similar organizational documents and its operating agreement, limited liability company agreement, membership agreement or other similar agreement; (d) in the case of a trust, its certificate of trust, certificate of formation or similar organizational document and its trust agreement or other similar agreement; and (e) in the case of any other entity, the organizational and governing documents of such entity.

“ PCAOB ” means the Public Company Accounting Oversight Board (United States).

“ preliminary prospectus ” means any prospectus together with, if applicable, the accompanying preliminary prospectus supplement used in connection with the offering of the

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Securities that omitted the public offering price of the Securities or that was captioned “Subject to Completion,” together with the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act. The term “preliminary prospectus” includes, without limitation, the Pre-Pricing Prospectus.

“ Registration Statement ” means the Company’s registration statement on Form S–3 (Registration No. 333-198523) as amended (if applicable), including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S–3 under the 1933 Act and the Rule 430B Information; provided that any Rule 430B Information shall be deemed part of the Registration Statement only from and after the time specified pursuant to Rule 430B.

“ Rule 163 ,” “ Rule 164 ,” “ Rule 172 ,” “ Rule 173 ,” “ Rule 401 ,” “ Rule 405 ,” “ Rule 424(b) ” “ Rule 430B ” and “ Rule 433 ” refer to such rules under the 1933 Act.

“ Rule 430B Information ” means the information included in any preliminary prospectus or the Prospectus or any amendment or supplement to any of the foregoing that was omitted from the Registration Statement at the time it first became effective but is deemed to be part of and included in the Registration Statement pursuant to Rule 430B.

“ Sarbanes-Oxley Act ” means the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated thereunder or implementing the provisions thereof.

“ 1933 Act ” means the Securities Act of 1933, as amended.

“ 1933 Act Regulations ” means the rules and regulations of the Commission under the 1933 Act.

“ 1934 Act ” means the Securities Exchange Act of 1934, as amended.

“ 1934 Act Regulations ” means the rules and regulations of the Commission under the 1934 Act.

“ 1940 Act ” means the Investment Company Act of 1940, as amended.

All references in this Agreement to the Registration Statement, any preliminary prospectus, the Prospectus, any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing shall be deemed to include the version thereof filed with the Commission pursuant to EDGAR and all versions thereof delivered (physically or electronically) to the Representative or the Underwriters.

All references in this Agreement to financial statements and schedules and other information which is “contained,” “included” or “stated” in the Registration Statement, any preliminary prospectus or the Prospectus (and all other references of like import) shall be deemed to mean and include all such financial statements and schedules and other information which is incorporated by reference in or otherwise deemed by 1933 Act Regulations to be a part of or included in the Registration Statement, any preliminary prospectus or the Prospectus, as the case may be; and all references in this Agreement to amendments or supplements to the

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Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to mean and include the filing of any document under the 1934 Act which is incorporated by reference in or otherwise deemed by 1933 Act Regulations to be a part of or included in the Registration Statement, such preliminary prospectus or the Prospectus, as the case may be.

SECTION 17. Permitted Free Writing Prospectuses . The Company represents, warrants and agrees that it has not made and, unless it obtains the prior written consent of the Representative, it will not make, and each Underwriter, severally and not jointly, represents, warrants and agrees that it has not made and, unless it obtains the prior written consent of the Company and the Representative, it will not make, any offer relating to the Securities that constitutes or would constitute an “issuer free writing prospectus” (as defined in Rule 433) or that otherwise constitutes or would constitute a “free writing prospectus” (as defined in Rule 405) or portion thereof required, in the case of any Underwriters, to be filed with the Commission or, in the case of the Company, whether or not required to be filed with the Commission; provided that the prior written consent of the Company and the Representative shall be deemed to have been given in respect of the Issuer General Use Free Writing Prospectuses, if any, listed on Exhibit D hereto and to any electronic road show in the form previously provided by the Company to and approved by the Representative. Any such free writing prospectus consented to or deemed to have been consented to as aforesaid is hereinafter referred to as a “Permitted Free Writing Prospectus.” The Company represents, warrants and agrees that it has treated and will treat each Permitted Free Writing Prospectus as an “issuer free writing prospectus,” as defined in Rule 433, and has complied and will comply with the requirements of Rule 433 applicable to any Permitted Free Writing Prospectus, including timely filing with the Commission where required, legending and record keeping.

SECTION 18. Absence of Fiduciary Relationship . The Company acknowledges and agrees that:

(a) each of the Underwriters is acting solely as an underwriter in connection with the sale of the Securities and no fiduciary, advisory or agency relationship between the Company, on the one hand, and any of the Underwriters, on the other hand, has been created in respect of any of the transactions contemplated by this Agreement, irrespective of whether or not any of the Underwriters has advised or is advising the Company on other matters;

(b) the public offering price of the Securities and the price to be paid by the Underwriters for the Securities set forth in this Agreement were established by the Company following discussions and arms-length negotiations with the Representative;

(c) it is capable of evaluating and understanding, and understands and accepts, the terms, risks and conditions of the transactions contemplated by this Agreement;

(d) it is aware that the Underwriters and their respective affiliates are engaged in a broad range of transactions which may involve interests that differ from those of the Company and that none of the Underwriters has any obligation to disclose such interests and transactions to the Company by virtue of any fiduciary, advisory or agency relationship or otherwise; and

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(e) it waives, to the fullest extent permitted by law, any claims it may have against any of the Underwriters for breach of fiduciary duty or alleged breach of fiduciary duty and agrees that none of the Underwriters shall have any liability (whether direct or indirect, in contract, tort or otherwise) to it in respect of such a fiduciary duty claim or to any person asserting a fiduciary duty claim on its behalf or in right of it or the Company or any stockholders, employees or creditors of Company.

SECTION 19. Research Analyst Independence . The Company acknowledges that the Underwriters’ research analysts and research departments are required to be independent from their respective investment banking divisions and are subject to certain regulations and internal policies, and that such Underwriters’ research analysts may hold views and make statements or investment recommendations and/or publish research reports with respect to the Company and/or the offering that differ from the views of their respective investment banking divisions. The Company hereby waives and releases, to the fullest extent permitted by applicable law, any claims that the Company may have against the Underwriters with respect to any conflict of interest related to the issuance and sale by the Company of the Securities that may arise from the fact that the views expressed by their independent research analysts and research departments may be different from or inconsistent with the views or advice communicated to the Company by such Underwriters’ investment banking divisions. The Company acknowledges that each of the Underwriters is a full service securities firm and as such from time to time, subject to applicable securities laws, may effect transactions for its own account or the account of its customers and hold long or short positions in debt or equity securities of the companies that may be the subject of the transactions contemplated by this Agreement.

SECTION 20. Consent to Jurisdiction . The parties hereby irrevocably submit to the non-exclusive jurisdiction of any New York State or federal court sitting in the Borough of Manhattan in The City of New York in any action or proceeding arising out of or relating to the terms of this Agreement and the transactions contemplated herein, and the parties hereby irrevocably agree that all claims in respect of such action or proceeding may be heard and determined in such New York State or federal court. The parties hereby irrevocably waive, to the fullest extent that they may legally do so, the defense of an inconvenient forum to the maintenance of such action or proceeding. The parties agree that a final judgment in any such action or proceeding shall be conclusive and may be enforced in other jurisdictions by suit on the judgment or in any other manner provided by law. To the extent that either party has or hereafter may acquire any immunity from jurisdiction of any court or from any legal process (whether through service or notice, attachment prior to judgment, attachment in aid of execution or otherwise) with respect to its obligations hereunder, each waives such immunity to the extent permitted by applicable law.

SECTION 21. Patriot Act . In accordance with the requirements of the USA Patriot Act (Title III of Pub. L. 107-56 (signed into law October 26, 2001)), the Underwriters are required to obtain, verify and record information that identifies their respective clients, including the Company, which information may include the name and address of their respective clients, as well as other information that will allow the underwriters to properly identify their respective clients.

[Signature Page Follows]

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If the foregoing is in accordance with your understanding of our agreement, please sign and return to the Company a counterpart hereof, whereupon this instrument, along with all counterparts, will become a binding agreement between the Underwriters and the Company in accordance with its terms.

EXHIBITS

ii

WPX ENERGY, INC.

7,000,000 Shares of 6.25% Series A Mandatory Convertible Preferred Stock

(initial liquidation preference of $50 per share)

UNDERWRITING AGREEMENT

July 16, 2015

Barclays Capital Inc.

As Representative of the several Underwriters

c/o Barclays Capital Inc.

745 Seventh Avenue

New York, New York 10019

Ladies and Gentlemen:

WPX Energy, Inc., a Delaware corporation (the “Company”), confirms its agreement with Barclays Capital Inc. (“Barclays”) and each of the other Underwriters named in Exhibit A hereto (collectively, the “Underwriters,” which term shall also include any underwriter substituted as hereinafter provided in Section 10 hereof), for whom Barclays is acting as representative (in such capacity, the “Representative”), with respect to the issue and sale by the Company and the purchase by the Underwriters, acting severally and not jointly, as set forth in said Exhibit A hereto, of (i) an aggregate of 7,000,000 shares of the Company’s 6.25% Series A Mandatory Convertible Preferred Stock, with an initial liquidation preference of $50 per share (“Mandatory Convertible Preferred Stock”), and (ii) at the option of the Underwriters, up to an additional 1,050,000 shares of Mandatory Convertible Preferred Stock. The aforesaid 7,000,000 shares of Mandatory Convertible Preferred Stock (the “Initial Securities”) to be purchased by the Underwriters and all or any part of the 1,050,000 shares of Mandatory Convertible Preferred Stock subject to the option described in Section 2(b) hereof (the “Option Securities”) are hereinafter called, collectively, the “Securities.” The Mandatory Convertible Preferred Stock will be convertible into a variable number of shares of the common stock (the “Conversion Shares”), par value $0.01 per share, of the Company (“Common Stock”).

The Company understands that the Underwriters propose to make a public offering of the Securities as soon as the Representative deems advisable after this Agreement has been executed and delivered.

The Securities are being issued in connection with the proposed merger of Thunder Merger Sub, LLC, a Delaware limited liability company (“Merger Sub”) and subsidiary of the Company into RKI Exploration & Production, LLC, a Delaware limited liability company (“Thunder”, and together with its subsidiaries, the “Thunder Entities”)), pursuant to that certain Agreement and Plan of Merger, dated July 13, 2015, among the Company, Merger Sub and Thunder (together with all exhibits, schedules and other disclosure letters thereto, collectively, as may be amended, the “Acquisition Agreement”). Prior to the consummation of the merger, Thunder will dispose of its Powder River Basin assets and certain non-core assets in accordance

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with the Acquisition Agreement. These transactions (including the proposed merger) are herein collectively referred to as the “Acquisition.” The date of the consummation of the Acquisition is referred to herein as the “Acquisition Closing Date.”

In connection with the Acquisition, the Company is seeking an amendment to its Amended and Restated Credit Agreement, dated as of October 28, 2014, by and among the Company, the lenders party thereto, and Citibank, N.A., as Administrative Agent and Swingline Lender (the “Existing Facility”).

The terms of the Mandatory Convertible Preferred Stock will be set forth in a certificate of designation (the “Certificate of Designation”) to be filed by the Company with the Secretary of State of the State of Delaware as an amendment to the Company’s Amended and Restated Certificate of Incorporation.

The Company has prepared and previously delivered to you a preliminary prospectus supplement dated July 14, 2015 relating to the Securities and pursuant to the Registration Statement, an automatic shelf registration statement as defined in Rule 405, as amended by a post-effective amendment filed on July 14, 2015, which includes the base prospectus dated September 3, 2014 (the “Base Prospectus”). Such preliminary prospectus supplement and Base Prospectus, including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, are hereinafter called, collectively, the “Pre-Pricing Prospectus.” Promptly after the execution and delivery of this Agreement, the Company will prepare a prospectus supplement dated July 16, 2015 (the “Prospectus Supplement”) and will file the Prospectus Supplement and the Base Prospectus with the Commission, all in accordance with the provisions of Rule 430B and Rule 424(b), and the Company has previously advised you of all information (financial and other) that will be set forth therein. The Prospectus Supplement and the Base Prospectus, in the form first furnished to the Underwriters for use in connection with the offering of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), are herein called, collectively, the “Prospectus.” Any reference in this Agreement to the Registration Statement, any Pre-Pricing Prospectus or the Prospectus shall be deemed to refer to and include the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, as of the effective date of the Registration Statement or the date of such Pre-Pricing Prospectus or the Prospectus, as the case may be and any reference to “amend”, “amendment” or “supplement” with respect to the Registration Statement, any Pre-Pricing Prospectus or the Prospectus shall be deemed to refer to and include any documents filed after such date under the 1934 Act that are deemed to be incorporated by reference therein.

SECTION 1. Representations and Warranties .

(a) Representations and Warranties by the Company . The Company represents and warrants to each Underwriter as of the date hereof, as of the Applicable Time, and as of the Closing Date referred to in Section 2(b) hereof, and agrees with each Underwriter, as follows:

(1) Status as a Well-Known Seasoned Issuer . (A) At the respective times the Registration Statement or any amendments thereto were filed with the Commission, (B) at the time of the most recent amendment to the Registration Statement for the

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purposes of complying with Section 10(a)(3) of the 1933 Act (whether such amendment was by post-effective amendment, incorporated report filed pursuant to Section 13 or 15(d) of the 1934 Act or form of prospectus), (C) at any time the Company or any person acting on its behalf (within the meaning, for this clause only, of Rule 163(c)) made any offer relating to the Securities in reliance on the exemption of Rule 163 and (D) at the date hereof, the Company was and is a “well-known seasoned issuer” as defined in Rule 405. The Registration Statement is an “automatic shelf registration statement,” as defined in Rule 405 and the Securities, since their registration on the Registration Statement, have been and remain eligible for registration by the Company on such an “automatic shelf registration statement.” The Company has not received from the Commission any notice pursuant to Rule 401(g)(2) objecting to the use of an automatic shelf registration statement. Any written communication that was an offer relating to the Securities made by the Company or any person acting on its behalf (within the meaning, for this sentence only, of Rule 163(c)) prior to the filing of the Registration Statement has been filed with the Commission in accordance with Rule 163 and otherwise complied with the requirements of Rule 163, including without limitation the legending requirement, to qualify such offer for the exemption from Section 5(c) of the 1933 Act provided by Rule 163.

(2) Compliance with Registration Requirements . The Company meets the requirements for use of Form S-3 under the 1933 Act and the Securities have been duly registered under the 1933 Act pursuant to the Registration Statement. The Registration Statement and any post-effective amendments thereto have become effective under the 1933 Act and no stop order suspending the effectiveness of the Registration Statement has been issued under the 1933 Act and no proceedings for that purpose or pursuant to Section 8A of the 1933 Act against the Company or related to the issuance and sale by the Company of the Securities have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission, and any request on the part of the Commission for additional information has been complied with. The Registration Statement was filed with the Commission on July 14, 2015.

(3) Registration Statement, Prospectus and Disclosure at Time of Sale . At the respective times that the Registration Statement and any amendments thereto became effective, at each time subsequent to the filing of the Registration Statement that the Company filed an Annual Report on Form 10-K (or any amendment thereto) with the Commission, at each deemed effective date with respect to the Underwriters pursuant to Rule 430B(f)(2), and at the Closing Date (and, if any Option Securities are purchased, at the Date of Delivery (as defined in Section 2(b))), the Registration Statement and any amendments to any of the foregoing complied and will comply in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations and did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

As of its date, at the respective times the Prospectus or any amendment or supplement thereto was filed pursuant to Rule 424(b), at the Closing Date (and, if any Option Securities are purchased, at the Date of Delivery), and at any time when a prospectus is required (or, but for the provisions of Rule 172, would be required) by

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applicable law to be delivered in connection with sales of Securities (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise), neither the Prospectus nor any amendments or supplements thereto included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

As of the Applicable Time and as of each time prior to the Closing Date that an investor agrees (orally or in writing) to purchase any Securities from the Underwriters, neither (x) the Pricing Term Sheet (as defined in Section 3(m) below), any other Issuer General Use Free Writing Prospectuses, if any, issued at or prior to the Applicable Time and the Pre-Pricing Prospectus as of the Applicable Time, all considered together (collectively, the “General Disclosure Package”), nor (y) any individual Issuer Limited Use Free Writing Prospectus, when considered together with the General Disclosure Package, included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

Each preliminary prospectus and the Prospectus and any amendments or supplements to any of the foregoing filed as part of the Registration Statement or any amendment thereto, filed pursuant to Rule 424 under the 1933 Act, or delivered to the Underwriters for use in connection with the offering of the Securities, complied when so filed or when so delivered, as the case may be, in all material respects with the 1933 Act and the 1933 Act Regulations.

The representations and warranties in the preceding paragraphs of this Section 1(a)(3) do not apply to statements in or omissions from the Registration Statement, any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative expressly for use therein, it being understood and agreed that the only such information furnished by the Underwriters as aforesaid consists of the information described as such in Section 6(b) hereof.

At the respective times that the Registration Statement or any amendment thereto was filed, as of the earliest time after the filing of the Registration Statement that the Company or any other offering participant made a bona fide offer of the Securities within the meaning of Rule 164(h)(2), and at the date hereof, the Company was not and is not an “ineligible issuer” as defined in Rule 405, in each case without taking into account any determination made by the Commission pursuant to paragraph (2) of the definition of such term in Rule 405; and without limitation to the foregoing, the Company has at all relevant times met, meets and will at all relevant times meet the requirements of Rule 164 for the use of a free writing prospectus (as defined in Rule 405) in connection with the offering contemplated hereby.

The copies of the Registration Statement and any amendments thereto and the copies of each preliminary prospectus, each Issuer Free Writing Prospectus that is

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required to be filed with the Commission pursuant to Rule 433 and the Prospectus and any amendments or supplements to any of the foregoing, that have been or subsequently are delivered to the Underwriters in connection with the offering of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise) were and will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T of the Commission. For purposes of this Agreement, references to the “delivery” or “furnishing” of any of the foregoing documents to the Underwriters, and any similar terms, include, without limitation, electronic delivery.

Each Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the completion of the public offering and sale of the Securities did not, does not and will not include any information that conflicted, conflicts or will conflict with the information contained in the Registration Statement, any preliminary prospectus or the Prospectus that has not been superseded or modified.

(4) Incorporated Documents . The documents incorporated or deemed to be incorporated by reference in the Registration Statement, any preliminary prospectus and the Prospectus, at the respective times they were or hereafter are filed with the Commission, complied and will comply in all material respects with the requirements of the 1934 Act and the 1934 Act Regulations and did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

(5) Independent Accountants . Ernst & Young LLP, who have reported upon the audited financial statements and any supporting schedules included in the Registration Statement, the General Disclosure Package and the Prospectus are independent public accountants with respect to the Company as required by the 1933 Act, the 1933 Act Regulations, the 1934 Act, the 1934 Act Regulations and the PCAOB.

(6) Financial Statements . The historical financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus comply as to form in all material respects with the applicable requirements of Regulation S-X under the 1933 Act and present fairly in all material respects the financial condition, results of operations and cash flows of the consolidated businesses purported to be shown thereby at the dates and for the periods indicated, all in conformity with GAAP applied on a consistent basis throughout the periods involved (except as otherwise noted therein).

To the knowledge of the Company, the historical financial statements of the Thunder Entities included in the Registration Statement, the General Disclosure Package and the Prospectus present fairly in all material respects the financial condition, results of operations and cash flows of the consolidated businesses purported to be shown thereby at the dates and for the periods indicated, and except as described in the Registration Statement, the General Disclosure Package and the Prospectus, in conformity with GAAP applied on a consistent basis throughout the periods involved (except as otherwise noted therein).

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The unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus include assumptions that provide a reasonable basis for presenting the significant effects directly attributable to the transactions and events described therein, the related pro forma adjustments give appropriate effect to those assumptions, and the pro forma adjustments reflect the proper application of those adjustments to the historical financial statement amounts in the unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus. The aforementioned unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus comply as to form in all material respects with the applicable requirements of Regulation S-X under the 1933 Act.

The Company’s ratios of earnings to fixed charges and preferred stock dividends included in the Registration Statement, the General Disclosure Package and the Prospectus comply with Item 503(d) of Regulation S-K of the Commission. All “non-GAAP financial measures” (as such term is defined in the rules and regulations of the Commission), if any, contained in the Registration Statement, the General Disclosure Package and the Prospectus comply with Item 10 of Regulation S-K of the Commission, to the extent applicable.

(7) No Material Adverse Change in Business . Since the date of the latest audited financial statements included in the General Disclosure Package, none of the Company, its Significant Subsidiaries (as defined below) or, to the knowledge of the Company, the Thunder Entities have sustained any loss or interference with its business from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree, or incurred any material liability or obligation, direct or contingent, other than liabilities and obligations that were incurred in the ordinary course of business, which would be reasonably likely to result in any Material Adverse Effect (as defined below), nor has there been any development involving a material adverse change in or affecting the financial condition, results of operations, business or prospects of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, otherwise than as disclosed in the General Disclosure Package and the Prospectus. Since the respective dates as of which information is given in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) or since the date of the General Disclosure Package, after giving effect to the Acquisition, there has not been (i) any material change in the capital stock or long-term debt of the Company or its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities, (ii) any material adverse change in or affecting the financial condition, results of operations, business or prospects of the Company or its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities, or (iii) any transaction entered into by any of the Company or its Significant Subsidiaries, other than in the ordinary course of business, that is material to the Company and its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities other than as disclosed, in the case of each of (i), (ii) or (iii) above, in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto).

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(8) Good Standing of the Company and Significant Subsidiaries . Each of the Company, its “significant subsidiaries,” as defined in Rule 1-02(w) of Regulation S-X under the 1934 Act (each, a “ Significant Subsidiary ”) and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, has been duly organized, is validly existing and in good standing as a corporation or other business entity under the laws of its jurisdiction of organization and is duly qualified to do business and in good standing as a foreign corporation or other business entity in each jurisdiction in which its ownership or lease of property or the conduct of its businesses requires such qualification, except where the failure to be so qualified or in good standing would not have a material adverse effect on the financial condition, results of operations, business or prospects of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition (a “ Material Adverse Effect ”). Each of the Company, its Significant Subsidiaries and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition has all power and authority necessary to own or hold its properties and to conduct its business as described in the General Disclosure Package and the Prospectus. The subsidiaries listed on Exhibit B hereto are (a) the only Significant Subsidiaries of the Company as of the date hereof and (b) the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition.

(9) Capitalization . The Company has the capitalization as set forth in each of the General Disclosure Package and the Prospectus; all the issued shares of capital stock of the Company have been duly authorized and validly issued, are fully paid and non-assessable; all of the issued shares of capital stock or other equity interests, as applicable, of each Significant Subsidiary of the Company that are owned directly or indirectly by the Company have been duly authorized and validly issued and are fully paid (to the extent required under such entities’ Organizational Documents) and non-assessable (except as such non-assessability may be affected by Sections 18-607 and 18-804 of the Delaware Limited Liability Company Act or Sections 17-303, 17-607 and 17-804 of the Delaware Revised Uniform Limited Partnership Act) and are owned directly or indirectly by the Company free and clear of all liens, encumbrances, security interests, equities charges or claims (collectively, “ Liens ”) except (i) as disclosed in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) or (ii) to the extent any such Liens would not have a Material Adverse Effect.

(10) Due Authorization; Authorization of Agreement; Certificate of Designation . The Company has all requisite corporate power and authority to execute, deliver and perform its obligations under this Agreement. This Agreement has been duly authorized, executed and delivered by the Company and, assuming due authorization, execution and delivery by the Representative, constitutes the valid and binding agreement of the Company, enforceable against the Company in accordance with its terms, subject to (i) the effects of bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other similar laws relating to or affecting creditors’ rights generally, (ii) general equitable principles (whether considered in a proceeding in equity or at law), and (iii) except as rights to indemnity and contribution hereunder may be limited by federal or state securities laws or principles of public policy.

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The Certificate of Designation has been duly authorized by the Company. The Certificate of Designation sets forth the rights, preferences and priorities of the Mandatory Convertible Preferred Stock, and the holders of the Mandatory Convertible Preferred Stock will have the rights set forth in the Certificate of Designation upon filing with the Secretary of State for the State of Delaware. The Certificate of Designation conforms in all material respects to the description thereof in the General Disclosure Package and the Prospectus.

(11) [Reserved].

(12) The Securities and the Conversion Shares . The Securities to be purchased by the Underwriters from the Company have been duly authorized for issuance and sale to the Underwriters pursuant to this Agreement and, when issued and delivered by the Company pursuant to this Agreement against payment of the consideration set forth herein, will be validly issued and fully paid and non-assessable; and the issuance of the Securities is not subject to the preemptive or other similar rights of any securityholder of the Company.

Upon issuance of the Securities in accordance with this Agreement and the Prospectus and the filing and effectiveness of the Certificate of Designation, the Mandatory Convertible Preferred Stock will be convertible into the Conversion Shares in accordance with the terms of the Mandatory Convertible Preferred Stock and the Certificate of Designation; a number of Conversion Shares (the “Maximum Number of Conversion Shares”) equal to the sum of the maximum number of shares of Common Stock deliverable by the Company upon conversion of the Mandatory Convertible Preferred Stock (including the maximum number of shares of Common Stock deliverable by the Company upon conversion in connection with a fundamental change (as defined in the General Disclosure Package) (including the maximum number of shares of Common Stock deliverable by the Company in respect of any fundamental change dividend make-whole amount and any accumulated dividend amount (in each case, as defined in the General Disclosure Package))), the maximum number of shares of Common Stock deliverable by the Company in respect of any early conversion additional conversion amount and any additional conversion amount (each as defined in the General Disclosure Package) (assuming the Company elects to issue and deliver the maximum number of shares of Common Stock in connection with any such early conversion additional conversion amount and any such additional conversion amount) and the maximum number of shares of Common Stock deliverable by the Company in respect of any acquisition termination event (as defined in the General Disclosure Package) (including the maximum number of shares of Common Stock deliverable by the Company in respect of any acquisition termination make-whole amount (as defined in the General Disclosure Package), in each case, in accordance with the terms of the Certificate of Designation, has been duly authorized and reserved for issuance by all necessary corporate action and such Conversion Shares, when issued upon such conversion or delivery (as the case may be) in accordance with the terms of the Mandatory Convertible Preferred Stock and the Certificate of Designation will be validly issued, fully paid and non-assessable, will conform in all material respects to the descriptions thereof in the Registration Statement,

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the General Disclosure Package and the Prospectus and will not be subject to the preemptive or other similar rights of any securityholder of the Company.

(13) Description of the Securities . The Securities conform and will conform in all material respects to the statements relating thereto contained in the Registration Statement, the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) and are and will be in substantially the respective forms filed or incorporated by reference, as the case may be, as exhibits to the Registration Statement.

(14) Absence of Defaults and Conflicts . None of the Company, its Significant Subsidiaries or, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is (i) in violation of its Organizational Documents, (ii) in default, and no event has occurred which, with notice or lapse of time or both, would constitute such a default, in the due performance or observance of any term, obligation, agreement, covenant or condition contained in any material contract, indenture, mortgage, deed of trust, loan agreement, lease or other agreement or instrument to which it is a party or by which it is bound or which any of its properties or assets may be subject or (iii) in violation of any law, ordinance, governmental rule, regulation or court decree to which it or its property or assets may be subject, except, with respect to (ii) or (iii), for any such violations or defaults that would not be reasonably likely, singly or in the aggregate, to have a Material Adverse Effect. The execution and delivery of this Agreement and the Certificate of Designation by the Company, the consummation of the transactions contemplated hereby, the application of the proceeds from the sale of the Securities as described under “Use of Proceeds” in the General Disclosure Package and the Prospectus will not (i) conflict with or result in a breach or violation of any of the terms or provisions of, impose any Lien, charge or encumbrance upon any property or assets of the Company, its Significant Subsidiaries and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition under, or constitute a default under, any indenture, mortgage, deed of trust, loan agreement, license, lease or other agreement or instrument to which the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is a party or by which the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is bound or to which any of the property or assets of the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is subject; (ii) result in any violation of the provisions of the Organizational Documents of the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition; or (iii) result in any violation of any statute or any judgment, order, decree, rule or regulation of any court or governmental agency or body having jurisdiction over the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of

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the Company upon giving effect to the Acquisition, or any of their respective properties or assets, except with respect to clauses (i) and (iii), conflicts, breaches, violations or defaults that would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.

(15) Absence of Labor Dispute . No labor disturbance by or dispute with the employees of the Company or any of its affiliates that are dedicated to the Company’s business or, to the knowledge of the Company, any of the Thunder Entities, exists or, to the knowledge of the Company, is imminent that would reasonably be expected to have a Material Adverse Effect.

(16) Absence of Proceedings . Except as described in the General Disclosure Package and the Prospectus, there are no legal or governmental proceedings pending to which the Company or any of its subsidiaries or, to the knowledge of the Company, any of the Thunder Entities, is a party or of which any property or assets of the Company or any of its subsidiaries or, to the knowledge of the Company, any of the Thunder Entities, is the subject that would, in the aggregate, reasonably be expected to have a Material Adverse Effect or would, in the aggregate, reasonably be expected to have a material adverse effect on the performance by the Company of its obligations under this Agreement or the consummation of the transactions contemplated hereby; and to the Company’s knowledge, no such proceedings are threatened or contemplated by governmental authorities or others.

(17) Accuracy of Descriptions and Exhibits . The information in the Pre-Pricing Prospectus and the Prospectus under the captions “Description of Mandatory Convertible Preferred Stock,” “Description of Capital Stock” and “Material U.S. Federal Income Tax Considerations” and the information in the Company’s Annual Report on Form 10-K for the fiscal year ended 2014 under the captions “Business—Regulatory Matters,” “Business—Environmental Matters” and “Legal Proceedings,” insofar as they purport to constitute summaries of the terms of statutes, rules or regulations, legal or governmental proceedings or contracts and other documents, constitute accurate summaries of the terms of such statutes, rules and regulations, legal and governmental proceedings and contracts and other documents in all material respects; and there are no franchises, contracts, indentures, mortgages, deeds of trust, loan or credit agreements, bonds, notes, debentures, evidences of indebtedness, leases or other instruments, agreements or documents required to be described or referred to in the Registration Statement, the Pre-Pricing Prospectus or the Prospectus or the documents incorporated or deemed to be incorporated by reference therein or to be filed as exhibits thereto which have not been so described and filed as required.

(18) Absence of Further Requirements . No filing with, or authorization, approval, consent, license, order, registration, qualification or decree of, any court or governmental authority or agency, domestic or foreign is necessary or required for the execution, delivery or performance by the Company of its obligations under this Agreement, for the offering, issuance, sale or delivery of the Securities hereunder, for the issuance of a number of Conversion Shares equal to the Maximum Number of Conversion Shares issuable by the Company in accordance with the terms of the

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Certificate of Designation or for the consummation of any of the other transactions contemplated by this Agreement, in each case on the terms contemplated by the Registration Statement, the General Disclosure Package and the Prospectus, except such as have been obtained under the 1933 Act or the 1933 Act Regulations, except for the filing of the Prospectus and the Pricing Term Sheet pursuant to Rules 424(b) and 433, respectively, except as have been obtained prior to the execution hereof and except that no representation is made as to such as may be required under state or foreign securities laws.

(19) Possession of Licenses and Permits . The Company and each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, have such permits, licenses, franchises, certificates of need and other approvals or authorizations of governmental or regulatory authorities (“ Permits ”) as are necessary under applicable law to own, hold or lease, as the case may be, and to operate their properties and conduct their businesses in the manner described in the Registration Statement, the General Disclosure Package or the Prospectus, except where the failure to possess such Permits would not reasonably be expected to have a Material Adverse Effect. None of the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, has received notice of any revocation or modification of any such Permits except to the extent that any such revocation or modification would not have a Material Adverse Effect.

(20) Title to Property . Except as described in the Registration Statement, the General Disclosure Package or the Prospectus, the Company has, directly or indirectly through its subsidiaries, and, to the knowledge of the Company, Thunder, directly or indirectly through its subsidiaries, has, good and marketable title to all real property and good title to all personal property described in the Registration Statement, the General Disclosure Package or the Prospectus as being owned by it and valid, legal and defensible title to the interests in oil and gas properties underlying the estimates of the Company’s proved reserves described in the Registration Statement, the General Disclosure Package or the Prospectus, in each case free and clear of all liens, encumbrances and defects except (i) as are described in the Registration Statement, the General Disclosure Package or the Prospectus, (ii) as do not materially interfere with the use made in the aggregate of such properties, as described in the Registration Statement, the General Disclosure Package or the Prospectus, (iii) as are permitted under the Existing Facility, or (iv) as would not reasonably be expected to have a Material Adverse Effect; and the working interests derived from oil, gas and mineral leases or mineral interests which constitute a portion of the real property held or leased by the Company, its subsidiaries and the Thunder Entities reflect in all material respects the right of the Company and its subsidiaries and, to the knowledge of the Company, each of the Thunder Entities, to explore, develop or produce hydrocarbons from such real property, and the care taken by the Company and its subsidiaries and, to the knowledge of the Company, each of the Thunder Entities, with respect to acquiring or otherwise procuring such leases or mineral interests was generally consistent with standard industry practices in the areas in which

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the Company and its subsidiaries operate for acquiring or procuring leases and interests therein to explore, develop or produce hydrocarbons.

(21) Investment Company Act . The Company is not, and after giving effect to the offer and sale of the Securities and the application of the proceeds therefrom as described in the General Disclosure Package and the Prospectus, will not be, an “investment company” as defined in the 1940 Act.

(22) Reserve Engineers . Netherland, Sewell & Associates Inc., who issued a report with respect to certain of the Company’s oil and natural gas reserves and who has delivered or will deliver the letters referred to in Sections 5(j) and 5(k) hereof, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Company.

To the knowledge of the Company, LaRoche Petroleum Consultants, Ltd., who issued a report with respect to certain of the Thunder Entities’ oil and natural gas reserves and who has delivered or will deliver the letters referred to in Sections 5(l) and 5(m) hereof, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Thunder Entities.

(23) Reserve Data . The factual information underlying the estimates of reserves of the Company and, to the knowledge of the Company, Thunder, which was supplied to the independent petroleum engineers referenced in Section 1(a)(22) for the purposes of preparing the audit reports of the estimates of proved reserves included in the Registration Statement, the General Disclosure Package and the Prospectus, including, without limitation, production, costs of operation and development, current prices for production, agreements relating to current and future operations and sales of production, was true and correct in all material respects on the dates such estimates were made and such information was supplied and was prepared in accordance with customary industry practices; other than normal production of the reserves, intervening market commodity price fluctuations, fluctuations in demand for such products, adverse weather conditions, unavailability or increased costs of rigs, equipment, supplies or personnel, the timing of third party operations and other factors, in each case in the ordinary course of business, the Company is not aware of any facts or circumstances that would result in a material adverse change in the aggregate net reserves, or the present value of future net cash flows therefrom, as described in the Registration Statement, the General Disclosure Package and the Prospectus; estimates of such reserves and present values as described in the Registration Statement, the General Disclosure Package and the Prospectus comply in all material respects with the applicable requirements of Regulation S-X and Subpart 1200 of Regulation S-K under the Act.

(24) Environmental Laws . The Company, each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, (i) is in compliance with all laws, regulations, ordinances, rules, orders, judgments, decrees, permits or other legal requirements of any governmental authority, including without limitation any international, foreign, national, state, provincial,

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regional, or local authority, relating to pollution, the protection of human health or safety, the environment, or natural resources, or to the use, handling, storage, manufacturing, transportation, treatment, discharge, disposal or release of hazardous or toxic substances or wastes, pollutants or contaminants (“ Environmental Laws ”) applicable to such entity, which compliance includes, without limitation, obtaining, maintaining and complying with all permits, authorizations and approvals required by Environmental Laws to conduct its respective business, and (ii) has not received notice or otherwise has knowledge of any actual or alleged violation of Environmental Laws, or of any actual or potential liability for or other obligation concerning the presence, disposal or release of hazardous or toxic substances or wastes, pollutants or contaminants, except, with respect to (i) and (ii), as may be disclosed in the Registration Statement, the General Disclosure Package and the Prospectus and except where such noncompliance with Environmental Laws, failure to obtain or maintain required permits, authorizations or approvals or failure to comply with the terms and conditions of such permits, authorizations or approvals would not be reasonably likely to have a Material Adverse Effect.

(25) Absence of Registration Rights . There are no persons with registration rights or other similar rights to have any securities (debt or equity) registered pursuant to the Registration Statement or included in the offering contemplated by this Agreement.

(26) FINRA Matters . All of the information provided to the Representative or to counsel for the Underwriters in connection with any letters, filings or other supplemental information provided to FINRA pursuant to FINRA Rule 5110 or 5121 is true, complete and correct.

(27) Tax Returns . The Company, all of its subsidiaries and, to the knowledge of the Company, all of the Thunder Entities, have filed all federal, state, local and foreign income and franchise tax returns which are required to be filed by them and have paid all taxes due, other than those which, if not filed or paid, would not be reasonably expected to have a Material Adverse Effect, or which are being contested in good faith by appropriate proceedings. Except as would not be reasonably expected to have a Material Adverse Effect, no tax deficiency has been determined adversely to the Company, any of its subsidiaries or, to the knowledge of the Company, the Thunder Entities, and the Company has no knowledge of any tax deficiencies that have been, or would reasonably be expected to be asserted.

(28) Insurance . The Company, each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition carry, or are covered by, insurance in such amounts and covering such risks as is reasonable in accordance with customary practices for companies engaged in similar businesses in similar industries for the conduct of their respective businesses and the value of their respective properties.

(29) Accounting and Disclosure Controls . The Company maintains a system of internal control over financial reporting (as such term is defined in Rule 13a-15(f) of the 1934 Act) that complies with the requirements of the 1934 Act and that has been

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designed by, or under the supervision of, the Company’s principal executive and principal financial officers, or persons performing similar functions, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles in the United States. The Company maintains internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorization, (ii) transactions are recorded as necessary to permit preparation of the Company’s financial statements in conformity with accounting principles generally accepted in the United States and to maintain accountability for its assets, (iii) access to the Company’s assets is permitted only in accordance with management’s general or specific authorization, (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences, and (v) the interactive data in eXtensible Business Reporting Language included or incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus is prepared in accordance with the Commission’s rules and guidelines applicable thereto. As of the date of the most recent balance sheet of the Company reviewed or audited by Ernst & Young LLP and the audit committee of the board of directors of the Company, there were no material weaknesses in the Company’s internal controls, except as may be disclosed in the Registration Statement, the General Disclosure Package and the Prospectus.

The Company maintains disclosure controls and procedures (as such term is defined in Rules 13a-15(e) and 15d-15(e) under the 1934 Act); and such disclosure controls and procedures (i) are designed to ensure that information required to be disclosed by the Company in the reports it files or submits under the 1934 Act is accumulated and communicated to the Company’s management, including the Company’s principal executive officer and principal financial officer, as appropriate, to allow timely decisions regarding required disclosure and (ii) except with respect to the material weaknesses in internal controls disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, such disclosure controls and procedures are effective at a reasonable assurance level to perform the functions for which they were established.

Except as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, since the date of the most recent balance sheet of the Company reviewed or audited by Ernst & Young LLP and the audit committee of the board of directors of the Company, (i) the Company has not been advised of or become aware of (A) any significant deficiencies in the design or operation of internal controls that could adversely affect the ability of the Company or any of its subsidiaries to record, process, summarize and report financial data, or any material weaknesses in internal controls, or (B) any fraud, whether or not material, that involves management or other employees who have a significant role in the internal controls of the Company and each of its subsidiaries; and (ii) there have been no significant changes in internal controls or in other factors that could significantly affect internal controls, including any corrective actions with regard to significant deficiencies and material weaknesses.

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(30) Compliance with the Sarbanes-Oxley Act . The Company is in compliance in all material respects with the applicable provisions of the Sarbanes-Oxley Act and the rules and regulations promulgated in connection therewith.

(31) Pending Proceedings and Examinations; Comment Letters . The Registration Statement is not the subject of a pending proceeding or examination under Section 8(d) or 8(e) of the 1933 Act, and the Company is not the subject of a pending proceeding under Section 8A of the 1933 Act. The Company has provided the Representative with true, complete and correct copies of any written comments received from the Commission by the Company or its legal counsel or accountants, and of any transcripts made by the Company, its legal counsel or accountants of any oral comments received from the Commission, with respect to the Registration Statement, any preliminary prospectus, the Prospectus, any Issuer Free Writing Prospectus or any document incorporated or deemed to be incorporated by reference therein or any amendments or supplements to any of the foregoing and of all written responses thereto (in each case other than comment letters or written responses that are publicly available on EDGAR).

(32) Absence of Manipulation . The Company and its affiliates (as defined in Rule 501(b) of Regulation D under the 1933 Act) have not taken, directly or indirectly, any action designed to or that might reasonably be expected to cause or result, under the 1934 Act or otherwise, in stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(33) Statistical and Market-Related Data . The statistical and market-related data included in the Registration Statement, the General Disclosure Package or the Prospectus is based on or derived from sources that the Company believes to be reliable in all material respects.

(34) No Unlawful Payments . Neither the Company nor any of its subsidiaries nor, to the knowledge of the Company, any of the Thunder Entities, or any director, officer, agent, employee or affiliate of the Company or any of its subsidiaries is aware of or has taken any action, directly or indirectly, that could result in a violation or a sanction for violation by such persons of the Foreign Corrupt Practices Act of 1977 or the U.K. Bribery Act 2010, each as may be amended, or similar law of any other relevant jurisdiction, or the rules or regulations thereunder; and the Company and its subsidiaries and, to the knowledge of the Company, the Thunder Entities, have instituted and maintain policies and procedures to ensure compliance therewith. No part of the proceeds of the offering will be used, directly or indirectly, in violation of the Foreign Corrupt Practices Act of 1977 or the U.K. Bribery Act 2010, each as may be amended, or similar law of any other relevant jurisdiction, or the rules or regulations thereunder.

(35) Money Laundering Laws . The operations of the Company and its subsidiaries and, to the knowledge of the Company, the Thunder Entities, are and have been conducted at all times in compliance with applicable financial recordkeeping and reporting requirements and the money laundering statutes and the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered

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or enforced by any governmental agency (collectively, the “Money Laundering Laws”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries or, to the knowledge of the Company, any of the Thunder Entities, with respect to the Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(36) No Conflicts with Sanctions Laws . None of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities and, to the knowledge of the Company, none of the Company’s or its subsidiaries’ directors, officers, agents, employees or affiliates (i) is, or is controlled or 50% or more owned by or is acting on behalf of, an individual or entity that is currently subject to any sanctions administered or enforced by the United States (including any administered or enforced by the Office of Foreign Assets Control of the U.S. Treasury Department, the U.S. Department of State, or the Bureau of Industry and Security of the U.S. Department of Commerce), the United Nations Security Council, the European Union, the United Kingdom (including sanctions administered or enforced by Her Majesty’s Treasury) or other relevant sanctions authority (collectively, “Sanctions” and such persons, “Sanctioned Persons”), (ii) is located, organized or resident in a country or territory that is, or whose government is, the subject of Sanctions that broadly prohibit dealings with that country or territory (collectively, “Sanctioned Countries” and each, a “Sanctioned Country”) or (iii) will, directly or indirectly, use the proceeds of this offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other individual or entity in any manner that would result in a violation of any Sanctions by, or could result in the imposition of Sanctions against, any individual or entity (including any individual or entity participating in the offering, whether as underwriter, advisor, investor or otherwise). Except as has been disclosed to the Underwriters or is not material to the analysis under any Sanctions, none of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities has engaged in any dealings or transactions with or for the benefit of a Sanctioned Person, or with or in a Sanctioned Country, in the preceding 3 years, and none of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities have any plans to increase its dealings or transactions with or for the benefit of Sanctioned Persons, or with or in Sanctioned Countries.

(37) Offering Materials . Without limitation to the provisions of Section 17 hereof, the Company has not distributed and will not distribute, directly or indirectly (other than through the Underwriters), any “written communication” (as defined Rule 405 under the 1933 Act) or other offering materials in connection with the offering or sale of the Securities, other than the Pre-Pricing Prospectus, the Prospectus, any amendment or supplements to any of the foregoing that are filed with the SEC and any Permitted Free Writing Prospectuses (as defined in Section 17).

(38) Brokers . The Company has not paid or agreed to pay to any person any compensation for soliciting another to purchase the Securities (except as contemplated in this Agreement).

(b) Certificates . Any certificate signed by any officer of the Company or any of its subsidiaries (whether signed on behalf of such officer, the Company or such subsidiary) and

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delivered to the Representative or to counsel for the Underwriters shall be deemed a representation and warranty by the Company to each Underwriter as to the matters covered thereby.

SECTION 2. Sale and Delivery to Underwriters; Closing .

(a) The Initial Securities . On the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Company agrees to sell to each Underwriter, severally and not jointly, and each Underwriter, severally and not jointly, agrees to purchase from the Company, at a price per share of $48.50, the number of Initial Securities set forth in Exhibit A opposite the name of such Underwriter.

(b) The Option Securities . In addition, on the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Company hereby grants an option to the several Underwriters to purchase up to an additional 1,050,000 shares of Mandatory Convertible Preferred Stock, as set forth in Exhibit A, at the price per share of $48.50, less an amount per share equal to any dividends or distributions declared by the Company and payable on the Initial Securities but not payable on the Option Securities.

If any Option Securities are to be purchased, the number of Option Securities to be purchased by each Underwriter shall be the number of Option Securities which bears the same ratio to the aggregate number of Option Securities being purchased as the number of Initial Securities set forth opposite the name of such Underwriter in Exhibit A (or such number increased as set forth in Section 10 hereof) bears to the aggregate number of Initial Securities being purchased from the Company by the several Underwriters, subject, however, to such adjustments to eliminate any fractional Securities as the Representative in its discretion shall make.

The option hereby granted will expire 30 days after the date hereof and may be exercised in whole or in part from time to time upon notice by the Representative to the Company setting forth the number of Option Securities as to which the Underwriters are then exercising the option and the time and date of payment and delivery for such Option Securities. Any such time and date of delivery (a “Date of Delivery”) shall be determined by the Representative, but shall not be later than seven full business days after the exercise of said option, nor in any event prior to the Closing Date.

(c) Payment . Payment of the purchase price for, and delivery of, the Initial Securities shall be made at the offices of Simpson Thacher & Bartlett LLP, 425 Lexington Avenue, New York, New York 10017, or at such other place as shall be agreed upon by the Representative and the Company, at 10:00 A.M. (New York City time) on July 22, 2015 (unless postponed in accordance with the provisions of Section 10), or such other time not later than five business days after such date as shall be agreed upon by the Representative and the Company (such time and date of payment and delivery being herein called “Closing Date”).

In addition, in the event that any or all of the Option Securities are purchased by the Underwriters, payment of the purchase price for, and delivery of certificates for, such Option Securities shall be made at the above-mentioned offices, or at such other place as shall be agreed

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upon by the Representative and the Company on each Date of Delivery as specified in the notice from the Representative to the Company.

Payment shall be made to the Company by wire transfer of immediately available funds to a single bank account designated by the Company against delivery to the Representative for the respective accounts of the Underwriters of the Securities to be purchased by them. It is understood that each Underwriter has authorized the Representative, for its account, to accept delivery of, receipt for, and make payment of the purchase price for, the Securities which it has agreed to purchase. Barclays, individually and not as representative of the Underwriters, may (but shall not be obligated to) make payment of the purchase price for the Securities to be purchased by any Underwriter whose funds have not been received by the Closing Date, but such payment shall not relieve such Underwriter from its obligations hereunder. Delivery of the Securities shall be made through the facilities of The Depository Trust Company (“DTC”) unless the Representative shall otherwise instruct.

(d) Registration . The Initial Securities and the Option Securities, if any, shall be registered in such names as the Representative may request in writing at least one full business day before the Closing Date or the relevant Date of Delivery, as the case may be.

SECTION 3. Covenants of the Company . The Company covenants with each Underwriter as follows:

(a) Compliance with Securities Regulations and Commission Requests . The Company, subject to Section 3(b), will comply with the requirements of Rule 430B and Rule 433 and will notify the Representative immediately, and confirm the notice in writing from the Applicable Time through the Closing Date or the relevant Date of Delivery, as the case may be (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)), (i) when the Registration Statement or any post-effective amendment to the Registration Statement shall become effective, or when any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing shall have been filed, (ii) of the receipt of any comments from the Commission (and shall promptly furnish the Representative with a copy of any comment letters and any transcript of oral comments, and shall furnish the Representative with copies of any written responses thereto a reasonable amount of time prior to the proposed filing thereof with the Commission and will not file any such response to which the Representative or counsel for the Underwriters shall reasonably object), (iii) of any request by the Commission for any amendment to the Registration Statement or any amendment or supplement to any preliminary prospectus or the Prospectus or any Issuer Free Writing Prospectus or for additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any order preventing or suspending the use of any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing or any notice from the Commission objecting to the use of the form of the Registration Statement or any post-effective amendment thereto, or of the suspension of the qualification of the Securities for offering

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or sale in any jurisdiction or of the loss or suspension of any exemption from any such qualification, or of the initiation or threatening of any proceedings for any of such purposes, or of any examination pursuant to Section 8(e) of the 1933 Act concerning the Registration Statement and (v) of the initiation or threatening of any proceeding under Section 8A of the 1933 Act in connection with the offering of the Securities. The Company will make every reasonable effort to prevent the issuance of any stop order and the suspension or loss of any qualification of the Securities for offering or sale and any loss or suspension of any exemption from any such qualification, and if any such stop order is issued, or any such suspension or loss occurs, to obtain the lifting thereof at the earliest possible moment. The Company shall pay the required Commission filing fees relating to the Securities within the time required by Rule 456(b)(1)(i) of the 1933 Act Regulations without regard to the proviso therein and otherwise in accordance with Rules 456(b) and 457(r) of the 1993 Act Regulations, except to the extent such filing fees have been paid prior to the date hereof.

(b) Filing of Amendments . From the Applicable Time through the Closing Date or the relevant Date of Delivery, as the case may be (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)), the Company will give the Representative notice of its intention to file or prepare any amendment to the Registration Statement, any Issuer Free Writing Prospectus or any amendment, supplement or revision to any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus, whether pursuant to the 1933 Act or otherwise, and the Company will furnish the Representative with copies of any such documents within a reasonable amount of time prior to such proposed filing or use, as the case may be, and will not file or use any such document to which the Representative or counsel for the Underwriters shall reasonably object. The Company has given the Representative notice of any filings made pursuant to the 1934 Act or the 1934 Act Regulations within 48 hours prior to the Applicable Time; the Company will give the Representative notice of its intention to make any such filing from the Applicable Time through the Closing Date or the relevant Date of Delivery, as the case may be (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)) and will furnish the Representative with copies of any such documents a reasonable amount of time prior to such proposed filing, as the case may be, and will not file or use any such document to which the Representative or counsel for the Underwriters shall reasonably object.

(c) Delivery of Registration Statements . If requested, the Company has furnished or will deliver to the Representative and counsel for the Underwriters, without charge, copies of the Registration Statement and of each amendment thereto (including exhibits filed therewith or incorporated by reference therein and documents incorporated or deemed to be incorporated by reference therein or otherwise deemed to be a part thereof) and copies of all consents and certificates of experts. The copies of the Registration Statement and each amendment thereto furnished to the Underwriters will be

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identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(d) Delivery of Prospectuses . The Company has delivered to each Underwriter, without charge, as many copies of each preliminary prospectus and any amendments or supplements thereto as such Underwriter reasonably requested, and the Company hereby consents to the use of such copies for purposes permitted by the 1933 Act. The Company will furnish to each Underwriter, without charge, during the period when the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), such number of copies of the Pre-Pricing Prospectus, the Prospectus and any Issuer Free Writing Prospectus and any amendments or supplements to any of the foregoing as such Underwriter may reasonably request. Each preliminary prospectus, the Prospectus, each Issuer Free Writing Prospectus and any amendments or supplements to any of the foregoing furnished to the Underwriters were and will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(e) Continued Compliance with Securities Laws . The Company will comply with the 1933 Act, the 1933 Act Regulations, the 1934 Act and the 1934 Act Regulations so as to permit the completion of the distribution of the Securities as contemplated by this Agreement, the General Disclosure Package and the Prospectus. If at any time when a prospectus is required (or, but for the provisions of Rule 172, would be required) by the applicable law to be delivered in connection with sales of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), any event shall occur or condition shall exist as a result of which it is necessary to amend the Registration Statement or amend or supplement the General Disclosure Package or the Prospectus (or, in each case, any documents incorporated or deemed to be incorporated by reference therein) so that the Registration Statement, the General Disclosure Package or the Prospectus, as the case may be, will not include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made or then prevailing, not misleading or if it is necessary to amend the Registration Statement or amend or supplement the General Disclosure Package or the Prospectus (or, in each case, any documents incorporated or deemed to be incorporated by reference therein) in order to comply with the requirements of the 1933 Act, the 1933 Act Regulations, the 1934 Act or the 1934 Act Regulations, the Company will promptly notify the Representative of such event or condition and of its intention to file such amendment or supplement and will promptly prepare and file with the Commission, subject to Section 3(b) hereof, such amendment or supplement as may be necessary to correct such untrue statement or omission or to comply with such requirements, and, in the case of an amendment or post-effective amendment to the Registration Statement, the Company will use its commercially reasonable efforts to have such amendment declared or become effective as soon as practicable and the Company, if requested, will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request. If at any time an Issuer Free Writing Prospectus conflicts with the information contained in the Registration Statement or if an event shall occur or condition shall exist as a result of which it is necessary to

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amend or supplement such Issuer Free Writing Prospectus so that it will not include an untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made or then prevailing, not misleading, or if it is necessary to amend or supplement such Issuer Free Writing Prospectus in order to comply with the requirements of the 1933 Act or the 1933 Act Regulations, the Company will promptly notify the Representative of such event or condition and of its intention to file such amendment or supplement and will promptly prepare and, if required by the 1933 Act or the 1933 Act Regulations, file with the Commission, subject to Section 3(b) hereof, such amendment or supplement as may be necessary to eliminate or correct such conflict, untrue statement or omission or to comply with such requirements, and the Company will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request.

(f) Blue Sky and Other Qualifications . The Company will furnish such information as may be required and otherwise cooperate with the Underwriters to qualify the Securities for offering and sale, or to obtain an exemption for the Securities to be offered and sold, under the applicable securities laws of such states and other jurisdictions (domestic or foreign) as the Representative may reasonably designate and to maintain such qualifications and exemptions in effect for so long as required for the distribution of the Securities (but in no event for a period of not less than one year from the date of this Agreement); provided, however, that the Company shall not be obligated to file any general consent to service of process or to qualify as a foreign corporation or as a dealer in securities in any jurisdiction in which it is not so qualified or to subject itself to taxation in respect of doing business in any jurisdiction in which it is not otherwise so subject. In each jurisdiction in which the Securities have been so qualified or exempt, the Company will file such statements and reports as may be required by the laws of such jurisdiction to continue such qualification or exemption, as the case may be, in effect for so long as required for the distribution of the Securities (but in no event for a period of not less than one year from the date of this Agreement).

(g) Rule 158 . The Company will make generally available to its securityholders and the Underwriters as soon as practicable an earnings statement that satisfies the last paragraph of Section 11(a) of the 1933 Act and Rule 158 promulgated thereunder.

(h) Use of Proceeds . The Company will use the net proceeds received by it from the sale of the Securities in the manner specified in the Pre-Pricing Prospectus and the Prospectus under “Use of Proceeds.”

(i) Restriction on Sale of Securities . For a period commencing on the date hereof and ending on the 90th day after the date of the Prospectus (the “Lock-Up Period”), not to, directly or indirectly, (A) offer for sale, sell, pledge, or otherwise dispose of (or enter into any transaction or device that is designed to, or could be expected to, result in the disposition by any person at any time in the future of) any shares of Common Stock or securities convertible into or exercisable or exchangeable for Common Stock (other than the Securities and shares issued pursuant to employee benefit plans, qualified

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stock option plans or other employee compensation plans existing on the date hereof or pursuant to currently outstanding options, warrants or rights not issued under one of those plans), or sell or grant options, rights or warrants with respect to any shares of Common Stock or securities convertible into or exchangeable for Common Stock (other than the grant of options pursuant to option plans existing on the date hereof), (B) enter into any swap or other derivatives transaction that transfers to another, in whole or in part, any of the economic benefits or risks of ownership of such shares of Common Stock, whether any such transaction described in clause (A) or (B) above is to be settled by delivery of Common Stock or other securities, in cash or otherwise, (C) file or cause to be filed a registration statement, including any amendments thereto, with respect to the registration of any shares of Common Stock or securities convertible, exercisable or exchangeable into Common Stock or any other securities of the Company (other than any registration statement on Form S-8), or (D) publicly disclose the intention to do any of the foregoing, in each case without the prior written consent of the Representative, on behalf of the Underwriters; provided that this Section 3(i) shall not apply to (i) the conversion of any Initial Securities or Option Securities, (ii) the concurrent offering by the Company of 30,000,000 shares of Common Stock (or 34,500,000 shares if the underwriters exercise their option to purchase additional shares in full), (iii) the issuance to Thunder of 40,000,000 shares of Common Stock in connection with the Acquisition and the granting of registration rights to Thunder with respect to such shares and (iv) the filing of registration statements, including any amendments thereto, with respect to the registration of the securities described in clauses (i), (ii) and (iii) of this proviso. Additionally, the Company shall cause each executive officer and director of the Company set forth on Exhibit G-1 hereto to furnish to the Representative, on or prior to the date hereof, a letter or letters, substantially in the form of Exhibit G-2 hereto (the “Lock-Up Agreements”).

(j) Reporting Requirements . The Company, during the period when the Prospectus is required (or, but for the provisions of Rule 172, would be required) by applicable law to be delivered (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), will file all documents required to be filed with the Commission pursuant to the 1934 Act and the 1934 Act Regulations within the time periods required by the 1934 Act and the 1934 Act Regulations.

(k) Preparation of Prospectus . Immediately following the execution of this Agreement, the Company will, subject to Section 3(b) hereof, prepare the Prospectus, which shall contain the public offering price and terms of the Securities, the plan of distribution thereof and such other information as may be required by the 1933 Act or the 1933 Act Regulations or as the Representative and the Company may deem appropriate, and will file or transmit for filing with the Commission, in accordance with the provisions of Rule 430B and in the manner and within the time period required by Rule 424(b) (without reliance on Rule 424(b)(8)), the Prospectus.

(l) DTC . The Company will use their best efforts to permit the Securities to be eligible for clearance and settlement through DTC.

(m) Pricing Term Sheet . The Company will prepare a pricing term sheet (the “ Pricing Term Sheet ”) in substantially the form attached hereto as Exhibit C and

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otherwise in form and substance satisfactory to the Representative, and shall file such Pricing Term Sheet as an “issuer free writing prospectus” pursuant to Rule 433 prior to the close of business on the business day following the date hereof; provided that the Company shall furnish the Representative with copies of any such Pricing Term Sheet a reasonable amount of time prior to such proposed filing and will not use or file any such document to which the Representative or counsel to the Underwriters shall reasonably object.

(n) Listing . The Company will use its commercially reasonable efforts to effect the listing of the Securities, and a number of Conversion Shares equal to the Maximum Number of Conversion Shares, on the NYSE.

(o) No Stabilization . The Company will not take, directly or indirectly, any action designed to or that could reasonably be expected to cause or result in any stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities and will not take any action prohibited by Regulation M under the Exchange Act in connection with the distribution of the Securities contemplated hereby.

(p) Reservation of the Conversion Shares . The Company will reserve and keep available at all times, free of preemptive or similar rights, a number of Conversion Shares equal to the Maximum Number of Conversion Shares.

(q) Fixed Conversion Rates of the Mandatory Convertible Preferred Stock . Between the date hereof and the Closing Date or the relevant Date of Delivery, as the case may be, the Company will not do or authorize any act or thing that would result in an adjustment of the fixed conversion rates of the Mandatory Convertible Preferred Stock.

SECTION 4. Payment of Expenses .

(a) Expenses . The Company will pay all expenses incident to the performance of its obligations under this Agreement, including (i) the preparation, printing and filing of the Registration Statement and each amendment thereto (in each case including exhibits) and any costs associated with electronic delivery of any of the foregoing, and the filing of the Certificate of Designation with the Secretary of State of the State of Delaware, (ii) the printing (or reproduction) and delivery to the Underwriters of this Agreement and such other documents as may be required in connection with the offering, purchase, sale, issuance or delivery of the Securities, (iii) the preparation, issuance and delivery of the certificates for the Securities and the issuance and delivery of the Securities to the Underwriters, including any issue or other transfer taxes and any stamp or other taxes or duties payable in connection with the sale, issuance or delivery of the Securities to the Underwriters, (iv) the fees and disbursements of the counsel, accountants and other advisors to the Company and Thunder, (v) the qualification or exemption of the Securities under securities laws in accordance with the provisions of Section 3(f) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters in connection therewith and in connection with the preparation of the Blue Sky Survey and any supplements thereto, (vi) the preparation, printing and delivery to the Underwriters of copies of

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each preliminary prospectus, any Permitted Free Writing Prospectus and the Prospectus and any amendments or supplements to any of the foregoing and any costs associated with electronic delivery of any of the foregoing, (vii) the preparation, printing and delivery to the Underwriters of copies of the Blue Sky Survey and any supplements thereto and any costs associated with electronic delivery of any of the foregoing, (viii) fees and expenses of the transfer agent and any registrar, including the fees and disbursements of counsel for the transfer agent, (ix) the filing fees incident to, and the reasonable fees and disbursements of counsel to the Underwriters in connection with, the review, if any, by FINRA of the terms of the sale of the Securities, (x) all expenses and application fees incurred in connection with the approval of the Securities for clearance, settlement and book-entry transfer through DTC, (x) the costs and expenses of the Company and any of its officers, directors, counsel or other representatives in connection with presentations or meetings undertaken in connection with the offering of the Securities, including, without limitation, expenses associated with the production of road show slides and graphics and the production and hosting of any electronic road shows, fees and expenses of any consultants engaged in connection with road show presentations, travel, lodging, transportation, and other expenses of the officers, directors, counsel or other representatives of the Company incurred in connection with any such presentations or meetings and (xi) the fees and expenses incurred in connection with the inclusion of the Securities, the Conversion Shares and any shares of Common Stock issued and paid as a dividend on the Securities on the NYSE. Notwithstanding the foregoing, except as otherwise expressly provided in this Section 4(a) and Sections 4(b), 6 and 7 hereof, the Underwriters shall bear their own costs and expenses related to the issuance and sale by the Company of the Securities, including transfer taxes on resale of any Securities by them, and any advertising expenses in connection with any offers they make.

(b) Termination of Agreement . If this Agreement is terminated by the Representative in accordance with the provisions of Section 5 or Section 9 hereof, the Company shall reimburse the Underwriters for all of their out-of-pocket expenses, including the reasonable fees and disbursements of counsel for the Underwriters.

SECTION 5. Conditions of Underwriters’ Obligations . The obligations of the several Underwriters hereunder to purchase the Initial Securities on the Closing Date or the Option Securities on the Date of Delivery, as the case may be, are subject to the accuracy of the representations and warranties of the Company contained in this Agreement, or in certificates signed by any officer of the Company or any subsidiary of the Company (whether signed on behalf of such officer, the Company or such subsidiary) delivered to the Representative or counsel for the Underwriters, to the performance by the Company of its covenants and other obligations hereunder, and to the following further conditions:

(a) Effectiveness of Registration Statement . The Registration Statement shall have become effective, and no stop order suspending the effectiveness of the Registration Statement shall have been issued under the 1933 Act or proceedings therefor, pursuant to Rule 401(g)(2) or Section 8A of the 1933 Act, initiated or, to the knowledge of the Company, threatened by the Commission, and any request on the part of the Commission for additional information shall have been complied with to the reasonable satisfaction of the Representative and the Commission shall not have notified the Company of any objection to the use of the form of the Registration Statement. The Prospectus shall have been filed with the Commission in the manner and within the time period required by

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Rule 424(b) (without reliance upon Rule 424(b)(8)) and each Issuer Free Writing Prospectus required to be filed with the Commission shall have been filed in the manner and within the time period required by Rule 433, and, prior to the Closing Date or the Date of Delivery, as the case may be, the Company shall have provided evidence satisfactory to the Representative of such timely filings.

(b) Opinion and 10b-5 Statement of Counsel for Company . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received the favorable opinion and 10b-5 statement, dated as of Closing Date or the Date of Delivery, as the case may be, of Weil, Gotshal & Manges LLP, counsel for the Company (“ Company Counsel ”), in form and substance satisfactory to the Representative, together with signed or reproduced copies of such opinion and 10b-5 statement for each of the other Underwriters, to the effect set forth in Exhibit E hereto and to such further effect as the Representative may reasonably request.

(c) Opinion of Company’s General Counsel . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received the favorable opinion, dated as of the Closing Date or the Date of Delivery, as the case may be, of Dennis C. Cameron, Senior Vice President and General Counsel of the Company, in form and substance satisfactory to the Representative, together with signed or reproduced copies of such opinion for each of the other Underwriters, to the effect set forth in Exhibit F hereto and to such further effect as the Representative may reasonably request.

(d) Opinion and 10b-5 Statement of Counsel for Underwriters . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received the favorable opinion and 10b-5 statement, dated as of Closing Date or the Date of Delivery, as the case may be, of Simpson Thacher & Bartlett LLP, counsel for the Underwriters, together with signed or reproduced copies of such opinion and 10b-5 statement for each of the other Underwriters, with respect to the Securities to be sold by the Company pursuant to this Agreement, the Registration Statement, the General Disclosure Package and the Prospectus and any amendments or supplements thereto and such other matters as the Representative may reasonably request.

(e) Officers’ Certificate . At the Closing Date or the Date of Delivery, as the case may be, there shall not have been, since the date hereof or since the respective dates as of which information is given in the Registration Statement, the General Disclosure Package and the Prospectus (in each case exclusive of any amendments or supplements thereto subsequent to the date of this Agreement), any material adverse change or any development that would reasonably be expected to result in a prospective material adverse change, in the financial condition, earnings, business or operations of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, from that set forth or contemplated in the General Disclosure Package and the Prospectus (in each case exclusive of any amendments or supplements thereto subsequent to the date of this Agreement), and, at the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received a certificate of the Company, signed by an executive officer of the Company, dated as of Closing Date or the Date of Delivery, as the case may be, (a) making representations and warranties with respect to the written comments

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received from the Commission and (b) to the effect that (i) there has been no such material adverse change, (ii) the representations and warranties of the Company in this Agreement are true and correct at and as of the Closing Date or the Date of Delivery, as the case may be, with the same force and effect as though expressly made at and as of Closing Date or the Date of Delivery, as the case may be, (iii) the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied at or prior to Closing Date or the Date of Delivery, as the case may be, under or pursuant to this Agreement, and (iv) no stop order suspending the effectiveness of the Registration Statement has been issued and no proceedings for that purpose, pursuant to Rule 401(g)(2) or Section 8A under the 1933 Act, have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission and the Commission has not notified the Company of any objection to the use of the form of the Registration Statement, and to the effect set forth in Section 5(n) below.

(f) Accountant’s Comfort Letter . At the time of the execution of this Agreement, the Representative shall have received from Ernst & Young LLP a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information of the Company contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(g) Bring-down Comfort Letter . At Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from Ernst & Young LLP a letter, dated as of Closing Date or the Date of Delivery, as the case may be, and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (f) of this Section, except that the specified date referred to shall be a date not more than three business days prior to Closing Date or the Date of Delivery, as the case may be.

(h) Thunder Comfort Letter . At the time of the execution of this Agreement, the Representative shall have received from Grant Thornton LLP a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information of the Thunder Entities contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(i) Thunder Bring-Down Comfort Letter . At Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from Grant Thornton LLP a letter, dated as of Closing Date or the Date of Delivery, as the case may be, and in

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form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (h) of this Section, except that the specified date referred to shall be a date not more than three business days prior to Closing Date or the Date of Delivery, as the case may be.

(j) Reserve Engineer’s Letter . At the time of the execution of this Agreement, the Representative shall have received from Netherland, Sewell & Associates, Inc. a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, covering certain matters relating to information about the reserves of the Company contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(k) Bring-Down Reserve Engineer’s Letter . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from Netherland, Sewell & Associates, Inc. a letter, dated as of the Closing Date or the Date of Delivery, as the case may be, and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (j) of this Section.

(l) Thunder Engineer’s Letter . At the time of the execution of this Agreement, the Representative shall have received from LaRoche Petroleum Consultants, Ltd. a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, covering certain matters relating to information about the reserves of the Thunder Entities contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(m) Thunder Bring-Down Reserve Engineer’s Letter . At the Closing Date or the Date of Delivery, as the case may be, the Representative shall have received from LaRoche Petroleum Consultants, Ltd. a letter, dated as of the Closing Date or the Date of Delivery, as the case may be, and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (l) of this Section.

(n) No Downgrade . There shall not have occurred, on or after the date of this Agreement, any downgrading in the rating of any debt securities of or guaranteed by the Company or any preferred securities of the Company by any “nationally recognized statistical rating organization” (as defined by the Commission in Section 3(a)(62) of the 1934 Act) or any public announcement that any such organization has placed its rating on the Company or any such debt or preferred securities under surveillance or review or on a so-called “watch list” (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement by any such organization that the Company or any such debt or preferred securities has been placed on negative outlook.

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(o) No Objection . Prior to the date of this Agreement, FINRA shall have confirmed in writing that it has no objection with respect to the fairness and reasonableness of the underwriting terms and arrangements.

(p) No Material Adverse Change . Since the date of the most recent financial statements included in the General Disclosure Package (exclusive of any amendment or supplement thereto) and the Prospectus (exclusive of any amendment or supplement thereto), there shall not have been any change, or any development that would reasonably be expected to result in a prospective change, in the financial condition, earnings, business or operations of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, from that set forth in the Pre-Pricing Prospectus, the effect of which is, in the sole judgment of the Representative, so material and adverse as to make it impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto).

(q) Additional Documents . At the Closing Date or the Date of Delivery, as the case may be, counsel for the Underwriters shall have been furnished with such documents and opinions as they may reasonably require for the purpose of enabling them to pass upon the issuance and sale of the Securities as herein contemplated, or in order to evidence the accuracy of any of the representations or warranties, or the fulfillment of any of the conditions, contained in this Agreement, or as the Representative or counsel for the Underwriters may otherwise reasonably request; and all proceedings taken by the Company in connection with the issuance and sale of the Securities as herein contemplated and in connection with the other transactions contemplated by this Agreement shall be satisfactory in form and substance to the Representative.

(r) Lock-up Agreements . The Lock-Up Agreements between the Representative and the executive officers and directors of the Company set forth on Exhibit G-1, delivered to the Representative on or before the date of this Agreement, shall be in full force and effect on the Closing Date or the Date of Delivery, as the case may be.

(s) Approval of Listing . The Company shall have filed the requisite listing applications with the NYSE for the listing of the Securities and the Maximum number of Conversion Shares (subject to any adjustments as described in the Certificate of Designations).

(t) Termination of Agreement . If any condition specified in this Section 5 shall not have been fulfilled when and as required to be fulfilled, this Agreement, or, in the case of any condition to the purchase of Option Securities on a Date of Delivery which is after the Closing Date, the obligations of the Underwriters to purchase the relevant Option Securities, may be terminated by the Representative by notice to the Company at any time on or prior to the Closing Date or such Date of Delivery, as the case may be, and such termination shall be without liability of any party to any other party except as provided in Section 4 hereof and except that Sections 1, 6, 7, 8, 11, 12,

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13, 14, 15, 16, 18, 19 and 20 and hereof shall survive any such termination of this Agreement and remain in full force and effect.

(u) Certificate of Designation . The Certificate of Designation shall have been filed with the Secretary of State of the State of Delaware and shall have become effective.

SECTION 6. Indemnification .

(a) Indemnification by the Company . The Company agrees to indemnify and hold harmless each Underwriter, its affiliates, and its and their officers, directors, employees, partners and members and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act as follows:

(i) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, arising out of any untrue statement or alleged untrue statement of a material fact in the Registration Statement (or any amendment thereto), or the omission or alleged omission therefrom of a material fact required to be stated therein or necessary to make the statements therein not misleading, or arising out of any untrue statement or alleged untrue statement of a material fact in any preliminary prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package or the Prospectus (or any amendment or supplement to any of the foregoing), or in any “issuer information” (as defined in Rule 433) or “road show” (as defined in Rule 433) that does not constitute an Issuer Free Writing Prospectus, or the omission or alleged omission therefrom of a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading and agrees to reimburse each such indemnified party, as incurred, for any legal or other expenses reasonably incurred by them in connection with defending any such loss, liability, claim, damage or action;

provided , however , that this indemnity agreement shall not apply to any loss, liability, claim, damage or expense to the extent arising out of any untrue statement or omission or alleged untrue statement or omission made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative expressly for use in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package or the Prospectus (or in any amendment or supplement to any of the foregoing), it being understood and agreed that the only such information furnished by the Underwriters as aforesaid consists of the information described as such in Section 6(b) hereof.

(b) Indemnification by the Underwriters . Each Underwriter agrees, severally and not jointly, to indemnify and hold harmless the Company, its directors, each of its officers who signed the Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act against any and all loss, liability, claim, damage and expense described in the indemnity contained in subsection (a)(1) of this Section 6, as incurred, but only with respect to untrue statements or omissions, or alleged untrue statements or omissions, made in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement to any of the foregoing), in reliance upon and in conformity with

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written information furnished to the Company by such Underwriter through the Representative expressly for use therein. The Company hereby acknowledges and agrees that the information furnished to the Company by the Underwriters through the Representative expressly for use in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement to any of the foregoing), consists exclusively of the information appearing under the caption “Underwriting” in the Pre-Pricing Prospectus and the Prospectus regarding stabilization, syndicate covering transactions, penalty bids and discretionary sales appearing in the 15th, 16th and 17th paragraphs under such caption (but only insofar as such information concerns the Underwriters).

(c) Actions Against Parties; Notification . Each indemnified party shall give notice as promptly as reasonably practicable to each indemnifying party of any action commenced against it in respect of which indemnity may be sought hereunder, but failure to so notify an indemnifying party shall not relieve such indemnifying party from any liability hereunder unless and to the extent it did not otherwise learn of such action and such failure results in the forfeiture by the indemnifying party of substantial rights and defenses. The indemnifying party shall be entitled to appoint counsel of the indemnifying party’s choice at the indemnifying party’s expense to represent the indemnified party in any action for which indemnification is sought (in which case the indemnifying party shall not thereafter be responsible for the fees and expenses of any separate counsel retained by the indemnified party or parties except as set forth below); provided , however , that such counsel shall be reasonably satisfactory to the indemnified party. Notwithstanding the indemnifying party’s election to appoint counsel to represent the indemnified party in an action, the indemnified party shall have the right to employ separate counsel (including local counsel), and the indemnifying party shall bear the reasonable fees, costs and expenses of such separate counsel if (i) the use of counsel chosen by the indemnifying party to represent the indemnified party would present such counsel with a conflict of interest, (ii) the actual or potential defendants in, or targets of, any such action include both the indemnified party and the indemnifying party and the indemnified party shall have reasonably concluded that there may be legal defenses available to it and/or other indemnified parties which are different from or additional to those available to the indemnifying party, (iii) the indemnifying party shall not have employed counsel reasonably satisfactory to the indemnified party to represent the indemnified party within a reasonable time after notice of the institution of such action or (iv) the indemnifying party shall authorize the indemnified party to employ separate counsel at the expense of the indemnifying party. In no event shall the indemnifying party be liable for the fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for the Underwriters and the other indemnified parties referred to in Section 6(a)(1) above; and the fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for the Company, its directors, each of its officers who signed the Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act, in each case in connection with any one action or separate but similar or related actions in the same jurisdiction arising out of the same general allegations or circumstances. No indemnifying party shall, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever in respect of which indemnification or contribution could be sought under this Section 6 or Section 7 hereof (whether or not the indemnified parties are actual or potential

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parties thereto), unless such settlement, compromise or consent (i) includes an unconditional release of each indemnified party from all liability arising out of such litigation, investigation, proceeding or claim and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party.

SECTION 7. Contribution . If the indemnification provided for in Section 6 hereof is for any reason unavailable to or insufficient to hold harmless an indemnified party in respect of any losses, liabilities, claims, damages or expenses referred to therein, then each indemnifying party shall contribute to the aggregate amount of such losses, liabilities, claims, damages and expenses incurred by such indemnified party, as incurred, (i) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other hand from the offering of the Securities pursuant to this Agreement or (ii) if the allocation provided by clause (i) is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause (i) above but also the relative fault of the Company on the one hand and of the Underwriters on the other hand in connection with the statements or omissions which resulted in such losses, liabilities, claims, damages or expenses, as well as any other relevant equitable considerations.

The relative benefits received by the Company on the one hand and the Underwriters on the other hand in connection with the offering of the Securities pursuant to this Agreement shall be deemed to be in the same respective proportions as the total net proceeds from the offering of the Securities pursuant to this Agreement (before deducting expenses) received by the Company and the total underwriting discounts and commissions received by the Underwriters, in each case as set forth on the cover of the Prospectus, bear to the aggregate initial public offering price of the Securities as set forth on such cover.

The relative fault of the Company on the one hand and the Underwriters on the other hand shall be determined by reference to, among other things, whether any such untrue or alleged untrue statement of a material fact or omission or alleged omission to state a material fact relates to information supplied by the Company on the one hand or by the Underwriters on the other hand and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission.

The Company and the Underwriters agree that it would not be just and equitable if contribution pursuant to this Section 7 were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to above in this Section 7. The aggregate amount of losses, liabilities, claims, damages and expenses incurred by an indemnified party and referred to above in this Section 7 shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue or alleged untrue statement or omission or alleged omission.

Notwithstanding the provisions of this Section 7, no Underwriter shall be required to contribute any amount in excess of the amount by which the total price at which the Securities underwritten by it and distributed to the public were offered to the public exceeds the amount of

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any damages which such Underwriter has otherwise been required to pay by reason of any such untrue or alleged untrue statement or omission or alleged omission.

No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the 1933 Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

For purposes of this Section 7, each affiliate, officer, director, employee, partner and member of each Underwriter and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as such Underwriter, and each director of the Company, each officer of the Company who signed the Registration Statement, and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as the Company. The Underwriters’ respective obligations to contribute pursuant to this Section 7 are several in proportion to the principal amount of Securities set forth opposite their respective names in Exhibit A hereto and not joint.

SECTION 8. Representations, Warranties and Agreements to Survive Delivery . All representations, warranties and agreements contained in this Agreement or in certificates signed by any officer of the Company or any of its subsidiaries (whether signed on behalf of such officer, the Company or such subsidiary) and delivered to the Representative or counsel to the Underwriters, shall remain operative and in full force and effect, regardless of any investigation made by or on behalf of any Underwriter, any officer, director, employee, partner, member or agent of any Underwriter or any person controlling any Underwriter, or by or on behalf of the Company, any officer, director or employee of the Company or any person controlling the Company.

SECTION 9. Termination of Agreement .

(a) Termination; General . This Agreement shall be subject to termination in the absolute discretion of the Representative, by notice given to the Company prior to delivery of and payment for the Securities, if at any time prior to such time (i) trading in the Company’s shares shall have been suspended by the Commission or the NYSE or trading in securities generally on the NYSE shall have been suspended or limited or minimum prices shall have been established on such exchange, (ii) a banking moratorium shall have been declared either by federal or New York State authorities or (iii) there shall have occurred any outbreak or escalation of hostilities, declaration by the United States of a national emergency or war, or other calamity or crisis the effect of which on financial markets is such as to make it, in the sole judgment of the Representative, impractical or inadvisable to proceed with the offering, sale or delivery of the Securities as contemplated by any Pre-Pricing Prospectus or the Prospectus (exclusive of any amendment or supplement thereto).

(b) Liabilities . If this Agreement is terminated pursuant to this Section 9, such termination shall be without liability of any party to any other party except as provided in Section 4 hereof, and except that Sections 1, 6, 7, 8, 11, 12, 13, 14, 15, 16, 18, 19 and 20 hereof shall survive such termination and remain in full force and effect.

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SECTION 10. Default by One or More of the Underwriters . (a) If one or more of the Underwriters shall fail at the Closing Date to purchase the amount of Securities which it or they are obligated to purchase under this Agreement (the “ Defaulted Securities ”), the Representative shall have the right, within 24 hours thereafter, to make arrangements for one or more of the non-defaulting Underwriters, or any other underwriters, to purchase all, but not less than all, of the Defaulted Securities in such amounts as may be agreed upon and upon the terms herein set forth; if, however, the Representative shall not have completed such arrangements within such 24-hour period, then:

(i) if the amount of Defaulted Securities does not exceed 10% of the aggregate amount of Securities, each of the non-defaulting Underwriters shall be obligated, severally and not jointly, to purchase the full amount of such Defaulted Securities in the proportions that their respective underwriting obligations hereunder bear to the underwriting obligations of all non-defaulting Underwriters; or

(ii) if the number of Defaulted Securities exceeds 10% of the aggregate amount of Securities, this Agreement shall terminate without liability on the part of any non-defaulting Underwriter.

(b) No action taken pursuant to this Section 10 shall relieve any defaulting Underwriter from liability in respect of its default.

In the event of any such default which does not result in a termination of this Agreement, the Representative shall have the right to postpone the Closing Date for a period not exceeding seven days in order to effect any required changes in the Registration Statement, the General Disclosure Package or Prospectus or in any other documents or arrangements. As used herein, the term “Underwriter” includes any person substituted for an Underwriter under this Section 10.

SECTION 11. Notices . All notices and other communications hereunder shall be in writing, shall be effective only upon receipt and shall be mailed, delivered by hand or overnight courier, or transmitted by fax (with the receipt of any such fax to be confirmed by telephone). Notices to the Underwriters shall be directed to the Representative at Barclays Capital Inc. 745 Seventh Avenue, New York, New York 10019, Attention: Syndicate Registration; and notices to the Company shall be directed to it at WPX Energy, Inc., 3500 One Williams Center, Tulsa, Oklahoma 74172, Attention: Chief Financial Officer (Fax: (539) 573-0026), Attention: Treasurer (Fax: (539) 573-0026) and Attention: General Counsel (Fax: (539) 573-5608), with a copy mailed, delivered or telefaxed to Weil, Gotshal & Manges LLP, Attention: Todd R. Chandler, Esq. (Fax: (212) 310-8007 and confirmed at (212) 310-8000).

SECTION 12. Parties . This Agreement shall each inure to the benefit of and be binding upon the Underwriters and the Company and their respective successors. Nothing expressed or mentioned in this Agreement is intended or shall be construed to give any person, firm or corporation, other than the Underwriters and the Company and their respective successors and the controlling persons and other indemnified parties referred to in Sections 6 and 7 and their successors, heirs and legal representatives, any legal or equitable right, remedy or claim under or in respect of this Agreement or any provision herein contained. This Agreement and all conditions and provisions hereof are intended to be for the sole and exclusive benefit of the

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Underwriters and the Company and their respective successors, and said controlling persons and other indemnified parties and their successors, heirs and legal representatives, and for the benefit of no other person or entity. No purchaser of Securities from any Underwriter shall be deemed to be a successor by reason merely of such purchase.

SECTION 13. Governing Law and Time . THIS AGREEMENT AND ANY CLAIM, CONTROVERSY OR DISPUTE ARISING UNDER OR RELATED TO THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK. EXCEPT AS OTHERWISE EXPRESSLY SET FORTH HEREIN, SPECIFIED TIMES OF DAY REFER TO NEW YORK CITY TIME.

SECTION 14. Waiver of Jury Trial . The Company and the Underwriters hereby irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.

“ GAAP ” means generally accepted accounting principles.

“ Issuer Free Writing Prospectus ” means any “issuer free writing prospectus,” as defined in Rule 433, relating to the Securities that (i) is required to be filed with the Commission by the Company, (ii) is a “road show” that is a “written communication” within the meaning of Rule 433(d)(8)(i), whether or not required to be filed with the Commission, or (iii) is exempt from filing pursuant to Rule 433(d)(5)(i) because it contains a description of the Securities or of the offering that does not reflect the final terms, and all free writing prospectuses that are listed in Exhibit D hereto, in each case in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g).

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“ Issuer General Use Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being specified in Exhibit D hereto.

“ Issuer Limited Use Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is not an Issuer General Use Free Writing Prospectus.

“ NYSE ” means the New York Stock Exchange.

“ Organizational Documents ” means (a) in the case of a corporation, its charter and by-laws; (b) in the case of a limited or general partnership, its partnership certificate, certificate of formation or similar organizational document and its partnership agreement; (c) in the case of a limited liability company, its articles of organization, certificate of formation or similar organizational documents and its operating agreement, limited liability company agreement, membership agreement or other similar agreement; (d) in the case of a trust, its certificate of trust, certificate of formation or similar organizational document and its trust agreement or other similar agreement; and (e) in the case of any other entity, the organizational and governing documents of such entity.

“ PCAOB ” means the Public Company Accounting Oversight Board (United States).

“ preliminary prospectus ” means any prospectus together with, if applicable, the accompanying preliminary prospectus supplement used in connection with the offering of the Securities that omitted the public offering price of the Securities or that was captioned “Subject to Completion,” together with the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act. The term “preliminary prospectus” includes, without limitation, the Pre-Pricing Prospectus.

“ Registration Statement ” means the Company’s registration statement on Form S–3 (Registration No. 333-198523) as amended (if applicable), including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S–3 under the 1933 Act and the Rule 430B Information; provided that any Rule 430B Information shall be deemed part of the Registration Statement only from and after the time specified pursuant to Rule 430B.

“ Rule 163 ,” “ Rule 164 ,” “ Rule 172 ,” “ Rule 173 ,” “ Rule 401 ,” “ Rule 405 ,” “ Rule 424(b) ” “ Rule 430B ” and “ Rule 433 ” refer to such rules under the 1933 Act.

“ Rule 430B Information ” means the information included in any preliminary prospectus or the Prospectus or any amendment or supplement to any of the foregoing that was omitted from the Registration Statement at the time it first became effective but is deemed to be part of and included in the Registration Statement pursuant to Rule 430B.

“ Sarbanes-Oxley Act ” means the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated thereunder or implementing the provisions thereof.

“ 1933 Act ” means the Securities Act of 1933, as amended.

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“ 1933 Act Regulations ” means the rules and regulations of the Commission under the 1933 Act.

“ 1934 Act ” means the Securities Exchange Act of 1934, as amended.

“ 1934 Act Regulations ” means the rules and regulations of the Commission under the 1934 Act.

“ 1940 Act ” means the Investment Company Act of 1940, as amended.

All references in this Agreement to the Registration Statement, any preliminary prospectus, the Prospectus, any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing shall be deemed to include the version thereof filed with the Commission pursuant to EDGAR and all versions thereof delivered (physically or electronically) to the Representative or the Underwriters.

All references in this Agreement to financial statements and schedules and other information which is “contained,” “included” or “stated” in the Registration Statement, any preliminary prospectus or the Prospectus (and all other references of like import) shall be deemed to mean and include all such financial statements and schedules and other information which is incorporated by reference in or otherwise deemed by 1933 Act Regulations to be a part of or included in the Registration Statement, any preliminary prospectus or the Prospectus, as the case may be; and all references in this Agreement to amendments or supplements to the Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to mean and include the filing of any document under the 1934 Act which is incorporated by reference in or otherwise deemed by 1933 Act Regulations to be a part of or included in the Registration Statement, such preliminary prospectus or the Prospectus, as the case may be.

SECTION 17. Permitted Free Writing Prospectuses . The Company represents, warrants and agrees that it has not made and, unless it obtains the prior written consent of the Representative, it will not make, and each Underwriter, severally and not jointly, represents, warrants and agrees that it has not made and, unless it obtains the prior written consent of the Company and the Representative, it will not make, any offer relating to the Securities that constitutes or would constitute an “issuer free writing prospectus” (as defined in Rule 433) or that otherwise constitutes or would constitute a “free writing prospectus” (as defined in Rule 405) or portion thereof required, in the case of any Underwriters, to be filed with the Commission or, in the case of the Company, whether or not required to be filed with the Commission; provided that the prior written consent of the Company and the Representative shall be deemed to have been given in respect of the Issuer General Use Free Writing Prospectuses, if any, listed on Exhibit D hereto and to any electronic road show in the form previously provided by the Company to and approved by the Representative. Any such free writing prospectus consented to or deemed to have been consented to as aforesaid is hereinafter referred to as a “Permitted Free Writing Prospectus.” The Company represents, warrants and agrees that it has treated and will treat each Permitted Free Writing Prospectus as an “issuer free writing prospectus,” as defined in Rule 433, and has complied and will comply with the requirements of Rule 433 applicable to any Permitted Free Writing Prospectus, including timely filing with the Commission where required, legending and record keeping.

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SECTION 18. Absence of Fiduciary Relationship . The Company acknowledges and agrees that:

(a) each of the Underwriters is acting solely as an underwriter in connection with the sale of the Securities and no fiduciary, advisory or agency relationship between the Company, on the one hand, and any of the Underwriters, on the other hand, has been created in respect of any of the transactions contemplated by this Agreement, irrespective of whether or not any of the Underwriters has advised or is advising the Company on other matters;

(b) the public offering price of the Securities and the price to be paid by the Underwriters for the Securities set forth in this Agreement were established by the Company following discussions and arms-length negotiations with the Representative;

(c) it is capable of evaluating and understanding, and understands and accepts, the terms, risks and conditions of the transactions contemplated by this Agreement;

(d) it is aware that the Underwriters and their respective affiliates are engaged in a broad range of transactions which may involve interests that differ from those of the Company and that none of the Underwriters has any obligation to disclose such interests and transactions to the Company by virtue of any fiduciary, advisory or agency relationship or otherwise; and

(e) it waives, to the fullest extent permitted by law, any claims it may have against any of the Underwriters for breach of fiduciary duty or alleged breach of fiduciary duty and agrees that none of the Underwriters shall have any liability (whether direct or indirect, in contract, tort or otherwise) to it in respect of such a fiduciary duty claim or to any person asserting a fiduciary duty claim on its behalf or in right of it or the Company or any stockholders, employees or creditors of Company.

SECTION 19. Research Analyst Independence . The Company acknowledges that the Underwriters’ research analysts and research departments are required to be independent from their respective investment banking divisions and are subject to certain regulations and internal policies, and that such Underwriters’ research analysts may hold views and make statements or investment recommendations and/or publish research reports with respect to the Company and/or the offering that differ from the views of their respective investment banking divisions. The Company hereby waives and releases, to the fullest extent permitted by applicable law, any claims that the Company may have against the Underwriters with respect to any conflict of interest related to the issuance and sale by the Company of the Securities that may arise from the fact that the views expressed by their independent research analysts and research departments may be different from or inconsistent with the views or advice communicated to the Company by such Underwriters’ investment banking divisions. The Company acknowledges that each of the Underwriters is a full service securities firm and as such from time to time, subject to applicable securities laws, may effect transactions for its own account or the account of its customers and hold long or short positions in debt or equity securities of the companies that may be the subject of the transactions contemplated by this Agreement.

SECTION 20. Consent to Jurisdiction . The parties hereby irrevocably submit to the non-exclusive jurisdiction of any New York State or federal court sitting in the Borough of

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Manhattan in The City of New York in any action or proceeding arising out of or relating to the terms of this Agreement and the transactions contemplated herein, and the parties hereby irrevocably agree that all claims in respect of such action or proceeding may be heard and determined in such New York State or federal court. The parties hereby irrevocably waive, to the fullest extent that they may legally do so, the defense of an inconvenient forum to the maintenance of such action or proceeding. The parties agree that a final judgment in any such action or proceeding shall be conclusive and may be enforced in other jurisdictions by suit on the judgment or in any other manner provided by law. To the extent that either party has or hereafter may acquire any immunity from jurisdiction of any court or from any legal process (whether through service or notice, attachment prior to judgment, attachment in aid of execution or otherwise) with respect to its obligations hereunder, each waives such immunity to the extent permitted by applicable law.

SECTION 21. Patriot Act . In accordance with the requirements of the USA Patriot Act (Title III of Pub. L. 107-56 (signed into law October 26, 2001)), the Underwriters are required to obtain, verify and record information that identifies their respective clients, including the Company, which information may include the name and address of their respective clients, as well as other information that will allow the underwriters to properly identify their respective clients.

[Signature Page Follows]

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If the foregoing is in accordance with your understanding of our agreement, please sign and return to the Company a counterpart hereof, whereupon this instrument, along with all counterparts, will become a binding agreement between the Underwriters and the Company in accordance with its terms.

EXHIBITS

ii

WPX ENERGY, INC.

$500,000,000 7.50% Senior Notes due 2020

$500,000,000 8.25% Senior Notes due 2023

UNDERWRITING AGREEMENT

July 17, 2015

Barclays Capital Inc.

As Representative of the several Underwriters

c/o Barclays Capital Inc.

745 Seventh Avenue

New York, New York 10019

Ladies and Gentlemen:

WPX Energy, Inc., a Delaware corporation (the “Company”), confirms its agreement with Barclays Capital Inc. (“Barclays”) and each of the other Underwriters named in Exhibit A hereto (collectively, the “Underwriters,” which term shall also include any underwriter substituted as hereinafter provided in Section 10 hereof), for whom Barclays is acting as representative (in such capacity, the “Representative”), with respect to the issue and sale by the Company and the purchase by the Underwriters, acting severally and not jointly, of the respective principal amounts set forth in said Exhibit A hereto of (i) $500,000,000 aggregate principal amount of the Company’s 7.50% Senior Notes due 2020 (the “2020 Notes”) and (ii) $500,000,000 aggregate principal amount of the Company’s 8.25% Senior Notes due 2023 (the “2023 Notes” and, together with the 2020 Notes, the “Securities”). The Securities will be issued pursuant to that certain indenture (the “Base Indenture”) dated as of September 8, 2014 between the Company and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”). The term “Indenture” as used herein includes the Base Indenture and the Second Supplemental Indenture to be dated as of the Closing Date (as defined below), between the Company and the Trustee (the “Second Supplemental Indenture”), establishing the form and terms of the 2020 Notes and the 2023 Notes. Certain terms used in this Agreement are defined in Section 16 hereof.

The Company understands that the Underwriters propose to make a public offering of the Securities as soon as the Representative deems advisable after this Agreement has been executed and delivered.

The Securities are being issued in connection with the proposed merger of Thunder Merger Sub, LLC, a Delaware limited liability company (“Merger Sub”) and subsidiary of the Company into RKI Exploration & Production, LLC, a Delaware limited liability company (“Thunder”, and together with its subsidiaries, the “Thunder Entities”)), pursuant to that certain Agreement and Plan of Merger, dated July 13, 2015, among the Company, Merger Sub and Thunder (together with all exhibits, schedules and other disclosure letters thereto, collectively, as may be amended, the “Acquisition Agreement”). Prior to the consummation of the merger, Thunder will dispose of its Powder River Basin assets and certain non-core assets in accordance

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with the Acquisition Agreement. These transactions (including the proposed merger) are herein collectively referred to as the “Acquisition.” The date of the consummation of the Acquisition is referred to herein as the “Acquisition Closing Date.”

In connection with the Acquisition, the Company is seeking an amendment to its Amended and Restated Credit Agreement, dated as of October 28, 2014, by and among the Company, the lenders party thereto, and Citibank, N.A., as Administrative Agent and Swingline Lender (the “Existing Facility”).

Subject to the terms and conditions set forth in the Indenture, the Securities will be redeemed (the “Special Mandatory Redemption”) at a price equal to 100% of the initial issue price of the Securities, plus accrued and unpaid interest on the Securities from the Closing Date to, but excluding the date of such redemption, in the event that either the Acquisition is not consummated by November 30, 2015 (the “Outside Date”) or the Acquisition Agreement is terminated at any time prior thereto.

The Company has prepared and previously delivered to you a preliminary prospectus supplement dated July 14, 2015 relating to the Securities and pursuant to the Registration Statement, an automatic shelf registration statement as defined in Rule 405, as amended by a post-effective amendment filed on July 14, 2015, which includes the base prospectus dated September 3, 2014 (the “Base Prospectus”). Such preliminary prospectus supplement and Base Prospectus, including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, are hereinafter called, collectively, the “Pre-Pricing Prospectus.” Promptly after the execution and delivery of this Agreement, the Company will prepare a prospectus supplement dated July 17, 2015 (the “Prospectus Supplement”) and will file the Prospectus Supplement and the Base Prospectus with the Commission, all in accordance with the provisions of Rule 430B and Rule 424(b), and the Company has previously advised you of all information (financial and other) that will be set forth therein. The Prospectus Supplement and the Base Prospectus, in the form first furnished to the Underwriters for use in connection with the offering of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), are herein called, collectively, the “Prospectus.” Any reference in this Agreement to the Registration Statement, any Pre-Pricing Prospectus or the Prospectus shall be deemed to refer to and include the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, as of the effective date of the Registration Statement or the date of such Pre-Pricing Prospectus or the Prospectus, as the case may be and any reference to “amend”, “amendment” or “supplement” with respect to the Registration Statement, any Pre-Pricing Prospectus or the Prospectus shall be deemed to refer to and include any documents filed after such date under the 1934 Act that are deemed to be incorporated by reference therein.

SECTION 1. Representations and Warranties .

(a) Representations and Warranties by the Company . The Company represents and warrants to each Underwriter as of the date hereof, as of the Applicable Time, and as of the Closing Date referred to in Section 2(b) hereof, and agrees with each Underwriter, as follows:

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(1) Status as a Well-Known Seasoned Issuer . (A) At the respective times the Registration Statement or any amendments thereto were filed with the Commission, (B) at the time of the most recent amendment to the Registration Statement for the purposes of complying with Section 10(a)(3) of the 1933 Act (whether such amendment was by post-effective amendment, incorporated report filed pursuant to Section 13 or 15(d) of the 1934 Act or form of prospectus), (C) at any time the Company or any person acting on its behalf (within the meaning, for this clause only, of Rule 163(c)) made any offer relating to the Securities in reliance on the exemption of Rule 163 and (D) at the date hereof, the Company was and is a “well-known seasoned issuer” as defined in Rule 405. The Registration Statement is an “automatic shelf registration statement,” as defined in Rule 405 and the Securities, since their registration on the Registration Statement, have been and remain eligible for registration by the Company on such an “automatic shelf registration statement.” The Company has not received from the Commission any notice pursuant to Rule 401(g)(2) objecting to the use of an automatic shelf registration statement. Any written communication that was an offer relating to the Securities made by the Company or any person acting on its behalf (within the meaning, for this sentence only, of Rule 163(c)) prior to the filing of the Registration Statement has been filed with the Commission in accordance with Rule 163 and otherwise complied with the requirements of Rule 163, including without limitation the legending requirement, to qualify such offer for the exemption from Section 5(c) of the 1933 Act provided by Rule 163.

(2) Compliance with Registration Requirements . The Company meets the requirements for use of Form S-3 under the 1933 Act and the Securities have been duly registered under the 1933 Act pursuant to the Registration Statement. The Registration Statement and any post-effective amendments thereto have become effective under the 1933 Act and no stop order suspending the effectiveness of the Registration Statement has been issued under the 1933 Act and no proceedings for that purpose or pursuant to Section 8A of the 1933 Act against the Company or related to the issuance and sale by the Company of the Securities have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission, and any request on the part of the Commission for additional information has been complied with. The Registration Statement was filed with the Commission on July 14, 2015.

(3) Registration Statement, Prospectus and Disclosure at Time of Sale . At the respective times that the Registration Statement and any amendments thereto became effective, at each time subsequent to the filing of the Registration Statement that the Company filed an Annual Report on Form 10-K (or any amendment thereto) with the Commission, at each deemed effective date with respect to the Underwriters pursuant to Rule 430B(f)(2), and at the Closing Date, the Registration Statement and any amendments to any of the foregoing complied and will comply in all material respects with the requirements of the 1933 Act, the 1933 Act Regulations and the 1939 Act and did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

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As of its date, at the respective times the Prospectus or any amendment or supplement thereto was filed pursuant to Rule 424(b), at the Closing Date, and at any time when a prospectus is required (or, but for the provisions of Rule 172, would be required) by applicable law to be delivered in connection with sales of Securities (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise), neither the Prospectus nor any amendments or supplements thereto included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

As of the Applicable Time and as of each time prior to the Closing Date that an investor agrees (orally or in writing) to purchase any Securities from the Underwriters, neither (x) the Pricing Term Sheet (as defined in Section 3(m) below), any other Issuer General Use Free Writing Prospectuses, if any, issued at or prior to the Applicable Time and the Pre-Pricing Prospectus as of the Applicable Time, all considered together (collectively, the “ General Disclosure Package ”), nor (y) any individual Issuer Limited Use Free Writing Prospectus, when considered together with the General Disclosure Package, included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

Each preliminary prospectus and the Prospectus and any amendments or supplements to any of the foregoing filed as part of the Registration Statement or any amendment thereto, filed pursuant to Rule 424 under the 1933 Act, or delivered to the Underwriters for use in connection with the offering of the Securities, complied when so filed or when so delivered, as the case may be, in all material respects with the 1933 Act and the 1933 Act Regulations.

The representations and warranties in the preceding paragraphs of this Section 1(a)(3) do not apply to statements in or omissions from the Registration Statement, any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative expressly for use therein, it being understood and agreed that the only such information furnished by the Underwriters as aforesaid consists of the information described as such in Section 6(b) hereof.

At the respective times that the Registration Statement or any amendment thereto was filed, as of the earliest time after the filing of the Registration Statement that the Company or any other offering participant made a bona fide offer of the Securities within the meaning of Rule 164(h)(2), and at the date hereof, the Company was not and is not an “ineligible issuer” as defined in Rule 405, in each case without taking into account any determination made by the Commission pursuant to paragraph (2) of the definition of such term in Rule 405; and without limitation to the foregoing, the Company has at all relevant times met, meets and will at all relevant times meet the requirements of Rule 164 for the use of a free writing prospectus (as defined in Rule 405) in connection with the offering contemplated hereby.

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The copies of the Registration Statement and any amendments thereto and the copies of each preliminary prospectus, each Issuer Free Writing Prospectus that is required to be filed with the Commission pursuant to Rule 433 and the Prospectus and any amendments or supplements to any of the foregoing, that have been or subsequently are delivered to the Underwriters in connection with the offering of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise) were and will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T of the Commission. For purposes of this Agreement, references to the “delivery” or “furnishing” of any of the foregoing documents to the Underwriters, and any similar terms, include, without limitation, electronic delivery.

Each Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the completion of the public offering and sale of the Securities did not, does not and will not include any information that conflicted, conflicts or will conflict with the information contained in the Registration Statement, any preliminary prospectus or the Prospectus that has not been superseded or modified.

(4) Incorporated Documents . The documents incorporated or deemed to be incorporated by reference in the Registration Statement, any preliminary prospectus and the Prospectus, at the respective times they were or hereafter are filed with the Commission, complied and will comply in all material respects with the requirements of the 1934 Act and the 1934 Act Regulations and did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

(5) Independent Accountants . Ernst & Young LLP, who have reported upon the audited financial statements and any supporting schedules included in the Registration Statement, the General Disclosure Package and the Prospectus are independent public accountants with respect to the Company as required by the 1933 Act, the 1933 Act Regulations, the 1934 Act, the 1934 Act Regulations and the PCAOB.

(6) Financial Statements . The historical financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus comply as to form in all material respects with the applicable requirements of Regulation S-X under the 1933 Act and present fairly in all material respects the financial condition, results of operations and cash flows of the consolidated businesses purported to be shown thereby at the dates and for the periods indicated, all in conformity with GAAP applied on a consistent basis throughout the periods involved (except as otherwise noted therein).

To the knowledge of the Company, the historical financial statements of the Thunder Entities included in the Registration Statement, the General Disclosure Package and the Prospectus present fairly in all material respects the financial condition, results of operations and cash flows of the consolidated businesses purported to be shown thereby at the dates and for the periods indicated, and except as described in the Registration Statement, the General Disclosure Package and the Prospectus, in conformity with GAAP

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applied on a consistent basis throughout the periods involved (except as otherwise noted therein).

The unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus include assumptions that provide a reasonable basis for presenting the significant effects directly attributable to the transactions and events described therein, the related pro forma adjustments give appropriate effect to those assumptions, and the pro forma adjustments reflect the proper application of those adjustments to the historical financial statement amounts in the unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus. The aforementioned unaudited pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Prospectus comply as to form in all material respects with the applicable requirements of Regulation S-X under the 1933 Act.

The Company’s ratios of earnings to fixed charges included in the Registration Statement, the General Disclosure Package and the Prospectus comply with Item 503(d) of Regulation S-K of the Commission. All “non-GAAP financial measures” (as such term is defined in the rules and regulations of the Commission), if any, contained in the Registration Statement, the General Disclosure Package and the Prospectus comply with Item 10 of Regulation S-K of the Commission, to the extent applicable.

(7) No Material Adverse Change in Business . Since the date of the latest audited financial statements included in the General Disclosure Package, none of the Company, its Significant Subsidiaries (as defined below) or, to the knowledge of the Company, the Thunder Entities have sustained any loss or interference with its business from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree, or incurred any material liability or obligation, direct or contingent, other than liabilities and obligations that were incurred in the ordinary course of business, which would be reasonably likely to result in any Material Adverse Effect (as defined below), nor has there been any development involving a material adverse change in or affecting the financial condition, results of operations, business or prospects of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, otherwise than as disclosed in the General Disclosure Package and the Prospectus. Since the respective dates as of which information is given in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) or since the date of the General Disclosure Package, after giving effect to the Acquisition, there has not been (i) any material change in the capital stock or long-term debt of the Company or its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities, (ii) any material adverse change in or affecting the financial condition, results of operations, business or prospects of the Company or its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities, or (iii) any transaction entered into by any of the Company or its Significant Subsidiaries, other than in the ordinary course of business, that is material to the Company and its Significant Subsidiaries (taken as a whole) or, to the knowledge of the Company, the Thunder Entities other than as disclosed, in the case of each of (i), (ii) or (iii) above, in the General

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Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto).

(8) Good Standing of the Company and Significant Subsidiaries . Each of the Company, its “significant subsidiaries,” as defined in Rule 1-02(w) of Regulation S-X under the 1934 Act (each, a “ Significant Subsidiary ”) and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, has been duly organized, is validly existing and in good standing as a corporation or other business entity under the laws of its jurisdiction of organization and is duly qualified to do business and in good standing as a foreign corporation or other business entity in each jurisdiction in which its ownership or lease of property or the conduct of its businesses requires such qualification, except where the failure to be so qualified or in good standing would not have a material adverse effect on the financial condition, results of operations, business or prospects of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition (a “ Material Adverse Effect ”). Each of the Company, its Significant Subsidiaries and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition has all power and authority necessary to own or hold its properties and to conduct its business as described in the General Disclosure Package and the Prospectus. The subsidiaries listed on Exhibit B hereto are (a) the only Significant Subsidiaries of the Company as of the date hereof and (b) the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition.

(9) Capitalization . The Company has the capitalization as set forth in each of the General Disclosure Package and the Prospectus; all the issued shares of capital stock of the Company have been duly authorized and validly issued, are fully paid and non-assessable; all of the issued shares of capital stock or other equity interests, as applicable, of each Significant Subsidiary of the Company that are owned directly or indirectly by the Company have been duly authorized and validly issued and are fully paid (to the extent required under such entities’ Organizational Documents) and non-assessable (except as such non-assessability may be affected by Sections 18-607 and 18-804 of the Delaware Limited Liability Company Act or Sections 17-303, 17-607 and 17-804 of the Delaware Revised Uniform Limited Partnership Act) and are owned directly or indirectly by the Company free and clear of all liens, encumbrances, security interests, equities charges or claims (collectively, “ Liens ”) except (i) as disclosed in the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) or (ii) to the extent any such Liens would not have a Material Adverse Effect.

(10) Due Authorization; Authorization of Agreement . The Company has all requisite corporate power and authority to execute, deliver and perform its obligations under this Agreement. This Agreement has been duly authorized, executed and delivered by the Company and, assuming due authorization, execution and delivery by the Representative, constitutes the valid and binding agreement of the Company, enforceable against the Company in accordance with its terms, subject to (i) the effects of bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other similar laws relating to or affecting creditors’ rights generally, (ii) general equitable principles

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(whether considered in a proceeding in equity or at law), and (iii) except as rights to indemnity and contribution hereunder may be limited by federal or state securities laws or principles of public policy.

(11) The Indenture . The Company has all requisite corporate power and authority to execute, deliver and perform its obligations under the Indenture. The Base Indenture has been duly authorized, executed and delivered by the Company, and, assuming due authorization, execution and delivery by the Trustee, constitutes the valid and binding agreement of the Company, enforceable against the Company in accordance with its terms, subject to (i) the effects of bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other similar laws relating to or affecting creditors’ rights generally and (ii) general equitable principles (whether considered in a proceeding in equity or at law); the Second Supplemental Indenture has been duly authorized, and upon its execution and delivery by the Company, and, assuming due authorization, execution and delivery by the Trustee, will constitute the valid and binding agreement of the Company, enforceable against the Company in accordance with its terms, subject to (i) the effects of bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other similar laws relating to or affecting creditors’ rights generally and (ii) general equitable principles (whether considered in a proceeding in equity or at law). The Indenture has been duly qualified under the 1939 Act.

(12) The Securities . The Company has all requisite corporate power and authority to execute, deliver and perform its obligations under the Securities. The Securities have been duly authorized by the Company and when duly executed by the Company in accordance with the terms of the Indenture and, assuming due authentication, execution and delivery of the Securities by the Trustee in accordance with the terms of the Indenture, upon delivery to the Underwriters against payment therefor in accordance with the terms hereof, will have been validly issued and delivered, and will constitute valid and binding obligations of the Company entitled to the benefits of the Indenture, enforceable against the Company in accordance with their terms, subject to (i) the effects of bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance and other similar laws relating to or affecting creditors’ rights generally, (ii) general equitable principles (whether considered in a proceeding in equity or at law) and (iii) except as rights to indemnity and contribution thereunder may be limited by federal or state securities laws or principles of public policy.

(13) Description of the Securities and the Indenture . The Securities and the Indenture conform and will conform in all material respects to the respective statements relating thereto contained in the Registration Statement, the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) and are and will be in substantially the respective forms filed or incorporated by reference, as the case may be, as exhibits to the Registration Statement.

(14) Absence of Defaults and Conflicts . None of the Company, its Significant Subsidiaries or, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is (i) in violation of its Organizational Documents, (ii) in default, and no

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event has occurred which, with notice or lapse of time or both, would constitute such a default, in the due performance or observance of any term, obligation, agreement, covenant or condition contained in any material contract, indenture, mortgage, deed of trust, loan agreement, lease or other agreement or instrument to which it is a party or by which it is bound or which any of its properties or assets may be subject or (iii) in violation of any law, ordinance, governmental rule, regulation or court decree to which it or its property or assets may be subject, except, with respect to (ii) or (iii), for any such violations or defaults that would not be reasonably likely, singly or in the aggregate, to have a Material Adverse Effect. The execution and delivery of the Transaction Documents by the Company, the consummation of the transactions contemplated hereby and thereby, the application of the proceeds from the sale of the Securities as described under “Use of Proceeds” in the General Disclosure Package and the Prospectus will not (i) conflict with or result in a breach or violation of any of the terms or provisions of, impose any Lien, charge or encumbrance upon any property or assets of the Company, its Significant Subsidiaries and, to the knowledge of the Company, the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition under, or constitute a default under, any indenture, mortgage, deed of trust, loan agreement, license, lease or other agreement or instrument to which the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is a party or by which the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is bound or to which any of the property or assets of the Company, any of its Significant Subsidiaries or any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition is subject; (ii) result in any violation of the provisions of the Organizational Documents of the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition; or (iii) result in any violation of any statute or any judgment, order, decree, rule or regulation of any court or governmental agency or body having jurisdiction over the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, or any of their respective properties or assets, except with respect to clauses (i) and (iii), conflicts, breaches, violations or defaults that would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.

(15) Absence of Labor Dispute . No labor disturbance by or dispute with the employees of the Company or any of its affiliates that are dedicated to the Company’s business or, to the knowledge of the Company, any of the Thunder Entities, exists or, to the knowledge of the Company, is imminent that would reasonably be expected to have a Material Adverse Effect.

(16) Absence of Proceedings . Except as described in the General Disclosure Package and the Prospectus, there are no legal or governmental proceedings pending to which the Company or any of its subsidiaries or, to the knowledge of the Company, any

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of the Thunder Entities, is a party or of which any property or assets of the Company or any of its subsidiaries or, to the knowledge of the Company, any of the Thunder Entities, is the subject that would, in the aggregate, reasonably be expected to have a Material Adverse Effect or would, in the aggregate, reasonably be expected to have a material adverse effect on the performance by the Company of its obligations under the Transaction Documents or the consummation of the transactions contemplated hereby and thereby; and to the Company’s knowledge, no such proceedings are threatened or contemplated by governmental authorities or others.

(17) Accuracy of Descriptions and Exhibits . The information in the Pre-Pricing Prospectus and the Prospectus under the captions “Description of Debt Securities,” “Description of Notes” and “Material U.S. Federal Income Tax Considerations” and the information in the Company’s Annual Report on Form 10-K for the fiscal year ended 2014 under the captions “Business—Regulatory Matters,” “Business—Environmental Matters” and “Legal Proceedings,” insofar as they purport to constitute summaries of the terms of statutes, rules or regulations, legal or governmental proceedings or contracts and other documents, constitute accurate summaries of the terms of such statutes, rules and regulations, legal and governmental proceedings and contracts and other documents in all material respects; and there are no franchises, contracts, indentures, mortgages, deeds of trust, loan or credit agreements, bonds, notes, debentures, evidences of indebtedness, leases or other instruments, agreements or documents required to be described or referred to in the Registration Statement, the Pre-Pricing Prospectus or the Prospectus or the documents incorporated or deemed to be incorporated by reference therein or to be filed as exhibits thereto which have not been so described and filed as required.

(18) Absence of Further Requirements . No filing with, or authorization, approval, consent, license, order, registration, qualification or decree of, any court or governmental authority or agency, domestic or foreign is necessary or required for the execution, delivery or performance by the Company of its obligations under the Transaction Documents, for the offering, issuance, sale or delivery of the Securities hereunder, or for the consummation of any of the other transactions contemplated by this Agreement, in each case on the terms contemplated by the Registration Statement, the General Disclosure Package and the Prospectus, except such as have been obtained under the 1933 Act, the 1933 Act Regulations or the 1939 Act, except for the filing of the Prospectus and the Pricing Term Sheet pursuant to Rules 424(b) and 433, respectively, except as have been obtained prior to the execution hereof and except that no representation is made as to such as may be required under state or foreign securities laws.

(19) Possession of Licenses and Permits . The Company and each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, have such permits, licenses, franchises, certificates of need and other approvals or authorizations of governmental or regulatory authorities (“ Permits ”) as are necessary under applicable law to own, hold or lease, as the case may be, and to operate their properties and conduct their businesses in the manner described in

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the Registration Statement, the General Disclosure Package or the Prospectus, except where the failure to possess such Permits would not reasonably be expected to have a Material Adverse Effect. None of the Company, any of its Significant Subsidiaries or, to the knowledge of the Company, any of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, has received notice of any revocation or modification of any such Permits except to the extent that any such revocation or modification would not have a Material Adverse Effect.

(20) Title to Property . Except as described in the Registration Statement, the General Disclosure Package or the Prospectus, the Company has, directly or indirectly through its subsidiaries, and, to the knowledge of the Company, Thunder, directly or indirectly through its subsidiaries, has, good and marketable title to all real property and good title to all personal property described in the Registration Statement, the General Disclosure Package or the Prospectus as being owned by it and valid, legal and defensible title to the interests in oil and gas properties underlying the estimates of the Company’s proved reserves described in the Registration Statement, the General Disclosure Package or the Prospectus, in each case free and clear of all liens, encumbrances and defects except (i) as are described in the Registration Statement, the General Disclosure Package or the Prospectus, (ii) as do not materially interfere with the use made in the aggregate of such properties, as described in the Registration Statement, the General Disclosure Package or the Prospectus, (iii) as are permitted under the Existing Facility, or (iv) as would not reasonably be expected to have a Material Adverse Effect; and the working interests derived from oil, gas and mineral leases or mineral interests which constitute a portion of the real property held or leased by the Company, its subsidiaries and the Thunder Entities reflect in all material respects the right of the Company and its subsidiaries and, to the knowledge of the Company, each of the Thunder Entities, to explore, develop or produce hydrocarbons from such real property, and the care taken by the Company and its subsidiaries and, to the knowledge of the Company, each of the Thunder Entities, with respect to acquiring or otherwise procuring such leases or mineral interests was generally consistent with standard industry practices in the areas in which the Company and its subsidiaries operate for acquiring or procuring leases and interests therein to explore, develop or produce hydrocarbons.

(21) Investment Company Act . The Company is not, and after giving effect to the offer and sale of the Securities and the application of the proceeds therefrom as described in the General Disclosure Package and the Prospectus, will not be, an “investment company” as defined in the 1940 Act.

(22) Reserve Engineers . Netherland, Sewell & Associates Inc., who issued a report with respect to certain of the Company’s oil and natural gas reserves and who has delivered or will deliver the letters referred to in Sections 5(j) and 5(k) hereof, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Company.

To the knowledge of the Company, LaRoche Petroleum Consultants, Ltd., who issued a report with respect to certain of the Thunder Entities’ oil and natural gas reserves and who has delivered or will deliver the letters referred to in Sections 5(l) and 5(m)

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hereof, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Thunder Entities.

(23) Reserve Data . The factual information underlying the estimates of reserves of the Company and, to the knowledge of the Company, Thunder, which was supplied to the independent petroleum engineers referenced in Section 1(a)(22) for the purposes of preparing the audit reports of the estimates of proved reserves included in the Registration Statement, the General Disclosure Package and the Prospectus, including, without limitation, production, costs of operation and development, current prices for production, agreements relating to current and future operations and sales of production, was true and correct in all material respects on the dates such estimates were made and such information was supplied and was prepared in accordance with customary industry practices; other than normal production of the reserves, intervening market commodity price fluctuations, fluctuations in demand for such products, adverse weather conditions, unavailability or increased costs of rigs, equipment, supplies or personnel, the timing of third party operations and other factors, in each case in the ordinary course of business, the Company is not aware of any facts or circumstances that would result in a material adverse change in the aggregate net reserves, or the present value of future net cash flows therefrom, as described in the Registration Statement, the General Disclosure Package and the Prospectus; estimates of such reserves and present values as described in the Registration Statement, the General Disclosure Package and the Prospectus comply in all material respects with the applicable requirements of Regulation S-X and Subpart 1200 of Regulation S-K under the Act.

(24) Environmental Laws . The Company, each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition, (i) is in compliance with all laws, regulations, ordinances, rules, orders, judgments, decrees, permits or other legal requirements of any governmental authority, including without limitation any international, foreign, national, state, provincial, regional, or local authority, relating to pollution, the protection of human health or safety, the environment, or natural resources, or to the use, handling, storage, manufacturing, transportation, treatment, discharge, disposal or release of hazardous or toxic substances or wastes, pollutants or contaminants (“ Environmental Laws ”) applicable to such entity, which compliance includes, without limitation, obtaining, maintaining and complying with all permits, authorizations and approvals required by Environmental Laws to conduct its respective business, and (ii) has not received notice or otherwise has knowledge of any actual or alleged violation of Environmental Laws, or of any actual or potential liability for or other obligation concerning the presence, disposal or release of hazardous or toxic substances or wastes, pollutants or contaminants, except, with respect to (i) and (ii), as may be disclosed in the Registration Statement, the General Disclosure Package and the Prospectus and except where such noncompliance with Environmental Laws, failure to obtain or maintain required permits, authorizations or approvals or failure to comply with the terms and conditions of such permits, authorizations or approvals would not be reasonably likely to have a Material Adverse Effect.

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(25) Absence of Registration Rights . There are no persons with registration rights or other similar rights to have any securities (debt or equity) registered pursuant to the Registration Statement or included in the offering contemplated by this Agreement.

(26) FINRA Matters . All of the information provided to the Representative or to counsel for the Underwriters in connection with any letters, filings or other supplemental information provided to FINRA pursuant to FINRA Rule 5110 or 5121 is true, complete and correct.

(27) Tax Returns . The Company, all of its subsidiaries and, to the knowledge of the Company, all of the Thunder Entities, have filed all federal, state, local and foreign income and franchise tax returns which are required to be filed by them and have paid all taxes due, other than those which, if not filed or paid, would not be reasonably expected to have a Material Adverse Effect, or which are being contested in good faith by appropriate proceedings. Except as would not be reasonably expected to have a Material Adverse Effect, no tax deficiency has been determined adversely to the Company, any of its subsidiaries or, to the knowledge of the Company, the Thunder Entities, and the Company has no knowledge of any tax deficiencies that have been, or would reasonably be expected to be asserted.

(28) Insurance . The Company, each of its Significant Subsidiaries and, to the knowledge of the Company, each of the Thunder Entities that the Company expects to be Significant Subsidiaries of the Company upon giving effect to the Acquisition carry, or are covered by, insurance in such amounts and covering such risks as is reasonable in accordance with customary practices for companies engaged in similar businesses in similar industries for the conduct of their respective businesses and the value of their respective properties.

(29) Accounting and Disclosure Controls . The Company maintains a system of internal control over financial reporting (as such term is defined in Rule 13a-15(f) of the 1934 Act) that complies with the requirements of the 1934 Act and that has been designed by, or under the supervision of, the Company’s principal executive and principal financial officers, or persons performing similar functions, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles in the United States. The Company maintains internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorization, (ii) transactions are recorded as necessary to permit preparation of the Company’s financial statements in conformity with accounting principles generally accepted in the United States and to maintain accountability for its assets, (iii) access to the Company’s assets is permitted only in accordance with management’s general or specific authorization, (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences, and (v) the interactive data in eXtensible Business Reporting Language included or incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus is prepared in accordance with the Commission’s rules and guidelines applicable thereto. As of the date

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of the most recent balance sheet of the Company reviewed or audited by Ernst & Young LLP and the audit committee of the board of directors of the Company, there were no material weaknesses in the Company’s internal controls.

The Company maintains disclosure controls and procedures (as such term is defined in Rules 13a-15(e) and 15d-15(e) under the 1934 Act); and such disclosure controls and procedures (i) are designed to ensure that information required to be disclosed by the Company in the reports it files or submits under the 1934 Act is accumulated and communicated to the Company’s management, including the Company’s principal executive officer and principal financial officer, as appropriate, to allow timely decisions regarding required disclosure and (ii) except with respect to the material weaknesses in internal controls disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, such disclosure controls and procedures are effective at a reasonable assurance level to perform the functions for which they were established.

Except as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, since the date of the most recent balance sheet of the Company reviewed or audited by Ernst & Young LLP and the audit committee of the board of directors of the Company, (i) the Company has not been advised of or become aware of (A) any significant deficiencies in the design or operation of internal controls that could adversely affect the ability of the Company or any of its subsidiaries to record, process, summarize and report financial data, or any material weaknesses in internal controls, or (B) any fraud, whether or not material, that involves management or other employees who have a significant role in the internal controls of the Company and each of its subsidiaries; and (ii) there have been no significant changes in internal controls or in other factors that could significantly affect internal controls, including any corrective actions with regard to significant deficiencies and material weaknesses, except as may be disclosed in the Registration Statement, the General Disclosure Package and the Prospectus.

(30) Compliance with the Sarbanes-Oxley Act . The Company is in compliance in all material respects with the applicable provisions of the Sarbanes-Oxley Act and the rules and regulations promulgated in connection therewith.

(31) Pending Proceedings and Examinations; Comment Letters . The Registration Statement is not the subject of a pending proceeding or examination under Section 8(d) or 8(e) of the 1933 Act, and the Company is not the subject of a pending proceeding under Section 8A of the 1933 Act. The Company has provided the Representative with true, complete and correct copies of any written comments received from the Commission by the Company or its legal counsel or accountants, and of any transcripts made by the Company, its legal counsel or accountants of any oral comments received from the Commission, with respect to the Registration Statement, any preliminary prospectus, the Prospectus, any Issuer Free Writing Prospectus or any document incorporated or deemed to be incorporated by reference therein or any amendments or supplements to any of the foregoing and of all written responses thereto

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(in each case other than comment letters or written responses that are publicly available on EDGAR).

(32) Absence of Manipulation . The Company and its affiliates (as defined in Rule 501(b) of Regulation D under the 1933 Act) have not taken, directly or indirectly, any action designed to or that might reasonably be expected to cause or result, under the 1934 Act or otherwise, in stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(33) Statistical and Market-Related Data . The statistical and market-related data included in the Registration Statement, the General Disclosure Package or the Prospectus is based on or derived from sources that the Company believes to be reliable in all material respects.

(34) No Unlawful Payments . Neither the Company nor any of its subsidiaries nor, to the knowledge of the Company, any of the Thunder Entities, or any director, officer, agent, employee or affiliate of the Company or any of its subsidiaries is aware of or has taken any action, directly or indirectly, that could result in a violation or a sanction for violation by such persons of the Foreign Corrupt Practices Act of 1977 or the U.K. Bribery Act 2010, each as may be amended, or similar law of any other relevant jurisdiction, or the rules or regulations thereunder; and the Company and its subsidiaries and, to the knowledge of the Company, the Thunder Entities, have instituted and maintain policies and procedures to ensure compliance therewith. No part of the proceeds of the offering will be used, directly or indirectly, in violation of the Foreign Corrupt Practices Act of 1977 or the U.K. Bribery Act 2010, each as may be amended, or similar law of any other relevant jurisdiction, or the rules or regulations thereunder.

(35) Money Laundering Laws . The operations of the Company and its subsidiaries and, to the knowledge of the Company, the Thunder Entities, are and have been conducted at all times in compliance with applicable financial recordkeeping and reporting requirements and the money laundering statutes and the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “ Money Laundering Laws ”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries or, to the knowledge of the Company, any of the Thunder Entities, with respect to the Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(36) No Conflicts with Sanctions Laws . None of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities and, to the knowledge of the Company, none of the Company’s or its subsidiaries’ directors, officers, agents, employees or affiliates (i) is, or is controlled or 50% or more owned by or is acting on behalf of, an individual or entity that is currently subject to any sanctions administered or enforced by the United States (including any administered or enforced by the Office of Foreign Assets Control of the U.S. Treasury Department, the U.S. Department of State, or the Bureau of Industry and Security of the U.S. Department of Commerce), the United Nations Security Council, the European Union, the United Kingdom (including sanctions

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administered or enforced by Her Majesty’s Treasury) or other relevant sanctions authority (collectively, “Sanctions” and such persons, “Sanctioned Persons”), (ii) is located, organized or resident in a country or territory that is, or whose government is, the subject of Sanctions that broadly prohibit dealings with that country or territory (collectively, “Sanctioned Countries” and each, a “Sanctioned Country”) or (iii) will, directly or indirectly, use the proceeds of this offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other individual or entity in any manner that would result in a violation of any Sanctions by, or could result in the imposition of Sanctions against, any individual or entity (including any individual or entity participating in the offering, whether as underwriter, advisor, investor or otherwise). Except as has been disclosed to the Underwriters or is not material to the analysis under any Sanctions, none of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities has engaged in any dealings or transactions with or for the benefit of a Sanctioned Person, or with or in a Sanctioned Country, in the preceding 3 years, and none of the Company, its subsidiaries or, to the knowledge of the Company, the Thunder Entities have any plans to increase its dealings or transactions with or for the benefit of Sanctioned Persons, or with or in Sanctioned Countries.

(37) Offering Materials . Without limitation to the provisions of Section 17 hereof, the Company has not distributed and will not distribute, directly or indirectly (other than through the Underwriters), any “written communication” (as defined Rule 405 under the 1933 Act) or other offering materials in connection with the offering or sale of the Securities, other than the Pre-Pricing Prospectus, the Prospectus, any amendment or supplements to any of the foregoing that are filed with the SEC and any Permitted Free Writing Prospectuses (as defined in Section 17).

(38) Brokers . The Company has not paid or agreed to pay to any person any compensation for soliciting another to purchase the Securities (except as contemplated in this Agreement).

(b) Certificates . Any certificate signed by any officer of the Company or any of its subsidiaries (whether signed on behalf of such officer, the Company or such subsidiary) and delivered to the Representative or to counsel for the Underwriters shall be deemed a representation and warranty by the Company to each Underwriter as to the matters covered thereby.

SECTION 2. Sale and Delivery to Underwriters; Closing .

(a) The Securities . On the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Company agrees to sell to each Underwriter, severally and not jointly, and each Underwriter, severally and not jointly, agrees to purchase from the Company, the aggregate principal amount of Securities set forth opposite such Underwriter’s name in Exhibit A hereto plus any additional principal amount of Securities which such Underwriter may become obligated to purchase pursuant to the provisions of Section 10 hereof, at a price equal to 98.75% of the principal amount thereof with respect to the 2020 Notes and 98.75% of the principal amount thereof with respect to the 2023 Notes.

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(b) Payment . Payment of the purchase price for, and delivery of, the Securities shall be made at the offices of Simpson Thacher & Bartlett LLP, 425 Lexington Avenue, New York, New York 10017, or at such other place as shall be agreed upon by the Representative and the Company, at 10:00 A.M. (New York City time) on July 22, 2015 (unless postponed in accordance with the provisions of Section 10), or such other time not later than five business days after such date as shall be agreed upon by the Representative and the Company (such time and date of payment and delivery being herein called “ Closing Date ”).

Payment shall be made to the Company by wire transfer of immediately available funds to a single bank account designated by the Company against delivery to the Representative for the respective accounts of the Underwriters of the Securities to be purchased by them. It is understood that each Underwriter has authorized the Representative, for its account, to accept delivery of, receipt for, and make payment of the purchase price for, the Securities which it has agreed to purchase. Barclays, individually and not as representative of the Underwriters, may (but shall not be obligated to) make payment of the purchase price for the Securities to be purchased by any Underwriter whose funds have not been received by the Closing Date, but such payment shall not relieve such Underwriter from its obligations hereunder.

(c) Delivery of Securities . The Company shall make one or more global certificates (collectively, the “ Global Securities ”) representing the Securities available for inspection by the Representative not later than 3:00 p.m., New York City time, on the business day prior to the Closing Date and, on or prior to the Closing Date, the Company shall deliver the Global Securities to DTC or to the Trustee, acting as custodian for DTC, as applicable. Delivery of the Securities to the Underwriters on the Closing Date shall be made through the facilities of DTC unless the Representative shall otherwise instruct.

SECTION 3. Covenants of the Company . The Company covenants with each Underwriter as follows:

(a) Compliance with Securities Regulations and Commission Requests . The Company, subject to Section 3(b), will comply with the requirements of Rule 430B and Rule 433 and will notify the Representative immediately, and confirm the notice in writing from the Applicable Time through the Closing Date (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)), (i) when the Registration Statement or any post-effective amendment to the Registration Statement shall become effective, or when any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing shall have been filed, (ii) of the receipt of any comments from the Commission (and shall promptly furnish the Representative with a copy of any comment letters and any transcript of oral comments, and shall furnish the Representative with copies of any written responses thereto a reasonable amount of time prior to the proposed filing thereof with the Commission and will not file any such response to which the Representative or counsel for the Underwriters shall reasonably object), (iii) of any request by the Commission for any amendment to the Registration Statement or any amendment or supplement to any preliminary prospectus or the Prospectus or any Issuer Free Writing Prospectus or for

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additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any order preventing or suspending the use of any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing or any notice from the Commission objecting to the use of the form of the Registration Statement or any post-effective amendment thereto, or of the suspension of the qualification of the Securities for offering or sale in any jurisdiction or of the loss or suspension of any exemption from any such qualification, or of the initiation or threatening of any proceedings for any of such purposes, or of any examination pursuant to Section 8(e) of the 1933 Act concerning the Registration Statement and (v) of the initiation or threatening of any proceeding under Section 8A of the 1933 Act in connection with the offering of the Securities. The Company will make every reasonable effort to prevent the issuance of any stop order and the suspension or loss of any qualification of the Securities for offering or sale and any loss or suspension of any exemption from any such qualification, and if any such stop order is issued, or any such suspension or loss occurs, to obtain the lifting thereof at the earliest possible moment. The Company shall pay the required Commission filing fees relating to the Securities within the time required by Rule 456(b)(1)(i) of the 1933 Act Regulations without regard to the proviso therein and otherwise in accordance with Rules 456(b) and 457(r) of the 1993 Act Regulations, except to the extent such filing fees have been paid prior to the date hereof.

(b) Filing of Amendments . From the Applicable Time through the Closing Date (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)), the Company will give the Representative notice of its intention to file or prepare any amendment to the Registration Statement, any Issuer Free Writing Prospectus or any amendment, supplement or revision to any preliminary prospectus, the Prospectus or any Issuer Free Writing Prospectus, whether pursuant to the 1933 Act or otherwise, and the Company will furnish the Representative with copies of any such documents within a reasonable amount of time prior to such proposed filing or use, as the case may be, and will not file or use any such document to which the Representative or counsel for the Underwriters shall reasonably object. The Company has given the Representative notice of any filings made pursuant to the 1934 Act or the 1934 Act Regulations within 48 hours prior to the Applicable Time; the Company will give the Representative notice of its intention to make any such filing from the Applicable Time through the Closing Date (or, if later, through the end of the period during which the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the requests of purchasers pursuant to Rule 173(d) or otherwise)) and will furnish the Representative with copies of any such documents a reasonable amount of time prior to such proposed filing, as the case may be, and will not file or use any such document to which the Representative or counsel for the Underwriters shall reasonably object.

(c) Delivery of Registration Statements . If requested, the Company has furnished or will deliver to the Representative and counsel for the Underwriters, without

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charge, copies of the Registration Statement and of each amendment thereto (including exhibits filed therewith or incorporated by reference therein and documents incorporated or deemed to be incorporated by reference therein or otherwise deemed to be a part thereof) and copies of all consents and certificates of experts. The copies of the Registration Statement and each amendment thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(d) Delivery of Prospectuses . The Company has delivered to each Underwriter, without charge, as many copies of each preliminary prospectus and any amendments or supplements thereto as such Underwriter reasonably requested, and the Company hereby consents to the use of such copies for purposes permitted by the 1933 Act. The Company will furnish to each Underwriter, without charge, during the period when the Prospectus is required (or, but for the provisions of Rule 172, would be required) to be delivered by applicable law (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), such number of copies of the Pre-Pricing Prospectus, the Prospectus and any Issuer Free Writing Prospectus and any amendments or supplements to any of the foregoing as such Underwriter may reasonably request. Each preliminary prospectus, the Prospectus, each Issuer Free Writing Prospectus and any amendments or supplements to any of the foregoing furnished to the Underwriters were and will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(e) Continued Compliance with Securities Laws . The Company will comply with the 1933 Act, the 1933 Act Regulations, the 1934 Act and the 1934 Act Regulations so as to permit the completion of the distribution of the Securities as contemplated by this Agreement, the General Disclosure Package and the Prospectus. If at any time when a prospectus is required (or, but for the provisions of Rule 172, would be required) by the applicable law to be delivered in connection with sales of the Securities (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), any event shall occur or condition shall exist as a result of which it is necessary to amend the Registration Statement or amend or supplement the General Disclosure Package or the Prospectus (or, in each case, any documents incorporated or deemed to be incorporated by reference therein) so that the Registration Statement, the General Disclosure Package or the Prospectus, as the case may be, will not include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made or then prevailing, not misleading or if it is necessary to amend the Registration Statement or amend or supplement the General Disclosure Package or the Prospectus (or, in each case, any documents incorporated or deemed to be incorporated by reference therein) in order to comply with the requirements of the 1933 Act, the 1933 Act Regulations, the 1934 Act or the 1934 Act Regulations, the Company will promptly notify the Representative of such event or condition and of its intention to file such amendment or supplement and will promptly prepare and file with the Commission, subject to Section 3(b) hereof, such amendment or supplement as may be necessary to correct such untrue statement or omission or to comply with such requirements, and, in the case of an amendment or post-effective amendment to the Registration Statement, the Company will use its commercially reasonable efforts to have

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such amendment declared or become effective as soon as practicable and the Company, if requested, will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request. If at any time an Issuer Free Writing Prospectus conflicts with the information contained in the Registration Statement or if an event shall occur or condition shall exist as a result of which it is necessary to amend or supplement such Issuer Free Writing Prospectus so that it will not include an untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made or then prevailing, not misleading, or if it is necessary to amend or supplement such Issuer Free Writing Prospectus in order to comply with the requirements of the 1933 Act or the 1933 Act Regulations, the Company will promptly notify the Representative of such event or condition and of its intention to file such amendment or supplement and will promptly prepare and, if required by the 1933 Act or the 1933 Act Regulations, file with the Commission, subject to Section 3(b) hereof, such amendment or supplement as may be necessary to eliminate or correct such conflict, untrue statement or omission or to comply with such requirements, and the Company will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request.

(f) Blue Sky and Other Qualifications . The Company will furnish such information as may be required and otherwise cooperate with the Underwriters to qualify the Securities for offering and sale, or to obtain an exemption for the Securities to be offered and sold, under the applicable securities laws of such states and other jurisdictions (domestic or foreign) as the Representative may reasonably designate and to maintain such qualifications and exemptions in effect for so long as required for the distribution of the Securities (but in no event for a period of not less than one year from the date of this Agreement); provided, however, that the Company shall not be obligated to file any general consent to service of process or to qualify as a foreign corporation or as a dealer in securities in any jurisdiction in which it is not so qualified or to subject itself to taxation in respect of doing business in any jurisdiction in which it is not otherwise so subject. In each jurisdiction in which the Securities have been so qualified or exempt, the Company will file such statements and reports as may be required by the laws of such jurisdiction to continue such qualification or exemption, as the case may be, in effect for so long as required for the distribution of the Securities (but in no event for a period of not less than one year from the date of this Agreement).

(g) Rule 158 . The Company will make generally available to its securityholders and the Underwriters as soon as practicable an earnings statement that satisfies the last paragraph of Section 11(a) of the 1933 Act and Rule 158 promulgated thereunder.

(h) Use of Proceeds . The Company will use the net proceeds received by it from the sale of the Securities in the manner specified in the Pre-Pricing Prospectus and the Prospectus under “Use of Proceeds.”

(i) Restriction on Sale of Securities . From and including the date of this Agreement through and including the 45th day after the date of this Agreement, the

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Company will not, without the prior written consent of the Representative, directly or indirectly issue, offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option or right to sell or otherwise transfer or dispose of any debt securities of or guaranteed by the Company that are similar to the Securities (other than the Securities issued under this Agreement or in connection with any securities demand by the Representative as contemplated in connection with the financing of the Acquisition) or any securities convertible into or exercisable or exchangeable for any debt securities of or guaranteed by the Company that are similar to the Securities.

(j) Reporting Requirements . The Company, during the period when the Prospectus is required (or, but for the provisions of Rule 172, would be required) by applicable law to be delivered (whether to meet the request of purchasers pursuant to Rule 173(d) or otherwise), will file all documents required to be filed with the Commission pursuant to the 1934 Act and the 1934 Act Regulations within the time periods required by the 1934 Act and the 1934 Act Regulations.

(k) Preparation of Prospectus . Immediately following the execution of this Agreement, the Company will, subject to Section 3(b) hereof, prepare the Prospectus, which shall contain the public offering price and terms of the Securities, the plan of distribution thereof and such other information as may be required by the 1933 Act or the 1933 Act Regulations or as the Representative and the Company may deem appropriate, and will file or transmit for filing with the Commission, in accordance with the provisions of Rule 430B and in the manner and within the time period required by Rule 424(b) (without reliance on Rule 424(b)(8)), the Prospectus.

(l) DTC . The Company will use their best efforts to permit the Securities to be eligible for clearance and settlement through DTC.

(m) Pricing Term Sheet . The Company will prepare a pricing term sheet (the “ Pricing Term Sheet ”) reflecting the final terms of the Securities, in substantially the form attached hereto as Exhibit C and otherwise in form and substance satisfactory to the Representative, and shall file such Pricing Term Sheet as an “issuer free writing prospectus” pursuant to Rule 433 prior to the close of business on the business day following the date hereof; provided that the Company shall furnish the Representative with copies of any such Pricing Term Sheet a reasonable amount of time prior to such proposed filing and will not use or file any such document to which the Representative or counsel to the Underwriters shall reasonably object.

SECTION 4. Payment of Expenses .

(a) Expenses . The Company will pay all expenses incident to the performance of its obligations under this Agreement, including (i) the preparation, printing and filing of the Registration Statement and each amendment thereto (in each case including exhibits) and any costs associated with electronic delivery of any of the foregoing, (ii) the printing (or reproduction) and delivery to the Underwriters of this Agreement, the Indenture and such other documents as may be required in connection with the offering, purchase, sale, issuance or

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delivery of the Securities, (iii) the preparation, issuance and delivery of the certificates for the Securities and the issuance and delivery of the Securities to the Underwriters, including any issue or other transfer taxes and any stamp or other taxes or duties payable in connection with the sale, issuance or delivery of the Securities to the Underwriters, (iv) the fees and disbursements of the counsel, accountants and other advisors to the Company and Thunder, (v) the qualification or exemption of the Securities under securities laws in accordance with the provisions of Section 3(f) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters in connection therewith and in connection with the preparation of the Blue Sky Survey and any supplements thereto, (vi) the preparation, printing and delivery to the Underwriters of copies of each preliminary prospectus, any Permitted Free Writing Prospectus and the Prospectus and any amendments or supplements to any of the foregoing and any costs associated with electronic delivery of any of the foregoing, (vii) the preparation, printing and delivery to the Underwriters of copies of the Blue Sky Survey and any supplements thereto and any costs associated with electronic delivery of any of the foregoing, (viii) the fees and expenses of the Trustee, including the fees and disbursements of counsel for the Trustee in connection with the Indenture and the Securities, (ix) the filing fees incident to, and the reasonable fees and disbursements of counsel to the Underwriters in connection with, the review, if any, by FINRA of the terms of the sale of the Securities, (x) all fees charged by any rating agencies for rating the Securities and all expenses and application fees incurred in connection with the approval of the Securities for clearance, settlement and book-entry transfer through DTC and (xi) the costs and expenses of the Company and any of its officers, directors, counsel or other representatives in connection with presentations or meetings undertaken in connection with the offering of the Securities, including, without limitation, expenses associated with the production of road show slides and graphics and the production and hosting of any electronic road shows, fees and expenses of any consultants engaged in connection with road show presentations, travel, lodging, transportation, and other expenses of the officers, directors, counsel or other representatives of the Company incurred in connection with any such presentations or meetings. Notwithstanding the foregoing, except as otherwise expressly provided in this Section 4(a) and Sections 4(b), 6 and 7 hereof, the Underwriters shall bear their own costs and expenses related to the issuance and sale by the Company of the Securities, including transfer taxes on resale of any Securities by them, and any advertising expenses in connection with any offers they make.

(b) Termination of Agreement . If this Agreement is terminated by the Representative in accordance with the provisions of Section 5 or Section 9 hereof, the Company shall reimburse the Underwriters for all of their out-of-pocket expenses, including the reasonable fees and disbursements of counsel for the Underwriters.

SECTION 5. Conditions of Underwriters’ Obligations . The obligations of the several Underwriters hereunder are subject to the accuracy of the representations and warranties of the Company contained in this Agreement, or in certificates signed by any officer of the Company or any subsidiary of the Company (whether signed on behalf of such officer, the Company or such subsidiary) delivered to the Representative or counsel for the Underwriters, to the performance by the Company of its covenants and other obligations hereunder, and to the following further conditions:

(a) Effectiveness of Registration Statement . The Registration Statement shall have become effective, and no stop order suspending the effectiveness of the Registration

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Statement shall have been issued under the 1933 Act or proceedings therefor, pursuant to Rule 401(g)(2) or Section 8A of the 1933 Act, initiated or, to the knowledge of the Company, threatened by the Commission, and any request on the part of the Commission for additional information shall have been complied with to the reasonable satisfaction of the Representative and the Commission shall not have notified the Company of any objection to the use of the form of the Registration Statement. The Prospectus shall have been filed with the Commission in the manner and within the time period required by Rule 424(b) (without reliance upon Rule 424(b)(8)) and each Issuer Free Writing Prospectus required to be filed with the Commission shall have been filed in the manner and within the time period required by Rule 433, and, prior to the Closing Date, the Company shall have provided evidence satisfactory to the Representative of such timely filings.

(b) Opinion and 10b-5 Statement of Counsel for Company . At the Closing Date, the Representative shall have received the favorable opinion and 10b-5 statement, dated as of Closing Date, of Weil, Gotshal & Manges LLP, counsel for the Company (“ Company Counsel ”), in form and substance satisfactory to the Representative, together with signed or reproduced copies of such opinion and 10b-5 statement for each of the other Underwriters, to the effect set forth in Exhibit E hereto and to such further effect as the Representative may reasonably request.

(c) Opinion of Company’s General Counsel . At the Closing Date, the Representative shall have received the favorable opinion, dated as of the Closing Date, of Dennis C. Cameron, Senior Vice President and General Counsel of the Company, in form and substance satisfactory to the Representative, together with signed or reproduced copies of such opinion for each of the other Underwriters, to the effect set forth in Exhibit F hereto and to such further effect as the Representative may reasonably request.

(d) Opinion and 10b-5 Statement of Counsel for Underwriters . At the Closing Date, the Representative shall have received the favorable opinion and 10b-5 statement, dated as of Closing Date, of Simpson Thacher & Bartlett LLP, counsel for the Underwriters, together with signed or reproduced copies of such opinion and 10b-5 statement for each of the other Underwriters, with respect to the Securities to be sold by the Company pursuant to this Agreement, this Agreement, the Indenture, the Registration Statement, the General Disclosure Package and the Prospectus and any amendments or supplements thereto and such other matters as the Representative may reasonably request.

(e) Officers’ Certificate . At the Closing Date, there shall not have been, since the date hereof or since the respective dates as of which information is given in the Registration Statement, the General Disclosure Package and the Prospectus (in each case exclusive of any amendments or supplements thereto subsequent to the date of this Agreement), any material adverse change or any development that would reasonably be expected to result in a prospective material adverse change, in the financial condition, earnings, business or operations of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, from that set forth or contemplated in the General Disclosure Package and the Prospectus (in each case exclusive of any amendments or supplements thereto subsequent to the date of this Agreement), and, at the Closing Date,

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the Representative shall have received a certificate of the Company, signed by an executive officer of the Company, dated as of Closing Date (a) making representations and warranties with respect to the written comments received from the Commission and (b) to the effect that (i) there has been no such material adverse change, (ii) the representations and warranties of the Company in this Agreement are true and correct at and as of the Closing Date with the same force and effect as though expressly made at and as of Closing Date, (iii) the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied at or prior to Closing Date under or pursuant to this Agreement, and (iv) no stop order suspending the effectiveness of the Registration Statement has been issued and no proceedings for that purpose, pursuant to Rule 401(g)(2) or Section 8A under the 1933 Act, have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission and the Commission has not notified the Company of any objection to the use of the form of the Registration Statement, and to the effect set forth in Section 5(n) below.

(f) Accountant’s Comfort Letter . At the time of the execution of this Agreement, the Representative shall have received from Ernst & Young LLP a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information of the Company contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(g) Bring-down Comfort Letter . At Closing Date, the Representative shall have received from Ernst & Young LLP a letter, dated as of Closing Date and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (f) of this Section, except that the specified date referred to shall be a date not more than three business days prior to Closing Date.

(h) Thunder Comfort Letter . At the time of the execution of this Agreement, the Representative shall have received from Grant Thornton LLP a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information of the Thunder Entities contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(i) Thunder Bring-Down Comfort Letter . At Closing Date, the Representative shall have received from Grant Thornton LLP a letter, dated as of Closing Date and in form and substance satisfactory to the Representative, to the effect that they

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reaffirm the statements made in the letter furnished pursuant to subsection (h) of this Section, except that the specified date referred to shall be a date not more than three business days prior to Closing Date.

(j) Reserve Engineer’s Letter . At the time of the execution of this Agreement, the Representative shall have received from Netherland, Sewell & Associates, Inc. a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, covering certain matters relating to information about the reserves of the Company contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(k) Bring-Down Reserve Engineer’s Letter . At the Closing Date, the Representative shall have received from Netherland, Sewell & Associates, Inc. a letter, dated as of the Closing Date and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (j) of this Section.

(l) Thunder Engineer’s Letter . At the time of the execution of this Agreement, the Representative shall have received from LaRoche Petroleum Consultants, Ltd. a letter, dated the date of this Agreement and in form and substance satisfactory to the Representative, together with signed or reproduced copies of such letter for each of the other Underwriters, covering certain matters relating to information about the reserves of the Thunder Entities contained in the Registration Statement, the General Disclosure Package, any Issuer Free Writing Prospectuses (other than any electronic road show) and the Prospectus and any amendments or supplements to any of the foregoing.

(m) Thunder Bring-Down Reserve Engineer’s Letter . At the Closing Date, the Representative shall have received from LaRoche Petroleum Consultants, Ltd. a letter, dated as of the Closing Date and in form and substance satisfactory to the Representative, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (l) of this Section.

(n) No Downgrade . There shall not have occurred, on or after the date of this Agreement, any downgrading in the rating of any debt securities of or guaranteed by the Company or any preferred securities of the Company by any “nationally recognized statistical rating organization” (as defined by the Commission in Section 3(a)(62) of the 1934 Act) or any public announcement that any such organization has placed its rating on the Company or any such debt or preferred securities under surveillance or review or on a so-called “watch list” (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement by any such organization that the Company or any such debt or preferred securities has been placed on negative outlook.

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(o) No Objection . Prior to the date of this Agreement, FINRA shall have confirmed in writing that it has no objection with respect to the fairness and reasonableness of the underwriting terms and arrangements.

(p) No Material Adverse Change . Since the date of the most recent financial statements included in the General Disclosure Package (exclusive of any amendment or supplement thereto) and the Prospectus (exclusive of any amendment or supplement thereto), there shall not have been any change, or any development that would reasonably be expected to result in a prospective change, in the financial condition, earnings, business or operations of the Company and its subsidiaries taken as a whole after giving effect to the Acquisition, from that set forth in the Pre-Pricing Prospectus, the effect of which is, in the sole judgment of the Representative, so material and adverse as to make it impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the General Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto).

(q) Additional Documents . At the Closing Date, counsel for the Underwriters shall have been furnished with such documents and opinions as they may reasonably require for the purpose of enabling them to pass upon the issuance and sale of the Securities as herein contemplated, or in order to evidence the accuracy of any of the representations or warranties, or the fulfillment of any of the conditions, contained in this Agreement, or as the Representative or counsel for the Underwriters may otherwise reasonably request; and all proceedings taken by the Company in connection with the issuance and sale of the Securities as herein contemplated and in connection with the other transactions contemplated by this Agreement shall be satisfactory in form and substance to the Representative.

(r) Termination of Agreement . If any condition specified in this Section 5 shall not have been fulfilled when and as required to be fulfilled, this Agreement may be terminated by the Representative by notice to the Company at any time on or prior to Closing Date and such termination shall be without liability of any party to any other party except as provided in Section 4 hereof and except that Sections 1, 6, 7, 8, 11, 12, 13, 14, 15, 16, 18, 19 and 20 and hereof shall survive any such termination of this Agreement and remain in full force and effect.

SECTION 6. Indemnification .

(a) Indemnification by the Company . The Company agrees to indemnify and hold harmless each Underwriter, its affiliates, and its and their officers, directors, employees, partners and members and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act as follows:

(i) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, arising out of any untrue statement or alleged untrue statement of a material fact in the Registration Statement (or any amendment thereto), or the omission or alleged omission therefrom of a material fact required to be stated therein or necessary to make the statements therein not misleading, or arising out of any untrue statement or alleged

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untrue statement of a material fact in any preliminary prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package or the Prospectus (or any amendment or supplement to any of the foregoing), or in any “issuer information” (as defined in Rule 433) or “road show” (as defined in Rule 433) that does not constitute an Issuer Free Writing Prospectus, or the omission or alleged omission therefrom of a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading and agrees to reimburse each such indemnified party, as incurred, for any legal or other expenses reasonably incurred by them in connection with defending any such loss, liability, claim, damage or action;

provided , however , that this indemnity agreement shall not apply to any loss, liability, claim, damage or expense to the extent arising out of any untrue statement or omission or alleged untrue statement or omission made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representative expressly for use in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package or the Prospectus (or in any amendment or supplement to any of the foregoing), it being understood and agreed that the only such information furnished by the Underwriters as aforesaid consists of the information described as such in Section 6(b) hereof.

(b) Indemnification by the Underwriters . Each Underwriter agrees, severally and not jointly, to indemnify and hold harmless the Company, its directors, each of its officers who signed the Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act against any and all loss, liability, claim, damage and expense described in the indemnity contained in subsection (a)(1) of this Section 6, as incurred, but only with respect to untrue statements or omissions, or alleged untrue statements or omissions, made in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement to any of the foregoing), in reliance upon and in conformity with written information furnished to the Company by such Underwriter through the Representative expressly for use therein. The Company hereby acknowledges and agrees that the information furnished to the Company by the Underwriters through the Representative expressly for use in the Registration Statement (or any amendment thereto), or in any preliminary prospectus, any Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement to any of the foregoing), consists exclusively of the information appearing under the caption “Underwriting” in the Pre-Pricing Prospectus and the Prospectus regarding market making, stabilization and syndicate covering transactions appearing in the 10th paragraph under such caption (but only insofar as such information concerns the Underwriters).

(c) Actions Against Parties; Notification . Each indemnified party shall give notice as promptly as reasonably practicable to each indemnifying party of any action commenced against it in respect of which indemnity may be sought hereunder, but failure to so notify an indemnifying party shall not relieve such indemnifying party from any liability hereunder unless and to the extent it did not otherwise learn of such action and such failure results in the forfeiture by the indemnifying party of substantial rights and defenses. The indemnifying party shall be entitled to appoint counsel of the indemnifying party’s choice at the indemnifying party’s expense to represent the indemnified party in any action for which indemnification is sought

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(in which case the indemnifying party shall not thereafter be responsible for the fees and expenses of any separate counsel retained by the indemnified party or parties except as set forth below); provided , however , that such counsel shall be reasonably satisfactory to the indemnified party. Notwithstanding the indemnifying party’s election to appoint counsel to represent the indemnified party in an action, the indemnified party shall have the right to employ separate counsel (including local counsel), and the indemnifying party shall bear the reasonable fees, costs and expenses of such separate counsel if (i) the use of counsel chosen by the indemnifying party to represent the indemnified party would present such counsel with a conflict of interest, (ii) the actual or potential defendants in, or targets of, any such action include both the indemnified party and the indemnifying party and the indemnified party shall have reasonably concluded that there may be legal defenses available to it and/or other indemnified parties which are different from or additional to those available to the indemnifying party, (iii) the indemnifying party shall not have employed counsel reasonably satisfactory to the indemnified party to represent the indemnified party within a reasonable time after notice of the institution of such action or (iv) the indemnifying party shall authorize the indemnified party to employ separate counsel at the expense of the indemnifying party. In no event shall the indemnifying party be liable for the fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for the Underwriters and the other indemnified parties referred to in Section 6(a)(1) above; and the fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for the Company, its directors, each of its officers who signed the Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act, in each case in connection with any one action or separate but similar or related actions in the same jurisdiction arising out of the same general allegations or circumstances. No indemnifying party shall, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever in respect of which indemnification or contribution could be sought under this Section 6 or Section 7 hereof (whether or not the indemnified parties are actual or potential parties thereto), unless such settlement, compromise or consent (i) includes an unconditional release of each indemnified party from all liability arising out of such litigation, investigation, proceeding or claim and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party.

SECTION 7. Contribution . If the indemnification provided for in Section 6 hereof is for any reason unavailable to or insufficient to hold harmless an indemnified party in respect of any losses, liabilities, claims, damages or expenses referred to therein, then each indemnifying party shall contribute to the aggregate amount of such losses, liabilities, claims, damages and expenses incurred by such indemnified party, as incurred, (i) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other hand from the offering of the Securities pursuant to this Agreement or (ii) if the allocation provided by clause (i) is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause (i) above but also the relative fault of the Company on the one hand and of the Underwriters on the other hand in connection with the statements or omissions which resulted in such losses, liabilities, claims, damages or expenses, as well as any other relevant equitable considerations.

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The relative benefits received by the Company on the one hand and the Underwriters on the other hand in connection with the offering of the Securities pursuant to this Agreement shall be deemed to be in the same respective proportions as the total net proceeds from the offering of the Securities pursuant to this Agreement (before deducting expenses) received by the Company and the total underwriting discounts and commissions received by the Underwriters, in each case as set forth on the cover of the Prospectus, bear to the aggregate initial public offering price of the Securities as set forth on such cover.

The relative fault of the Company on the one hand and the Underwriters on the other hand shall be determined by reference to, among other things, whether any such untrue or alleged untrue statement of a material fact or omission or alleged omission to state a material fact relates to information supplied by the Company on the one hand or by the Underwriters on the other hand and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission.

The Company and the Underwriters agree that it would not be just and equitable if contribution pursuant to this Section 7 were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to above in this Section 7. The aggregate amount of losses, liabilities, claims, damages and expenses incurred by an indemnified party and referred to above in this Section 7 shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue or alleged untrue statement or omission or alleged omission.

Notwithstanding the provisions of this Section 7, no Underwriter shall be required to contribute any amount in excess of the amount by which the total price at which the Securities underwritten by it and distributed to the public were offered to the public exceeds the amount of any damages which such Underwriter has otherwise been required to pay by reason of any such untrue or alleged untrue statement or omission or alleged omission.

No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the 1933 Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

For purposes of this Section 7, each affiliate, officer, director, employee, partner and member of each Underwriter and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as such Underwriter and each director of the Company, each officer of the Company who signed the Registration Statement, and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as the Company. The Underwriters’ respective obligations to contribute pursuant to this Section 7 are several in proportion to the principal amount of Securities set forth opposite their respective names in Exhibit A hereto and not joint.

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SECTION 8. Representations, Warranties and Agreements to Survive Delivery . All representations, warranties and agreements contained in this Agreement or in certificates signed by any officer of the Company or any of its subsidiaries (whether signed on behalf of such officer, the Company or such subsidiary) and delivered to the Representative or counsel to the Underwriters, shall remain operative and in full force and effect, regardless of any investigation made by or on behalf of any Underwriter, any officer, director, employee, partner, member or agent of any Underwriter or any person controlling any Underwriter, or by or on behalf of the Company, any officer, director or employee of the Company or any person controlling the Company.

SECTION 9. Termination of Agreement .

(a) Termination; General . This Agreement shall be subject to termination in the absolute discretion of the Representative, by notice given to the Company prior to delivery of and payment for the Securities, if at any time prior to such time (i) trading in the Company’s shares shall have been suspended by the Commission or the NYSE or trading in securities generally on the NYSE shall have been suspended or limited or minimum prices shall have been established on such exchange, (ii) a banking moratorium shall have been declared either by federal or New York State authorities or (iii) there shall have occurred any outbreak or escalation of hostilities, declaration by the United States of a national emergency or war, or other calamity or crisis the effect of which on financial markets is such as to make it, in the sole judgment of the Representative, impractical or inadvisable to proceed with the offering, sale or delivery of the Securities as contemplated by any Pre-Pricing Prospectus or the Prospectus (exclusive of any amendment or supplement thereto).

(b) Liabilities . If this Agreement is terminated pursuant to this Section 9, such termination shall be without liability of any party to any other party except as provided in Section 4 hereof, and except that Sections 1, 6, 7, 8, 11, 12, 13, 14, 15, 16, 18, 19 and 20 hereof shall survive such termination and remain in full force and effect.

SECTION 10. Default by One or More of the Underwriters . (a) If one or more of the Underwriters shall fail at the Closing Date to purchase the aggregate principal amount of Securities which it or they are obligated to purchase under this Agreement (the “ Defaulted Securities ”), the Representative shall have the right, within 24 hours thereafter, to make arrangements for one or more of the non-defaulting Underwriters, or any other underwriters, to purchase all, but not less than all, of the Defaulted Securities in such amounts as may be agreed upon and upon the terms herein set forth; if, however, the Representative shall not have completed such arrangements within such 24-hour period, then:

(i) if the aggregate principal amount of Defaulted Securities does not exceed 10% of the aggregate principal amount of Securities, each of the non-defaulting Underwriters shall be obligated, severally and not jointly, to purchase the full amount of such Defaulted Securities in the proportions that their respective underwriting obligations hereunder bear to the underwriting obligations of all non-defaulting Underwriters; or

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(ii) if the number of Defaulted Securities exceeds 10% of the aggregate principal amount of Securities, this Agreement shall terminate without liability on the part of any non-defaulting Underwriter.

(b) No action taken pursuant to this Section 10 shall relieve any defaulting Underwriter from liability in respect of its default.

In the event of any such default which does not result in a termination of this Agreement, the Representative shall have the right to postpone the Closing Date for a period not exceeding seven days in order to effect any required changes in the Registration Statement, the General Disclosure Package or Prospectus or in any other documents or arrangements. As used herein, the term “Underwriter” includes any person substituted for an Underwriter under this Section 10.

SECTION 11. Notices . All notices and other communications hereunder shall be in writing, shall be effective only upon receipt and shall be mailed, delivered by hand or overnight courier, or transmitted by fax (with the receipt of any such fax to be confirmed by telephone). Notices to the Underwriters shall be directed to the Representative at Barclays Capital Inc. 745 Seventh Avenue, New York, New York 10019, Attention: Syndicate Registration; and notices to the Company shall be directed to it at WPX Energy, Inc., 3500 One Williams Center, Tulsa, Oklahoma 74172, Attention: Chief Financial Officer (Fax: (539) 573-0026), Attention: Treasurer (Fax: (539) 573-0026) and Attention: General Counsel (Fax: (539) 573-5608), with a copy mailed, delivered or telefaxed to Weil, Gotshal & Manges LLP, Attention: Todd R. Chandler, Esq. (Fax: (212) 310-8007 and confirmed at (212) 310-8000).

SECTION 12. Parties . This Agreement shall each inure to the benefit of and be binding upon the Underwriters and the Company and their respective successors. Nothing expressed or mentioned in this Agreement is intended or shall be construed to give any person, firm or corporation, other than the Underwriters and the Company and their respective successors and the controlling persons and other indemnified parties referred to in Sections 6 and 7 and their successors, heirs and legal representatives, any legal or equitable right, remedy or claim under or in respect of this Agreement or any provision herein contained. This Agreement and all conditions and provisions hereof are intended to be for the sole and exclusive benefit of the Underwriters and the Company and their respective successors, and said controlling persons and other indemnified parties and their successors, heirs and legal representatives, and for the benefit of no other person or entity. No purchaser of Securities from any Underwriter shall be deemed to be a successor by reason merely of such purchase.

SECTION 13. Governing Law and Time . THIS AGREEMENT AND ANY CLAIM, CONTROVERSY OR DISPUTE ARISING UNDER OR RELATED TO THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK. EXCEPT AS OTHERWISE EXPRESSLY SET FORTH HEREIN, SPECIFIED TIMES OF DAY REFER TO NEW YORK CITY TIME.

SECTION 14. Waiver of Jury Trial . The Company and the Underwriters hereby irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.

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SECTION 15. Effect of Headings . The Section and Exhibit headings herein are for convenience only and shall not affect the construction hereof.

“ GAAP ” means generally accepted accounting principles.

“ Issuer Free Writing Prospectus ” means any “issuer free writing prospectus,” as defined in Rule 433, relating to the Securities that (i) is required to be filed with the Commission by the Company, (ii) is a “road show” that is a “written communication” within the meaning of Rule 433(d)(8)(i), whether or not required to be filed with the Commission, or (iii) is exempt from filing pursuant to Rule 433(d)(5)(i) because it contains a description of the Securities or of the offering that does not reflect the final terms, and all free writing prospectuses that are listed in Exhibit D hereto, in each case in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g).

“ Issuer General Use Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being specified in Exhibit D hereto.

“ Issuer Limited Use Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is not an Issuer General Use Free Writing Prospectus.

“ NYSE ” means the New York Stock Exchange.

“ Organizational Documents ” means (a) in the case of a corporation, its charter and by-laws; (b) in the case of a limited or general partnership, its partnership certificate, certificate of formation or similar organizational document and its partnership agreement; (c) in the case of a limited liability company, its articles of organization, certificate of formation or similar organizational documents and its operating agreement, limited liability company agreement, membership agreement or other similar agreement; (d) in the case of a trust, its certificate of trust, certificate of formation or similar organizational document and its trust agreement or other

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similar agreement; and (e) in the case of any other entity, the organizational and governing documents of such entity.

“ PCAOB ” means the Public Company Accounting Oversight Board (United States).

“ preliminary prospectus ” means any prospectus together with, if applicable, the accompanying preliminary prospectus supplement used in connection with the offering of the Securities that omitted the public offering price of the Securities or that was captioned “Subject to Completion,” together with the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act. The term “preliminary prospectus” includes, without limitation, the Pre-Pricing Prospectus.

“ Registration Statement ” means the Company’s registration statement on Form S–3 (Registration No. 333-198523) as amended (if applicable), including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S–3 under the 1933 Act and the Rule 430B Information; provided that any Rule 430B Information shall be deemed part of the Registration Statement only from and after the time specified pursuant to Rule 430B.

“ Rule 163 ,” “ Rule 164 ,” “ Rule 172 ,” “ Rule 173 ,” “ Rule 401 ,” “ Rule 405 ,” “ Rule 424(b) ” “ Rule 430B ” and “ Rule 433 ” refer to such rules under the 1933 Act.

“ Rule 430B Information ” means the information included in any preliminary prospectus or the Prospectus or any amendment or supplement to any of the foregoing that was omitted from the Registration Statement at the time it first became effective but is deemed to be part of and included in the Registration Statement pursuant to Rule 430B.

“ Sarbanes-Oxley Act ” means the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated thereunder or implementing the provisions thereof.

“ Transaction Documents ” means this Agreement, the Indenture and the Securities, collectively.

“ 1933 Act ” means the Securities Act of 1933, as amended.

“ 1933 Act Regulations ” means the rules and regulations of the Commission under the 1933 Act.

“ 1934 Act ” means the Securities Exchange Act of 1934, as amended.

“ 1934 Act Regulations ” means the rules and regulations of the Commission under the 1934 Act.

“ 1939 Act ” means the Trust Indenture Act of 1939, as amended, and the rules and regulations of the Commission thereunder.

“ 1940 Act ” means the Investment Company Act of 1940, as amended.

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All references in this Agreement to the Registration Statement, any preliminary prospectus, the Prospectus, any Issuer Free Writing Prospectus or any amendment or supplement to any of the foregoing shall be deemed to include the version thereof filed with the Commission pursuant to EDGAR and all versions thereof delivered (physically or electronically) to the Representative or the Underwriters.

All references in this Agreement to financial statements and schedules and other information which is “contained,” “included” or “stated” in the Registration Statement, any preliminary prospectus or the Prospectus (and all other references of like import) shall be deemed to mean and include all such financial statements and schedules and other information which is incorporated by reference in or otherwise deemed by 1933 Act Regulations to be a part of or included in the Registration Statement, any preliminary prospectus or the Prospectus, as the case may be; and all references in this Agreement to amendments or supplements to the Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to mean and include the filing of any document under the 1934 Act which is incorporated by reference in or otherwise deemed by 1933 Act Regulations to be a part of or included in the Registration Statement, such preliminary prospectus or the Prospectus, as the case may be.

SECTION 17. Permitted Free Writing Prospectuses . The Company represents, warrants and agrees that it has not made and, unless it obtains the prior written consent of the Representative, it will not make, and each Underwriter, severally and not jointly, represents, warrants and agrees that it has not made and, unless it obtains the prior written consent of the Company and the Representative, it will not make, any offer relating to the Securities that constitutes or would constitute an “issuer free writing prospectus” (as defined in Rule 433) or that otherwise constitutes or would constitute a “free writing prospectus” (as defined in Rule 405) or portion thereof required, in the case of any Underwriters, to be filed with the Commission or, in the case of the Company, whether or not required to be filed with the Commission; provided that the prior written consent of the Company and the Representative shall be deemed to have been given in respect of the Issuer General Use Free Writing Prospectuses, if any, listed on Exhibit D hereto and to any electronic road show in the form previously provided by the Company to and approved by the Representative. Any such free writing prospectus consented to or deemed to have been consented to as aforesaid is hereinafter referred to as a “ Permitted Free Writing Prospectus .” The Company represents, warrants and agrees that it has treated and will treat each Permitted Free Writing Prospectus as an “issuer free writing prospectus,” as defined in Rule 433, and has complied and will comply with the requirements of Rule 433 applicable to any Permitted Free Writing Prospectus, including timely filing with the Commission where required, legending and record keeping.

SECTION 18. Absence of Fiduciary Relationship . The Company acknowledges and agrees that:

(a) each of the Underwriters is acting solely as an underwriter in connection with the sale of the Securities and no fiduciary, advisory or agency relationship between the Company, on the one hand, and any of the Underwriters, on the other hand, has been created in respect of any of the transactions contemplated by this Agreement, irrespective of whether or not any of the Underwriters has advised or is advising the Company on other matters;

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(b) the public offering price of the Securities and the price to be paid by the Underwriters for the Securities set forth in this Agreement were established by the Company following discussions and arms-length negotiations with the Representative;

(c) it is capable of evaluating and understanding, and understands and accepts, the terms, risks and conditions of the transactions contemplated by this Agreement;

(d) it is aware that the Underwriters and their respective affiliates are engaged in a broad range of transactions which may involve interests that differ from those of the Company and that none of the Underwriters has any obligation to disclose such interests and transactions to the Company by virtue of any fiduciary, advisory or agency relationship or otherwise; and

(e) it waives, to the fullest extent permitted by law, any claims it may have against any of the Underwriters for breach of fiduciary duty or alleged breach of fiduciary duty and agrees that none of the Underwriters shall have any liability (whether direct or indirect, in contract, tort or otherwise) to it in respect of such a fiduciary duty claim or to any person asserting a fiduciary duty claim on its behalf or in right of it or the Company or any stockholders, employees or creditors of Company.

SECTION 19. Research Analyst Independence . The Company acknowledges that the Underwriters’ research analysts and research departments are required to be independent from their respective investment banking divisions and are subject to certain regulations and internal policies, and that such Underwriters’ research analysts may hold views and make statements or investment recommendations and/or publish research reports with respect to the Company and/or the offering that differ from the views of their respective investment banking divisions. The Company hereby waives and releases, to the fullest extent permitted by applicable law, any claims that the Company may have against the Underwriters with respect to any conflict of interest related to the issuance and sale by the Company of the Securities that may arise from the fact that the views expressed by their independent research analysts and research departments may be different from or inconsistent with the views or advice communicated to the Company by such Underwriters’ investment banking divisions. The Company acknowledges that each of the Underwriters is a full service securities firm and as such from time to time, subject to applicable securities laws, may effect transactions for its own account or the account of its customers and hold long or short positions in debt or equity securities of the companies that may be the subject of the transactions contemplated by this Agreement.

SECTION 20. Consent to Jurisdiction . The parties hereby irrevocably submit to the non-exclusive jurisdiction of any New York State or federal court sitting in the Borough of Manhattan in The City of New York in any action or proceeding arising out of or relating to the terms of this Agreement and the transactions contemplated herein, and the parties hereby irrevocably agree that all claims in respect of such action or proceeding may be heard and determined in such New York State or federal court. The parties hereby irrevocably waive, to the fullest extent that they may legally do so, the defense of an inconvenient forum to the maintenance of such action or proceeding. The parties agree that a final judgment in any such action or proceeding shall be conclusive and may be enforced in other jurisdictions by suit on the judgment or in any other manner provided by law. To the extent that either party has or hereafter may acquire any immunity from jurisdiction of any court or from any legal process (whether

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through service or notice, attachment prior to judgment, attachment in aid of execution or otherwise) with respect to its obligations hereunder, each waives such immunity to the extent permitted by applicable law.

SECTION 21. Patriot Act . In accordance with the requirements of the USA Patriot Act (Title III of Pub. L. 107-56 (signed into law October 26, 2001)), the Underwriters are required to obtain, verify and record information that identifies their respective clients, including the Company, which information may include the name and address of their respective clients, as well as other information that will allow the underwriters to properly identify their respective clients.

[Signature Page Follows]

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If the foregoing is in accordance with your understanding of our agreement, please sign and return to the Company a counterpart hereof, whereupon this instrument, along with all counterparts, will become a binding agreement between the Underwriters and the Company in accordance with its terms.