Plains Exploration & Production Company $3.0 Billion Senior SecuredRevolving Credit Facility $750.0 Million Senior Secured 5-Year Term Loan Facility $1,250.0 Million Senior Secured 7-Year Term Loan Facility $2.0 Billion Bridge Credit Facility Commitment Letter

Exhibit 2.3

Execution Version

September 4, 2012

Plains Exploration & Production Company

700 Milam, Suite 3100

Houston, TX 77002

Attention: Winston M. Talbert,

Executive Vice President & Chief Financial Officer

Plains Exploration & Production Company

$3.0 Billion Senior Secured Revolving Credit Facility

$750.0 Million Senior Secured 5-Year Term Loan Facility

$1,250.0 Million Senior Secured 7-Year Term Loan Facility

$2.0 Billion Bridge Credit Facility

Commitment Letter

Dear Mr. Talbert:

You have advised JPMorgan Chase Bank, N.A. (“JPMorgan Chase Bank”) and J.P. Morgan Securities LLC (“JPMorgan” and together with JPMorgan Chase Bank, the “Commitment Parties”, “us” or “we”) that Plains Exploration & Production Company, a Delaware corporation (“you” or the “Borrower”) intends to consummate the Acquisition described in the Transaction Summary attached hereto as Exhibit A . The Acquisition, the closing of the Facilities, the sale of the Senior Notes and the other transactions described on Exhibit A hereto are also referred to herein as the “Transactions”.

Capitalized terms used but not defined herein are used with the meanings assigned to them on Exhibits B, C and D attached hereto (collectively, the “Term Sheets” and the Term Sheets, together with this letter, the “Commitment Letter”).

1. Commitments

In connection with the Transactions, each of JPMorgan Chase Bank (the “Initial Lender”) is pleased to advise you of its commitment to provide the entire amount of each of the Facilities, in each case subject only to the satisfaction or waiver of the conditions referenced in numbered paragraph 6 hereof.

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2. Titles and Roles

It is agreed that (i) JPMorgan will act as senior lead arranger and lead bookrunner for the Facilities (acting in such capacities, the “Senior Lead Arranger”) and (ii) JPMorgan Chase Bank will act as sole administrative agent for each Facility. It is further agreed that JPMorgan will have “left” placement in any marketing materials or other documentation used in connection with the Credit Facilities. At any time additional agents, co-agents or co-managers (any such agent, co-agent or co-manager, an “Additional Commitment Party”) may be appointed or additional titles conferred in respect of the Facilities in a manner and with economics determined by the Senior Lead Arranger in consultation with you and reasonably acceptable to you (it being understood that, to the extent you appoint Additional Commitment Parties or confer other titles in respect of the Facilities, the commitments of the Commitment Parties in respect of the Facilities will be reduced by the amount of the commitments of such appointed entities upon the execution by such financial institution of customary joinder documentation in a form reasonably satisfactory to you and, thereafter, each such financial institution shall constitute a “Commitment Party” hereunder and under certain Fee Letters (as referred to below)). You agree that no other agents, co-agents, arrangers, co-arrangers, bookrunners, co-bookrunners, managers or co-managers will be appointed, no other titles will be awarded and no compensation (other than that expressly contemplated by the Term Sheets and Fee Letters and other than in connection with any additional appointments referred to above) will be paid in connection with the Facilities unless you and the Senior Lead Arranger shall so reasonably agree (it being understood and agreed that no other agent, co-agent, arranger, co-arranger, bookrunner, co-bookrunner, manager or co-manager shall be entitled to greater economics in respect of the Facilities than the Commitment Parties).

3. Syndication

We intend to syndicate each Facility to a group of lenders identified by us in consultation with you (together with the Initial Lender, the “Lenders”); provided that notwithstanding our right to syndicate the Facilities and receive commitments with respect thereto, (i) the Initial Lender shall not be relieved, released or novated from its obligations hereunder (including their respective obligations to fund the Facilities on the Closing Date) in connection with any syndication, assignment or participation of the Facilities, including its commitments in respect thereof, until after the initial funding of the Facilities has occurred, (ii) no assignment or novation shall become effective with respect to all or any portion of the Initial Lender’s commitments under this Commitment Letter in respect of the Facilities until the funding of the Facilities and (iii) unless you otherwise agree in writing, the Initial Lender shall retain exclusive control over all rights and obligations with respect to its commitments in respect of the Facilities, including all rights with respect to consents, modifications, supplements, waivers and amendments, until the Closing Date has occurred; provided, further that clauses (i) through (iii) shall not apply to any Additional Commitment Parties appointed pursuant to Section 2 hereof or if the syndication, assignment or participation was consented to by the Borrower in writing. Without limiting your obligations to assist with syndication efforts as set forth herein, it is understood that the Commitment Parties’ commitments hereunder are not conditioned upon the syndication of, or receipt of commitments or participations in respect of all or any portion of, the Facilities and in no event shall the commencement or successful completion of syndication of the Facilities constitute a condition to the availability of the Facilities on the Closing Date.

The Commitment Parties intend to commence syndication efforts promptly, and you agree actively to assist the Commitment Parties in completing a syndication satisfactory to the Commitment Parties. Such assistance shall include, until the earlier to occur of (x) a Successful Syndication (as defined in the Fee Letter) and (y) 180 days after the Closing Date (such earlier date, the “Syndication Date”) (A) your using commercially reasonable efforts to ensure that the syndication efforts benefit from your and your subsidiaries’ existing banking relationships, (B) direct contact between your senior management and advisors and the proposed Lenders, in all such cases at times mutually agreed upon, (C) your preparing and

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providing to the Commitment Parties all customary information with respect to you and the Acquisition, including all customary financial information and Projections (as defined below), as the Commitment Parties may reasonably request in connection with the arrangement and syndication of the Credit Facilities and your assistance in the preparation of one or more customary confidential information memoranda (each, a “Confidential Information Memorandum”) and other customary marketing materials to be used in connection with the syndication (all such information, memoranda and material, “Information Materials”), (D) your hosting, with the Commitment Parties, of one or more meetings of prospective Lenders at times and locations to be mutually agreed, (E) prior to the Syndication Date your ensuring that there is no competing offering, placement, arrangement or syndication of any debt securities or bank financing (other than the Facilities and Senior Notes) or announcement thereof by or on behalf of you or your subsidiaries if in the Senior Lead Arranger’s reasonable judgment, such issuance, offering, placement or arrangement could reasonably be expected to materially impair the primary syndication of the Facilities (it is understood that your and your subsidiaries’ deferred purchase price obligations, ordinary course working capital facilities (including borrowings under your existing revolving credit facility and money-market lines) and ordinary course capital lease, purchase money, equipment financings and other indebtedness permitted under your existing revolving credit facility will not be deemed to materially impair the primary syndication of the Facilities) and (F) your promptly commencing the preparation of a Registration Statement or a Rule 144A Offering Memorandum relating to the Senior Notes and your reasonable efforts to provide to us as soon as possible (but in any event no later than the earlier of (x) 60 days after the Closing Date and (y) the date after the Closing Date which is at least ten (10) business days after the day on which pro forma and audited financial statements in respect of the Assets are made available), the completed preliminary prospectus or the preliminary offering memorandum relating to the Senior Notes. Notwithstanding anything to the contrary contained in this Commitment Letter or the Fee Letter or any other letter agreement or undertaking concerning the financing of the Transactions to the contrary, the compliance with any of the provisions set forth in clauses (A) through (F) above or any other provision of this paragraph shall not constitute a condition to the commitments hereunder or the funding of the Facilities on the Closing Date or at any time thereafter.

The Senior Lead Arranger will manage, in consultation with you, all aspects of the syndication, including decisions as to the selection of institutions to be approached and when they will be approached, when commitments will be accepted, which institutions will participate (subject to your consent rights and rights of appointment set forth above), the allocation of the commitments among the Lenders and the amount and distribution of fees among the Lenders. You hereby acknowledge and agree that the Commitment Parties will have no responsibility other than to arrange the syndication as set forth herein and in no event shall the Commitment Parties be subject to any fiduciary or other implied duties in connection with the transactions contemplated hereby.

At the request of the Commitment Parties, you agree to assist in the preparation of a version of each Confidential Information Memorandum or other Information Material (a “Public Version”) consisting exclusively of information with respect to you and your subsidiaries, the Assets and the Acquisition that is either publicly available or not material with respect to you and your subsidiaries, the Assets, any of your or their respective securities or the Acquisition for purposes of United States federal and state securities laws or that would reasonably be expected to be included in an offering memorandum for an offering of high yield debt securities under Rule 144A concurrent with the syndication of the Facilities (such information, “Non-MNPI”). Such Public Versions, together with any other information prepared by you, your subsidiaries or your representatives and conspicuously marked “Public” (collectively, the “Public Information”), which at a minimum means that the word “Public” will appear prominently on the first page of any such information, may be distributed by us to prospective Lenders who have advised us that they wish to receive only Non-MNPI (“Public Side Lenders”). You acknowledge and agree that, in addition to Public Information and unless you promptly notify us otherwise, (a) drafts and final definitive documentation with respect to the Facilities, (b) administrative materials prepared by the Commitment Parties for prospective Lenders (such as a lender meeting invitation, allocations and funding and closing memoranda) and (c) notifications of changes in the terms of the Facilities may be distributed to Public Side Lenders.

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In connection with our distribution to prospective Lenders of any Confidential Information Memorandum and, upon our request, any other Information Materials, you will execute and deliver to us a customary authorization letter authorizing such distribution and, in the case of any Public Version thereof or other Public Information, representing that it only contains Non-MNPI. Each Confidential Information Memorandum will be accompanied by a disclaimer exculpating us with respect to any use thereof and of any related Information Materials by the recipients thereof.

4. Information

You hereby represent and warrant that (a) all written information (including all Information Materials), other than the Projections and information of a general economic or industry specific nature (the “Information”), that has been or will be made available to us by you or any of your representatives in connection with the transactions contemplated hereby, when taken as a whole, does not or will not, when furnished to us, contain any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements contained therein not materially misleading in light of the circumstances under which such statements are made (giving effect to all supplements thereto but excluding any omissions that pertain to matters of a general economic nature or matters of public knowledge that generally affect any of the industry segments of the Borrower or its subsidiaries) and (b) the financial projections and other forward-looking information (the “Projections”) that have been or will be made available to us by you or any of your representatives in connection with the transactions contemplated hereby have been or will be prepared in good faith based upon assumptions believed by you to be reasonable at the time furnished to us (it being recognized by the Commitment Parties that (x) such Projections are not to be viewed as facts and that actual results during the period or periods covered by any such Projections may differ from the projected results, and such differences may be material, (y) there are industry-wide risks normally associated with the types of business conducted by the Borrower and its subsidiaries and (z) projections concerning volume attributable to oil and gas properties and production and cost estimates in reserve reports are necessarily based upon professional opinions, estimates and projections and that the Borrower does not warrant that such opinions, estimates and projections will ultimately prove to have been accurate). The foregoing representation regarding Information and Projections with respect to the Assets is limited to your knowledge. You agree that if, at any time prior to the Closing Date (or, if a Successful Syndication has not been achieved as of the Closing Date, until the Syndication Date), you become aware that any of the representations in the preceding sentence would be incorrect if the same was remade, in any material respect, then you will use commercially reasonable efforts to promptly supplement the Information and the Projections so that (to the best of your knowledge with respect to Information and Projections related to the Assets) such representations when remade would be correct, in all material respects, under those circumstances. You understand that in arranging and syndicating the Facilities we may use and rely on the Information and Projections without independent verification thereof.

5. Fees

As consideration for the commitments and agreements of the Commitment Parties hereunder, you agree to pay or cause to be paid the nonrefundable fees described in the Fee Letters dated the date hereof and delivered herewith (the Fee Letter among you and the Commitment Parties, the “Arranger Fee Letter” and together with any other fee letters, the “Fee Letters”) on the terms and subject to the conditions set forth therein.

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6. Conditions

Each Commitment Party’s commitments and agreements hereunder are subject to the conditions set forth in this Section 6, in Exhibit D and, solely with respect to the Credit Facilities, in Exhibit B under the heading “CERTAIN CONDITIONS – Initial Conditions” and, solely with respect to the Bridge Facility, in Exhibit C under the heading “Certain Conditions”.

Notwithstanding anything in this Commitment Letter, the Fee Letters, the Credit Facilities Documentation or the Bridge Facility Documentation (as defined in Exhibits B and C) to the contrary, the only representations the accuracy of which shall be a condition to availability of the Credit Facilities or the Bridge Facility on the Closing Date shall be (i) such of the representations made by the Seller with respect to the Assets in the Purchase Agreement as are material to the interests of the Lenders, but only to the extent that the accuracy of any such representation is a condition to your obligations to close under the Purchase Agreement or you have the right to terminate your obligations under the Purchase Agreement as a result of a breach of such representations in the Purchase Agreement (the “Purchase Agreement Representations”) and (ii) the Specified Representations (as defined below). For purposes hereof, “Specified Representations” means the representations and warranties referred to in the Term Sheets relating to corporate existence, power and authority, due authorization, execution and delivery of, and enforceability of, the Credit Facilities Documentation or Bridge Facility Documentation, as applicable, effectiveness, validity and perfection of liens under the security documents to be perfected on the Closing Date (subject to the following provisions of this paragraph relating to Collateral), the incurrence of the loans and the provision of the guaranties, in each case under the Facilities, and the granting of security interests in the Collateral to secure the Facilities not conflicting with organizational documents and material debt instruments, use of proceeds, Investment Company Act, solvency (on an consolidated basis after giving effect to the Transactions), Patriot Act, Federal Reserve margin regulations, and OFAC and FCPA compliance. Notwithstanding anything in this Commitment Letter or the Fee Letters to the contrary, the only conditions to availability of the Credit Facilities and the Bridge Facility on the Closing Date are set forth in each of the relevant Term Sheets under the heading “CERTAIN CONDITIONS–Initial Conditions” (in the case of Exhibit B) or “CERTAIN CONDITIONS” (in the case of Exhibit C) and in Exhibit D. It being understood that, to the extent any security interest in the intended Collateral or any deliverable related to the perfection of security interests in the intended Collateral (other than (x) any Collateral the security interest in which may be perfected by the filing of a UCC financing statement, (y) pledge and perfection of security interests in the certificated equity securities of the Borrower and (z) Collateral comprising of the Assets) is not or cannot be provided and/or perfected on the Closing Date, after your use of commercially reasonable efforts to do so, then the provision and/or perfection of a security interest in such Collateral or delivery of such deliverable shall not constitute a condition precedent to the availability of the Facilities on the Closing Date but instead shall be required to be delivered after the Closing Date pursuant to arrangements and timing to be mutually agreed by the Administrative Agent and the Borrower acting reasonably (but, in any event, not later than 30 days after the Closing Date or such longer period as may be agreed by the Administrative Agent); provided that, the Specified Representations relating to the effectiveness, validity and perfection of liens under the security documents with respect to Collateral comprising of the Assets shall (A) deemed to be satisfied by the delivery of unrecorded real property mortgages in appropriate form for filing, reasonably satisfactory to the Administrative Agent and (B) be subject to the receipt of approvals from the Bureau of Ocean Energy Management or other applicable governmental authority customarily obtained after the closing of sales or transfers involving assets in the Gulf of Mexico.

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7. Indemnification and Expenses

You agree (a) to indemnify and hold harmless the Commitment Parties, their affiliates and their respective directors, officers, employees, advisors, agents and other representatives (each, an “indemnified person”) from and against any and all losses, claims, damages and liabilities to which any such indemnified person may become subject arising out of or in connection with this Commitment Letter, the Fee Letters, the Credit Facilities, the use of the proceeds thereof or the Acquisition and the Transactions or any claim, litigation, investigation or proceeding (a “Proceeding”) relating to any of the foregoing, regardless of whether any indemnified person is a party thereto, whether or not such Proceedings are brought by you, your equity holders, affiliates, creditors or any other person, and to reimburse each indemnified person upon demand for any reasonable and duly documented legal expenses of one firm of counsel for all such indemnified persons, taken as a whole and, if necessary, of a single local counsel in each appropriate jurisdiction (which may include a single special counsel acting in multiple jurisdictions) for all such indemnified persons, taken as a whole (and, in the case of an actual or perceived conflict of interest where the indemnified person affected by such conflict informs you of such conflict and thereafter, after receipt of your consent (which consent shall not be unreasonably withheld or delayed) retains its own counsel, of another firm of counsel for such affected indemnified person) or other reasonable and documented out-of-pocket expenses incurred in connection with investigating or defending any of the foregoing, provided that the foregoing indemnity will not, as to any indemnified person, apply to (A) losses, claims, damages, liabilities or related expenses to the extent they are found by a final, nonappealable judgment of a court of competent jurisdiction to arise from (i) the willful misconduct, bad faith or gross negligence of such indemnified person or its control affiliates, directors, officers or employees (collectively, the “Related Parties”), (ii) a material breach of the obligations of such indemnified person or any of its Related Parties (or the successors of any of the foregoing) under this Commitment Letter, the Term Sheet or the Fee Letter or (iii) any Proceeding not arising from any act or omission by you or any of your affiliates that is brought by an indemnified person against any other indemnified person (other than disputes involving claims against the Senior Lead Arranger, Joint Bookrunner, Joint Lead Arranger or Administrative Agent in its capacity as such), or (B) any settlement of a Proceeding entered into by such indemnified person without your written consent (such consent not to be unreasonably withheld or delayed) and (b) regardless of whether the Closing Date occurs, to reimburse each Commitment Party and its affiliates for all reasonable and documented or invoiced out-of-pocket expenses that have been invoiced prior to the Closing Date (including due diligence expenses, syndication expenses, travel expenses, and the reasonable fees, charges and disbursements of counsel identified in the Term Sheet and of a single local counsel to the Commitment Parties in each appropriate jurisdiction (which may include a single special counsel acting in multiple jurisdictions) and of such other counsel retained with your prior written consent (such consent not to be unreasonably withheld or delayed)) incurred in connection with each of the Credit Facilities and any related documentation (including this Commitment Letter and the definitive financing documentation) or the administration, amendment, modification or waiver thereof. No indemnified person shall be liable for any damages arising from the use by others of Information or other materials obtained through electronic, telecommunications or other information transmission systems, except to the extent any such damages are found by a final, nonappealable judgment of a court of competent jurisdiction to arise from the gross negligence, bad faith or willful misconduct of such indemnified person (or any of its Related Parties). None of the indemnified persons or you or any of your affiliates or the respective directors, officers, employees, advisors, and agents of the foregoing shall be liable for any indirect, special, punitive or consequential damages in connection with this Commitment Letter, the Fee Letters, the Credit Facilities or the transactions contemplated hereby, provided that nothing contained in this sentence shall limit your indemnity obligations to the extent set forth in this Section 7.

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8. Sharing of Information, Absence of Fiduciary Relationship, Affiliate Activities

You acknowledge that each Commitment Party (or an affiliate) is a full service securities firm and such person may from time to time effect transactions, for its own or its affiliates’ account or the account of customers, and hold positions in loans, securities or options on loans or securities of you or your affiliates and of other companies that may be the subject of the transactions contemplated by this Commitment Letter. In addition, each Commitment Party and its affiliates will not use confidential information obtained from you or your affiliates or on your or their behalf by virtue of the transactions contemplated hereby in connection with the performance by such Commitment Party and its affiliates of services for other companies or persons and the Commitment Party and its affiliates will not furnish any such information to any of their other customers. You also acknowledge that the Commitment Parties and their respective affiliates have no obligation to use in connection with the transactions contemplated hereby, or to furnish to you, confidential information obtained from other companies or persons.

You further acknowledge and agree that (a) no fiduciary, advisory or agency relationship between you and the Commitment Parties is intended to be or has been created in respect of any of the transactions contemplated by this Commitment Letter, irrespective of whether the Commitment Parties have advised or are advising you on other matters, (b) the Commitment Parties, on the one hand, and you, on the other hand, have an arm’s length business relationship that does not directly or indirectly give rise to, nor do you rely on, any fiduciary duty to you or your affiliates on the part of the Commitment Parties, (c) you are capable of evaluating and understanding, and you understand and accept, the terms, risks and conditions of the transactions contemplated by this Commitment Letter, (d) you have been advised that the Commitment Parties are engaged in a broad range of transactions that may involve interests that differ from your interests and that the Commitment Parties have no obligation to disclose such interests and transactions to you, (e) you have consulted your own legal, accounting, regulatory and tax advisors to the extent you have deemed appropriate, (f) each Commitment Party has been, is, and will be acting solely as a principal and, except as otherwise expressly agreed in writing by it and the relevant parties, has not been, is not, and will not be acting as an advisor, agent or fiduciary for you, any of your affiliates or any other person or entity and (g) none of the Commitment Parties has any obligation to you or your affiliates with respect to the transactions contemplated hereby except those obligations expressly set forth herein or in any other express writing executed and delivered by such Commitment Party and you or any such affiliate.

9. Confidentiality

This Commitment Letter is delivered to you on the understanding that neither this Commitment Letter nor the Fee Letters nor any of their terms or substance shall be disclosed by you, directly or indirectly, to any other person except (a) you and your officers, directors, employees, affiliates, members, partners, stockholders, attorneys, accountants, agents and advisors and those of the Seller and its subsidiaries and the Seller itself, in each case on a confidential and need-to-know basis (provided that any disclosure of any Fee Letters or their terms or substance to the Seller or its officers, directors, employees, attorneys, accountants, agents or advisors shall be redacted in respect of the amount of fees or market flex set forth in numbered paragraphs 1 and 2 thereof, unless the Commitment Parties otherwise agree) and (b) in any legal, judicial or administrative proceeding or as otherwise required by law or regulation or as requested by a governmental authority (in which case you agree, to the extent practicable and permitted by law, rule or regulation, to inform us promptly in advance thereof); provided that (i) you may disclose the Commitment Letter and its contents (but not the Fee Letters) in any syndication or other marketing materials in connection with the Facilities, in any offering or private placement memoranda relating to the Senior Notes or in connection with any public filing requirement relating to the Transactions, (ii) you may disclose the Term Sheets and the other exhibits and annexes to the Commitment Letter and the contents thereof, to potential Lenders and their affiliates involved in the related commitments (provided that any such party is advised of its obligation to retain such information as confidential), and to rating agencies in

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connection with obtaining ratings for the Borrower, the Bridge Facility and Notes and (iii) you may disclose the aggregate fee amounts contained in the Fee Letters as part of Projections, pro forma information or a generic disclosure of aggregate sources and uses related to fee amounts related to the Transactions to the extent customary or required in offering and marketing materials for the Bridge Facility and/or the Senior Notes or in any public or regulatory filing relating to the Transactions.

The Commitment Parties shall use all nonpublic information received by them in connection with the Acquisition and the related transactions solely for the purposes of providing the services that are the subject of this Commitment Letter and shall treat confidentially all such information; provided, however, that nothing herein shall prevent any Commitment Party from disclosing any such information (a) to rating agencies, (b) to any Lenders or participants or prospective Lenders or participants, (c) in any legal, judicial, administrative proceeding or other compulsory process or as required by applicable law or regulations (in which case such Commitment Party shall promptly notify you, in advance, to the extent permitted by law), (d) upon the request or demand of any regulatory authority having jurisdiction over such Commitment Party or its affiliates (in which case such Commitment Party agrees (except with respect to any audit or examination conducted by bank accountants or any governmental or bank regulatory authority exercising examination or regulatory authority), to the extent practicable and not prohibited by applicable law, rule or regulation, to promptly notify you thereof prior to disclosure), (e) to the employees, legal counsel, independent auditors, professionals and other experts or agents of such Commitment Party (collectively, “Representatives”) who are informed of the confidential nature of such information and are or have been advised of their obligation to keep information of this type confidential, (f) to any of its respective affiliates and their respective Representatives (provided that any such affiliate or Representative is advised of its obligation to retain such information as confidential, and such Commitment Party shall be responsible for its affiliates’ (including any Representative of such affiliates’) compliance with this paragraph) solely in connection with the Acquisition and any related transactions, (g) to the extent any such information becomes publicly available other than by reason of disclosure by such Commitment Party, its affiliates or Representatives in breach of this Commitment Letter and (h) for purposes of establishing a “due diligence” defense; provided that the disclosure of any such information to any Lenders or prospective Lenders or participants or prospective participants referred to above shall be made subject to the acknowledgment and acceptance by such Lender or prospective Lender or participant or prospective participant that such information is being disseminated on a confidential basis in accordance with the standard syndication processes of such Commitment Party or customary market standards for dissemination of such type of information. The provisions of this paragraph shall automatically terminate one year following the date of this Commitment Letter.

10. Miscellaneous

This Commitment Letter shall not be assignable by you (except to one or more of your subsidiaries immediately prior to or otherwise substantially concurrently with the consummation of the Acquisition) without the prior written consent of each Commitment Party (and any purported assignment without such consent shall be null and void), is intended to be solely for the benefit of the parties hereto and the indemnified persons and is not intended to and does not confer any benefits upon, or create any rights in favor of, any person other than the parties hereto and the indemnified persons to the extent expressly set forth herein. The Commitment Parties reserve the right to employ the services of their affiliates in providing services contemplated hereby and to allocate, in whole or in part, to their affiliates certain fees payable to the Commitment Parties in such manner as the Commitment Parties and their affiliates may agree in their sole discretion. This Commitment Letter may not be amended or waived except by an instrument in writing signed by you and each Commitment Party. This Commitment Letter may be executed in any number of counterparts, each of which shall be an original, and all of which, when taken together, shall constitute one agreement. Delivery of an executed signature page of this Commitment Letter by facsimile or electronic transmission (e.g., “pdf” or “tif”) shall be effective as delivery of a manually

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executed counterpart hereof. This Commitment Letter and the Fee Letters are the only agreements that have been entered into among us and you with respect to the Credit Facilities and set forth the entire understanding of the parties with respect thereto. There are no unwritten oral agreements among the parties. This Commitment Letter shall be governed by, and construed and interpreted in accordance with, the laws of the State of New York; provided, that, notwithstanding the preceding sentence and the governing law provisions of this Commitment Letter and the Fee Letters, it is understood and agreed that (a) the interpretation of the definition of “Material Adverse Effect” (and whether or not a Material Adverse Effect has occurred), (b) the determination of the accuracy of any Purchase Agreement Representations and whether as a result of any inaccuracy thereof you have the right to terminate your obligations under the Purchase Agreement and (c) the determination of whether the Acquisition has been consummated in accordance with the terms of the Purchase Agreement and claims or disputes arising out of such determination or any aspect of such determination, in each case, shall be governed by, and construed and interpreted in accordance with, the laws of the State of Texas, regardless of the laws that might otherwise govern under applicable principles of conflicts of laws thereof.

You and we hereby irrevocably and unconditionally submit to the exclusive jurisdiction of any state or Federal court sitting in the Borough of Manhattan in the City of New York over any suit, action or proceeding arising out of or relating to the Transactions or the other transactions contemplated hereby, this Commitment Letter or the Fee Letters or the performance of services hereunder or thereunder. You and we agree that service of any process, summons, notice or document by registered mail addressed to you or us shall be effective service of process for any suit, action or proceeding brought in any such court. You and we hereby irrevocably and unconditionally waive any objection to the laying of venue of any such suit, action or proceeding brought in any such court and any claim that any such suit, action or proceeding has been brought in any inconvenient forum. You and we hereby irrevocably agree to waive trial by jury in any suit, action, proceeding, claim or counterclaim brought by or on behalf of any party related to or arising out of the Transactions, this Commitment Letter or the Fee Letters or the performance of services hereunder or thereunder.

Each of the Commitment Parties hereby notifies you that, pursuant to the requirements of the USA PATRIOT Act, Title III of Pub. L. 107-56 (signed into law on October 26, 2001) (the “PATRIOT Act”), it is required to obtain, verify and record information that identifies the Borrower and each Guarantor, which information includes names, addresses, tax identification numbers and other information that will allow such Lender to identify the Borrower and each Guarantor in accordance with the PATRIOT Act. This notice is given in accordance with the requirements of the PATRIOT Act and is effective for the Commitment Parties and each Lender.

The indemnification, fee, expense, jurisdiction, syndication and confidentiality provisions contained herein and in the Fee Letters shall remain in full force and effect regardless of whether definitive financing documentation shall be executed and delivered and notwithstanding the termination of this Commitment Letter or the commitments hereunder; provided that your obligations under this Commitment Letter (other than your obligations with respect to (a) assistance to be provided in connection with the syndication thereof (including as to the provision of information and representations with respect thereto) prior to the Syndication Date and (b) confidentiality) shall automatically terminate and be superseded, to the extent comparable, by the provisions of the Credit Documentation upon the initial funding thereunder, and you shall automatically be released from all liability in connection therewith at such time. You may terminate this Commitment Letter at any time subject to the provisions of the preceding sentence.

If the foregoing correctly sets forth our agreement, please indicate your acceptance of the terms of this Commitment Letter and the Fee Letters by returning to us executed counterparts of this Commitment Letter and the Fee Letters not later than 11:59 p.m., New York City time, on September 4, 2012. This offer will automatically expire at such time if we have not received such executed counterparts in accordance

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with the preceding sentence. In the event that the Closing Date does not occur on or before the Expiration Date, then this Commitment Letter and the commitments hereunder shall automatically terminate unless we shall, in our discretion, agree to an extension. “Expiration Date” means the earlier of (i) the 180^th day after the execution of this Commitment Letter and (ii) the termination of the Purchase Agreement prior to closing of the Acquisition.

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We are pleased to have been given the opportunity to assist you in connection with this important financing.

Accepted and agreed to as of the date first written above:

EXHIBIT A

TRANSACTION SUMMARY

Capitalized terms used but not defined in this Exhibit A shall have the meanings set forth in the Commitment Letter to which this Exhibit A is attached and in Exhibits B, C and D thereto.

The Borrower intends to acquire from (a) BP Exploration & Production Inc. and BP America Production Company (together, the “BP Seller”), directly or through one or more wholly owned subsidiaries, 100% of the working interest in the Marlin, Dorado and King fields (excluding deep exploration rights) operated by the BP Seller (collectively, the “Marlin Hub”), 100% of the working interest in the Horn Mountain field operated by the BP Seller and a deep exploration prospect (collectively, “Horn Mountain”), 50% of the working interest in the Holstein field owned by the BP Seller (collectively, “Holstein” and collectively with Marlin, and Horn Mountain the “BP Seller Operated Assets”), 33% of the working interest in the Diana & Hoover field owned by the BP Seller (“Diana & Hoover”) and 31% of the working interest in the Ram Powell field owned by the BP Seller (“Ram Powell” and collectively with Diana & Hoover, the “BP Seller Non-Operated Assets” and collectively with the BP Seller Operated Assets, the “BP Assets”) pursuant to a Purchase and Sale Agreement (together with all exhibits, schedules and disclosure letters thereto, the “Purchase Agreement”) dated as of September 4, 2012 among the Borrower, the Seller and, as applicable, their respective affiliates and (b) Shell Offshore Inc. (the “Shell Seller”, and, together with the BP Seller, the “Seller”), directly or through one or more wholly owned subsidiaries, 50% of the working interest in the Holstein field owned by the Shell Seller (the “Shell Assets” and, together with the BP Assets, the “Assets”) . The acquisition of the Assets is referred to herein as the “Acquisition”. In connection therewith, it is intended that:

(a) The Borrower will obtain senior secured revolving and term loan credit facilities (the “Credit Facilities”), as described in Exhibit B, in an aggregate amount of $5.0 billion, with an initial Borrowing Base of $5.3 billion, comprised of:

(i) a $3.0 billion 5-year revolving credit facility (the “Revolving Credit Facility”),

(ii) a $750.0 million 5-year term loan (the “5-Year Term Loan Facility”), and

(iii) a $1.25 billion 7-year term loan (the “7-Year Term Loan Facility” and together with the 5-Year Term Loan Facility, the “Term Loan Facilities”).

(b) The Borrower will issue up to $2.0 billion of senior unsecured notes (the “Senior Notes”) in a public offering or in a Rule 144A or other private placement, and/or (ii) if and to the extent that the Borrower does not, or is unable to, issue the full amount of the Senior Notes on or prior to the Closing Date, the incurrence of senior unsecured loans in an aggregate principal amount of up to $2.0 billion pursuant to a new senior unsecured bridge credit facility (the “Bridge Facility”; together with the Credit Facilities, the “Facilities”) as further described in Exhibit C hereto (the “Bridge Term Sheet”).

(c) The proceeds of the Credit Facilities and the Senior Notes and/or the Bridge Facility on the Closing Date will be applied (i) to refinance certain existing indebtedness of the Borrower, (ii) to pay the cash consideration for the Acquisition, (iii) to pay the fees and expenses incurred in connection with the Transactions (such fees and expenses, the “Transaction Costs”) and (iv) other general corporate purposes.

For purposes of this Commitment Letter and the Fee Letters, “Closing Date” shall mean the date of the satisfaction or waiver of the conditions set forth in Exhibit D.

EXHIBIT B

$3.0 Billion Senior Secured Revolving Credit Facility

$750.0 Million Senior Secured 5-Year Term Loan Facility

$1,250.0 Million Senior Secured 7-Year Term Loan Facility

Summary of Terms and Conditions

Set forth below is a summary of the principal terms and conditions for the Credit Facilities. Capitalized terms used but not defined shall have the meanings set forth in the Commitment Letter to which this Exhibit B is attached and in Exhibits A and D hereto. Reference herein is made to the Amended and Restated Credit Agreement dated as of August 3, 2010 among the Borrower, JPMorgan Chase Bank, N.A., as administrative agent and the lenders from time to time party thereto (as amended to date, the “Existing Credit Agreement”). The definitive documentation evidencing the Credit Facilities shall amend and restate the Existing Credit Agreement.

1. PARTIES

B-1

2. TYPE AND AMOUNT OF CREDIT FACILITIES

B-2

B-3

B-4

B-5

3. CERTAIN PAYMENT PROVISIONS

B-6

B-7

5. CERTAIN CONDITIONS

B-8

B-9

B-10

B-11

B-12

B-13

B-14

Annex I to Exhibit B

INTEREST AND CERTAIN FEES

B-I-1

B-I-2

B-I-3

EXHIBIT C

$2.0 Billion Bridge Facility

Summary of Terms and Conditions

Set forth below is a summary of the principal terms and conditions for the Bridge Facility. Capitalized terms used but not defined herein shall have the meanings set forth in the Commitment Letter to which this Exhibit C is attached and Exhibits A, B and D attached thereto.

1. PARTIES

2. TYPE AND AMOUNT OF INTERIM FACILITY

C-2

3. CERTAIN PAYMENT PROVISIONS

C-3

4. CERTAIN CONDITIONS

5. DOCUMENTATION

C-4

C-5

C-6

Annex I to Exhibit C

Summary of Terms and Conditions

of Exchange Notes and Extended Term Loans

Capitalized terms used but not defined herein have the meanings set forth or referred to in the Exhibit C to which this Annex I is attached.

C-I-2

C-I-3

EXHIBIT D

Conditions Precedent

The availability of the Revolving Credit Facility, the Term Loan Facilities and the Bridge Facility shall be subject to the satisfaction of the following conditions. Capitalized terms used but not defined herein have the meanings set forth in the Commitment Letter to which this Exhibit D is attached and in Exhibits A, B and C thereto.

1. Each party thereto shall have executed and delivered the Credit Facilities Documentation and, if applicable, the Bridge Facility Documentation on terms consistent with the Commitment Letter and otherwise reasonably satisfactory to both the Loan Parties and the Commitment Parties, and the Commitment Parties shall have received:

2. Substantially concurrently with the initial fundings contemplated by the Commitment Letter, as a condition to the funding of the Term Loan Facilities and the Bridge Facility, the Borrower shall have closed the Revolving Credit Facility with a Borrowing Base of not less than $5.3 billion (or such lesser amount as adjusted as a result of any Borrowing Base adjustments referred to in paragraph 4 below), (b) as a condition to the funding of the Revolving Credit Facility and the Bridge Facility, the Borrower shall have received $2.0 billion in gross proceeds from the borrowing of the Term Loans under the Term Loan Facilities and (c) as a condition to the funding of the Revolving Credit Facility and the Term Loan Facilities, the Borrower shall have received $2.0 billion in gross proceeds from the issuance of the Senior Notes and/or borrowings under the Bridge Loan Facility.

3. On the Closing Date, after giving effect to the Transactions, neither the Borrower nor any of its restricted subsidiaries shall have any material indebtedness for borrowed money other than (i) the Facilities and the Senior Notes, (ii) indebtedness permitted to be incurred or outstanding under the Facilities, and (iii) such other debt identified in the Borrower’s most recent quarterly report on Form 10-Q,.

4. The terms of the Purchase Agreement shall be reasonably satisfactory to the Senior Lead Arranger, it being agreed that the draft Purchase Agreement dated September 4, 2012 provided to the Senior Lead Arranger is reasonably satisfactory to the Senior Lead Arranger. The Acquisition shall have been, or substantially concurrent with the closing of the Facilities shall be, consummated pursuant to the Purchase Agreement, without giving effect to any modifications, amendments or express waivers that are materially adverse to the Commitment Parties, the Lenders or the Bridge Lenders without the approval of the Administrative Agent (such approval not to be unreasonably withheld, conditioned or delayed); provided that (x) any reduction in the purchase price for the Acquisition shall not be deemed to be materially adverse to such Persons and (y) if oil and gas properties evaluated in the Initial Reserve Report which are not acquired under the Acquisition have a discounted present value for proved reserves that is greater than $200.0 million, the Commitment Parties may adjust the initial Borrowing Base to reflect the omission of such properties.

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5. Except as set forth on the disclosure schedules to the Purchase Agreement, since the Signing Date (as defined in the Purchase Agreement), there has been no Material Adverse Effect (as defined in the Purchase Agreement).

6. The Borrower shall have in place hedging arrangements reasonably satisfactory to the Administrative Agent to support the initial Borrowing Base.

7. The closing of the Credit Facilities shall have occurred on or before the Expiration Date.

8. The Commitment Parties shall have received the most recently prepared reserve reports for the proved oil and gas properties of the Borrower and its restricted subsidiaries and for the Assets (collectively, the “Initial Reserve Reports”).

9. The Administrative Agent shall have received, at least three Business Days prior to the Closing Date, all documentation and other information required by regulatory authorities under applicable “know your customer” and anti-money laundering rules and regulations, including the PATRIOT Act, that has been reasonably requested in writing at least five business days prior to the Closing Date by the Initial Lender.

10. All fees and expenses due to the Commitment Parties, the Lenders and the Bridge Lenders shall have been paid or shall have been authorized to be deducted from the proceeds of the initial fundings under the Credit Facilities, to the extent invoiced at least two business days prior to the Closing Date (or such later date as the Borrower may reasonably agree).

11. The Administrative Agent shall have received UCC lien searches for the Borrower and its restricted subsidiaries and the Seller as they relate to the Assets reflecting the absence of other liens and security interests other than those being released or which are otherwise permitted.

12. The 7-Year Term Loan Facility and the Bridge Facility shall have received a rating from Moody’s Investors Service, Inc. and Standard & Poor’s Financial Services LLC no later than 15 days prior to the Closing Date.

13. On the Closing Date, there shall be minimum liquidity (undrawn availability under the Revolving Facility and unrestricted cash) of at least $300.0 million.

14. As a condition to the availability of the Credit Facilities and the Bridge Facilities, the Senior Lead Arranger (a) shall have received one or more customary confidential information memoranda (with financial and operating data in a form and substance reasonably satisfactory to the Borrower and the Senior Lead Arranger; provided that the financial data shall not include pro forma or audited financial statements on the Assets unless such financial statements are available to the Borrower) and other marketing material customarily used for the syndication of the Facilities and (b) shall have been afforded no less than 30 consecutive days from the date of delivery of the confidential information memorandum to the Lenders, which period shall exclude certain market holiday related “blackout” periods as reasonably determined by the Senior Lead Arranger.

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