Underwriting Agreement

Exhibit 1.1

Encore Acquisition Company

Underwriting Agreement

New York, New York
March 29, 2006

Citigroup Global Markets Inc.
 388 Greenwich Street
 New York, New York 10013

Ladies and Gentlemen:

          Encore Acquisition Company, a corporation organized under the laws of Delaware (the “Company”), proposes to sell to you as the sole underwriter (the “Underwriter”), the number of shares of Common Stock, $0.01 par value (“Common Stock”), of the Company set forth in Schedule I hereto (said shares to be issued and sold by the Company being hereinafter called the “Underwritten Securities” or the “Securities”)). The Company is not granting to the Underwriter any option to purchase any additional shares of Common Stock in connection with this offering. Any reference herein to the Registration Statement, the Basic Prospectus, any Preliminary Final Prospectus or the Final Prospectus shall be deemed to refer to and include the documents incorporated by reference therein pursuant to Item 12 of Form S-3 which were filed under the Exchange Act on or before the Effective Date of the Registration Statement or the issue date of the Basic Prospectus, any Preliminary Final Prospectus or the Final Prospectus, as the case may be; and any reference herein to the terms “amend,” “amendment” or “supplement” with respect to the Registration Statement, the Basic Prospectus, any Preliminary Final Prospectus or the Final Prospectus shall be deemed to refer to and include the filing of any document under the Exchange Act after the Effective Date of the Registration Statement or the issue date of the Basic Prospectus, any Preliminary Final Prospectus or the Final Prospectus, as the case may be, deemed to be incorporated therein by reference. Certain terms used herein are defined in Section 19 hereof.

          1. Representations and Warranties. The Company represents and warrants to, and agrees with, the Underwriter as set forth below in this Section 1.

     (a) The Company meets, and as of the effective date of the Registration Statement met, the requirements for use of Form S-3 under the Act. The Company has prepared and filed with the Commission a registration statement (the file number of which is set forth in Schedule I hereto) on Form S-3, including a related basic prospectus, for registration under the Act of the offering and sale of the Securities. Such Registration Statement, including any post-effective amendments thereto filed prior to the Execution Time, have become effective. The Company may have filed with the Commission, as part of an amendment to the Registration Statement or pursuant to Rule 424(b), one or more Preliminary Final Prospectuses, each of which has previously been furnished to

you. The Company will file with the Commission a final prospectus supplement relating to the Securities in accordance with Rule 424(b). As filed, such final prospectus supplement shall contain all information required by the Act and the rules thereunder, and, except to the extent the Underwriter shall agree in writing to a modification, shall be in all substantive respects in the form furnished to you prior to the Execution Time or, to the extent not completed at the Execution Time, shall contain only such specific additional information and other changes (beyond that contained in the Basic Prospectus and any Preliminary Final Prospectus) as the Company has advised you, prior to the Execution Time, will be included or made therein. The Registration Statement, at the Execution Time, meets the requirements set forth in Rule 415(a)(1)(x).

     (b) On the Effective Date, the Registration Statement did, and when the Final Prospectus is first filed (if required) in accordance with Rule 424(b) and on the Closing Date (as defined herein) (a “settlement date”), the Final Prospectus (and any supplement thereto) will, comply in all material respects with the applicable requirements of the Act and the Exchange Act and the respective rules thereunder; on the Effective Date and at the Execution Time, the Registration Statement did not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading; and on the date of the Final Prospectus and on the Closing Date and any settlement date, the Final Prospectus (together with any supplement thereto) 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, not misleading; provided, however, that the Company makes no representations or warranties as to the information contained in or omitted from the Registration Statement or the Final Prospectus (or any supplement thereto) in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of the Underwriter specifically for inclusion in the Registration Statement or the Final Prospectus (or any supplement thereto), it being understood and agreed that the only such information furnished by or on behalf of the Underwriter consists of the information described as such in Section 8 hereof.

     (c) The Disclosure Package, when taken together as a whole at the Execution Time, together with the price to public, number of Underwritten Securities and the underwriting discount on the cover page of the Final Prospectus, does not contain any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The preceding sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by the Underwriter specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of the Underwriter consists of the information described as such in Section 8 hereof.

     (d) (i) At the earliest time after the filing of the Registration Statement that the Company or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2)) of the Securities and (ii) as of the Execution Time (with such date being used as the determination date for purposes of this clause (ii)), the Company was not and is not an Ineligible Issuer (as defined in Rule 405), without taking account of any

determination by the Commission pursuant to Rule 405 that it is not necessary that the Company be considered an Ineligible Issuer.

     (e) Each Issuer Free Writing Prospectus does not include any information that conflicts with the information contained in the Registration Statement, including any document incorporated therein and any prospectus supplement deemed to be a part thereof that has not been superseded or modified. The foregoing sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by the Underwriter specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of the Underwriter consists of the information described as such in Section 8 hereof.

     (f) The documents incorporated by reference in the Registration Statement, Disclosure Package and the Final Prospectus, when they became effective or were filed with the Commission, as the case may be, conformed or will conform in all material respects to the requirements of the Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder, and none of such documents, when read together with the other information in the Final Prospectus, (a) at the time the Registration Statement became effective, (b) at the earlier of the time the prospectus was first used and the date and time of the first contract of sale of the Securities in this offering, and (c) on the Closing Date, 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. The preceding sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by the Underwriter specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of the Underwriter consists of the information described as such in Section 8 hereof.

     (g) Neither the Company nor any of its subsidiaries has sustained since the date of the latest audited financial statements included or incorporated by reference in the Final Prospectus any material 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, otherwise than as set forth or contemplated in the Final Prospectus; and, since the respective dates as of which information is given in the Registration Statement and the Final Prospectus, there has not been any change in the capital stock or long-term debt of the Company or any of its subsidiaries (other than shares of the Company’s common stock issued upon exercise of options granted under the Company’s employee stock option plans existing on the date of the Final Prospectus) or any material adverse change, or any development involving a prospective material adverse change, in or affecting the general affairs, management, financial position, stockholders’ equity or results of operations of the Company and its subsidiaries, except as set forth in or contemplated in the Disclosure Package and the Final Prospectus (exclusive of any supplement thereto).

     (h) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Delaware, with power and authority (corporate and other) to own its properties and conduct its business as described in the Final Prospectus; and the Company is duly qualified to do business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to be so qualified would, individually or in the aggregate, not have a material adverse effect on the condition (financial or other), business, properties, earnings, assets, stockholders’ equity, prospects or results of operations of the Company and its subsidiaries taken as a whole (a “Material Adverse Effect”).

     (i) As of March 15, 2006, the Company has 49,766,021 shares of Common Stock issued and outstanding; all the outstanding shares of capital stock of the Company have been duly and validly authorized and issued and are fully paid and nonassessable and are not subject to any pre-emptive or similar rights; except as described in or expressly contemplated by the Disclosure Package and the Final Prospectus, there are no outstanding rights (including, without limitation, pre-emptive rights), warrants or options (other than restricted stock and any options granted or shares of Common Stock of the Company issued upon exercise of options granted or to be granted under the Company’s employee stock option plans existing on the date of the Final Prospectus) to acquire, or instruments convertible into or exchangeable for, any shares of capital stock or other equity interest in the Company or any of its subsidiaries, or any contract, commitment, agreement, understanding or arrangement of any kind relating to the issuance of any capital stock of the Company or any such subsidiary, any such convertible or exchangeable securities or any such rights, warrants or options (other than restricted stock and any options granted or shares of Common Stock of the Company issued upon exercise of options granted or to be granted under the Company’s employee stock option plans existing on the date of the Final Prospectus); the capital stock of the Company conforms in all material respects to the description thereof contained in the Registration Statement, the Disclosure Package and the Final Prospectus.

     (j) Each subsidiary of the Company has been duly incorporated or organized and is an existing corporation, limited partnership or limited liability company in good standing under the laws of the jurisdiction of its incorporation or organization, with power and authority (corporate and other) to own its properties and conduct its business as described in the Final Prospectus; and each subsidiary of the Company is duly qualified to do business as a foreign corporation, limited partnership or limited liability company in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to be so qualified would not have a Material Adverse Effect; all outstanding shares of capital stock of each subsidiary that is a corporation have been duly and validly authorized and issued and are fully paid and non-assessable, and the limited partnership agreements or limited liability company agreements governing all outstanding limited partnership interests or limited liability company interests of each subsidiary that is a limited partnership or limited liability company, as the case may be, have been validly executed and delivered, and all capital contributions required under such limited partnership agreements or limited liability company agreements have been paid in full;

and the capital stock, limited partnership interests or limited liability company interests of each subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects, except for liens under or permitted by the Company’s Amended and Restated Credit Agreement dated August 19, 2004, as amended (the “Senior Credit Facility”), among the Company, Encore Operating, L.P., Bank of America, N.A., as Administrative Agent and L/C Issuer, Fortis Capital Corp. and Wachovia Bank, N.A., as Co-Syndication Agents, BNP Paribas and Citibank, N.A., as Co-Documentation Agents, and the financial institutions listed on Schedule 2.01 thereto as Lenders. The subsidiaries listed on Schedule III of this Agreement are the only subsidiaries of the Company.

     (k) This Agreement has been duly authorized, executed and delivered by the Company.

     (l) The statements set forth in the Final Prospectus under the captions “Description of Common Stock”, insofar as they purport to constitute a summary of the terms of the Securities, and under the caption “Underwriting,” insofar as it purports to describe the provisions of the laws and documents referred to therein, are accurate, complete and fair. The preceding sentence does not apply to statements under the caption “Underwriting” based upon and in conformity with written information furnished to the Company by the Underwriter specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of the Underwriter consists of the information described as such in Section 8 hereof.

     (m) The execution, delivery and performance by the Company of this Agreement, the issuance and sale of the Securities, and the consummation of the transactions contemplated herein and in the Final Prospectus (including the use of proceeds from the sale of the Securities as described in the Final Prospectus), and compliance with the terms and provisions thereof do not and will not (i) conflict with or result in a breach or violation of any of the terms and provisions of, or constitute a default under, any statute, any rule, regulation or order of any governmental agency or body or any court, domestic or foreign, having jurisdiction over the Company or any subsidiary of the Company or any of their properties, or any agreement or instrument to which the Company or any such subsidiary is a party or by which the Company or any such subsidiary is bound or to which any of the properties of the Company or any such subsidiary is subject, except for such breaches, violations and defaults as would not have a Material Adverse Effect, or (ii) result in any violation of the charter or by-laws of the Company or any such subsidiary.

     (n) No consent, approval, authorization, or order of, or registration or filing with, any governmental agency or body or any court is required for the consummation of the transactions contemplated by this Agreement in connection with the issuance and sale of the Securities, except such as have been, or will have been prior to the Closing Date, obtained under the Act and such consents, approvals, authorizations, registrations or qualifications as may be required under state securities or Blue Sky laws in connection with the purchase and distribution of the Securities by the Underwriter.

     (o) Except as disclosed in the Disclosure Package and the Final Prospectus, there are no contracts, agreements or understandings between the Company or any subsidiary and any person that would give rise to a valid claim against the Company, any subsidiary or the Underwriter for a brokerage commission, finder’s fee or other like payment with respect to the offer and sale of the Securities.

     (p) Neither the Company nor any of its subsidiaries is in violation of its respective charter or by-laws or in default in the performance of any obligation, agreement, covenant or condition contained in any indenture, loan agreement, mortgage, lease or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which the Company or any of its subsidiaries or their respective property is bound except where such violations or defaults would not have a Material Adverse Effect.

     (q) The Company and its subsidiaries have (1) good and indefeasible title to all of their interests in the oil and gas properties described in the Disclosure Package and the Final Prospectus, (2) good and indefeasible title in fee simple to all other real property owned by the Company or any of its subsidiaries and (3) good title to all personal property owned by the Company or any of its subsidiaries, in each case, free and clear of all liens, encumbrances and defects, except (i) as described in the Disclosure Package and the Final Prospectus, (ii) liens securing taxes and other governmental charges, or claims of materialmen, mechanics and similar persons, not yet due and payable, (iii) liens and encumbrances under oil and gas leases, options to lease, operating agreements, utilization and pooling agreements, participation and drilling concessions agreements and gas sales contracts, securing payment of amounts not yet due and payable and of a scope and nature customary in the oil and gas industry, (iv) liens arising under or permitted by the Senior Credit Facility or (v) liens, encumbrances and defects that do not, individually or in the aggregate, materially affect the value of such properties, taken as a whole, or materially interfere with the use made or proposed to be made of such properties, taken as a whole, by the Company or its subsidiaries; except as described in the Disclosure Package and the Final Prospectus, the leases, options to lease, drilling concessions or other arrangements held by the Company and its subsidiaries reflect in all material respects the right of the Company and its subsidiaries to explore the unexplored and undeveloped acreage described in the Disclosure Package and the Final Prospectus, and the care taken by the Company and its subsidiaries with respect to acquiring or otherwise procuring such leases, options to lease, drilling concessions and other arrangements was generally consistent with standard industry practices for acquiring or procuring leases to explore acreage for hydrocarbons; and any real property and buildings held under lease by the Company and its subsidiaries are held by them under valid, subsisting and enforceable leases with such exceptions as are not material and do not interfere with the use made or proposed to be made of such real property and buildings by the Company or its subsidiaries.

     (r) The Company and its subsidiaries carry, or are covered by, insurance in such amounts and covering such risks as is adequate for the conduct of their business and the value of their respective properties as is customary for companies engaged in similar businesses in similar industries; and neither the Company nor any of its subsidiaries has

(i) received notice from any insurer or agent of such insurer that capital improvements or other expenditures are required or necessary to be made in order to continue such insurance or (ii) any reason to believe that it will not be able to renew its existing insurance coverage as and when such coverage expires or to obtain similar coverage at reasonable cost from similar insurers as may be necessary to continue its business.

     (s) Except as disclosed in the Disclosure Package and the Final Prospectus, no relationship, direct or indirect, exists between or among the Company or any of its subsidiaries on the one hand, and the directors, officers, stockholders, customers or suppliers of the Company or any of its subsidiaries on the other hand, that are required by the Act to be described in the Final Prospectus.

     (t) The Company and its subsidiaries possess all licenses, franchises, certificates, permits, approvals, consents and other authorizations (collectively, “Governmental Licenses”) issued by and have made all declarations and filings with, the appropriate federal, state, local or foreign governmental or regulatory authorities that are necessary for the ownership or lease of their respective properties or the conduct of their respective businesses as described in the Disclosure Package and the Final Prospectus except where the failure to possess such Governmental Licenses or make such declaration and filings would not, individually or in the aggregate, have a Material Adverse Effect. The Company and its subsidiaries are in compliance with the terms and conditions of all such Governmental Licenses except where the failure to so comply would not, individually or in the aggregate, be reasonably expected to have a Material Adverse Effect; all of such Governmental Licenses are valid and in full force and effect, except where the invalidity of such Governmental Licenses or the failure of such Governmental Licenses to be in full force and effect would not, individually or in the aggregate, be reasonably expected to have a Material Adverse Effect; and neither the Company nor any of its subsidiaries has received notice of any revocation or modification of any such license, certificate, permit or authorization or has any reason to believe that any such Governmental Licenses will not be renewed in the ordinary course, except for notices, modifications or non-renewals as would not, individually or in the aggregate, have a Material Adverse Effect.

     (u) No labor disturbance or dispute with employees of the Company or any of its subsidiaries exists or, to the best knowledge of the Company, is contemplated or threatened, which disturbance or dispute would have a Material Adverse Effect.

     (v) The Company and its subsidiaries own, possess or can acquire on reasonable terms adequate trademarks, trade names and other rights to inventions, know-how, patents, copyrights, confidential information and other intellectual property (collectively, “intellectual property rights”) necessary to conduct the business now operated by them, or presently employed by them, except where the failure to own, possess or acquire such intellectual property rights would not, individually or in the aggregate, have a Material Adverse Effect, and have not received any notice of infringement of or conflict with asserted rights of others with respect to any intellectual property rights that, if determined adversely to the Company or any of its subsidiaries, would individually or in the aggregate have a Material Adverse Effect.

     (w) Except as disclosed in the Disclosure Package and the Final Prospectus, neither the Company nor any of its subsidiaries is in violation of any statute, rule, regulation, decision or order of any governmental agency or body or any court, domestic or foreign, relating to the use, disposal or release of hazardous or toxic substances or relating to the protection or restoration of the environment or human exposure to hazardous or toxic substances (collectively, “environmental laws”), owns or operates any real property contaminated with any substance that is subject to any environmental laws, is liable for any off-site disposal or contamination pursuant to any environmental laws, or is subject to any claim relating to any environmental laws, which violation, contamination, liability or claim would individually or in the aggregate have a Material Adverse Effect; and the Company is not aware of any pending investigation which might lead to such a claim.

     (x) Except as disclosed in the Disclosure Package and the Final Prospectus, there are no pending actions, suits or proceedings against or affecting the Company, any of its subsidiaries or any of their respective properties that, if determined adversely to the Company or any of its subsidiaries, would individually or in the aggregate have a Material Adverse Effect, or would materially and adversely affect the ability of the Company to perform its obligations under this Agreement, or which are otherwise material in the context of the sale of the Securities; and no such actions, suits or proceedings are, to the Company’s knowledge, threatened or contemplated.

     (y) The financial statements and the notes related thereto of the Company and its consolidated subsidiaries included or incorporated by reference in the Disclosure Package and the Final Prospectus present fairly in all material respects the consolidated financial position of the Company and its consolidated subsidiaries as of the dates shown and their results of operations and changes in their consolidated cash flows for the periods shown, and such financial statements have been prepared in conformity with the generally accepted accounting principles in the United States applied on a consistent basis; the assumptions used in preparing any pro forma financial data included or incorporated by reference in the Disclosure Package and the Final Prospectus provide a reasonable basis for presenting the significant effects directly attributable to the transactions or events described therein, the related pro forma adjustments give appropriate effect to those assumptions, and the pro forma data therein reflect the proper application of those adjustments to the corresponding historical financial statement amounts; and the other financial information included or incorporated by reference in the Disclosure Package and the Final Prospectus, including oil and gas production information, has been derived from the accounting records of the Company and its subsidiaries and presents fairly in all material respects the information shown thereby.

     (z) Ernst & Young LLP, who has certified certain financial statements of the Company, is the independent registered public accounting firm with respect to the Company as required by the Act.

     (aa) Miller and Lents, Ltd. (the “Engineer”), whose reserve evaluations are referenced or appear, as the case may be, in the Final Prospectus were, as of December 31, 2003, 2004 and 2005, and are, as of the date hereof, independent engineers with

respect to the Company; and the historical information underlying the estimates of the reserves of the Company supplied by the Company to the Engineer for the purposes of preparing the reserve reports of the Company referenced in the Final Prospectus (the “Reserve Reports”), including, without limitation, production volumes, sales prices for production, contractual pricing provisions under oil or gas sales or marketing contracts or under hedging arrangements, costs of operations and development, and working interest and net revenue information relating to the Company’s ownership interests in properties, was true and correct on the date that each such Reserve Report was prepared in all material respects in accordance with customary industry practices.

     (bb) The Company is not and after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the Disclosure Package and the Final Prospectus, will not be an “investment company” as defined in the Investment Company Act, as amended.

     (cc) No “nationally recognized statistical rating organization” as such term is defined for purposes of Rule 436(g)(2) under the Act has notified the Company that it is considering (i) the downgrading, suspension or withdrawal of, or any review for a possible change that does not indicate the direction of the possible change in, any rating assigned to the Company or any securities of the Company or (ii) any change with negative implications in the outlook for any rating of the Company or any securities of the Company.

     (dd) The Company and its subsidiaries maintain systems of internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorizations; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles and to maintain asset accountability; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; and (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.

     (ee) Nothing has come to the attention of the Company that has caused the Company to believe that the statistical and market-related data included or incorporated by reference in the Disclosure Package and the Final Prospectus is not based on or derived from sources that are reliable and accurate in all material respects.

     (ff) The Company has established and maintains disclosure controls and procedures (as such term is defined in Rule 13a-15 and 15d-15 under the Exchange Act); such disclosure controls and procedures are designed to ensure that material information relating to the Company, including its consolidated subsidiaries, is made known to the Company’s principal executive officer and its principal financial officer by others within those entities, and such disclosure controls and procedures are effective at the reasonable assurance level to perform the functions for which they were established; the Company’s auditors and the Audit Committee of the Board of Directors have been advised of: (i) any significant deficiencies and material weaknesses in the design or operation of internal

control over financial reporting which are reasonably likely to adversely affect the Company’s ability to record, process, summarize, and report financial information; and (ii) any fraud, whether or not material, that involves management or other employees who have a significant role in the Company’s internal control over financial reporting; since the date of the most recent evaluation of such disclosure controls and procedures, there has not been any change in the Company’s internal control over financial reporting that has materially affected, or is reasonably likely to materially affect, the Company’s internal control over financial reporting; the principal executive officer and principal financial officer of the Company have made all certifications required by the Sarbanes-Oxley Act of 2002 (the “Sarbanes-Oxley Act”) and any related rules and regulations promulgated by the Commission, and the statements contained in any such certification are complete and correct; and the Company is otherwise in compliance with all applicable provisions of the Sarbanes-Oxley Act that are effective.

     (gg) There are no contracts, agreements or understandings between the Company or any subsidiary and any person granting such person the right to require the Company to file a registration statement under the Act with respect to any securities of the Company (except as disclosed in the Disclosure Package and the Final Prospectus) or to require the Company to include such securities with the Securities registered pursuant to the Registration Statement.

     (hh) The Company and its subsidiaries have paid all federal, state, local and foreign taxes and filed all tax returns required to be paid or filed through the date hereof to the extent that such taxes have become due and are not being contested in good faith with such exceptions as would not singly or in the aggregate result in a Material Adverse Effect; and except as otherwise disclosed in the Disclosure Package and the Final Prospectus, there is no tax deficiency that has been asserted against the Company or any of its subsidiaries or any of their respective properties or assets which has had, nor does the Company have any knowledge of any tax deficiency, which if determined adversely to the Company or its subsidiaries might have, a Material Adverse Effect.

     (ii) Except as described in the Disclosure Package and the Final Prospectus, no subsidiary of the Company is currently prohibited, directly or indirectly, under any agreement or other instrument to which it is a party or is subject, from paying any dividends to the Company, from making any other distribution to the Company on such subsidiary’s capital stock, from repaying to the Company any loans or advances to such subsidiary from the Company or from transferring any of such subsidiary’s properties or assets to the Company or any other subsidiary of the Company.

     Any certificate signed by any officer of the Company and delivered to the Underwriter or counsel for the Underwriter in connection with the offering of the Securities shall be deemed a representation and warranty by the Company, as to matters covered thereby, to the Underwriter.

     2. Purchase and Sale. Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company agrees to sell to the Underwriter, and the Underwriter agrees to purchase from the Company, at the purchase price set forth in Schedule I hereto, the Underwritten Securities.

          3. Delivery and Payment. Delivery of and payment for the Underwritten Securities shall be made on the date and at the time specified in Schedule I hereto or at such time on such later date not more than three Business Days after the foregoing date as the Underwriter shall designate, which date and time may be postponed by agreement between the Underwriter and the Company or as provided in Section 9 hereof (such date and time of delivery and payment for the Securities being herein called the “Closing Date”). Delivery of the Securities shall be made to the Underwriter against payment by the Underwriter of the purchase price thereof to or upon the order of the Company by wire transfer payable in same-day funds to an account specified by the Company. Delivery of the Underwritten Securities shall be made through the facilities of The Depository Trust Company unless the Underwriter shall otherwise instruct.

          4. Offering by the Underwriter. It is understood that the Underwriter proposes to offer the Securities for sale to the public as set forth in the Final Prospectus.

          5. Agreements. The Company agrees with the Underwriter that:

     (a) Prior to the termination of the offering of the Securities, the Company will not file any amendment of the Registration Statement or supplement (including the Final Prospectus or any Preliminary Final Prospectus) to the Basic Prospectus or any Rule 462(b) Registration Statement unless the Company has furnished you a copy for your review prior to filing and will not file any such proposed amendment or supplement to which you reasonably object. The Company will cause the Final Prospectus, properly completed, and any supplement thereto to be filed in a form approved by the Underwriter with the Commission pursuant to the applicable paragraph of Rule 424(b) within the time period prescribed and will provide evidence satisfactory to the Underwriter of such timely filing. The Company will promptly advise the Underwriter (1) when the Final Prospectus, and any supplement thereto, shall have been filed (if required) with the Commission pursuant to Rule 424(b) or when any Rule 462(b) Registration Statement shall have been filed with the Commission, (2) when, prior to termination of the offering of the Securities, any amendment to the Registration Statement shall have been filed or become effective, (3) of any request by the Commission or its staff for any amendment of the Registration Statement, or any Rule 462(b) Registration Statement, or for any supplement to the Final Prospectus or for any additional information, (4) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any notice that would prevent its use or the institution or threatening of any proceeding for that purpose and (5) of the receipt by the Company of any notification with respect to the suspension of the qualification of the Securities for sale in any jurisdiction or the institution or threatening of any proceeding for such purpose. The Company will use its best efforts to prevent the issuance of any such stop order or the occurrence of any such suspension or prevention and, upon such issuance, occurrence or prevention, to obtain as soon as possible the withdrawal of such stop order or relief from such occurrence or prevention, including, if necessary, by filing an amendment to the Registration Statement or a new registration statement and using its best efforts to have such amendment or new registration statement declared effective as soon as practicable.

     (b) [Reserved]

     (c) If there occurs an event or development as a result of which the Disclosure Package would include an untrue statement of a material fact or would omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances then prevailing, not misleading, the Company will notify promptly the Underwriter so that any use of the Disclosure Package may cease until it is amended or supplemented.

     (d) If, at any time when a prospectus relating to the Securities is required to be delivered under the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), any event occurs as a result of which the Final Prospectus as then supplemented would include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made not misleading, or if it shall be necessary to amend the Registration Statement or supplement the Final Prospectus to comply with the Act or the Exchange Act or the respective rules thereunder, including in connection with use or delivery of the Final Prospectus, the Company promptly will (1) notify the Underwriter of such event, (2) prepare and file with the Commission, subject to the second sentence of paragraph (a) of this Section 5, an amendment or supplement which will correct such statement or omission or effect such compliance, (3) use its best efforts to have any amendment to the Registration Statement declared effective as soon as practicable in order to avoid any disruption in use of the Final Prospectus and (4) supply any supplemented Final Prospectus to you in such quantities as you may reasonably request.

     (e) As soon as practicable, the Company will make generally available to its security holders and to the Underwriter an earnings statement or statements of the Company and its subsidiaries which will satisfy the provisions of Section 11(a) of the Act and Rule 158.

     (f) The Company will furnish to the Underwriter and counsel for the Underwriter, without charge, signed copies of the Registration Statement (including exhibits thereto) and, so long as delivery of a prospectus by an Underwriter or dealer may be required by the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), as many copies of each Preliminary Final Prospectus, the Final Prospectus and each Issuer Free Writing Prospectus and any supplement thereto as the Underwriter may reasonably request. The Company will pay the expenses of printing or other production of all documents relating to the offering.

     (g) The Company will arrange, if necessary, for the qualification of the Securities for sale under the laws of such jurisdictions as the Underwriter may designate, will maintain such qualifications in effect so long as required for the distribution of the Securities and will pay any fee of the National Association of Securities Dealers, Inc., in connection with its review of the offering; provided that in no event shall the Company be obligated to qualify to do business in any jurisdiction where it is not now so qualified or to take any action that would subject it to the imposition of any tax or service of process in suits, other than those arising out of the offering or sale of the Securities, in any jurisdiction where it is not now so subject.

     (h) The Company agrees that, unless it obtains the prior written consent of the Underwriter, and the Underwriter agrees with the Company that, unless it obtains the prior written consent of the Company, it will not make any offer relating to the Securities that would constitute an Issuer Free Writing Prospectus or that would otherwise constitute a “free writing prospectus” (as defined in Rule 405) required to be filed by the Company with the Commission or retained by the Company under Rule 433; provided that the prior written consent of the parties hereto shall be deemed to have been given in respect of the Free Writing Prospectuses included in Schedule II hereto. Any such free writing prospectus consented to by the Underwriter or the Company is hereinafter referred to as a “Permitted Free Writing Prospectus.” The Company agrees that (x) it has treated and will treat, as the case may be, each Permitted Free Writing Prospectus as an Issuer Free Writing Prospectus and (y) it has complied and will comply, as the case may be, with the requirements of Rules 164 and 433 applicable to any Permitted Free Writing Prospectus, including in respect of timely filing with the Commission, legending and record keeping.

     (i) The Company will not, without the prior written consent of Citigroup Global Markets Inc., offer, sell, contract to sell, pledge, or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition or effective economic disposition due to cash settlement or otherwise) by the Company or any affiliate of the Company or any person in privity with the Company or any affiliate of the Company) directly or indirectly, including the filing (or participation in the filing) of a registration statement with the Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Exchange Act, any other shares of Common Stock or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock; or publicly announce an intention to effect any such transaction, until the Business Day set forth on Schedule I hereto (the date 45 days after the date of this Agreement), provided, however, that (a) the Company may issue and sell Common Stock pursuant to any employee stock option plan, stock ownership plan or dividend reinvestment plan of the Company in effect at the Execution Time, (b) the Company may issue Common Stock issuable upon the conversion of securities or the exercise of options or warrants outstanding at the Execution Time and (c) the Company may contract to issue Common Stock in any business combination to be consummated after such 45-day period.

     (j) The Company will not take, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

     (k) The Company will apply the net proceeds from the sale of the Securities as described in the Final Prospectus under the heading “Use of Proceeds.”

     (l) The Company will use its reasonable best efforts to list, subject to notice of issuance, the Securities on the New York Stock Exchange.

          6. Conditions to the Obligations of the Underwriter. The obligations of the Underwriter to purchase the Underwritten Securities shall be subject to the accuracy of the representations and warranties on the part of the Company contained herein as of the Execution Time, the Closing Date and any settlement date pursuant to Section 3 hereof (except to the extent such representations and warranties expressly relate to a specific earlier date (in which case such representations and warranties shall be true and correct as of such specified earlier date)), to the accuracy of the statements of the Company made in any certificates pursuant to the provisions hereof, to the performance by the Company of its obligations hereunder and to the following additional conditions:

     (a) The Final Prospectus, and any supplement thereto, have been filed in the manner and within the time period required by Rule 424(b); any material required to be filed by the Company pursuant to Rule 433(d) under the Act shall have been filed with the Commission within the applicable time periods prescribed for such filings by Rule 433; and no stop order suspending the effectiveness of the Registration Statement or any notice that would prevent its use shall have been issued and no proceedings for that purpose shall have been instituted or threatened.

     (b) The Company shall have requested and caused Baker Botts L.L.P. , counsel for the Company, to have furnished to the Underwriter their opinion, dated the Closing Date and addressed to the Underwriter, to the effect that:

     (i) The Company and each of its subsidiaries listed on Schedule III of the Agreement (individually a “Subsidiary” and collectively the “Subsidiaries”) are validly existing and in good standing under the laws of their respective jurisdictions of organization. The Company and its Subsidiaries have all corporate, partnership or limited liability company power and authority necessary to own or hold their respective properties and to conduct their respective businesses as described in the Disclosure Package and the Final Prospectus;

     (ii) All the outstanding shares of capital stock or other equity interests of each subsidiary of the Company have been duly and validly authorized and issued, are fully paid (in the case of limited partnership or limited liability company interests, to the extent required under the respective partnership or limited liability company agreements) and non-assessable (in the case of limited partnership or limited liability company interests, except as such non-assessability may be limited by the limited partnership or limited liability company statute of the jurisdiction of organization of such entity), and, except as otherwise set forth in the Disclosure Package and the Final Prospectus or as set forth in or permitted by the Senior Credit Facility, all outstanding shares of capital stock of the Subsidiaries are owned by the Company either directly or through wholly owned subsidiaries free and clear of any perfected security interest;

     (iii) The Company’s authorized equity capitalization is contained in the Disclosure Package and set forth in the Final Prospectus; the capital stock of the Company conforms in all material respects to the description thereof contained in the Final Prospectus; the outstanding shares of Common Stock have been duly

and validly authorized and issued and are fully paid and nonassessable; the Securities have been duly and validly authorized, and, when issued and delivered to and paid for by the Underwriter pursuant to this Agreement, will be fully paid and nonassessable; the holders of outstanding shares of capital stock of the Company are not entitled to preemptive or other rights to subscribe for the Securities under the Company’s Second Amended and Restated Certificate of Incorporation or the Delaware General Corporation Law;

     (iv) To the knowledge of such counsel, except as described in the Disclosure Package and the Final Prospectus, there are no legal, governmental or regulatory investigations, actions, suits or proceedings pending to which the Company or any of its subsidiaries is or may be a party or to which any property of the Company or any of its subsidiaries is or may be the subject which, individually or in the aggregate, if determined adversely to the Company or any of its subsidiaries, could reasonably be expected to have a Material Adverse Effect; and to the knowledge of such counsel, no such investigations, actions, suits or proceedings are threatened or contemplated by any governmental or regulatory authority or threatened by others;

     (v) The statements included or incorporated by reference in the Final Prospectus under the heading “Description of Capital Stock” and in the Registration Statement in Item 15, insofar as such statements purport to summarize the provisions of law and documents referred to therein fairly summarize in all material respects the laws and documents described therein;

     (vi) The Registration Statement has become effective under the Act; any required filing of the Basic Prospectus, any Preliminary Final Prospectus and the Final Prospectus, and any supplements thereto, pursuant to Rule 424(b) has been made in the manner and within the time period required by Rule 424(b); to the knowledge of such counsel, no stop order suspending the effectiveness of the Registration Statement or any notice that would prevent its use has been issued, and, to the knowledge of such counsel, no proceedings for that purpose have been instituted or threatened;

     (vii) The Company has the corporate power and authority to execute and deliver this Agreement and to perform all of its obligations thereunder (including the use of proceeds from the sale of the Securities as described in the Disclosure Package and the Final Prospectus); and all action required to be taken by the Company for the due and proper authorization, execution and delivery of this Agreement and the consummation of the transactions contemplated thereby (including the use of proceeds from the sale of the Securities as described in the Disclosure Package and the Final Prospectus) have been duly and validly taken;

     (viii) This Agreement has been duly authorized, executed and delivered by the Company;

     (ix) The Company is not and, after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the Final Prospectus, will not be an “investment company” as defined in the Investment Company Act of 1940, as amended;

     (x) No consent, approval, authorization, filing with or order of any court or governmental or regulatory authority of the United States of America, the State of Delaware (solely with respect to the Delaware General Corporation Law) or the State of Texas is required in connection with the transactions contemplated herein, except such as have been obtained under the Act and such as may be required under the blue sky laws of any jurisdiction in connection with the purchase and distribution of the Securities by the Underwriter in the manner contemplated in this Agreement and in the Final Prospectus and such other approvals (specified in such opinion) as have been obtained;

     (xi) The execution, delivery and performance by the Company of this Agreement, the issuance and sale of the Securities being delivered on the Closing Date, and the consummation of the transactions contemplated by this Agreement (including the use of proceeds from the sale of the Securities as described in the Final Prospectus) will not (i) conflict with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, or result in the creation or imposition of any lien, charge or encumbrance upon any property or assets of the Company or any of its subsidiaries pursuant to, any agreement set forth on Exhibit A to such counsel’s opinion (to be limited to material contracts included in the Company’s Form 10-K for the fiscal year ended December 31, 2005 and any filings since such Form 10-K made by the Company with the Commission, (ii) result in any violation of the provisions of the charter or by-laws or similar organizational documents of the Company or any of its subsidiaries or (iii) result in the violation of any U.S. federal or Texas law or statute, the Delaware General Corporation Law or any judgment, order or regulation of any U.S. or Texas court or governmental or regulatory authority except, in the case of clauses (i) and (iii) above, for such conflicts, breaches or violations, liens, charges or encumbrances that would not, individually or in the aggregate, have a Material Adverse Effect; and

     (xii) To such counsel’s knowledge, except as have been waived, there are no persons with registration or similar rights to have any securities of the Company registered pursuant to the Registration Statement

     (xiii) The documents incorporated by reference in the Registration Statement and the Final Prospectus or any further amendment or supplement thereto made by the Company prior to the Closing Date, (other than the financial statements and related schedules, other financial data and oil and gas reserve and production data therein, as to which such counsel need express no opinion), when they became effective or were filed with the Commission, as the case may be, complied as to form in all material respects with the requirements of the Exchange Act and the rules and regulations of the Commission thereunder;

     (xiv) The Registration Statement and the Final Prospectus (other than (a) the financial statements (including the notes thereto and the auditors’ reports thereon), (b) the other financial and statistical information contained therein, (c) the estimated oil and natural gas reserve evaluations and related calculations of Miller and Lents, Ltd., independent petroleum engineers, and (d) the exhibits thereto, as to which such counsel need express no opinion) appear on their face to comply as to form in all material respects with the applicable requirements of the Act and the Exchange Act.

Such counsel shall also state that they have participated in conferences with officers and other representatives of the Company, with representatives of the Company’s independent registered public accounting firm and independent petroleum engineer and with you and your counsel, at which the contents of the Registration Statement, the Disclosure Package, the Final Prospectus and related matters were discussed, and although they did not independently verify the information in the Registration Statement, the Disclosure Package or the Final Prospectus, and are not passing upon and do not assume any responsibility for the accuracy, completeness or fairness of the statements contained in the Registration Statement, the Disclosure Package and the Final Prospectus (except in opinion (v) above) such counsel shall advise you that, on the basis of the foregoing (relying to a limited extent with respect to materiality upon statements by officers and other representatives of the Company), no facts have come to the attention of such counsel to lead such counsel to believe (1) that on the Effective Date the Registration Statement (other than (a) the financial statements, including the notes thereto and the auditors’ reports thereon, contained or incorporated by reference therein or omitted therefrom, (b) the other financial and statistical information contained or incorporated by reference therein or omitted therefrom, (c) the estimated oil and natural gas reserve evaluations and related calculations of Miller and Lents, Ltd., independent petroleum engineers contained or incorporated by reference therein or omitted therefrom, and (d) any statement or representation in any exhibits included or incorporated by reference therein, as to which such counsel need express no opinion) contained any untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (2) that the Final Prospectus (other than (a) the financial statements, including the notes thereto and the auditors’ reports thereon, contained or incorporated by reference therein or omitted therefrom, (b) the other financial and statistical information contained or incorporated by reference therein or omitted therefrom, and (c) the estimated oil and natural gas reserve evaluations and related calculations of Miller and Lents, Ltd., independent petroleum engineers, contained or incorporated by reference therein or omitted therefrom, as to which such counsel need express no opinion) as of its date and on the Closing Date included or includes any untrue statement of a material fact or omitted or omits to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading or (3) that the Disclosure Package, together with the price to the public, the number of Underwritten Securities and the underwriting discount on the cover page of the Final Prospectus (other than (a) the financial statements, including the notes thereto and the auditors’ reports thereon, contained or incorporated by reference therein or omitted therefrom, (b) the other financial and statistical information contained or incorporated by reference therein or omitted

therefrom therein, and (c) the estimated oil and natural gas reserve evaluations and related calculations of Miller and Lents, Ltd., independent petroleum engineers, contained or incorporated by reference therein or omitted therefrom, as to which such counsel need express no opinion) when taken together as a whole, as of the Execution Time contained any untrue statement of a material fact or omitted to state any material fact necessary in order to make the statements therein, in the light of circumstances under which they were made, not misleading.

In rendering such opinions, such counsel may rely (A) as to matters involving the application of laws of any jurisdiction other than the State of Texas or the Federal laws of the United States, to the extent they deem proper and specified in such opinion, upon the opinion of other counsel of good standing whom they believe to be reliable and who are satisfactory to counsel for the Underwriter and (B) as to matters of fact, to the extent they deem proper, on certificates of responsible officers of the Company and public officials. References to the Final Prospectus in this paragraph (b) shall also include any supplements thereto at the Closing Date.

     (c) The Underwriter shall have received from Andrews Kurth LLP, counsel for the Underwriter, such opinion or opinions, dated the Closing Date and addressed to the Underwriter, with respect to the issuance and sale of the Securities, the Registration Statement, the Disclosure Package, the Final Prospectus (together with any supplement thereto) and other related matters as the Underwriter may reasonably require, and the Company shall have furnished to such counsel such documents as they request for the purpose of enabling them to pass upon such matters.

     (d) The Company shall have furnished to the Underwriter a certificate of the Company, signed by the Chairman of the Board or the President and the principal financial or accounting officer of the Company, dated the Closing Date, to the effect that the signers of such certificate have carefully examined the Registration Statement, the Final Prospectus, the Disclosure Package and any supplements or amendments thereto and this Agreement and that:

     (i) the representations and warranties of the Company in this Agreement are true and correct on and as of the Closing Date with the same effect as if made on the Closing Date (except to the extent such representations and warranties expressly relate to a specific earlier date (in which case such representations and warranties shall be true and correct as of such specified earlier date)), and the Company has complied with all the agreements and satisfied all the conditions on its part to be performed or satisfied at or prior to the Closing Date;

     (ii) no stop order suspending the effectiveness of the Registration Statement or any notice that would prevent its use has been issued and no proceedings for that purpose have been instituted or, to the Company’s knowledge, threatened; and

     (iii) since the date of the most recent financial statements included or incorporated by reference in the Final Prospectus (exclusive of any supplement

thereto), there has been no material adverse effect on the condition (financial or otherwise), prospects, earnings, business or properties of the Company and its subsidiaries, taken as a whole, whether or not arising from transactions in the ordinary course of business, except as set forth in or contemplated in the Disclosure Package and the Final Prospectus (exclusive of any supplement thereto).

     (e) The Company shall have requested and caused Ernst & Young LLP to have furnished to the Underwriter, at the Execution Time and at the Closing Date, letters (which may refer to letters previously delivered to the Underwriter), dated respectively as of the Execution Time and as of the Closing Date, in form and substance reasonably satisfactory to the Underwriter, confirming that, with respect to the Company and its Subsidiaries, they are an independent registered public accounting firm within the meaning of the Act and the Exchange Act and the respective applicable rules and regulations adopted by the Commission thereunder, and stating in effect that:

     (i) in their opinion, the audited financial statements and financial statement schedules and, if applicable, any pro forma financial statements included or incorporated by reference in the Registration Statement and the Final Prospectus and reported on by them comply as to form in all material respects with the applicable accounting requirements of the Act and the Exchange Act and the related rules and regulations adopted by the Commission;

     (ii) on the basis of carrying out certain specified procedures (but not an examination in accordance with generally accepted auditing standards) which would not necessarily reveal matters of significance with respect to the comments set forth in such letter; a reading of the minutes of the meetings of the stockholders, directors and audit committee of the Company and the Subsidiaries; and inquiries of certain officials of the Company who have responsibility for financial and accounting matters of the Company and its subsidiaries as to transactions and events subsequent to December 31, 2005, nothing came to their attention which caused them to believe that:

     (1) with respect to the period subsequent to December 31, 2005, there were, as of a specified date not more than five days prior to the date of the letter, (a) any increases in the consolidated long-term debt of the Company and its subsidiaries, (b) any changes in the capital stock of the Company (other than issuances of capital stock upon the exercise of options and stock appreciation rights, upon earn-outs of performance shares and upon conversion of convertible securities, in each case which were outstanding on the date of the latest balance sheet included or incorporated by reference into the Registration Statement and Final Prospectus), (c) any decreases in the stockholders’ equity of the Company, (d) any decreases in the consolidated net current assets of the Company as compared with the amounts shown on the December 31, 2005 consolidated balance sheet included or incorporated by reference in the Registration Statement and the Final Prospectus, or for the period from

December 31, 2005 to such specified date there were any decreases, as compared with the period from January 1, 2005 to February 28, 2005, in (x) net revenues, (y) income before income taxes, or (z) in total or per share amounts of net income of the Company and its subsidiaries, except in all instances for changes or decreases set forth in such letter, in which case the letter shall be accompanied by an explanation by the Company as to the significance thereof unless said explanation is not deemed necessary by the Underwriter;

     (2) the information included or incorporated by reference in the Registration Statement and Final Prospectus in response to Regulation S-K, Item 301 (Selected Financial Data), Item 302 (Supplementary Financial Information), Item 402 (Executive Compensation) and Item 503(d) (Ratio of Earnings to Fixed Charges) is not in conformity with the applicable disclosure requirements of Regulation S-K; and

     (iii) they have performed certain other specified procedures as a result of which they determined that certain information of an accounting, financial or statistical nature (which is limited to accounting, financial or statistical information derived from the general accounting records of the Company and its subsidiaries) set forth in the Registration Statement and the Final Prospectus and in Exhibit 12 to the Registration Statement, including the information set forth under the captions “Ratio of Earnings to Fixed Charges” and “Summary Consolidated Financial and Operating Data” in the Final Prospectus, the information included or incorporated by reference in Items 1, 2, 6, 7 and 11 of the Company’s Annual Report on Form 10-K, incorporated by reference in the Registration Statement and the Final Prospectus, agrees with the accounting records of the Company and its subsidiaries, excluding any questions of legal interpretation.

     References to the Final Prospectus in this paragraph (e) include any supplement thereto at the date of the letter.

     (f) The Engineer shall have delivered to you at the Closing Date, a letter in form and substance reasonably satisfactory to you, stating, as of the date hereof and as of the Closing Date (or, with respect to matters involving changes or developments since the respective dates as of which specified information with respect to the oil and gas reserves is given or incorporated in the Disclosure Package and the Final Prospectus as of the date not more than five days prior to the date of such letter), the conclusions and findings of such firm with respect to the oil and gas reserves of the Company.

     (g) Subsequent to the Execution Time or, if earlier, the dates as of which information is given in the Registration Statement (exclusive of any amendment thereof) and the Final Prospectus (exclusive of any supplement thereto), there shall not have been (i) any change or decrease specified in the letter or letters referred to in paragraph (e) of this Section 6 or (ii) any change, or any development involving a prospective change, in or affecting the condition (financial or otherwise), earnings, business or properties of the

Company and its subsidiaries taken as a whole, whether or not arising from transactions in the ordinary course of business, except as set forth in or contemplated in the Disclosure Package and the Final Prospectus (exclusive of any supplement thereto) the effect of which, in any case referred to in clause (i) or (ii) above, is, in the sole judgment of the Underwriter, 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 Registration Statement (exclusive of any amendment thereof), the Disclosure Package and the Final Prospectus (exclusive of any supplement thereto).

     (h) Subsequent to the Execution Time, there shall not have been any decrease in the rating of any of the Company’s debt securities by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Act) or any notice given of any intended or potential decrease in any such rating or of a possible change in any such rating that does not indicate the direction of the possible change.

     (i) Prior to the Closing Date, the Company shall have furnished to the Underwriter such further information, certificates and documents as the Underwriter may reasonably request.

     (j) The Securities to be delivered on the Closing Date shall have been admitted and authorized for trading on the New York Stock Exchange, subject to official notice of issuance, and satisfactory evidence of such actions shall have been provided to the Underwriter.

     (k) At the Execution Time, the Company shall have furnished to the Underwriter a letter substantially in the form of Exhibit A hereto from each officer and director of the Company addressed to the Underwriter, and such letters shall be in full force and effect on the date hereof and on the Closing Date

     (l) There shall not have occurred any of the following: (i) a suspension or material limitation in trading in securities generally on the New York Stock Exchange; (ii) a suspension or material limitation in trading in the Company’s securities on the New York Stock Exchange; (iii) a general moratorium on commercial banking activities declared by either Federal or New York State authorities or a material disruption in commercial banking or securities settlement or clearance services in the United States; (iv) the outbreak or escalation of hostilities involving the United States or the declaration by the United States of a national emergency or war or (v) the occurrence of any other calamity or crisis or any change in financial, political or economic conditions in the United States or elsewhere, if the effect of any such event specified in clause (iv) or (v) in the judgment of Citigroup Global Markets Inc. makes it impracticable or inadvisable to proceed with the public offering or the delivery of the Securities on the terms and in the manner contemplated in the Prospectus as first amended or supplemented relating to the Securities.

     (m) The Underwriter shall have received on and as of the Closing Date satisfactory evidence of the good standing of the Company and its subsidiaries in their respective jurisdictions of organization and their good standing as foreign entities in such

other jurisdictions as the Underwriter may reasonably request, in each case (i) in writing or in any standard form of telecommunication from the appropriate Governmental Authorities of such jurisdictions and (ii) with respect to the good standing of the subsidiaries and the good standing as foreign entities, as of a time not more than three (3) business days prior to the Closing Date.

          If any of the conditions specified in this Section 6 shall not have been fulfilled when and as provided in this Agreement, or if any of the opinions and certificates mentioned above or elsewhere in this Agreement shall not be reasonably satisfactory in form and substance to the Underwriter and counsel for the Underwriter, this Agreement and all obligations of the Underwriter hereunder may be canceled at, or at any time prior to, the Closing Date by the Underwriter . Notice of such cancellation shall be given to the Company in writing or by telephone or facsimile confirmed in writing.

          The documents required to be delivered by this Section 6 shall be delivered at the office of Andrews Kurth LLP, counsel for the Underwriter, at 600 Travis, Suite 4200, Houston, Texas 77002, on the Closing Date.

          7. Reimbursement of Underwriter’s Expenses. If the sale of the Securities provided for herein is not consummated because any condition to the obligations of the Underwriter set forth in Section 6 hereof is not satisfied, because of any termination pursuant to Section 10 hereof or because of any refusal, inability or failure on the part of the Company to perform any agreement herein or comply with any provision hereof other than by reason of a default by any of the Underwriter, the Company will reimburse Citigroup Global Markets Inc. as the Underwriter on demand for all out-of-pocket expenses (including reasonable fees and disbursements of counsel) that shall have been incurred by them in connection with the proposed purchase and sale of the Securities.

     8. Indemnification and Contribution. (a) The Company agrees to indemnify and hold harmless the Underwriter, the directors, officers, employees and agents of the Underwriter and each person who controls the Underwriter within the meaning of either the Act or the Exchange Act against any and all losses, claims, damages or liabilities, joint or several, to which they or any of them may become subject under the Act, the Exchange Act or other Federal or state statutory law or regulation, at common law or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon (i) any untrue statement or alleged untrue statement of a material fact contained in the registration statement for the registration of the Securities as originally filed or in any amendment thereof, or any omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading or (ii) any untrue statement or alleged untrue statement of a material fact included in the Basic Prospectus, any Preliminary Final Prospectus, the Final Prospectus, any Issuer Free Writing Prospectus or in any amendment thereof or supplement thereto, or any omission or alleged omission to state therein a material fact required to be stated therein or necessary 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 investigating or defending any

such loss, claim, damage, liability or action; provided, however, that the Company will not be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon any such untrue statement or alleged untrue statement or omission or alleged omission made therein in reliance upon and in conformity with written information furnished to the Company by or on behalf of the Underwriter specifically for inclusion therein. This indemnity agreement will be in addition to any liability which the Company may otherwise have.

     (b) The Underwriter agrees to indemnify and hold harmless the Company, each of its directors, each of its officers who signs the Registration Statement, and each person who controls the Company within the meaning of either the Act or the Exchange Act, to the same extent as the foregoing indemnity from the Company to the Underwriter, but only with reference to written information relating to such Underwriter furnished to the Company by or on behalf of the Underwriter specifically for inclusion in the documents referred to in the foregoing indemnity. This indemnity agreement will be in addition to any liability which the Underwriter may otherwise have. The Company acknowledges that the statements set forth in the last paragraph of the cover page regarding delivery of the Securities and, under the heading “Underwriting”, (i) the name of the Underwriter and its participation in the sale of the Securities, (ii) the second and third sentences of the fifth paragraph and the sixth paragraph regarding sales by the underwriter, commissions and discounts and (iii) the tenth, eleventh and twelfth paragraphs related to stabilization, syndicate covering transactions and penalty bids in the Final Prospectus constitute the only information furnished in writing by the Underwriter for inclusion in the Final Prospectus.

     (c) Promptly after receipt by an indemnified party under this Section 8 of notice of the commencement of any action, such indemnified party will, if a claim in respect thereof is to be made against the indemnifying party under this Section 8, notify the indemnifying party in writing of the commencement thereof; but the failure so to notify the indemnifying party (i) will not relieve it from liability under paragraph (a) or (b) above 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 and (ii) will not, in any event, relieve the indemnifying party from any obligations to any indemnified party other than the indemnification obligation provided in paragraph (a) or (b) above. 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 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. An indemnifying party will not, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to any pending or threatened claim, action, suit or proceeding in respect of which indemnification or contribution may be sought hereunder (whether or not the indemnified parties are actual or potential parties to such claim or action) unless such settlement, compromise or consent includes an unconditional release of each indemnified party from all liability arising out of such claim, action, suit or proceeding.

     (d) In the event that the indemnity provided in paragraph (a), (b) or (c) of this Section 8 is unavailable to or insufficient to hold harmless an indemnified party for any reason, the Company and the Underwriter agree to contribute to the aggregate losses, claims, damages and liabilities (including legal or other expenses reasonably incurred in connection with investigating or defending same) (collectively “Losses”) to which the Company and the Underwriter may be subject in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and by the Underwriter on the other from the offering of the Securities; provided, however, that in no case shall the Underwriter be responsible for any amount in excess of the underwriting discount or commission applicable to the Securities purchased by the Underwriter hereunder. If the allocation provided by the immediately preceding sentence is unavailable for any reason, the Company and the Underwriter shall contribute in such proportion as is appropriate to reflect not only such relative benefits but also the relative fault of the Company on the one hand and of the Underwriter on the other in connection with the statements or omissions which resulted in such Losses as well as any other relevant equitable considerations. Benefits received by the Company shall be deemed to be equal to the total net proceeds from the offering (before deducting expenses) received by it, and benefits received by the Underwriter shall be deemed to be equal to the total underwriting discounts and commissions, in each case as set forth on the cover page of the Final Prospectus. Relative fault shall be determined by reference to, among other things, whether any untrue or any alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information provided by the Company on the one hand or the Underwriter on the other, the intent of the parties and their relative knowledge, access to information and opportunity to correct or prevent such untrue statement or omission. The Company and the Underwriter agree that it would not be just and equitable if contribution were determined by pro rata allocation or any other method of allocation which does not take account of the equitable considerations referred to above. Notwithstanding the provisions of this paragraph (d), no person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation. For purposes of this Section 8, each person who controls an Underwriter within the meaning of either the Act or the Exchange Act and each director, officer, employee and agent of an Underwriter shall have the same rights to

contribution as such Underwriter, and each person who controls the Company within the meaning of either the Act or the Exchange Act, each officer of the Company who shall have signed the Registration Statement and each director of the Company shall have the same rights to contribution as the Company, subject in each case to the applicable terms and conditions of this paragraph (d).

          9. [RESERVED].

          10. Termination. This Agreement shall be subject to termination in the absolute discretion of the Underwriter, 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 Common Stock shall have been suspended by the Commission or the New York Stock Exchange or trading in securities generally on the New York Stock Exchange 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 Underwriter, impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the Final Prospectus (exclusive of any supplement thereto).

          11. Representations and Indemnities to Survive. The respective agreements, representations, warranties, indemnities and other statements of the Company or its officers and of the Underwriter set forth in or made pursuant to this Agreement will remain in full force and effect, regardless of any investigation made by or on behalf of the Underwriter or the Company or any of the officers, directors, employees, agents or controlling persons referred to in Section 8 hereof, and will survive delivery of and payment for the Securities. The provisions of Sections 7 and 8 hereof shall survive the termination or cancellation of this Agreement.

          12. Notices. All communications hereunder will be in writing and effective only on receipt, and, if sent to the Underwriter, will be mailed, delivered or telefaxed to the Citigroup Global Markets Inc. General Counsel (fax no.: (212)  ###-###-####) and confirmed to the General Counsel, Citigroup Global Markets Inc., at 388 Greenwich Street, New York, New York, 10013, Attention: General Counsel; or, if sent to the Company, will be mailed, delivered or telefaxed to (817)  ###-###-#### and confirmed to it at 777 Main Street, Suite 1400, Fort Worth, Texas 76102, attention of Chief Financial Officer, with a copy to Baker Botts L.L.P., 910 Louisiana Street, Houston, Texas 77002, Attn: Sean T. Wheeler.

          13. Successors. This Agreement will inure to the benefit of and be binding upon the parties hereto and their respective successors and the officers, directors, employees, agents and controlling persons referred to in Section 8 hereof, and no other person will have any right or obligation hereunder.

          14. No fiduciary duty. The Company hereby acknowledges that (a) the purchase and sale of the Securities pursuant to this Agreement is an arm’s-length commercial transaction between the Company, on the one hand, and the Underwriter and any affiliate through which it may be acting, on the other, (b) the Underwriter is acting as principal and not as

25

an agent or fiduciary of the Company and (c) the Company’s engagement of the Underwriter in connection with the offering and the process leading up to the offering is as independent contractor and not in any other capacity. Furthermore, the Company agrees that it is solely responsible for making its own judgments in connection with the offering (irrespective of whether any of the Underwriter has advised or is currently advising the Company on related or other matters). The Company agrees that it will not claim that the Underwriter has rendered advisory services of any nature or respect, or owes an agency, fiduciary or similar duty to the Company, in connection with such transaction or the process leading thereto.

          15. Integration. This Agreement supersedes all prior agreements and understandings (whether written or oral) between the Company and the Underwriter, or any of them, with respect to the subject matter hereof.

          16. Applicable Law. This Agreement will be governed by and construed in accordance with the laws of the State of New York applicable to contracts made and to be performed within the State of New York.

          17. Counterparts. This Agreement may be signed in one or more counterparts, each of which shall constitute an original and all of which together shall constitute one and the same agreement.

          18. Headings. The section headings used herein are for convenience only and shall not affect the construction hereof.

          19. Definitions. The terms which follow, when used in this Agreement, shall have the meanings indicated.

     “Act” shall mean the Securities Act of 1933, as amended, and the rules and regulations of the Commission promulgated thereunder.

     “Basic Prospectus” shall mean the prospectus referred to in paragraph 1(a) above contained in the Registration Statement at the Effective Date.

     “Business Day” shall mean any day other than a Saturday, a Sunday or a legal holiday or a day on which banking institutions or trust companies are authorized or obligated by law to close in New York City, New York or Ft. Worth, Texas.

     “Commission” shall mean the Securities and Exchange Commission.

     “Disclosure Package” shall mean (i) the Basic Prospectus, as amended and supplemented to the Execution Time, (ii) the Issuer Free Writing Prospectuses, if any, identified in Schedule II hereto, and (iii) any other Free Writing Prospectus that the parties hereto shall hereafter expressly agree in writing to treat as part of the Disclosure Package.

     “Effective Date” shall mean each date and time that the Registration Statement, and any post-effective amendment or amendments thereto and any Rule 462(b) Registration Statement became or become effective.

     “Exchange Act” shall mean the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission promulgated thereunder.

     “Execution Time” shall mean the date and time that this Agreement is executed and delivered by the parties hereto.

     “Final Prospectus” shall mean the prospectus supplement relating to the Securities that was first filed pursuant to Rule 424(b) after the Execution Time, together with the Basic Prospectus.

     “Free Writing Prospectus” shall mean a free writing prospectus, as defined in Rule 405.

     “Issuer Free Writing Prospectus” shall mean an issuer free writing prospectus, as defined in Rule 433.

     “Preliminary Final Prospectus” shall mean any preliminary prospectus supplement to the Basic Prospectus which describes the Securities and the offering thereof and is used prior to filing of the Final Prospectus, together with the Basic Prospectus.

     “Registration Statement” shall mean the registration statement referred to in paragraph 1(a) above, including (i) all documents filed as part thereof or incorporated or deemed to be incorporated by reference therein, (ii) any information contained or incorporated by reference in any prospectus supplement relating to the Securities that is filed with the Commission pursuant to Rule 424(b) and deemed part of such registration statement pursuant to Rule 430B, as amended at the Execution Time and, in the event any post-effective amendment thereto or any Rule 462(b) Registration Statement becomes effective prior to the Closing Date, shall also mean such registration statement as so amended or such Rule 462(b) Registration Statement, as the case may be.

     “Rule 158”, “Rule 163”, “Rule 164”, “Rule 172”, “Rule 405”, “Rule 415”, “Rule 424”, “Rule 430B”, “Rule 433” and “Rule 462” refer to such rules under the Act.

     “Rule 462(b) Registration Statement” shall mean a registration statement and any amendments thereto filed pursuant to Rule 462(b) relating to the offering covered by the registration statement referred to in Section 1(a) hereof.

          If the foregoing is in accordance with your understanding of our agreement, please sign and return to us the enclosed duplicate hereof, whereupon this letter and your acceptance shall represent a binding agreement among the Company and the Underwriter.

		Very truly yours,
		Encore Acquisition Company
		By:		/s/ L. Ben Nivens
				L. Ben Nivens
				Senior Vice President, Chief Financial
				Officer, Treasurer and Corporate
				Secretary

The foregoing Agreement is
hereby confirmed and accepted
as of the date specified in
Schedule I hereto.
Citigroup Global Markets Inc.
By:		/s/ John C. Bishop
		Name: John C. Bishop
		Title: Vice President

SCHEDULE I

Underwriting Agreement dated March 29, 2006

Registration Statement No. 333-117036

Underwriter: Citigroup Global Markets Inc.

Title, Purchase Price and Description of Securities:

Title: Common Stock, par value $0.01 per share

Number of Underwritten Securities to be sold by the Company: 4,000,000

Price per Share to Public (include accrued dividends, if any): $32.00*

Price per Share to the Underwriter – total: $31.81

* Other provisions: In addition to the underwriting discount, the underwriter may receive a commission equivalent from the investors up to $0.05 for each share of Common Stock sold to the investors in the offering.

Closing Date, Time and Location: April 4, 2006 at 9:00 a.m. CST at Baker Botts L.L.P., 910 Louisiana Street, Houston, Texas 77002

Type of Offering: Non-Delayed

Date referred to in Section 5(i) after which the Company may offer or sell securities issued by the Company without the consent of the Representative: May 13, 2006

SCHEDULE II

Schedule of Free Writing Prospectuses included in the Disclosure Package

None

SCHEDULE III

Subsidiaries

Subsidiary		Jurisdiction of Formation
Encore Operating, L.P.		Texas
EAP Operating, Inc.		Delaware
EAP Properties, Inc.		Delaware
EAP Energy, Inc.		Delaware
EAP Energy Services, L.P.		Texas
Encore Operating Louisiana, LLC		Delaware

[Form of Lock-Up Agreement]		EXHIBIT A

ENCORE ACQUISITION COMPANY
Public Offering of Common Stock

March 29, 2006

Citigroup Global Markets Inc.
388 Greenwich Street
New York, New York 10013

Ladies and Gentlemen:

          This letter is being delivered to you in connection with the proposed Underwriting Agreement (the “Underwriting Agreement”), between Encore Acquisition Company, a Delaware corporation (the “Company”), and you as the sole Underwriter named therein, relating to an underwritten public offering of Common Stock, $0.01 par value (the “Common Stock”), of the Company.

          In order to induce you as the Underwriter to enter into the Underwriting Agreement, the undersigned will not, without the prior written consent of Citigroup Global Markets Inc., offer, sell, contract to sell, pledge or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition or effective economic disposition due to cash settlement or otherwise) by the undersigned or any affiliate of the undersigned or any person in privity with the undersigned or any affiliate of the undersigned), directly or indirectly, including the filing (or participation in the filing) of a registration statement with the Securities and Exchange Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Securities and Exchange Commission promulgated thereunder with respect to, any shares of capital stock of the Company or any securities convertible into or exercisable or exchangeable for such capital stock, or publicly announce an intention to effect any such transaction, for a period of 45 days after the date of the Underwriting Agreement, other than shares of Common Stock disposed of as a bona fide gift or gift, provided that the donee or donees thereof agree in writing to be bound by the terms of this letter and the transaction is not reportable on Form 4.

          If for any reason the Underwriting Agreement shall be terminated prior to the Closing Date (as defined in the Underwriting Agreement), the agreement set forth above shall likewise be terminated.

		Yours very truly,
		[Signature of officer or director]
		[Name and address of officer or director]