Chesapeake Energy (CHK)

(b) The Underwriter shall have been filed with the Commission in accordance with the Act and Section 5(a) of this Agreement. No stop order suspending the effectiveness of the Registration Statement or of any part thereof shall have been issued and no proceedings for that purpose shall have been instituted or, to the knowledge of the Company or the Underwriter, shall be contemplated by the Commission.

(c) Subsequent to the execution and delivery of this Agreement, there shall not have occurred (i) any change, or any development or event involving a prospective change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as one enterprise which, in the judgment of the Underwriter , is material and adverse and makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities; (ii) any downgrading in the rating of any debt securities of the Company by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Act), or any public announcement that any such organization has under surveillance or review its rating of any debt securities of the Company (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement that the Company has been placed on negative outlook; (iii) any change in U.S. or international financial, political or economic conditions or currency exchange rates or exchange controls as would, in the judgment of the Underwriter, be likely to prejudice materially the success of the proposed issue, sale or distribution of the Offered Securities, whether in the primary market or in respect of dealings in the secondary market; (iv) any material suspension or material limitation of trading in securities generally on the New York Stock Exchange, or any setting of minimum prices for trading on such exchange, or any suspension of trading of any securities of the Company on any exchange or in the over-the-counter market; (v) any banking moratorium declared by U.S. Federal or New York authorities; (vi) any major disruption of settlements of securities or clearance services in the United States; or (vii) any attack on, outbreak or escalation of hostilities or acts of terrorism involving the United States, any declaration of war by Congress or any other national or international calamity or emergency if, in the judgment of the Underwriter , the effect of any such attack, outbreak, escalation, act, declaration, calamity or emergency makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities.

(d) The Underwriter shall have received an opinion, dated such Closing Date, of Vinson & Elkins L.L.P., counsel for the Company, that:

(i) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Oklahoma, with corporate power and

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authority to own its properties and conduct its business as described in the General Disclosure Package.

(ii) Each subsidiary of the Company has been duly organized and is in good standing under the laws of the jurisdiction of its organization, with power and authority (corporate and other) to own its property and conduct its business as described in the General Disclosure Package; except where the failure to be so qualified would not reasonably be expected to individually or in the aggregate have a Material Adverse Effect; and the capital stock or similar equity interests of each subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects.

(iii) The Offered Securities have been duly authorized and are validly issued, are fully paid and nonassessable; are consistent with the information in the General Disclosure Package and conform to the description thereof contained in the Prospectus; and the stockholders of the Company have no preemptive rights with respect to the Offered Securities;

(iv) No consent, approval, authorization or order of, 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 or sale of the Offered Securities by the Company, except such as may be required under applicable securities laws in connection with the purchase and resale of the Offered Securities by the Underwriter.

(v) None of the execution, delivery and performance of this Agreement, the issuance and sale of the Offered Securities and compliance with the terms and provisions hereof will result in a breach or violation of any of the terms and provisions of, or constitute a default under, (1) any statute, rule, regulation or order of any governmental agency or body or any court having jurisdiction over the Company or any subsidiary of the Company or any of their properties which is, in the experience of such counsel, customarily applicable to securities offerings or (2) any agreement or instrument filed or referenced as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2005, or to any report on Form 8-K or Form 10-Q filed since December 31, 2005, to which the Company or any such subsidiary is 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, or (3) the charter or by-laws (or similar organizational documents) of the Company or any such subsidiary, and the Company has full power and authority to authorize, issue and sell the Offered Securities as contemplated by this Agreement except in the case of clause (2) for such breaches or violations that would not have a Material Adverse Effect.

(vi) Except as disclosed in the General Disclosure Package, 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 Offered Securities; and no such actions, suits or proceedings are threatened or, to such counsel’s knowledge, contemplated.

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

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(viii) The Registration Statement has become effective under the Act, the Prospectus was filed with the Commission pursuant to the subparagraph of Rule 424(b) specified in such opinion on the date specified therein in the manner and within the time period required by Rule 424 and in compliance with Rule 430B, and, to the best of the knowledge of such counsel, no stop order suspending the effectiveness of the Registration Statement or any part thereof has been issued and no proceedings for that purpose have been instituted or are pending or contemplated under the Act, and the Registration Statement, as of its effective date and as of the date of this Agreement, the Statutory Prospectus, as of the Applicable Time, and the Prospectus, as of its date and the Closing Date, and any amendment or supplement thereto, as of its date, complied as to form in all material respects with the requirements of the Act and the Rules and Regulations; the descriptions in the Registration Statement and the Prospectus of statutes, legal and governmental proceedings and contracts and other documents are accurate and fairly present the information required to be shown; and such counsel do not know of any legal or governmental proceedings required to be described in the Prospectus which are not described as required or of any contracts or documents of a character required to be described in the Registration Statement or Prospectus or to be filed as exhibits to the Registration Statement which are not described and filed as required.

It is understood and agreed that certain of the opinions set forth in paragraphs (i), (ii), (iii), (v) (with respect to conflicts with charters, by-laws or similar organizational documents and with respect to certain of the documents filed as exhibits to the filings described in such paragraph) and (vii) (with respect to due authorization) may be given by the Commercial Law Group, P.C., and certain opinions in paragraphs (vi) and (viii) may be given by Henry Hood, Esq.

In addition, Vinson & Elkins L.L.P. shall state that they have participated in conferences with officers and other representatives of the Company, representatives of the independent public accountants of the Company, general counsel of the Company, representatives of the Underwriter and counsel for the Underwriter, at which conferences the Registration Statement and the Prospectus were discussed. Such counsel shall further state that, although they have made certain additional inquiries and investigations in connection with the preparation of the Registration Statement and the Prospectus, they have not verified, are not passing on and do not assume any responsibility for the accuracy, completeness or fairness of the statements contained in the Registration Statement or the Prospectus or any documents incorporated by reference therein, based on the participation described above in the course of acting as counsel to the Company in this transaction, no information has come to their attention that has caused such counsel to believe that (i) the Registration Statement, at the time it became effective (other than the financial statements and schedules and other financial and accounting data and the oil and gas reserve data and related future net revenue data and exhibits, in each case contained or incorporated by reference therein (including the notes thereto and auditor’s report thereon), as to which such counsel need not express any comment or belief) contained an 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, (ii) the General Disclosure Package (other than the financial statements and schedules and other financial and accounting data and the oil and gas reserve data and related future net revenue data and exhibits, in each case contained or incorporated by reference therein (including the notes thereto and auditors’ report thereon), as to which such counsel need not express any comment or belief), as of the Applicable Time and as of the date of this Agreement, contained an untrue statement of a material fact or omitted to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, (iii) the Prospectus (other than the financial statements and schedules and other financial and accounting data and the oil and gas reserve data and related future net revenue data and exhibits, in each case contained or incorporated by reference therein (including the notes thereto and auditors’ report thereon), as to which such counsel need not express any comment or belief), as of its date and the date of this Agreement, contained an untrue statement of a material fact or omitted to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, (iv) any of the documents incorporated by reference in the Registration Statement (other than the financial statements and schedules and other financial and accounting data and the oil and gas reserve data and related future net revenue data and exhibits, in each case contained or incorporated by reference therein

[[NYCORP:2663970v5:3634D:12/07/06--12:56 p]]

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(including the notes thereto and auditors’ report thereon), as to which such counsel need not express any comment or belief), at the time such Registration Statement became effective or was filed with the Commission (or the time of filing of an amendment, if so amended or deemed amended), as the case may be, did not comply as to form in all material respects with the requirements of the Act or Exchange Act, as the case may be, and the Rules and Regulations.

(e) The Underwriter shall have received from Cravath, Swaine & Moore LLP, counsel for the Underwriter, such opinion or opinions, dated such Closing Date, with respect to the incorporation of the Company, the validity of the Offered Securities delivered on such Closing Date, the Registration Statement, the Prospectus and other related matters as the Underwriter may 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. In rendering such opinion, Cravath, Swaine & Moore LLP may rely as to the incorporation of the Company and all other matters governed by Oklahoma law upon the opinion of Commercial Law Group, P.C. referred to above.

(f) The Underwriter shall have received a certificate, dated such Closing Date, of the President or any Vice President and a principal financial or accounting officer of the Company in which such officers, on behalf of the Company, shall state that the representations and warranties of the Company in this Agreement are true and correct, that the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied hereunder at or prior to such Closing Date, that no stop order suspending the effectiveness of the Registration Statement or of any part thereof has been issued and no proceedings for that purpose have been instituted or are contemplated by the Commission and that, subsequent to the date of the most recent financial statements included or incorporated by reference into the Registration Statement and the General Disclosure Package, there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as a whole except as set forth in or contemplated by the Registration Statement and the General Disclosure Package or as described in such certificate.

(g) The Underwriter shall have received a letter (the “

•The Prospectus shall have been filed with the Commission in accordance with the Act and Section 5(a) of this Agreement. No stop order suspending the effectiveness of any Registration Statement or of any part thereof shall have been issued and no proceedings for that purpose shall have been instituted or, to the knowledge of the Company or any Underwriter, shall be contemplated by the Commission.

•Subsequent to the execution and delivery of this Agreement, there shall not have occurred (i) any change, or any development or event involving a prospective change, in the condition (financial or other), business, properties or results of operations of the Company and its

[[NYCORP:2642096v20:3642W:12/01/06--02:34 p]]

subsidiaries taken as one enterprise which, in the judgment of the Representatives, is material and adverse and makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities; (ii) any downgrading in the rating of any debt securities of the Company by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Act), or any public announcement that any such organization has under surveillance or review its rating of any debt securities of the Company (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement that the Company has been placed on negative outlook; (iii) any change in U.S., U.K., Irish or international financial, political or economic conditions or currency exchange rates or exchange controls as would, in the judgment of a majority in interest of the Underwriters including the Representatives, be likely to prejudice materially the success of the proposed issue, sale or distribution of the Offered Securities, whether in the primary market or in respect of dealings in the secondary market; (iv) any material suspension or material limitation of trading in securities generally on the New York Stock Exchange, London Stock Exchange or Irish Stock Exchange, or any setting of minimum prices for trading on such exchanges, or any suspension of trading of any securities of the Company on any exchange or in the over-the-counter market; (v) any banking moratorium declared by U.S. Federal or New York State authorities or regulatory authorities in the United Kingdom or Ireland; (vi) any major disruption of settlements of securities or clearance services in the United States, the United Kingdom or Ireland; or (vii) any attack on, outbreak or escalation of hostilities or acts of terrorism involving the United States, the United Kingdom or Ireland, any declaration of war by U.S. Congress or any other national or international calamity or emergency if, in the judgment of the Representatives, the effect of any such attack, outbreak, escalation, act, declaration, calamity or emergency makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities.

•The Representatives shall have received an opinion, dated such Closing Date, of Vinson & Elkins L.L.P., counsel for the Company, that:

•The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Oklahoma, with corporate power and authority to own its properties and conduct its business as described in the General Disclosure Package.

•Each subsidiary of the Company has been duly organized and is in good standing under the laws of the jurisdiction of its organization, with power and authority (corporate and other) to own its property and conduct its business as described in the General Disclosure Package; except where the failure to be so qualified would not reasonably be expected to individually or in the aggregate have a Material Adverse Effect; and the capital stock or similar equity interests of each subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects.

•The Indenture has been duly authorized, executed and delivered by the Company and each Subsidiary Guarantor; the Guarantees have been duly authorized by each Subsidiary Guarantor; the Offered Securities have been duly authorized; when the Offered Securities are delivered and paid for pursuant to this Agreement on the Closing Date, such Offered Securities will have been duly executed, authenticated, issued and delivered and will conform to the description thereof contained in the General Disclosure Package and the Indenture; and such Offered Securities will constitute valid and legally binding obligations of the Company and each Subsidiary Guarantor, enforceable in accordance with their terms, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles.

[[NYCORP:2642096v20:3642W:12/01/06--02:34 p]]

•No consent, approval, authorization or order of, 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 or sale of the Offered Securities by the Company, except such as have been obtained and made (i) under applicable securities laws in connection with the purchase and resale of the Offered Securities by the Underwriters and (ii) under the rules and regulations of the Irish Stock Exchange with respect to the listing thereon of the Offered Securities.

•None of the execution, delivery and performance of this Agreement and the Indenture, the issuance and sale of the Offered Securities and compliance with the terms and provisions hereof and thereof will result in a breach or violation of any of the terms and provisions of, or constitute a default under, (1) any statute, rule, regulation or order of any governmental agency or body or any court having jurisdiction over the Company or any subsidiary of the Company or any of their properties which is, in the experience of such counsel, customarily applicable to securities offerings or (2) any agreement or instrument filed or referenced as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2005, or to any report on Form 8-K or Form 10-Q filed since December 31, 2005, to which the Company or any such subsidiary is 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, or (3) the charter or by-laws (or similar organizational documents) of the Company or any such subsidiary, and the Company has full power and authority to authorize, issue and sell the Offered Securities as contemplated by this Agreement except in the case of clause (2) for such breaches or violations that would not have a Material Adverse Effect.

•The statements under the captions “Description of Notes” and “Material United States Federal Income Tax Considerations” in the Prospectus, insofar as such statements purport to describe or summarize the legal matters and documents therein, fairly present in all material respects such legal matters and documents.

•Except as disclosed in the General Disclosure Package, 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 or any Subsidiary Guarantor to perform its obligations under this Agreement or the Indenture, or which are otherwise material in the context of the sale of the Offered Securities; and no such actions, suits or proceedings are threatened or, to such counsel’s knowledge, contemplated.

•This Agreement has been duly authorized, executed and delivered by the Company and each Subsidiary Guarantor.

•Each Registration Statement has become effective under the Act, the Prospectus was filed with the Commission pursuant to the subparagraph of Rule 424(b) specified in such opinion on the date specified therein in the manner and within the time period required by Rule 424 and in compliance with Rule 430B, and, to the best of the knowledge of such counsel, no stop order suspending the effectiveness of any Registration Statement or any part thereof has been issued and no proceedings for that purpose have been instituted or are pending or contemplated under the Act, and each Registration Statement, as of its effective date and as of the date of this Agreement and the Prospectus as of the Applicable Time, and any amendment or supplement thereto, as of its date, complied as to form in all material respects with the requirements of the Act and the Rules and Regulations; the descriptions in each Registration Statement and the Prospectus of statutes, legal and governmental proceedings and contracts and other

[[NYCORP:2642096v20:3642W:12/01/06--02:34 p]]

documents are accurate and fairly present the information required to be shown; and such counsel do not know of any legal or governmental proceedings required to be described in the Prospectus which are not described as required or of any contracts or documents of a character required to be described in each Registration Statement or Prospectus or to be filed as exhibits to such Registration Statement which are not described and filed as required.

It is understood and agreed that certain of the opinions set forth in paragraphs (i), (ii), (iii), (v) (with respect to conflicts with charters, by-laws or similar organizational documents and with respect to certain of the documents filed as exhibits to the filings described in such paragraph) and (viii) (with respect to due authorization) may be given by the Commercial Law Group, P.C., and certain opinions in paragraphs (vii) and (ix) may be given by Henry Hood, Esq.

In addition, Vinson & Elkins L.L.P. shall state that they have participated in conferences with officers and other Representatives of the Company, Representatives of the independent public accountants of the Company, general counsel of the Company, Representatives of the Underwriters and counsel for the Underwriters, at which conferences the Registration Statements and the Prospectus were discussed. Such counsel shall further state that, although they have made certain additional inquiries and investigations in connection with the preparation of the Registration Statements and the Prospectus, they have not verified, are not passing on and do not assume any responsibility for the accuracy, completeness or fairness of the statements contained in the Registration Statements or the Prospectus or any documents incorporated by reference therein, based on the participation described above in the course of acting as counsel to the Company in this transaction, no information has come to their attention that has caused such counsel to believe that (i)  any Registration Statement, at the time it became effective (other than the financial statements and schedules and other financial data and the oil and gas reserve data in each case contained or incorporated by reference (including the notes thereto and auditor’s report thereon) as to which such counsel need not express any comment or belief) contained an 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 or (ii) any of the documents incorporated by reference in any Registration Statement, at the time it became effective or was filed with the Commission (or the time of filing of an amendment, if so amended), as the case may be, did not comply as to form in all material respects with the requirements of the Act or Exchange Act, as the case may be, and the Rules and Regulations; such counsel shall also state that no information has come to their attention that has caused such counsel to believe that the Prospectus, at the date hereof and as of the Closing Date, or the documents specified in a schedule to such counsel’s letter, consisting of those included in the General Disclosure Package, as of the Applicable Time and as of the Closing Date, 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 the circumstances under which they were made, not misleading (other than the financial statements and schedules and other financial data and the oil and gas reserve data, in each case contained or incorporated by reference (including the notes thereto and auditor’s report thereon) as to which such counsel need not express any comment or belief).

•The Representatives shall have received from Cravath, Swaine & Moore LLP, counsel for the Underwriters, such opinion or opinions, dated the Closing Date, with respect to the incorporation of the Company, the validity of the Offered Securities delivered on the Closing Date, the Registration Statements, the Prospectus and other related matters as the Representatives may 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. In rendering such opinion, Cravath, Swaine & Moore LLP may rely as to the incorporation of the Company and all other matters governed by Oklahoma law upon the opinion of Commercial Law Group, P.C. referred to above.

•The Representatives shall have received a certificate, dated the Closing Date, of the President or any Vice President and a principal financial or accounting officer of the Company in which such officers, on behalf of the Company, shall state that the representations and warranties of the Company in this Agreement are true and correct, that the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied hereunder at or prior

[[NYCORP:2642096v20:3642W:12/01/06--02:34 p]]

to the Closing Date, that no stop order suspending the effectiveness of any Registration Statement or of any part thereof has been issued and no proceedings for that purpose have been instituted or are contemplated by the Commission and that, subsequent to the date of the most recent financial statements included or incorporated by reference into the Registration Statements and the General Disclosure Package, there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as a whole except as set forth in or contemplated by the Registration Statements and the General Disclosure Package or as described in such certificate.

•The Representatives shall have received a letter (the “

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(b) The Prospectus shall have been filed with the Commission in accordance with the Act and Section 5(a) of this Agreement. No stop order suspending the effectiveness of the Registration Statement or of any part thereof shall have been issued and no proceedings for that purpose shall have been instituted or, to the knowledge of the Company or any Underwriter, shall be contemplated by the Commission.

(c) Subsequent to the execution and delivery of this Agreement, there shall not have occurred (i) any change, or any development or event involving a prospective change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as one enterprise which, in the judgment of the Representatives, is material and adverse and makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities; (ii) any downgrading in the rating of any debt securities of the Company by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Act), or any public announcement that any such organization has under surveillance or review its rating of any debt securities of the Company (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement that the Company has been placed on negative outlook; (iii) any change in U.S. or international financial, political or economic conditions or currency exchange rates or exchange controls as would, in the judgment of a majority in interest of the Underwriters including the Representatives, be likely to prejudice materially the success of the proposed issue, sale or distribution of the Offered Securities, whether in the primary market or in respect of dealings in the secondary market; (iv) any material suspension or material limitation of trading in securities generally on the New York Stock Exchange, or any setting of minimum prices for trading on such exchange, or any suspension of trading of any securities of the Company on any exchange or in the over-the-counter market; (v) any banking moratorium declared by U.S. Federal or New York authorities; (vi) any major disruption of settlements of securities or clearance services in the United States; or (vii) any attack on, outbreak or escalation of hostilities or acts of terrorism involving the United States, any declaration of war by Congress or any other national or international calamity or emergency if, in the judgment of the Representatives, the effect of any such attack, outbreak, escalation, act, declaration, calamity or emergency makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities.

(d) The Representatives shall have received an opinion, dated such Closing Date, of Vinson & Elkins L.L.P., counsel for the Company, that:

(i) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Oklahoma, with corporate power and authority to own its properties and conduct its business as described in the General Disclosure Package.

(ii) Each subsidiary of the Company has been duly organized and is in good standing under the laws of the jurisdiction of its organization, with power and authority (corporate and other) to own its property and conduct its business as described in the General Disclosure Package; except where the failure to be so qualified would not reasonably be expected to individually or in the aggregate have a Material Adverse Effect; and the capital stock or similar equity interests of each subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects.

(iii) The Indenture has been duly authorized, executed and delivered by the Company and each Subsidiary Guarantor; the Guarantees have been duly authorized by each Subsidiary Guarantor; the Offered Securities have been duly authorized; when the Offered Securities are delivered and paid for pursuant to this Agreement on the Closing Date, such Offered Securities will have been duly executed, authenticated, issued and delivered and will conform to the description thereof contained in the General Disclosure

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Package and the Indenture; and such Offered Securities will constitute valid and legally binding obligations of the Company and each Subsidiary Guarantor, enforceable in accordance with their terms, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles;

(iv) No consent, approval, authorization or order of, 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 or sale of the Offered Securities by the Company, except such as have been obtained and made under the Act and such as may be required under state securities laws.

(v) None of the execution, delivery and performance of this Agreement and the Indenture, the issuance and sale of the Offered Securities and compliance with the terms and provisions hereof and thereof will result in a breach or violation of any of the terms and provisions of, or constitute a default under, (1) any statute, rule, regulation or order of any governmental agency or body or any court having jurisdiction over the Company or any subsidiary of the Company or any of their properties which is, in the experience of such counsel, customarily applicable to securities offerings or (2) any agreement or instrument filed or referenced as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2005, or to any report on Form 8-K or Form 10-Q filed since December 31, 2005, to which the Company or any such subsidiary is 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, or (3) the charter or by-laws (or similar organizational documents) of the Company or any such subsidiary, and the Company has full power and authority to authorize, issue and sell the Offered Securities as contemplated by this Agreement except in the case of clause (2) for such breaches or violations that would not have a Material Adverse Effect.

(vi) The statements under the captions “Description of Notes” and “Material United States Federal Income Tax Considerations” in the Prospectus, insofar as such statements purport to describe or summarize the legal matters and documents therein, fairly present in all material respects such legal matters and documents

(vii) Except as disclosed in the General Disclosure Package, 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 or any Subsidiary Guarantor to perform its obligations under this Agreement or the Indenture, or which are otherwise material in the context of the sale of the Offered Securities; and no such actions, suits or proceedings are threatened or, to such counsel’s knowledge, contemplated.

(viii) This Agreement has been duly authorized, executed and delivered by the Company and each Subsidiary Guarantor.

(ix) The Registration Statement has become effective under the Act, the Prospectus was filed with the Commission pursuant to the subparagraph of Rule 424(b) specified in such opinion on the date specified therein in the manner and within the time period required by Rule 424 and in compliance with Rule 430B, and, to the best of the knowledge of such counsel, no stop order suspending the effectiveness of the Registration Statement or any part thereof has been issued and no proceedings for that purpose have been instituted or are pending or contemplated under the Act, and the Registration Statement, as of its effective date and as of the date of this Agreement and the Prospectus as of the Applicable Time, and any amendment or supplement thereto, as

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of its date, complied as to form in all material respects with the requirements of the Act and the Rules and Regulations; each of the documents incorporated by reference in the Registration Statement, at the time it became effective or was filed with the Commission (or the time of filing of an amendment, if so amended), as the case may be, complied as to form in all material respects with the requirements of the Act or Exchange Act, as the case may be, and the Rules and Regulations; the descriptions in the Registration Statement and the Prospectus of statutes, legal and governmental proceedings and contracts and other documents are accurate and fairly present the information required to be shown; and such counsel do not know of any legal or governmental proceedings required to be described in the Prospectus which are not described as required or of any contracts or documents of a character required to be described in the Registration Statement or Prospectus or to be filed as exhibits to the Registration Statement which are not described and filed as required.

It is understood and agreed that certain of the opinions set forth in paragraphs (i), (ii), (iii), (v) (with respect to conflicts with charters, by-laws or similar organizational documents and with respect to certain of the documents filed as exhibits to the filings described in such paragraph) and (viii) (with respect to due authorization) may be given by the Commercial Law Group, P.C., and certain opinions in paragraphs (vii) and (ix) may be given by Henry Hood, Esq.

In addition, Vinson & Elkins L.L.P. shall state that they have participated in conferences with officers and other representatives of the Company, representatives of the independent public accountants of the Company, general counsel of the Company, representatives of the Underwriters and counsel for the Underwriters, at which conferences the Registration Statement and the Prospectus were discussed. Such counsel shall further state that, although they have made certain additional inquiries and investigations in connection with the preparation of the Registration Statement and the Prospectus, they have not verified, are not passing on and do not assume any responsibility for the accuracy, completeness or fairness of the statements contained in the Registration Statement or the Prospectus or any documents incorporated by reference therein, based on the participation described above in the course of acting as counsel to the Company in this transaction, no information has come to their attention that has caused such counsel to believe that the Registration Statement, at the time it became effective, or the Prospectus, at the date hereof and as of the Closing Date (other than the financial statements and schedules and other financial data and the oil and gas reserve data, in each case contained or incorporated by reference (including the notes thereto and auditor’s report thereon) therein, as to which such counsel need not express any comment or belief) contained an 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; such counsel shall also state that they have no reason to believe that the documents specified in a schedule to such counsel’s letter, consisting of those included in the General Disclosure Package, as of the Applicable Time and as of the Closing Date, 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 the circumstances under which they were made, not misleading.

(e) The Representatives shall have received from Cravath, Swaine & Moore LLP, counsel for the Underwriters, such opinion or opinions, dated the Closing Date, with respect to the incorporation of the Company, the validity of the Offered Securities delivered on the Closing Date, the Registration Statement, the Prospectus and other related matters as the Representatives may 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. In rendering such opinion, Cravath, Swaine & Moore LLP may rely as to the incorporation of the Company and all other matters governed by Oklahoma law upon the opinion of Commercial Law Group, P.C. referred to above.

(f) The Representatives shall have received a certificate, dated the Closing Date, of the President or any Vice President and a principal financial or accounting officer of the Company in which such officers, on behalf of the Company, shall state that the representations and warranties of the Company in this Agreement are true and correct, that the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied hereunder at or prior

13

to the Closing Date, that no stop order suspending the effectiveness of the Registration Statement or of any part thereof has been issued and no proceedings for that purpose have been instituted or are contemplated by the Commission and that, subsequent to the date of the most recent financial statements included or incorporated by reference into the Registration Statement and the General Disclosure Package, there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as a whole except as set forth in or contemplated by the Registration Statement and the General Disclosure Package or as described in such certificate.

(g) The Representatives shall have received a letter (the “

(b) The Prospectus shall have been filed with the Commission in accordance with the Act and Section 5(a) of this Agreement. No stop order suspending the effectiveness of the Registration Statement or of any part thereof shall have been issued and no proceedings for that purpose shall have been instituted or, to the knowledge of the Company or any Underwriter, shall be contemplated by the Commission.

(c) Subsequent to the execution and delivery of this Agreement, there shall not have occurred (i) any change, or any development or event involving a prospective change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as one enterprise which, in the judgment of the Representatives, is material and adverse and makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities; (ii) any downgrading in the rating of any debt securities of the Company by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Act), or any public announcement that any such organization has under surveillance or review its rating of any debt securities of the Company (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement that the Company has been placed on negative outlook; (iii) any change in U.S. or international financial, political or economic conditions or currency exchange rates or exchange controls as would, in the judgment of a majority in interest of the Underwriters including the Representatives, be likely to prejudice materially the success of the proposed issue, sale or distribution of the Offered Securities, whether in the primary market or in respect of dealings in the secondary market; (iv) any material suspension or material limitation of trading in securities generally on the New York Stock Exchange, or any setting of minimum prices for trading on such exchange, or any suspension of trading of any securities of the Company on any exchange or in the over-the-counter market; (v) any banking moratorium declared by U.S. Federal or New York authorities; (vi) any major disruption of settlements of securities or clearance services in the United States; or (vii) any attack on, outbreak or escalation of hostilities or acts of terrorism involving the United States, any declaration of war by Congress or any other national or international calamity or emergency if, in the judgment of the Representatives, the effect of any such attack, outbreak, escalation, act, declaration, calamity or emergency makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities.

(d) The Representatives shall have received an opinion, dated such Closing Date, of Vinson & Elkins L.L.P., counsel for the Company, that:

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(i) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Oklahoma, with corporate power and authority to own its properties and conduct its business as described in the General Disclosure Package.

(ii) Each subsidiary of the Company has been duly organized and is in good standing under the laws of the jurisdiction of its organization, with power and authority (corporate and other) to own its property and conduct its business as described in the General Disclosure Package; except where the failure to be so qualified would not reasonably be expected to individually or in the aggregate have a Material Adverse Effect; and the capital stock or similar equity interests of each subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects.

(iii) The Offered Securities have been duly authorized and are validly issued, are fully paid and nonassessable; are consistent with the information in the General Disclosure Package and conform to the description thereof contained in the Prospectus; and the stockholders of the Company have no preemptive rights with respect to the Offered Securities;

(iv) No consent, approval, authorization or order of, 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 or sale of the Offered Securities by the Company, except such as have been obtained and made under the Act and such as may be required under state securities laws.

(v) None of the execution, delivery and performance of this Agreement, the issuance and sale of the Offered Securities and compliance with the terms and provisions hereof will result in a breach or violation of any of the terms and provisions of, or constitute a default under, (1) any statute, rule, regulation or order of any governmental agency or body or any court having jurisdiction over the Company or any subsidiary of the Company or any of their properties which is, in the experience of such counsel, customarily applicable to securities offerings or (2) any agreement or instrument filed or referenced as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2005, or to any report on Form 8-K or Form 10-Q filed since December 31, 2005, to which the Company or any such subsidiary is 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, or (3) the charter or by-laws (or similar organizational documents) of the Company or any such subsidiary, and the Company has full power and authority to authorize, issue and sell the Offered Securities as contemplated by this Agreement except in the case of clause (2) for such breaches or violations that would not have a Material Adverse Effect.

(vi) Except as disclosed in the General Disclosure Package, 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 Offered Securities; and no such actions, suits or proceedings are threatened or, to such counsel’s knowledge, contemplated.

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

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(viii) The Registration Statement has become effective under the Act, the Prospectus was filed with the Commission pursuant to the subparagraph of Rule 424(b) specified in such opinion on the date specified therein in the manner and within the time period required by Rule 424 and in compliance with Rule 430B, and, to the best of the knowledge of such counsel, no stop order suspending the effectiveness of the Registration Statement or any part thereof has been issued and no proceedings for that purpose have been instituted or are pending or contemplated under the Act, and the Registration Statement, as of its effective date and as of the date of this Agreement and the Prospectus as of the Applicable Time, and any amendment or supplement thereto, as of its date, complied as to form in all material respects with the requirements of the Act and the Rules and Regulations; each of the documents incorporated by reference in the Registration Statement, at the time it became effective or was filed with the Commission (or the time of filing of an amendment, if so amended), as the case may be, complied as to form in all material respects with the requirements of the Act or Exchange Act, as the case may be, and the Rules and Regulations; the descriptions in the Registration Statement and the Prospectus of statutes, legal and governmental proceedings and contracts and other documents are accurate and fairly present the information required to be shown; and such counsel do not know of any legal or governmental proceedings required to be described in the Prospectus which are not described as required or of any contracts or documents of a character required to be described in the Registration Statement or Prospectus or to be filed as exhibits to the Registration Statement which are not described and filed as required.

It is understood and agreed that certain of the opinions set forth in paragraphs (i), (ii), (iii), (v) (with respect to conflicts with charters, by-laws or similar organizational documents and with respect to certain of the documents filed as exhibits to the filings described in such paragraph) and (vii) (with respect to due authorization) may be given by the Commercial Law Group, P.C., and certain opinions in paragraphs (vi) and (viii) may be given by Henry Hood, Esq.

In addition, Vinson & Elkins L.L.P. shall state that they have participated in conferences with officers and other representatives of the Company, representatives of the independent public accountants of the Company, general counsel of the Company, representatives of the Underwriters and counsel for the Underwriters, at which conferences the Registration Statement and the Prospectus were discussed. Such counsel shall further state that, although they have made certain additional inquiries and investigations in connection with the preparation of the Registration Statement and the Prospectus, they have not verified, are not passing on and do not assume any responsibility for the accuracy, completeness or fairness of the statements contained in the Registration Statement or the Prospectus or any documents incorporated by reference therein, based on the participation described above in the course of acting as counsel to the Company in this transaction, no information has come to their attention that has caused such counsel to believe that the Registration Statement, at the time it became effective, or the Prospectus, at the date hereof and as of the Closing Date (other than the financial statements and schedules and other financial data and the oil and gas reserve data, in each case contained or incorporated by reference (including the notes thereto and auditor’s report thereon) therein, as to which such counsel need not express any comment or belief) contained an 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; such counsel shall also state that they have no reason to believe that the documents specified in a schedule to such counsel’s letter, consisting of those included in the General Disclosure Package, as of the Applicable Time and as of the Closing Date, 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 the circumstances under which they were made, not misleading.

(e) The Representatives shall have received from Cravath, Swaine & Moore LLP, counsel for the Underwriters, such opinion or opinions, dated such Closing Date, with respect to the incorporation of the Company, the validity of the Offered Securities delivered on such Closing Date, the Registration Statement, the Prospectus and other related matters as the Representatives may 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. In rendering such opinion,

13

Cravath, Swaine & Moore LLP may rely as to the incorporation of the Company and all other matters governed by Oklahoma law upon the opinion of Commercial Law Group, P.C. referred to above.

(f) The Representatives shall have received a certificate, dated such Closing Date, of the President or any Vice President and a principal financial or accounting officer of the Company in which such officers, on behalf of the Company, shall state that the representations and warranties of the Company in this Agreement are true and correct, that the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied hereunder at or prior to such Closing Date, that no stop order suspending the effectiveness of the Registration Statement or of any part thereof has been issued and no proceedings for that purpose have been instituted or are contemplated by the Commission and that, subsequent to the date of the most recent financial statements included or incorporated by reference into the Registration Statement and the General Disclosure Package, there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as a whole except as set forth in or contemplated by the Registration Statement and the General Disclosure Package or as described in such certificate.

(g) The Representatives shall have received a letter (the “

(b) The Prospectus shall have been filed with the Commission in accordance with the Act and Section 5(a) of this Agreement. No stop order suspending the effectiveness of the Registration Statement or of any part thereof shall have been issued and no proceedings for that purpose shall have been instituted or, to the knowledge of the Company or any Underwriter, shall be contemplated by the Commission.

(c) Subsequent to the execution and delivery of this Agreement, there shall not have occurred (i) any change, or any development or event involving a prospective change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as one enterprise which, in the judgment of the Representatives, is material and adverse and makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities; (ii) any downgrading in the rating of any debt securities of the Company by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Act), or any public announcement that any such organization has under surveillance or review its rating of any debt securities of the Company (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement that the Company has been placed on negative outlook; (iii) any change in U.S. or international financial, political or economic conditions or currency exchange rates or exchange controls as would, in the judgment of a majority in interest of the Underwriters including the Representatives, be likely to prejudice materially the success of the proposed issue, sale or distribution of the Offered Securities, whether in the primary market or in respect of dealings in the secondary market; (iv) any material

11

suspension or material limitation of trading in securities generally on the New York Stock Exchange, or any setting of minimum prices for trading on such exchange, or any suspension of trading of any securities of the Company on any exchange or in the over-the-counter market; (v) any banking moratorium declared by U.S. Federal or New York authorities; (vi) any major disruption of settlements of securities or clearance services in the United States; or (vii) any attack on, outbreak or escalation of hostilities or acts of terrorism involving the United States, any declaration of war by Congress or any other national or international calamity or emergency if, in the judgment of the Representatives, the effect of any such attack, outbreak, escalation, act, declaration, calamity or emergency makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities.

(d) The Representatives shall have received an opinion, dated such Closing Date, of Vinson & Elkins L.L.P., counsel for the Company, that:

(i) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Oklahoma, with corporate power and authority to own its properties and conduct its business as described in the General Disclosure Package.

(ii) Each subsidiary of the Company has been duly organized and is in good standing under the laws of the jurisdiction of its organization, with power and authority (corporate and other) to own its property and conduct its business as described in the General Disclosure Package; except where the failure to be so qualified would not reasonably be expected to individually or in the aggregate have a Material Adverse Effect; and the capital stock or similar equity interests of each subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects.

(iii) The Offered Securities delivered on such Closing Date have been duly authorized, have been validly issued, are fully paid and nonassessable and are convertible into the Underlying Shares of the Company in accordance with their terms; the Underlying Shares initially issuable upon conversion of such Offered Securities have been duly authorized and reserved for issuance upon such conversion and, when issued upon such conversion, will be validly issued, fully paid and nonassessable; the outstanding Underlying Shares have been duly authorized and validly issued, are fully paid and nonassessable; the Offered Securities, the outstanding Underlying Shares and all other shares of outstanding capital stock of the Company are consistent with the information in the General Disclosure Package and conform to the description thereof contained in the Prospectus; and the stockholders of the Company have no preemptive rights with respect to the Offered Securities or the Underlying Shares;

(iv) No consent, approval, authorization or order of, 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 or sale of the Offered Securities by the Company, except such as have been obtained and made under the Act and such as may be required under state securities laws.

(v) None of the execution, delivery and performance of this Agreement, the issuance and sale of the Offered Securities and compliance with the terms and provisions hereof will result in a breach or violation of any of the terms and provisions of, or constitute a default under, (1) any statute, rule, regulation or order of any governmental agency or body or any court having jurisdiction over the Company or any subsidiary of the Company or any of their properties which is, in the experience of such counsel, customarily applicable to securities offerings or (2) any agreement or instrument filed or referenced as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2005, or to any report on Form 8-K or Form 10-Q filed since

12

December 31, 2005, to which the Company or any such subsidiary is 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, or (3) the charter or by-laws (or similar organizational documents) of the Company or any such subsidiary, and the Company has full power and authority to authorize, issue and sell the Offered Securities as contemplated by this Agreement except in the case of clause (2) for such breaches or violations that would not have a Material Adverse Effect.

(vi) Except as disclosed in the General Disclosure Package, 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 Offered Securities; and no such actions, suits or proceedings are threatened or, to such counsel’s knowledge, contemplated.

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

(viii) The Registration Statement has become effective under the Act, the Prospectus was filed with the Commission pursuant to the subparagraph of Rule 424(b) specified in such opinion on the date specified therein in the manner and within the time period required by Rule 424 and in compliance with Rule 430B, and, to the best of the knowledge of such counsel, no stop order suspending the effectiveness of the Registration Statement or any part thereof has been issued and no proceedings for that purpose have been instituted or are pending or contemplated under the Act, and the Registration Statement, as of its effective date and as of the date of this Agreement and the Prospectus as of the Applicable Time, and any amendment or supplement thereto, as of its date, complied as to form in all material respects with the requirements of the Act and the Rules and Regulations; each of the documents incorporated by reference in the Registration Statement, at the time it became effective or was filed with the Commission (or the time of filing of an amendment, if so amended), as the case may be, complied as to form in all material respects with the requirements of the Act or Exchange Act, as the case may be, and the Rules and Regulations; the descriptions in the Registration Statement and the Prospectus of statutes, legal and governmental proceedings and contracts and other documents are accurate and fairly present the information required to be shown; and such counsel do not know of any legal or governmental proceedings required to be described in the Prospectus which are not described as required or of any contracts or documents of a character required to be described in the Registration Statement or Prospectus or to be filed as exhibits to the Registration Statement which are not described and filed as required.

It is understood and agreed that certain of the opinions set forth in paragraphs (i), (ii), (iii), (v) (with respect to conflicts with charters, by-laws or similar organizational documents and with respect to certain of the documents filed as exhibits to the filings described in such paragraph) and (vii) (with respect to due authorization) may be given by the Commercial Law Group, P.C., and certain opinions in paragraphs (vi) and (viii) may be given by Henry Hood, Esq.

In addition, Vinson & Elkins L.L.P. shall state that they have participated in conferences with officers and other representatives of the Company, representatives of the independent public accountants of the Company, general counsel of the Company, representatives of the Underwriters and counsel for the Underwriters, at which conferences the Registration Statement and the Prospectus were discussed. Such counsel shall further state that, although they have made certain additional inquiries and investigations in connection with the preparation of the Registration Statement and the Prospectus, they have not verified, are not passing on and do not assume any responsibility for the accuracy, completeness or fairness of the

13

statements contained in the Registration Statement or the Prospectus or any documents incorporated by reference therein, based on the participation described above in the course of acting as counsel to the Company in this transaction, no information has come to their attention that has caused such counsel to believe that the Registration Statement, at the time it became effective, or the Prospectus, at the date hereof and as of the Closing Date (other than the financial statements and schedules and other financial data and the oil and gas reserve data, in each case contained or incorporated by reference (including the notes thereto and auditor’s report thereon) therein, as to which such counsel need not express any comment or belief) contained an 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; such counsel shall also state that they have no reason to believe that the documents specified in a schedule to such counsel’s letter, consisting of those included in the General Disclosure Package, as of the Applicable Time and as of the Closing Date, 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 the circumstances under which they were made, not misleading.

(e) The Representatives shall have received from Cravath, Swaine & Moore LLP, counsel for the Underwriters, such opinion or opinions, dated such Closing Date, with respect to the incorporation of the Company, the validity of the Offered Securities delivered on such Closing Date, the Registration Statement, the Prospectus and other related matters as the Representatives may 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. In rendering such opinion, Cravath, Swaine & Moore LLP may rely as to the incorporation of the Company and all other matters governed by Oklahoma law upon the opinion of Commercial Law Group, P.C. referred to above.

(f) The Representatives shall have received a certificate, dated such Closing Date, of the President or any Vice President and a principal financial or accounting officer of the Company in which such officers, on behalf of the Company, shall state that the representations and warranties of the Company in this Agreement are true and correct, that the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied hereunder at or prior to such Closing Date, that no stop order suspending the effectiveness of the Registration Statement or of any part thereof has been issued and no proceedings for that purpose have been instituted or are contemplated by the Commission and that, subsequent to the date of the most recent financial statements included or incorporated by reference into the Registration Statement and the General Disclosure Package, there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as a whole except as set forth in or contemplated by the Registration Statement and the General Disclosure Package or as described in such certificate.

(g) The Representatives shall have received a letter (the “

(b) The Prospectus Supplement shall have been filed with the Commission in accordance with the Act and Section 5(a) of this Agreement. No stop order suspending the effectiveness of the Registration Statement, preventing or suspending the use of any Basic Prospectus, any Pre-Pricing Prospectus, the Prospectus Supplement, the Prospectus or any Permitted Free Writing Prospectus or of any part thereof shall have been issued and no proceedings for that purpose shall have been instituted or, to the knowledge of the Company or any Underwriter, shall be contemplated by the Commission.

(c) Subsequent to the execution and delivery of this Agreement, there shall not have occurred (i) any change, or any development or event involving a prospective change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as one enterprise which, in the judgment of the Representatives, is material and adverse and makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities; (ii) any downgrading in the rating of any debt securities of the Company by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Act), or any public announcement that any such organization has under surveillance or review its rating of any debt securities of the Company (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement that the Company has been placed on negative outlook; (iii) any change in U.S. or international financial, political or economic conditions or currency exchange rates or exchange controls as would, in the judgment of a majority in interest of the Underwriters including the Representatives, be likely to prejudice materially the success of the proposed issue, sale or distribution of the Offered Securities, whether in the primary market or in respect of dealings in the secondary market; (iv) any material suspension or material limitation of trading in securities generally on the New York Stock Exchange, or any setting of minimum prices for trading on such exchange, or any suspension of trading of any securities of the Company on any exchange or in the over-the-counter market; (v) any banking moratorium declared by U.S. Federal or New York authorities; (vi) any major disruption of settlements of securities or clearance services in the United States; or (vii) any attack on, outbreak or escalation of hostilities or acts of terrorism involving the United States, any

12

declaration of war by Congress or any other national or international calamity or emergency if, in the judgment of the Representatives, the effect of any such attack, outbreak, escalation, act, declaration, calamity or emergency makes it impractical or inadvisable to proceed with completion of the public offering or the sale of and payment for the Offered Securities.

(d) The Representatives shall have received an opinion, dated such Closing Date, of Vinson & Elkins L.L.P., counsel for the Company, that:

(i) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Oklahoma, with corporate power and authority to own its properties and conduct its business as described in the Disclosure Package and the Prospectus.

(ii) Each subsidiary of the Company has been duly organized and is in good standing under the laws of the jurisdiction of its organization, with power and authority (corporate and other) to own its property and conduct its business as described in the Disclosure Package and the Prospectus; except where the failure to be so qualified would not reasonably be expected to individually or in the aggregate have a Material Adverse Effect; and the capital stock or similar equity interests of each subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects.

(iii) The Offered Securities delivered on such Closing Date have been duly authorized and validly issued, are fully paid and nonassessable and conform to the description thereof contained in the Disclosure Package and the Prospectus; and the stockholders of the Company have no preemptive rights with respect to the Offered Securities.

(iv) No consent, approval, authorization or order of, 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 or sale of the Offered Securities by the Company, except such as have been obtained and made under the Act and such as may be required under state securities laws.

(v) None of the execution, delivery and performance of this Agreement, the issuance and sale of the Offered Securities and compliance with the terms and provisions hereof will result in a breach or violation of any of the terms and provisions of, or constitute a default under, (1) any statute, rule, regulation or order of any governmental agency or body or any court having jurisdiction over the Company or any subsidiary of the Company or any of their properties which is, in the experience of such counsel, customarily applicable to securities offerings or (2) any agreement or instrument filed or referenced as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2004, or to any report on Form 8-K or Form 10-Q filed since December 31, 2004, to which the Company or any such subsidiary is 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, or (3) the charter or by-laws (or similar organizational documents) of the Company or any such subsidiary, and the Company has full power and authority to authorize, issue and sell the Offered Securities as contemplated by this Agreement except in the case of clause (2) for such breaches or violations that would not have a Material Adverse Effect.

(vi) Except as disclosed in the Disclosure Package and the 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

13

Company to perform its obligations under this Agreement, or which are otherwise material in the context of the sale of the Offered Securities; and no such actions, suits or proceedings are threatened or, to such counsel’s knowledge, contemplated.

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

(viii) The Registration Statement has become effective under the Act, the Prospectus was filed with the Commission pursuant to the subparagraph of Rule 424(b) specified in such opinion on the date specified therein in the manner and within the time period required by Rule 424 and in compliance with Rule 430A/B, and, to the best of the knowledge of such counsel, no stop order suspending the effectiveness of the Registration Statement or any part thereof has been issued and no proceedings for that purpose have been instituted or are pending or contemplated under the Act, and the Registration Statement, as of its effective date and as of the date of this Agreement, the Pre-Pricing Prospectus as of the Applicable Time and the date of this Agreement and the Prospectus, as of the date of this Agreement, and any amendment or supplement thereto, as of its date, complied as to form in all material respects with the requirements of the Act and the Rules and Regulations; each of the documents incorporated by reference in the Pre-Pricing Prospectus and the Prospectus, at the time it became effective or was filed with the Commission (or the time of filing of an amendment, if so amended), as the case may be, complied as to form in all material respects with the requirements of the Act or Exchange Act, as the case may be, and the Rules and Regulations; the descriptions in the Registration Statement, the Pre-Pricing Prospectus and Prospectus of statutes, legal and governmental proceedings and contracts and other documents are accurate and fairly present the information required to be shown; and such counsel do not know of any legal or governmental proceedings required to be described in the Pre-Pricing Prospectus and Prospectus which are not described as required or of any contracts or documents of a character required to be described in the Registration Statement or Pre-Pricing Prospectus or Prospectus or to be filed as exhibits to the Registration Statement which are not described and filed as required.

It is understood and agreed that certain of the opinions set forth in paragraphs (i), (ii), (iii), (v) (with respect to conflicts with charters, by-laws or similar organizational documents and with respect to certain of the documents filed as exhibits to the filings described in such paragraph) and (vii) (with respect to due authorization) may be given by the Commercial Law Group, P.C., and certain opinions in paragraphs (vi) and (viii) may be given by Henry Hood, Esq.

In addition, Vinson & Elkins L.L.P. shall state that they have participated in conferences with officers and other representatives of the Company, representatives of the independent public accountants of the Company, general counsel of the Company, representatives of the Underwriters and counsel for the Underwriters, at which conferences the Registration Statement and the Prospectus were discussed. Such counsel shall further state that, although they have made certain additional inquiries and investigations in connection with the preparation of the Registration Statement and the Prospectus, they have not verified, are not passing on and do not assume any responsibility for the accuracy, completeness or fairness of the statements contained in the Registration Statement or the Prospectus or any documents incorporated by reference therein, based on the participation described above in the course of acting as counsel to the Company in this transaction, no information has come to their attention that has caused such counsel to believe that the Registration Statement or the Prospectus, at the date hereof and as of the Closing Date (other than the financial statements and schedules and other financial data and the oil and gas reserve data, in each case contained or incorporated by reference (including the notes thereto and auditor’s report thereon) therein, as to which such counsel need not express any comment or belief) contained an 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; such counsel shall also state that they have no reason to believe that the documents specified in a schedule to such counsel’s letter, consisting of those included in the Disclosure Package, as of the Applicable Time, taken together with the information set out in Schedule C

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hereto, 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 the circumstances under which they were made, not misleading.

(e) The Representatives shall have received from Cravath, Swaine & Moore LLP, counsel for the Underwriters, such opinion or opinions, dated such Closing Date, with respect to the incorporation of the Company, the validity of the Offered Securities delivered on such Closing Date, the Registration Statement, the Disclosure Package, the Prospectus and other related matters as the Representatives may 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. In rendering such opinion, Cravath, Swaine & Moore LLP may rely as to the incorporation of the Company and all other matters governed by Oklahoma law upon the opinion of Commercial Law Group, P.C. referred to above.

(f) The Representatives shall have received a certificate, dated such Closing Date, of the President or any Vice President and a principal financial or accounting officer of the Company in which such officers, on behalf of the Company, shall state that the representations and warranties of the Company in this Agreement are true and correct, that the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied hereunder at or prior to such Closing Date, that no stop order suspending the effectiveness of the Registration Statement or of any part thereof has been issued and no proceedings for that purpose have been instituted or are contemplated by the Commission and that, subsequent to the date of the most recent financial statements included or incorporated by reference into the Disclosure Package and the Prospectus, there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as a whole except as set forth in or contemplated by the Disclosure Package and the Prospectus or as described in such certificate.

(g) The Representatives shall have received a letter (the “