WHITING PETROLEUM CORPORATION (a Delaware corporation) 5,750,000 Shares of Common Stock PURCHASE AGREEMENT

Exhibit 1.1

Execution Copy

WHITING PETROLEUM CORPORATION
(a Delaware corporation)
5,750,000 Shares of Common Stock

PURCHASE AGREEMENT

Dated: September 28, 2005

WHITING PETROLEUM CORPORATION
(a Delaware corporation)
5,750,000 Shares of Common Stock
(Par Value $.001 Per Share)
PURCHASE AGREEMENT

September 28, 2005

MERRILL LYNCH & CO.
Merrill Lynch, Pierce, Fenner & Smith
      Incorporated
J.P. Morgan Securities Inc.
Wachovia Capital Markets, LLC
  as Representatives of the several Underwriters named in Schedule A hereto

c/o		Merrill Lynch & Co. Merrill Lynch, Pierce, Fenner & Smith                     Incorporated

4 World Financial Center
New York, New York 10080

c/o J.P. Morgan Securities Inc.
277 Park Avenue
New York, New York 10172

Ladies and Gentlemen:

     Whiting Petroleum Corporation, a Delaware corporation (the “Company”) confirms its agreement with Merrill Lynch & Co., Merrill Lynch, Pierce, Fenner & Smith Incorporated (“Merrill Lynch”), J.P. Morgan Securities Inc. (“JPMorgan”) and Wachovia Capital Markets, LLC (“Wachovia”) and each of the other Underwriters named in Schedule A hereto (collectively, the “Underwriters”, which term shall also include any underwriter substituted as hereinafter provided in Section 10 hereof), for whom Merrill Lynch, JPMorgan and Wachovia are acting as representatives (in such capacity, the “Representatives”), with respect to the issue and sale by the Company and the purchase by the Underwriters, acting severally and not jointly, of the respective numbers of shares of Common Stock, par value $.001 per share, of the Company (“Common Stock”) set forth in said Schedule A, and with respect to the grant by the Company to the Underwriters, acting severally and not jointly, of the option described in Section 2(b) hereof to purchase all or any part of 862,500 additional shares of Common Stock to cover overallotments, if any. The aforesaid 5,750,000 shares of Common Stock (the “Initial Securities”) to be purchased by the Underwriters and all or any part of the 862,500 shares of Common Stock subject to the option described in Section 2(b) hereof (the “Option Securities”) are hereinafter called, collectively, the “Securities.”

     Concurrent with the offering and sale of the Securities by the Company pursuant to the terms of this Agreement, the Company is offering to sell $250,000,000 in aggregate principal amount of Senior Subordinated Notes due 2014 (the “Concurrent Offering”) pursuant to the

terms of a Purchase Agreement, dated of even date herewith, among the Company, Merrill Lynch, JPMorgan and the other parties named therein. The offering, issuance and sale of the Securities by the Company pursuant to the terms of this Agreement are not contingent on the successful completion of the Concurrent Offering.

     Prior to the date hereof, the Company, Whiting Oil and Gas Corporation (“Whiting Oil and Gas”) and Celero Energy, LP, a Delaware limited partnership (“Celero”) entered into the Purchase and Sale Agreement, dated effective as of July 1, 2005 (the “North Ward PSA”) with respect to the purchase of certain oil and gas properties in Texas, Oklahoma and New Mexico.

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

     The Company has filed with the Securities and Exchange Commission (the “Commission”) a registration statement on Form S-3 (Registration No. 333-121615), including the related prospectus, for the registration of Common Stock and other securities of the Company (including the Securities) under the Securities Act of 1933, as amended (the “1933 Act”), and the offering thereof from time to time in accordance with Rule 415 of the rules and regulations of the Commission under the 1933 Act (the “1933 Act Regulations”). Such registration statement, including the Rule 462(b) Registration Statement (as defined below), has been declared effective by the Commission. A prospectus supplement reflecting the terms of the Securities, the terms of the offering thereof and the other matters set forth therein has been prepared and will be filed pursuant to Rule 424 of the 1933 Act Regulations. Such prospectus supplement, in the form first filed after the date hereof pursuant to Rule 424, is herein referred to as the “Prospectus Supplement.” Such registration statement on Form S-3 (Registration No. 333-121615), as amended at the date hereof, including the exhibits thereto, is herein called the “Registration Statement,” and the basic prospectus included therein relating to all offerings of securities under the Registration Statement, as supplemented by the Prospectus Supplement, is herein called the “Prospectus;” provided, however, that, if such basic prospectus is amended or supplemented on or after the date hereof but prior to the date on which the Prospectus Supplement is first filed pursuant to Rule 424, the term “Prospectus” shall refer to the basic prospectus as so amended or supplemented and as supplemented by the Prospectus Supplement; and provided, further, that all references to the “Registration Statement” and the “Prospectus” shall be deemed to include all documents incorporated therein by reference pursuant to the Securities Exchange Act of 1934, as amended (the “1934 Act”); and provided, further, that all references to the “Registration Statement” shall also be deemed to include the registration statement filed with the Commission on September 19, 2005 pursuant to Rule 462(b) of the 1933 Act Regulations (the “Rule 462(b) Registration Statement”). For purposes of this Agreement, all references to the Registration Statement, Prospectus, Prospectus Supplement or preliminary prospectus or to any amendment or supplement to any of the foregoing shall be deemed to include any copy filed with the Commission pursuant to its Electronic Data Gathering, Analysis and Retrieval system (“EDGAR”).

     All references in this Agreement to financial statements and schedules and other information that is “described,” “contained,” “included” or “stated” in the Registration Statement, any preliminary prospectus or the Prospectus (or other references of like import) shall

be deemed to mean and include all such financial statements and schedules and other information that is incorporated by reference in the Registration Statement, any preliminary prospectus or the Prospectus, as the case may be; and all references in this Agreement to amendments or supplements to the Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to mean and include the filing of any document under the 1934 Act that is incorporated by reference in the Registration Statement, such preliminary prospectus or the Prospectus, as the case may be.

     SECTION 1. Representations and Warranties.

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

     (i) Compliance with Registration Requirements. The Company meets the requirements for use of Form S-3 under the 1933 Act. Each of the Registration Statement, the Rule 462(b) Registration Statement and any post-effective amendment thereto has become effective under the 1933 Act and no stop order suspending the effectiveness of the Registration Statement, the Rule 462(b) Registration Statement or any post-effective amendment thereto has been issued under the 1933 Act and no proceedings for that purpose have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission, and any request on the part of the Commission for additional information has been complied with.

     At the respective times the Registration Statement, the Rule 462(b) Registration Statement and any post-effective amendments thereto became effective and at the Closing Time (and, if any Option Securities are purchased, at the Date of Delivery), the Registration Statement, the Rule 462(b) Registration Statement and any amendments and supplements thereto complied and will comply in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations and did not and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading. Neither the Prospectus nor any amendments or supplements thereto, at the time the Prospectus or any such amendment or supplement was issued and at the Closing Time (and, if any Option Securities are purchased, at the Date of Delivery), included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The representations and warranties in this paragraph shall not apply to statements in or omissions from the Registration Statement or Prospectus or any amendment or supplement thereto made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through Merrill Lynch expressly for use in the Registration Statement (or any amendment thereto) or the Prospectus (or any amendment or supplement thereto).

     Each preliminary prospectus and the prospectus filed as part of the Registration Statement as originally filed or as part of any amendment thereto complied when so filed

in all material respects with the 1933 Act Regulations and each preliminary prospectus and the Prospectus to be delivered to the Underwriters for use in connection with this offering will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

     (ii) Incorporated Documents. The documents incorporated or deemed to be incorporated by reference in the Registration Statement and the Prospectus, at the time they were or hereafter are filed with the Commission, complied and will comply in all material respects with the requirements of the 1934 Act and the rules and regulations of the Commission thereunder (the “1934 Act Regulations”), and, when read together with the other information in the Prospectus, at the time the Registration Statement became effective, at the time the Prospectus is issued and at the Closing Time, 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.

     (iii) Independent Accountants. The accountants who certified the financial statements and supporting schedules included in the Registration Statement are independent public accountants with respect to the Company as required by the 1933 Act and the 1933 Act Regulations.

     (iv) Financial Statements. The financial statements included in the Registration Statement and the Prospectus, together with the related schedules and notes, present fairly in all material respects, on the basis set forth in the Prospectus, the financial position of the Company and its consolidated subsidiaries at the dates indicated and the statement of income, stockholders’ equity and cash flows of Company and its consolidated subsidiaries for the periods specified; said financial statements have been prepared in conformity with generally accepted accounting principles in the United States (“GAAP”) applied on a consistent basis throughout the periods involved. The supporting schedules, if any, included in the Registration Statement present fairly in all material respects in accordance with GAAP the information required to be stated therein. The summary financial information included in the Prospectus present fairly in all material respects the information shown therein and have been compiled on a basis consistent with that of the audited financial statements included in the Registration Statement. The summary pro forma financial information, the pro forma financial statements and the related notes thereto included in the Registration Statement and the Prospectus present fairly in all material respects, on the basis set forth in the Prospectus, the information shown therein, have been prepared in all material respects in accordance with the Commission’s rules with respect to pro forma financial statements and have been properly compiled on the bases described therein, and the assumptions used in the preparation thereof are reasonable and are set forth in the Prospectus and the adjustments used therein are appropriate in all material respects to give effect to the transactions and circumstances referred to therein.

     All disclosures contained in the Registration Statement or the Prospectus regarding “non-GAAP financial measures” (as such term is defined by the rules and regulations of the Commission) comply in all material respects with Regulation G of the Exchange Act and Item 10 of Regulation S-K under the Act, to the extent applicable.

     (v) No Material Adverse Change in Business. Since the respective dates as of which information is given in the Registration Statement and the Prospectus, except as otherwise stated therein, (A) there has been no material adverse change in the condition, financial or otherwise, or in the earnings, business affairs or business prospects of the Company and its subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business (a “Material Adverse Effect”), (B) there have been no transactions entered into by the Company or any of its subsidiaries, other than those in the ordinary course of business, which are material with respect to the Company and its subsidiaries considered as one enterprise, and (C) except as described in the Prospectus, there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of its capital stock.

     (vi) Good Standing of the Company. The Company has been duly organized and is validly existing as a corporation in good standing under the laws of the State of Delaware and has corporate power and authority to own, lease and operate its properties and to conduct its business as described in the Prospectus and to enter into and perform its obligations under this Agreement; and the Company is duly qualified as a foreign corporation to transact business and is in good standing in each other jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except where the failure so to qualify or to be in good standing would not result in a Material Adverse Effect.

     (vii) Good Standing of Subsidiaries. Each of Whiting Oil and Gas, Whiting Programs, Inc. and Equity Oil Company (each a “Subsidiary” and, collectively, the “Subsidiaries”) has been duly organized and is validly existing as a corporation in good standing under the laws of the jurisdiction of its incorporation, has corporate power and authority to own, lease and operate its properties and to conduct its business as described in the Prospectus and is duly qualified as a foreign corporation to transact business and is in good standing in each jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except where the failure so to qualify or to be in good standing would not result in a Material Adverse Effect; except as otherwise disclosed in the Registration Statement, all of the issued and outstanding capital stock of each such Subsidiary has been duly authorized and validly issued, is fully paid and non-assessable and is owned by the Company, directly or through subsidiaries, free and clear of any security interest, mortgage, pledge, lien, encumbrance, claim or equity; none of the outstanding shares of capital stock of any Subsidiary was issued in violation of the preemptive or similar rights of any securityholder of such Subsidiary. As of the date of this Agreement, the only subsidiaries of the Company are the Subsidiaries, Whiting Transpetco LP, LLC and Whiting Transpetco GP, LLC. The subsidiaries of the Company, other than the Subsidiaries, considered in the aggregate as a single subsidiary, do not constitute a “significant subsidiary” as defined in Rule 1-02 of Regulation S-X.

     (viii) Capitalization. The authorized, issued and outstanding capital stock of the Company is as set forth in the Prospectus in the column entitled “Actual” under the caption “Capitalization” (except for subsequent issuances, if any, pursuant to reservations, agreements or employee benefit plans referred to in the Prospectus or

pursuant to the North Ward PSA). The shares of issued and outstanding capital stock of the Company have been duly authorized and validly issued and are fully paid and non-assessable; none of the outstanding shares of capital stock of the Company was issued in violation of the preemptive or other similar rights of any securityholder of the Company.

     (ix) Authorization and Enforceability of Agreements. This Agreement has been duly authorized, executed and delivered by the Company. The North Ward PSA has been duly authorized, executed and delivered by the Company and Whiting Oil and Gas, as applicable, and is a valid and legally binding agreement of the Company and Whiting Oil and Gas, as applicable, enforceable against each of them, as applicable, in accordance with its terms, except as the enforcement thereof may be limited by bankruptcy, insolvency (including, without limitation, all laws relating to fraudulent transfers), reorganization, moratorium or similar laws affecting enforcement of creditors’ rights generally and except as enforcement thereof is subject to general principles of equity (regardless of whether enforcement is considered in a proceeding in equity or at law).

     (x) Authorization and Description of Securities. The Securities to be purchased by the Underwriters from the Company have been duly authorized for issuance and sale to the Underwriters pursuant to this Agreement, and, when issued and delivered by the Company pursuant to this Agreement against payment of the consideration set forth herein, will be validly issued, fully paid and non-assessable; the Common Stock conforms in all material respects to all statements relating thereto contained in the Prospectus and such description conforms in all material respects to the rights set forth in the instruments defining the same; no holder of the Securities will be subject to personal liability by reason of being such a holder; and the Securities are not subject to the preemptive or other similar rights of any securityholder of the Company.

     (xi) Absence of Defaults and Conflicts. Neither the Company nor any of its subsidiaries is in violation of its respective charter or by-laws or in default in the performance or observance of any obligation, agreement, covenant or condition contained in any contract, indenture, mortgage, deed of trust, loan or credit agreement, note, lease or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which it or any of them may be bound, or to which any of the property or assets of the Company or any of its subsidiaries is subject (collectively, “Agreements and Instruments”), except for such violations or defaults that would not result in a Material Adverse Effect; and the execution, delivery and performance of this Agreement and the North Ward PSA and the consummation of the transactions contemplated herein and therein and in the Registration Statement (including the offering, issuance and sale of the Securities pursuant to this Agreement and the use of the proceeds to the Company from the sale of the Securities as described in the Prospectus under the caption “Use of Proceeds”) and compliance by the Company and Whiting Oil and Gas with their respective obligations hereunder and thereunder have been duly authorized by all necessary corporate action and do not and will not, whether with or without the giving of notice or passage of time or both, conflict with or constitute a breach of, or default or Repayment Event (as defined below) 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, the Agreements and Instruments (except for such conflicts, breaches, defaults or Repayment Events or liens, charges or encumbrances that would not result in a Material Adverse Effect), nor will such action result in any violation of the provisions of the charter or by-laws of the Company or any of its subsidiaries or any applicable law, statute, rule, regulation, judgment, order, writ or decree of any government, government instrumentality or court, domestic or foreign, having jurisdiction over the Company or any of its subsidiaries or any of their assets, properties or operations (except for such violations that would not result in a Material Adverse Effect). As used herein, a “Repayment Event” means any event or condition which gives the holder of any note, debenture or other evidence of indebtedness (or any person acting on such holder’s behalf) the right to require the repurchase, redemption or repayment of all or a portion of such indebtedness by the Company or any of its subsidiaries.

     (xii) Absence of Labor Dispute. No labor dispute with the employees of the Company or any subsidiary of the Company exists or, to the knowledge of the Company, is imminent, and the Company is not aware of any existing or imminent labor disturbance by the employees of any of their or any subsidiary’s principal suppliers, manufacturers, customers or contractors, which, in either case, would reasonably be expected to result in a Material Adverse Effect.

     (xiii) Absence of Proceedings. There is no action, suit, proceeding, inquiry or investigation before or brought by any court or governmental agency or body, domestic or foreign, now pending, or, to the knowledge of the Company, threatened, against or affecting the Company or any subsidiary of the Company, which is required to be disclosed in the Registration Statement (other than as disclosed therein), or which might reasonably be expected to result in a Material Adverse Effect, or which might reasonably be expected to materially and adversely affect the properties or assets thereof or the consummation of the transactions contemplated in this Agreement or the North Ward PSA or the performance by the Company or Whiting Oil and Gas of their respective obligations hereunder or thereunder. The aggregate of all pending legal or governmental proceedings to which the Company or any subsidiary of the Company is a party or of which any of their respective property or assets is the subject which are not described in the Registration Statement, including ordinary routine litigation incidental to the business, could not reasonably be expected to result in a Material Adverse Effect.

     (xiv) Accuracy of Exhibits. There are no contracts or documents which are required to be described in the Registration Statement, the Prospectus or the documents incorporated by reference therein or to be filed as exhibits thereto which have not been so described and filed as required.

     (xv) Possession of Intellectual Property. The Company and its subsidiaries own or possess, or can acquire on reasonable terms, adequate patents, patent rights, licenses, inventions, copyrights, know-how (including trade secrets and other unpatented and/or unpatentable proprietary or confidential information, systems or procedures), trademarks, service marks, trade names or other intellectual property (collectively, “Intellectual Property”) necessary to carry on the business now operated by them, and neither the Company nor any of its subsidiaries has received any written notice or is

otherwise aware of any infringement of or conflict with asserted rights of others with respect to any Intellectual Property or of any facts or circumstances which would render any Intellectual Property invalid or inadequate to protect the interest of the Company or any of its subsidiaries therein, and which infringement or conflict (if the subject of any unfavorable decision, ruling or finding) or invalidity or inadequacy, singly or in the aggregate, would result in a Material Adverse Effect.

     (xvi) Absence of Further Requirements. No filing with, or authorization, approval, consent, license, order, registration, qualification or decree of, any court or governmental authority or agency is necessary or required for the performance by the Company of its obligations hereunder, in connection with the offering, issuance or sale by the Company of the Securities hereunder or the consummation of the transactions contemplated by this Agreement or the North Ward PSA, except such as have been already obtained or made or as may be required under the 1933 Act or the 1933 Act Regulations or state securities laws and, in the case of the North Ward PSA, except such as (A)(i) are of a routine or administrative nature, (ii) are not customarily obtained or made prior to the consummation of transactions such as those contemplated by the North Ward PSA, and (iii) are expected in the reasonable judgment of the Company to be obtained in the ordinary course of business subsequent to the consummation of the transactions contemplated by the North Ward PSA, or (B) if not obtained, would not, individually or in the aggregate, have a Material Adverse Effect.

     (xvii) Absence of Manipulation. Neither the Company nor any affiliate of the Company has taken, nor will the Company or any affiliate take, directly or indirectly, any action which is designed to or which has constituted or which would be expected to cause or result in stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

     (xviii) Possession of Licenses and Permits. The Company and its subsidiaries possess such permits, licenses, approvals, consents and other authorizations (collectively, “Governmental Licenses”) issued by the appropriate federal, state, local or foreign regulatory agencies or bodies necessary to conduct the business now operated by them, except where the failure so to possess would not, singly or in the aggregate, result in 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 so to comply would not, singly or in the aggregate, result in a Material Adverse Effect; all of the Governmental Licenses are valid and in full force and effect, except when the invalidity of such Governmental Licenses or the failure of such Governmental Licenses to be in full force and effect would not, singly or in the aggregate, result in a Material Adverse Effect; and neither the Company nor any of its subsidiaries has received any written notice of proceedings relating to the revocation or modification of any such Governmental Licenses which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would result in a Material Adverse Effect.

     (xix) Title to Property. The Company and its subsidiaries have good and marketable title to all real property owned by the Company and its subsidiaries, including, without limitation, all oil and gas producing properties, and good title to all

other properties owned by them, including, without limitation, all assets and facilities used by the Company and its subsidiaries in the production and marketing of oil and gas, in each case, free and clear of all mortgages, pledges, liens, security interests, claims, restrictions or encumbrances of any kind except such as (a) are described in the Prospectus or (b) do not, singly or in the aggregate, materially affect the value of such property and do not interfere with the use made and proposed to be made of such property by the Company or any of its subsidiaries; and all of the leases and subleases material to the business of the Company and its subsidiaries, considered as one enterprise, and under which the Company or any of its subsidiaries holds properties described in the Prospectus, including, without limitation, all oil and gas producing properties of the Company and its subsidiaries and all assets and facilities used by the Company and its subsidiaries in the production and marketing of oil and gas, are in full force and effect, except where such would not have a Material Adverse Effect, and neither the Company nor any of its subsidiaries has any written notice of any material claim of any sort that has been asserted by anyone adverse to the rights of the Company or any of its subsidiaries under any of the leases or subleases mentioned above, or affecting or questioning the rights of the Company or such subsidiary to the continued possession of the leased or subleased premises under any such lease or sublease, except where such would not have a Material Adverse Effect.

     (xx) Environmental Laws. Except as described in the Registration Statement and except as would not, singly or in the aggregate, result in a Material Adverse Effect, (A) neither the Company nor any of its subsidiaries is in violation of any federal, state, local or foreign statute, law, rule, regulation, ordinance, code, policy or rule of common law or any judicial or administrative interpretation thereof, including any judicial or administrative order, consent, decree or judgment, relating to pollution or protection of human health, the environment (including, without limitation, ambient air, surface water, groundwater, land surface or subsurface strata) or wildlife, including, without limitation, laws and regulations relating to the release or threatened release of chemicals, pollutants, contaminants, wastes, toxic substances, hazardous substances, petroleum or petroleum products, asbestos-containing materials or mold (collectively, “Hazardous Materials”) or to the manufacture, processing, distribution, use, treatment, storage, disposal, transport or handling of Hazardous Materials (collectively, “Environmental Laws”), (B) the Company and its subsidiaries have all permits, authorizations and approvals required under any applicable Environmental Laws and are each in compliance with their requirements, (C) there are no pending or, to the knowledge of the Company, threatened administrative, regulatory or judicial actions, suits, demands, demand letters, claims, liens, notices of noncompliance or violation, investigation or proceedings relating to any Environmental Law against the Company or any of its subsidiaries and (D) there are no events or circumstances that would reasonably be expected to form the basis of an order for clean-up or remediation, or an action, suit or proceeding by any private party or governmental body or agency, against or affecting the Company or any of its subsidiaries relating to Hazardous Materials or any Environmental Laws.

     (xxi) Registration Rights. Other than persons granted registration rights pursuant to the registration rights agreement to be entered into in connection with the Concurrent Offering (the “Registration Rights Agreement”), there are no persons with registration rights or other similar rights to have any securities registered pursuant to the Registration Statement, except pursuant to the North Ward PSA, or otherwise registered by the Company under the 1933 Act.

     (xxii) Independent Petroleum Engineers. Cawley, Gillespie & Associates, Inc., whose report as of January 1, 2005 is referenced in the Prospectus, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Company and its subsidiaries. R.A. Lenser & Associates, Inc., whose report as of January 1, 2005 is referenced in the Prospectus, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Company and its subsidiaries. Ryder Scott Company, L.P., whose report as of January 1, 2005 is referenced in the Prospectus, was, as of the date of such report, and is, as of the date hereof, an independent petroleum engineer with respect to the Company and its subsidiaries. Netherland, Sewell and Associates, Inc., whose report as of July 1, 2005 is referenced in the Prospectus, was, as of the date of such report, an independent petroleum engineer with respect to the Company and, to the Company’s knowledge, with respect to Celero and its subsidiaries.

     (xxiii) Accuracy of Reserve Information. The information underlying the estimates of reserves of the Company and its subsidiaries, which was supplied by the Company to Cawley, Gillespie & Associates, Inc., R.A. Lenser & Associates, Inc. and Ryder Scott Company, L.P. for purposes of auditing the reserve reports and estimates of the Company and preparing the respective letters (the “Reserve Report Letters” and each a “Reserve Report Letter”) of each of Cawley, Gillespie & Associates, Inc., R.A. Lenser & Associates, Inc. and Ryder Scott Company, L.P., including, without limitation, production, costs of operation and development, current prices for production, agreements relating to current and future operations and sales of production, was true and correct in all material respects on the dates such estimates were made and such information was supplied and was prepared in accordance with customary industry practices; other than normal production of the reserves and intervening spot market product price fluctuations described in the Prospectus, neither the Company nor its subsidiaries is aware of any facts or circumstances that would result in an adverse change in the reserves, or the present value of future net cash flows therefrom, as described in the Prospectus and as reflected in each Reserve Report Letter, that would reasonably be expected to result in a Material Adverse Effect; estimates of such reserves and present values as described in the Prospectus and reflected in each Reserve Report Letter comply in all material respects with the applicable requirements of Regulation S-X and Industry Guide 2 under the 1933 Act.

     (xxiv) Oil and Gas Agreements. The participation agreements, joint development agreements, joint operating agreements, farm-out agreements and other agreements described in the Prospectus relating to the Company or its subsidiaries’ rights with respect to the ownership, lease or operation of oil and gas properties, the acquisition of interests in oil and gas properties or the exploration for, development of or production of oil and gas reserves thereon, constitute valid and binding agreements of the Company and its subsidiaries that are parties thereto and, to the best knowledge of the Company, of

the other parties thereto, enforceable in accordance with their terms, except as the enforcement thereof may be limited by bankruptcy, insolvency (including, without limitation, all laws relating to fraudulent transfers), reorganization, moratorium or similar laws affecting enforcement of creditors’ rights generally and except as enforcement thereof is subject to general principles of equity (regardless of whether enforcement is considered in a proceeding in equity or at law).

     (xxv) Insurance. The Company and each of its subsidiaries maintain insurance covering their properties, operations, personnel and businesses that, in the Company’s reasonable judgment, insures against such losses and risks as are adequate in accordance with customary industry practices to protect the Company and its subsidiaries and their businesses.

     (xxvi) Accounting Controls and Disclosure Controls. (A) The Company and each of its subsidiaries maintain a system of internal accounting controls sufficient to provide reasonable assurances that (1) transactions are executed in accordance with management’s general or specific authorization; (2) transactions are recorded as necessary to permit preparation of financial statements in conformity with GAAP and to maintain accountability for assets; (3) access to assets is permitted only in accordance with management’s general or specific authorization; and (4) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences. Except as described in the Prospectus, since the end of the Company’s most recent audited fiscal year, there has been (I) no material weakness in the Company’s internal control over financial reporting (whether or not remediated) and (II) no 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.

     (xxvii) (B) The Company maintains disclosure controls and procedures that are designed to ensure that information required to be disclosed by the Company in the reports that it files or submits under the 1934 Act is recorded, processed, summarized and reported, within the time periods specified in the Commission’s rules and forms, and is accumulated and communicated to the Company’s management, including its principal executive officer or officers and principal financial officer or officers, as appropriate, to allow timely decisions regarding disclosure.

     (b) Officer’s Certificates. Any certificate signed by any officer of the Company or any of its subsidiaries delivered to the Representatives or to counsel for the Underwriters shall be deemed a representation and warranty by the Company to each Underwriter as to the matters covered thereby.

     SECTION 2. Sale and Delivery to Underwriters; Closing.

     (a) Initial Securities. On the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Company agrees to sell to each Underwriter, and each Underwriter, severally and not jointly, agrees to purchase from the Company, at the price per share set forth in Schedule B, the number of Initial Securities set forth in Schedule A opposite the name of such Underwriter, plus any additional number of Initial Securities which such Underwriter may become obligated to purchase pursuant to the provisions of Section 10 hereof.

     (b) Option Securities. In addition, on the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Company hereby grants an option to the Underwriters, severally and not jointly, to purchase up to an additional 862,500 shares of Common Stock from the Company at the price per share set forth in Schedule B, less an amount per share equal to any dividends or distributions declared by the Company and payable on the Initial Securities but not payable on the Option Securities. The option hereby granted will expire 30 days after the date hereof and may be exercised in whole or in part from time to time only for the purpose of covering overallotments which may be made in connection with the offering and distribution of the Initial Securities upon notice by the Representatives to the Company setting forth the number of Option Securities as to which the several Underwriters are then exercising the option and the time and date of payment and delivery for such Option Securities. Any such time and date of delivery (a “Date of Delivery”) shall be determined by the Representatives, but shall not be later than seven full business days after the exercise of said option, nor in any event prior to the Closing Time, as hereinafter defined. If the option is exercised as to all or any portion of the Option Securities, each of the Underwriters, acting severally and not jointly, will purchase that proportion of the total number of Option Securities then being purchased which the number of Initial Securities set forth in Schedule A opposite the name of such Underwriter bears to the total number of Initial Securities, subject in each case to such adjustments as the Representatives in their discretion shall make to eliminate any sales or purchases of fractional shares.

     (c) Payment. Payment of the purchase price for, and delivery of certificates for, the Initial Securities shall be made via facsimile and email and at the office of Whiting Petroleum Corporation, 1700 Broadway, Suite 2300, Denver, Colorado 80290-2300, or at such other place as shall be agreed upon by the Representatives and the Company, at 9:00 A.M. (Eastern time) on the third (fourth, if the pricing occurs after 4:30 P.M. (Eastern time) on any given day) business day after the date hereof (unless postponed in accordance with the provisions of Section 10), or such other time not later than ten business days after such date as shall be agreed upon by the Representatives and the Company (such time and date of payment and delivery being herein called “Closing Time”).

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

     Payment shall be made to the Company by wire transfer of immediately available funds to a bank account designated by the Company, against delivery to Merrill Lynch for the respective accounts of the Underwriters of certificates for the Securities to be purchased by them. It is understood that each Underwriter has authorized Merrill Lynch, for its account, to accept delivery of, receipt for, and make payment of the purchase price for, the Initial Securities and the Option Securities, if any, which it has agreed to purchase. Merrill Lynch, individually and not as representative of the Underwriters, may (but shall not be obligated to) make payment of the

purchase price for the Initial Securities or the Option Securities, if any, to be purchased by any Underwriter whose funds have not been received by the Closing Time or the relevant Date of Delivery, as the case may be, but such payment shall not relieve such Underwriter from its obligations hereunder.

     (d) Denominations; Registration. Certificates for the Initial Securities and the Option Securities, if any, shall be in such denominations and registered in such names as Merrill Lynch may request in writing at least one full business day before the Closing Time or the relevant Date of Delivery, as the case may be. The Company will deliver the Initial Securities, and the Company shall deliver the Option Securities, if any, to Merrill Lynch for the accounts of the Underwriters through the facilities of the Depositary Trust Company (“DTC”), against payment of the purchase price in federal (same day) funds by official bank check or checks or wire transfer to an account for the Company at a bank reasonably acceptable to Merrill Lynch drawn to the order of the Company prior to the Closing Time or the relevant Date of Delivery, as the case may be.

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

     (a) Compliance with Securities Regulations and Commission Requests. The Company, subject to Section 3(b), will comply with the requirements of Rule 430A and will notify the Representatives immediately, and confirm the notice in writing, (i) when any post-effective amendment to the Registration Statement shall become effective, or any supplement to the Prospectus or any amended Prospectus shall have been filed, (ii) of the receipt of any comments from the Commission with respect to the Registration Statement, (iii) of any request by the Commission for any amendment to the Registration Statement or any amendment or supplement to the Prospectus or any document incorporated by reference therein or for additional information, and (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any order preventing or suspending the use of any preliminary prospectus, or of the suspension of the qualification of the Securities for offering or sale in any jurisdiction, or of the initiation or threatening of any proceedings for any of such purposes. The Company will promptly effect the filings necessary pursuant to Rule 424(b) and will take such steps as it deems necessary to ascertain promptly whether the form of prospectus transmitted for filing under Rule 424(b) was received for filing by the Commission and, in the event that it was not, it will promptly file such prospectus. The Company will make every reasonable effort to prevent the issuance of any stop order and, if any stop order is issued, to obtain the lifting thereof at the earliest possible moment.

     (b) Filing of Amendments. The Company will give the Representatives notice of its intention to file or prepare any amendment to the Registration Statement (including any filing under Rule 462(b)) or any amendment, supplement or revision to either the prospectus included in the Registration Statement at the time it became effective or to the Prospectus, whether pursuant to the 1933 Act, the 1934 Act or otherwise, and will furnish the Representatives with copies of any such documents a reasonable amount of time prior to such proposed filing or use, as the case may be, and will not file or use any such document to which the Representatives or counsel for the Underwriters shall reasonably object.

     (c) Delivery of Registration Statements. The Company has furnished or will deliver to the Representatives and counsel for the Underwriters, without charge, copies (one of which shall be manually signed) of the Registration Statement as originally filed and of each amendment thereto (including exhibits filed therewith or incorporated by reference therein) and copies (one of which shall be manually signed) of all consents and certificates of experts, and will also deliver to the Representatives, without charge, a conformed copy of the Registration Statement as originally filed and of each amendment thereto (without exhibits) for each of the Underwriters. The copies of the Registration Statement and each amendment thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

     (d) Delivery of Prospectuses. The Company has delivered to each Underwriter, without charge, as many copies of each preliminary prospectus as such Underwriter reasonably requested, and the Company hereby consents to the use of such copies for purposes permitted by the 1933 Act. The Company will furnish to each Underwriter, without charge, during the period when the Prospectus is required to be delivered under the 1933 Act, such number of copies of the Prospectus (as amended or supplemented) as such Underwriter may reasonably request. The Prospectus and any amendments or supplements thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

     (e) Continued Compliance with Securities Laws. The Company will comply with the 1933 Act and the 1933 Act Regulations and the 1934 Act and the 1934 Act Regulations so as to permit the completion of the distribution of the Securities as contemplated in this Agreement and in the Prospectus. If at any time when a prospectus is required by the 1933 Act to be delivered in connection with sales of the Securities, any event shall occur or condition shall exist as a result of which it is necessary, in the reasonable opinion of counsel for the Underwriters or for the Company, to amend the Registration Statement or amend or supplement the Prospectus in order that the Prospectus will not include any untrue statements of a material fact or omit to state a material fact necessary in order to make the statements therein not misleading in the light of the circumstances existing at the time it is delivered to a purchaser, or if it shall be necessary, in the reasonable opinion of such counsel, at any such time to amend the Registration Statement or amend or supplement the Prospectus in order to comply with the requirements of the 1933 Act or the 1933 Act Regulations, the Company will promptly prepare and file with the Commission, subject to Section 3(b), such amendment or supplement as may be necessary to correct such statement or omission or to make the Registration Statement or the Prospectus comply with such requirements, and the Company will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request.

     (f) Blue Sky Qualifications. The Company will use its best efforts, in cooperation with the Underwriters, to qualify the Securities for offering and sale under the applicable securities laws of such states and other jurisdictions (domestic or foreign) as the Representatives may designate and to maintain such qualifications in effect for a period of not less than one year from the later of the effective date of the Registration Statement and the Rule 462(b) Registration Statement; provided, however, that the Company shall not be obligated to file any general consent to service of process or to qualify as a foreign corporation or as a dealer in securities in any jurisdiction in which it is not so qualified or to subject itself to taxation in respect of doing business in any jurisdiction in which it is not otherwise so subject.

     (g) Rule 158. The Company will timely file such reports pursuant to the Securities Exchange Act of 1934, as amended (the “1934 Act”), as are necessary in order to make generally available to its securityholders as soon as practicable an earnings statement for the purposes of, and to provide the benefits contemplated by, the last paragraph of Section 11(a) of the 1933 Act.

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

     (i) Listing. The Company will use its best efforts to effect the listing of the Securities on the New York Stock Exchange.

     (j) Restriction on Sale of Securities. During a period of 90 days from the date of the Prospectus, the Company will not, without the prior written consent of Merrill Lynch and JPMorgan, (i) directly or indirectly, offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise transfer or dispose of any share of Common Stock or any securities convertible into or exercisable or exchangeable for Common Stock or file any registration statement under the 1933 Act with respect to any of the foregoing or (ii) enter into any swap or any other agreement or any transaction that transfers, in whole or in part, directly or indirectly, the economic consequence of ownership of the Common Stock, whether any such swap or transaction described in clause (i) or (ii) above is to be settled by delivery of Common Stock or such other securities, in cash or otherwise. The foregoing sentence shall not apply to (A) the Securities to be sold hereunder, (B) any shares of Common Stock issued by the Company upon the exercise of an option or warrant or the conversion of a security outstanding on the date hereof and referred to in the Prospectus, (C) any shares of Common Stock issued or options to purchase Common Stock granted pursuant to existing employee benefit plans of the Company referred to in the Prospectus, (D) any registration statement with respect to shares of Common Stock to be issued and sold by the Company and (E) 441,500 shares of Common Stock to be issued to Celero pursuant to the North Ward PSA. Notwithstanding the foregoing, if (1) during the last 17 days of the 90-day restricted period the Company issues an earnings release or material news or a material event relating to the Company occurs or (2) prior to the expiration of the 90-day restricted period, the Company announces that it will release earnings results or becomes aware that material news or a material event will occur during the 16-day period beginning on the last day of the 90-day restricted period, the restrictions imposed in this clause (j) shall continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event, as applicable, unless Merrill Lynch and JPMorgan waive, in writing, such extension.

     (k) Reporting Requirements. The Company, during the period when the Prospectus is required to be delivered under the 1933 Act, will file all documents required to be filed with the Commission pursuant to the 1934 Act within the time periods required by the 1934 Act and the 1934 Act Regulations.

     (l) No Advisory or Fiduciary Relationship. The Company acknowledges and agrees that (i) the purchase and sale of the Securities pursuant to this Agreement, including the determination of the public offering price of the Securities and any related discounts and commissions, is an arm’s-length commercial transaction between the Company, on the one hand, and the several Underwriters, on the other hand, (ii) in connection with the offering contemplated hereby and the process leading to such transaction each Underwriter is and has been acting solely as a principal and is not the agent or fiduciary of the Company or its stockholders, creditors, employees or any other party, (iii) no Underwriter has assumed or will assume an advisory or fiduciary responsibility in favor of the Company with respect to the offering contemplated hereby or the process leading thereto (irrespective of whether such Underwriter has advised or is currently advising the Company on other matters) and no Underwriter has any obligation to the Company with respect to the offering contemplated hereby (other than any confidentiality obligation that such Underwriter may generally have to the Company) except the obligations expressly set forth in this Agreement, (iv) the Underwriters and their respective affiliates may be engaged in a broad range of transactions that involve interests that differ from those of the Company, and (v) the Underwriters have not provided any legal, accounting, regulatory or tax advice with respect to the offering contemplated hereby and the Company has consulted its own legal, accounting, regulatory and tax advisors to the extent it deemed appropriate.

     SECTION 4. Payment of Expenses.

     (a) Expenses. The Company will pay all expenses incident to the performance of its obligations under this Agreement, including (i) the preparation, printing and filing of the Registration Statement (including financial statements and any schedules or exhibits) as originally filed and of each amendment thereto, (ii) the reproduction and delivery to the Underwriters of this Agreement, any Agreement among Underwriters and such other documents as may be required in connection with the offering, purchase, sale, issuance or delivery of the Securities, (iii) the preparation, issuance and delivery of the certificates for the Securities to the Underwriters, including any stock or other transfer taxes and any stamp or other duties payable upon the sale, issuance or delivery of the Securities to be issued and sold by the Company to the Underwriters, (iv) the fees and disbursements of the Company’s counsel, accountants and other advisors, (v) the qualification of the Securities under securities laws in accordance with the provisions of Section 3(f) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters in connection therewith and in connection with the preparation of one Blue Sky Survey, if any, and any supplement thereto for the Securities (provided that counsel fees in connection therewith do not exceed $5,000), (vi) the printing and delivery to the Underwriters of copies of each preliminary prospectus and of the Prospectus and any amendments or supplements thereto, (vii) the fees and expenses of any transfer agent or registrar for the Securities, (viii) the costs and expenses of the Company relating to investor presentations on any “road show” undertaken in connection with the marketing of the Securities, including without limitation, expenses associated with the production of road show slides and graphics, fees and expenses of any consultants engaged in connection with the road show presentations, travel and lodging expenses of the representatives and officers of the Company and any such consultants, and the cost of aircraft and other transportation chartered in connection with the road show, (ix) the filing fees incident to, and the reasonable fees and disbursements of counsel to the Underwriters in connection with, the review by the National Association of Securities Dealers, Inc. (the “NASD”) of the terms of the sale of the Securities, and (x) the fees and expenses incurred in connection with the listing of the Securities on the New York Stock Exchange.

     (b) Termination of Agreement. If this Agreement is terminated by the Representatives in accordance with the provisions of Section 5 or Section 9(a)(i) hereof, the Company shall reimburse the Underwriters for all of their out-of-pocket expenses, up to $200,000, including the reasonable fees and disbursements of counsel for the Underwriters.

     SECTION 5. Conditions of Underwriters’ Obligations. The obligations of the several Underwriters hereunder are subject to the accuracy of the representations and warranties of the Company contained in Section 1 hereof or in certificates of any officer of the Company or any of its subsidiaries delivered pursuant to the provisions hereof, to the performance by the Company of its covenants and other obligations hereunder, and to the following further conditions:

     (a) Effectiveness of Registration Statement. The Registration Statement, including the Rule 462(b) Registration Statement, has become effective and at Closing Time no stop order suspending the effectiveness of the Registration Statement shall have been issued under the 1933 Act or proceedings therefor initiated or threatened by the Commission, and any request on the part of the Commission for additional information shall have been complied with to the reasonable satisfaction of counsel to the Underwriters. A prospectus supplement reflecting the terms of the Securities, the terms of the offering thereof and the other matters set forth therein has been prepared and will be filed pursuant to Rule 424 of the 1933 Act Regulations.

     (b) Opinion of Counsel for Company. At Closing Time, the Representatives shall have received the favorable opinion, dated as of Closing Time, in form and substance reasonably satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters, of each of (i) Foley & Lardner LLP, counsel for the Company to the effect set forth in Exhibit A hereto; and (ii) Bruce R. DeBoer, Vice President, General Counsel and Corporate Secretary of the Company, to the effect set forth in Exhibit B hereto.

     (c) Opinion of Counsel for Underwriters. At Closing Time, the Representatives shall have received the favorable opinion, dated as of Closing Time, of Vinson & Elkins L.L.P., counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters with respect to the matters set forth in clauses (i), (iii), (v) through (ix), inclusive and (x) (solely as to the information in the Prospectus under “Description of Capital Stock—Common Stock”) and the penultimate paragraph of Exhibit A hereto. In giving such opinion such counsel may rely, as to all matters governed by the laws of jurisdictions other than the federal law of the United States and the General Corporation Law of the State of Delaware, upon the opinions of counsel satisfactory to the Representatives. Such counsel may also state that, insofar as such opinion involves factual matters, they have relied, to the extent they deem proper, upon certificates of officers of the Company and its subsidiaries and certificates of public officials.

     (d) Officers’ Certificate. At Closing Time, there shall not have been, since the date hereof or since the respective dates as of which information is given in the Prospectus, any material adverse change in the condition, financial or otherwise, or in the earnings, business

affairs or business prospects of the Company and its subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business, and the Representatives shall have received a certificate of the President or a Vice President of the Company and of the chief financial or chief accounting officer of the Company, dated as of Closing Time, to the effect that (i) there has been no such material adverse change, (ii) the representations and warranties in Section 1(a) hereof are true and correct with the same force and effect as though expressly made at and as of Closing Time, (iii) the Company has complied in all material respects with all agreements and satisfied all conditions on its part to be performed or satisfied at or prior to Closing Time, and (iv) no stop order suspending the effectiveness of the Registration Statement has been issued and no proceedings for that purpose have been instituted or are pending or, to their knowledge, contemplated by the Commission.

     (e) Accountant’s Comfort Letter. At the time of the execution of this Agreement, the Representatives shall have received from Deloitte & Touche LLP a letter dated such date, in form and substance satisfactory to the Representatives, together with signed or reproduced copies of such letter for each of the other Underwriters containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information contained in the Registration Statement and the Prospectus.

     (f) KPMG Comfort Letter. At the time of the execution of this Agreement, the Representatives shall have received from KPMG LLP a letter dated such date, in form and substance satisfactory to the Representatives, together with signed or reproduced copies of such letter for each of the other Underwriters containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements of Celero and certain financial information regarding Celero contained in the Registration Statement and the Prospectus.

     (g) Bring-down Comfort Letter. At Closing Time, the Representatives shall have received from Deloitte & Touche LLP a letter, dated as of Closing Time, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (e) of this Section, except that the specified date referred to shall be a date not more than three business days prior to Closing Time.

     (h) Approval of Listing. At Closing Time, the Securities shall have been approved for listing on the New York Stock Exchange, subject only to official notice of issuance.

     (i) No Objection. The NASD shall have confirmed that it has not raised any objection with respect to the fairness and reasonableness of the underwriting terms and arrangements.

     (j) Lock-up Agreements. At the date of this Agreement, the Representatives shall have received a lock-up agreement substantially in the form previously agreed to by the parties hereto signed by the persons or entities listed on Schedule C hereto.

     (k) Conditions to Purchase of Option Securities. In the event that the Underwriters exercise their option provided in Section 2(b) hereof to purchase all or any portion of the Option

Securities, the representations and warranties of the Company contained herein and the statements in any certificates furnished by the Company or any subsidiary of the Company hereunder shall be true and correct as of each Date of Delivery and, at the relevant Date of Delivery, the Representatives shall have received:

     (i) Officers’ Certificate. A certificate, dated such Date of Delivery, of the President or a Vice President of the Company and of the chief financial or chief accounting officer of the Company confirming that the certificate delivered at the Closing Time pursuant to Section 5(d) hereof remains true and correct as of such Date of Delivery.

     (ii) Opinion of Counsel for Company. The favorable opinion of Foley & Lardner LLP, counsel for the Company, together with the favorable opinion of Bruce R. DeBoer, Vice President, General Counsel and Corporate Secretary of the Company, each in form and substance reasonably satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(b) hereof.

     (iii) Opinion of Counsel for Underwriters. The favorable opinion of Vinson & Elkins L.L.P., counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(c) hereof.

     (iv) Bring-down Comfort Letter. A letter from Deloitte & Touche LLP, in form and substance satisfactory to the Representatives and dated such Date of Delivery, substantially in the same form and substance as the letter furnished to the Representatives pursuant to Section 5(g) hereof, except that the “specified date” in the letter furnished pursuant to this paragraph shall be a date not more than five days prior to such Date of Delivery.

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

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

     SECTION 6. Indemnification.

     (a) Indemnification of Underwriters. The Company agrees to indemnify and hold harmless each Underwriter, its affiliates, as such term is defined in Rule 501(b) under the 1933 Act (each, an “Affiliate”) and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act as follows:

     (i) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, arising out of any untrue statement or alleged untrue statement of a material fact contained in the Registration Statement (or any amendment thereto) or the omission or alleged omission therefrom of a material fact required to be stated therein or necessary to make the statements therein not misleading or arising out of any untrue statement or alleged untrue statement of a material fact included in any preliminary prospectus or the Prospectus (or any amendment or supplement thereto), or the omission or alleged omission therefrom of a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading;

     (ii) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, to the extent of the aggregate amount paid in settlement of any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or of any claim whatsoever based upon any such untrue statement or omission, or any such alleged untrue statement or omission; provided that (subject to Section 6(d) below) any such settlement is effected with the written consent of the Company; and

     (iii) against any and all expense whatsoever, as incurred (including the fees and disbursements of counsel chosen by the Representatives), reasonably incurred in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue statement or omission, or any such alleged untrue statement or omission, to the extent that any such expense is not paid under (i) or (ii) above;

provided, however, that this indemnity agreement shall not apply to any loss, liability, claim, damage or expense to the extent arising out of any untrue statement or omission or alleged untrue statement or omission made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives expressly for use in the Registration Statement (or any amendment thereto), including any preliminary prospectus or the Prospectus (or any amendment or supplement thereto); provided, further, that this indemnity agreement shall not inure to the benefit of any Underwriter or any person who controls such Underwriter on account of any such loss, liability, claim, damage or expense arising out of any such defect or alleged defect in any preliminary prospectus if a copy of the Prospectus shall not have been given or sent by such Underwriter with or prior to the written confirmation of the sale involved to the extent that (i) the Prospectus would have cured such defect or alleged defect and (ii) sufficient quantities of the Prospectus were timely made available to such Underwriter.

     (b) Indemnification of Company. Each Underwriter severally agrees to indemnify and hold harmless the Company, its directors, each of its officers who signed the Registration Statement, and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act against any and all loss, liability, claim, damage and expense described in the indemnity contained in Subsection (a)(1) of this Section 6, as incurred, but only with respect to untrue statements or omissions, or alleged untrue statements or omissions, made in the Registration Statement (or any amendment thereto), or any preliminary prospectus or the Prospectus (or any amendment or supplement thereto) in reliance upon and in conformity with written information furnished to the Company by such Underwriter through the Representatives expressly for use in the Registration Statement (or any amendment thereto) or such preliminary prospectus or the Prospectus (or any amendment or supplement thereto).

     (c) Actions against Parties; Notification. Each indemnified party shall give notice as promptly as reasonably practicable to each indemnifying party of any action commenced against it in respect of which indemnity may be sought hereunder, but failure to so notify an indemnifying party shall not relieve such indemnifying party from any liability hereunder to the extent it is not materially prejudiced as a result thereof and in any event shall not relieve it from any liability which it may have otherwise than on account of this indemnity agreement. In the case of parties indemnified pursuant to Section 6(a)(1) above, counsel to the indemnified parties shall be selected by Merrill Lynch, and, in the case of parties indemnified pursuant to Section 6(b) above, counsel to the indemnified parties shall be selected by the Company. An indemnifying party may participate at its own expense in the defense of any such action; provided, however, that counsel to the indemnifying party shall not (except with the consent of the indemnified party) also be counsel to the indemnified party. In no event shall the indemnifying parties be liable for fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for all indemnified parties in connection with any one action or separate but similar or related actions in the same jurisdiction arising out of the same general allegations or circumstances. In addition, the indemnifying party shall be entitled, to the extent that it wishes, jointly with any other similarly notified indemnifying party, to assume the defense of any claim or action brought against an indemnified party with counsel reasonably satisfactory to the indemnified party. After notice from the indemnifying party to the indemnified party of its election to assume the defense of such claim or action, the indemnifying party shall not be liable to the indemnified party under this Section 6 for any legal or other expenses subsequently incurred by the indemnified party in connection with the defense thereof other than reasonable costs of investigation; provided, however, that the Representatives shall have the right to employ one counsel (in addition to local counsel) to represent them and those other Underwriters and their respective officers, employees and controlling persons who may be subject to liability arising out of any claim in respect of which indemnity may be sought by the Underwriters against the indemnifying party under this Section 6 if, in the reasonable judgment of the Representatives, either (i) there is an actual or potential conflict between the position of the indemnifying party on the one hand and the Underwriters on the other hand or (ii) there may be defenses available to it or them that are different from or additional to those available to the indemnifying party (in any of which events the indemnifying party shall not have the right to direct the defense of such action on behalf of the Representatives with respect to such different defenses), in any of which events such reasonable fees and expenses shall be borne by the indemnifying party. No indemnifying party shall, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to

any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever in respect of which indemnification or contribution could be sought under this Section 6 or Section 7 hereof (whether or not the indemnified parties are actual or potential parties thereto), unless such settlement, compromise or consent (i) includes an unconditional release of each indemnified party from all liability arising out of such litigation, investigation, proceeding or claim and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party.

     (d) Settlement without Consent if Failure to Reimburse. If at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel, such indemnifying party agrees that it shall be liable for any settlement of the nature contemplated by Section 6(a)(ii) effected without its written consent if (i) such settlement is entered into more than 45 days after receipt by such indemnifying party of the aforesaid request, (ii) such indemnifying party shall have received notice of the terms of such settlement at least 30 days prior to such settlement being entered into and (iii) such indemnifying party shall not have reimbursed such indemnified party in accordance with such request prior to the date of such settlement.

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

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

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

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

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

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

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

     SECTION 8. Representations, Warranties and Agreements to Survive. All representations, warranties and agreements contained in this Agreement or in certificates of officers of the Company or any of its subsidiaries submitted pursuant hereto, shall remain operative and in full force and effect regardless of (i) any investigation made by or on behalf of any Underwriter or its Affiliates or selling agents, any person controlling any Underwriter, its officers or directors or any person controlling the Company and (ii) delivery of and payment for the Securities.

     SECTION 9. Termination of Agreement.

     (a) Termination; General. The Representatives may terminate this Agreement, by notice to the Company, at any time at or prior to Closing Time (i) if there has been, since the time of execution of this Agreement or since the respective dates as of which information is given in the Prospectus (exclusive of any amendment or supplement thereto subsequent to the date of this Agreement), any material adverse change in the condition, financial or otherwise, or in the earnings, business affairs or business prospects of the Company and its subsidiaries

considered as one enterprise, whether or not arising in the ordinary course of business, or (ii) if there has occurred after the date hereof and prior to the Closing Time any material adverse change in the financial markets in the United States or the international financial markets, any outbreak of hostilities or escalation thereof or other calamity or crisis or any change or development involving a prospective change in national or international political, financial or economic conditions, in each case the effect of which is such as to make it, in the reasonable judgment of the Representatives, impracticable or inadvisable to market the Securities or to enforce contracts for the sale of the Securities, or (iii) if trading in any securities of the Company has been suspended or materially limited by the Commission or the New York Stock Exchange, or if trading generally on the American Stock Exchange or the New York Stock Exchange or in the Nasdaq National Market has been suspended or materially limited, or minimum or maximum prices for trading have been fixed, or maximum ranges for prices have been required, by any of said exchanges or by such system or by order of the Commission, the NASD or any other governmental authority, or (iv) if a material disruption has occurred in commercial banking or securities settlement or clearance services in the United States, or (v) if a banking moratorium has been declared by either federal or New York authorities.

     (b) Liabilities. If this Agreement is terminated pursuant to this Section, such termination shall be without liability of any party to any other party except as provided in Section 4 hereof, and provided further that Sections 1, 6, 7 and 8 shall survive such termination and remain in full force and effect.

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

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

     (b) if the number of Defaulted Securities exceeds 10% of the number of Securities to be purchased on such date, this Agreement or, with respect to any Date of Delivery which occurs after the Closing Time, the obligation of the Underwriters to purchase and of the Company to sell the Option Securities to be purchased and sold on such Date of Delivery shall terminate without liability on the part of any non-defaulting Underwriter.

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

     In the event of any such default which does not result in a termination of this Agreement or, in the case of a Date of Delivery which is after the Closing Time, which does not result in a termination of the obligation of the Underwriters to purchase and the Company to sell the relevant Option Securities, as the case may be, either the Representatives or the Company shall have the right to postpone Closing Time or the relevant Date of Delivery, as the case may be, for a period not exceeding seven days in order to effect any required changes in the Registration Statement or Prospectus or in any other documents or arrangements. As used herein, the term “Underwriter” includes any person substituted for an Underwriter under this Section 10.

     SECTION 11. Tax Disclosure. Notwithstanding any other provision of this Agreement, immediately upon commencement of discussions with respect to the transactions contemplated hereby, the Company (and each employee, representative or other agent of the Company) may disclose to any and all persons, without limitation of any kind, the tax treatment and tax structure of the transactions contemplated by this Agreement and all materials of any kind (including opinions or other tax analyses) that are provided to the Company relating to such tax treatment and tax structure. For purposes of the foregoing, the term “tax treatment” is the purported or claimed federal income tax treatment of the transactions contemplated hereby, and the term “tax structure” includes any fact that may be relevant to understanding the purported or claimed federal income tax treatment of the transactions contemplated hereby.

     SECTION 12. Notices. All notices and other communications hereunder shall be in writing and shall be deemed to have been duly given if mailed or transmitted by any standard form of telecommunication. Notices to the Underwriters shall be directed to the Representatives at 1 Houston Center, 1221 McKinney Street, Suite 2700, Houston, Texas 77010, attention of Chris Mize; notices to the Company shall be directed to them at 1700 Broadway, Suite 2300, Denver, Colorado 80290-2300, attention of James J. Volker.

     SECTION 13. Parties. This Agreement shall inure to the benefit of and be binding upon the Underwriters and the Company and their respective successors. Nothing expressed or mentioned in this Agreement is intended or shall be construed to give any person, firm or corporation, other than the Underwriters and the Company and their respective successors and the controlling persons and officers and directors referred to in Sections 6 and 7 and their heirs and legal representatives, any legal or equitable right, remedy or claim under or in respect of this Agreement or any provision herein contained. This Agreement and all conditions and provisions hereof are intended to be for the sole and exclusive benefit of the Underwriters and the Company and their respective successors, and said controlling persons and officers and directors and their heirs and legal representatives, and for the benefit of no other person, firm or corporation. No purchaser of Securities from any Underwriter shall be deemed to be a successor by reason merely of such purchase.

     SECTION 14. GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

     SECTION 15. TIME. TIME SHALL BE OF THE ESSENCE OF THIS AGREEMENT. EXCEPT AS OTHERWISE SET FORTH HEREIN, SPECIFIED TIMES OF DAY REFER TO NEW YORK CITY TIME.

     SECTION 16. Counterparts. This Agreement may be executed in any number of counterparts, each of which shall be deemed to be an original, but all such counterparts shall together constitute one and the same Agreement.

     SECTION 17. Effect of Headings. The Section headings herein are for convenience only and shall not affect the construction hereof.

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

CONFIRMED AND ACCEPTED,
as of the date first above written:

MERRILL LYNCH & CO.
MERRILL LYNCH, PIERCE, FENNER & SMITH
                              INCORPORATED
J.P. MORGAN SECURITIES INC.
WACHOVIA CAPITAL MARKETS, LLC
BANC OF AMERICA SECURITIES LLC
LEHMAN BROTHERS INC.
KEYBANC CAPITAL MARKETS,
                                        A DIVISION OF MCDONALD INVESTMENTS, INC.
RAYMOND JAMES & ASSOCIATES, INC.
PETRIE PARKMAN & CO., INC.
RBC CAPITAL MARKETS CORPORATION
SIMMONS & COMPANY INTERNATIONAL

By:		MERRILL LYNCH, PIERCE, FENNER & SMITH                                                             INCORPORATED

By:		/s/ Joseph C. Gatto, Jr. Authorized Signatory

By:		J.P. MORGAN SECURITIES INC.

By:		/s/ Yaw Asamoah-Duodu Vice President

By:		WACHOVIA CAPITAL MARKETS, LLC

By:		/s/ Mark Waxman Authorized Signatory

     For themselves and as Representatives of each of the other Underwriters named in Schedule A hereto.

SCHEDULE A

		Number of
		Initial
Name of Underwriter		Securities
Merrill Lynch, Pierce, Fenner & Smith Incorporated			1,725,000
J.P. Morgan Securities Inc.			1,293,750
Wachovia Capital Markets, LLC			632,500
Banc of America Securities LLC			575,000
Lehman Brothers Inc.			575,000
KeyBanc Capital Markets, a Division of McDonald Investments Inc.			402,500
Raymond James & Associates, Inc.			316,250
Petrie Parkman & Co., Inc.			115,000
RBC Capital Markets Corporation			57,500
Simmons & Company International			57,500
Total			5,750,000