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                                                                 EXHIBIT (d)(2)

                             AMENDMENT TO AGREEMENT
                               AND PLAN OF MERGER


                  THIS AMENDMENT TO AGREEMENT AND PLAN OF MERGER dated as of
February 2, 2001 (this "Amendment") by and among MARATHON OIL COMPANY, an Ohio
corporation ("Parent"), MARATHON OIL ACQUISITION 1, LTD., a Delaware corporation
and a direct wholly owned subsidiary of Parent ("Sub"), and PENNACO ENERGY,
INC., a Delaware corporation (the "Company").

                              PRELIMINARY STATEMENT

                  The parties hereto also are the parties to an Agreement and
Plan of Merger dated as of December 22, 2000 (the "Merger Agreement"), and they
desire to amend the Merger Agreement as provided herein.

                  NOW, THEREFORE, in consideration of the premises and the
mutual agreements this Amendment contains, Parent, Sub and the Company hereby
agree as follows:

                  Section 1. Amendment. (a) Section 1.07 of the Merger Agreement
hereby is amended to read in its entirety as follows:

                  Section 1.07. Certificate of Incorporation and Bylaws.

                  (a) The Certificate of Incorporation of the Company, as in
         effect immediately prior to the Effective Time, shall be amended at the
         Effective Time to read in its entirety as set forth in Exhibit A
         hereto; and, as so amended, that Certificate of Incorporation shall be
         the Certificate of Incorporation of the Surviving Corporation until
         thereafter changed or amended in accordance with the provisions thereof
         and applicable Law.

                  (b) The Bylaws of the Company, as in effect immediately prior
         to the Effective Time, shall amended in their entirety at the Effective
         Time to read as the Bylaws of Sub, as in effect immediately prior to
         the Effective Time, provided that those amended Bylaws shall provide
         that the name of the Company is "Pennaco Energy, Inc."; and, as so
         amended, those Bylaws shall be the Bylaws of the Surviving Corporation
         until thereafter changed or amended in accordance with the provisions
         thereof and the provisions of the Certificate of Incorporation of the
         Surviving Corporation and applicable Law.

                  Section 2. Representatives and Warranties of the Company. The
Company represents and warrants to Parent and Sub as follows:

                  (a) The Company has all requisite corporate power and
         authority to execute and deliver this Amendment. The execution and
         delivery by the Company of this Amendment have been duly authorized by
         all necessary corporate action on the part of the Company, including
         approval of the Board of Directors of the Company in accordance with
         the provisions of Section 8.05 of the Merger Agreement.




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                  (b) The Company has duly executed and delivered this
         Amendment, and this Amendment constitutes the legal, valid and binding
         obligation, enforceable against the Company in accordance with the
         terms hereof, except as that enforceability may be limited by any
         applicable bankruptcy, insolvency, reorganization, moratorium or
         similar laws affecting the enforcement of creditor's rights generally
         and the application of general principles of equity (regardless of
         whether that enforceability is considered in a proceeding at law or in
         equity).

                  Section 3. Representations and Warranties of Parent and Sub.
Parent and Sub, jointly and severally represent and warrant to the Company as
follows:

                  (a) Each of Parent and Sub has all requisite corporate power
         and authority to execute and deliver this Amendment. The execution and
         delivery by each of Parent and Sub of this Amendment have been duly
         authorized by all necessary corporate action on the part of Parent and
         Sub.

                  (b) Each of Parent and Sub has duly executed and delivered
         this Amendment, and this Amendment constitutes its legal, valid and
         binding obligation, enforceable against it in accordance with the terms
         hereof, except as that enforceability may be limited by any applicable
         bankruptcy, insolvency, reorganization, moratorium or similar laws
         affecting the enforcement of creditor's rights generally and the
         application of general principles of equity (regardless of whether that
         enforceability is considered in a proceeding at law or in equity).

                  Section 4. Effect on Merger Agreement. When this Amendment
becomes effective pursuant to the provisions of Section 5 hereof, all references
to "this Agreement" in the Merger Agreement shall be deemed to refer to the
Merger Agreement as amended by this Amendment, unless the context otherwise
requires. Except as amended hereby, all provisions of the Merger Agreement are
and will remain in full force and effect.

                  Section 5. Execution in Counterparts; Effectiveness. This
Amendment may be executed in any number of counterparts, each of which will be
deemed for all purposes to be an original, but all of which together will
constitute one and the same Amendment. This Amendment will become effective
immediately on execution and delivery by the parties hereto.

                  Section 6. Governing Law. THIS AMENDMENT SHALL BE GOVERNED BY,
AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF DELAWARE, REGARDLESS
OF THE LAWS THAT MIGHT OTHERWISE GOVERN UNDER APPLICABLE PRINCIPLES OF CONFLICTS
OF LAWS THEREOF.




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                  IN WITNESS WHEREOF, the parties hereto have executed this
Amendment as of the date first above written.

                                  MARATHON OIL COMPANY


                                  By:   /s/ Clarence P. Cazalot, Jr.
                                     ------------------------------------------
                                       Clarence P. Cazalot, Jr.
                                       President

                                  MARATHON OIL ACQUISITION 1, LTD.


                                  By:   /s/ Richard J. Murphy
                                     ------------------------------------------
                                       Richard J. Murphy
                                       President

                                  PENNACO ENERGY, INC.


                                  By:   /s/ Paul M. Rady
                                     ------------------------------------------
                                       Paul M. Rady
                                       President




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                                                                       EXHIBIT A

                          CERTIFICATE OF INCORPORATION
                                       OF
                              PENNACO ENERGY, INC.


FIRST:            The name of the Corporation is PENNACO ENERGY, INC. (the
                  "Corporation").

SECOND:           The address of the registered office of the Corporation in the
                  State of Delaware is 1209 Orange Street, Wilmington, County of
                  New Castle, Delaware 19801. The name of the registered agent
                  of the Corporation at such address is The Corporation Trust
                  Company.

THIRD:            The purpose of the Corporation is to engage in, carry on and
                  conduct any lawful business, act or activity for which
                  corporations may be organized under the General Corporation
                  Law of the State of Delaware (the "DGCL").

FOURTH:           The total number of shares of stock which the Corporation will
                  have authority to issue is 1,000 shares of common stock, which
                  shares will be without par value ("Common Stock").

FIFTH:            Each holder of Common Stock shall have one vote in respect of
                  each share of Common Stock held by such holder on any matter
                  submitted to the stockholders of the Corporation. Cumulative
                  voting of shares of Common Stock is prohibited. Shares of
                  Common Stock may be issued for such consideration and for such
                  corporate purposes as the Board of Directors of the
                  Corporation may from time to time determine. In the event of
                  voluntary or involuntary liquidation, distribution or sale of
                  assets, dissolution or winding-up of the Corporation, the
                  holders of the Common Stock shall be entitled to receive all
                  the assets of the Corporation, tangible and intangible, of
                  whatever kind available for distribution to stockholders,
                  ratably in proportion to the number of shares of Common Stock
                  held by each.

SIXTH:            The number of directors that shall constitute the whole Board
                  of Directors of the Corporation shall be as from time to time
                  fixed by, or in the manner provided in, the by-laws of the
                  Corporation. The election of directors need not be by written
                  ballot, unless the by-laws so provide. Each director shall
                  hold office for the full term for which such director is
                  elected and until such director's successor shall have been
                  duly elected and qualified or until his earlier death,
                  resignation or removal.

SEVENTH:          The business and affairs of the Corporation shall be managed
                  by or under the direction of the Board of Directors. In
                  furtherance and not in limitation of the powers conferred by
                  the DGCL, the Board of Directors of the Corporation is
                  expressly authorized to adopt, amend or repeal the by-laws of
                  the Corporation; provided, however, that the grant of such
                  authority shall not divest the stockholders of the Corporation
                  of the power, nor limit their power to adopt, amend or repeal
                  the by-laws of the Corporation.




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EIGHTH:           No director of the Corporation shall be personally liable to
                  the Corporation or any of its stockholders for monetary
                  damages for breach of fiduciary duty as a director involving
                  any act or omission of any such director; provided, however,
                  that the foregoing provision shall not eliminate or limit the
                  liability of a director (a) for any breach of the director's
                  duty of loyalty to the Corporation or its stockholders, (b)
                  for acts or omissions not in good faith or which involve
                  intentional misconduct or a knowing violation of law, (c)
                  under Section 174 of the DGCL, as the same exists or hereafter
                  may be amended, supplemented, or replaced or (d) for any
                  transaction from which such director derived an improper
                  personal benefit. Any repeal or modification of this Article
                  EIGHTH shall be prospective only and shall not adversely
                  affect any limitation on the personal liability of a director
                  of the Corporation existing at the time of such repeal or
                  modification.




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