Sixth Amendment to
             Agreement and Certificate of Limited Partnership of
                Geodyne Energy Income Limited Partnership II-F



      This Sixth Amendment to Agreement and  Certificate of Limited  Partnership
of Geodyne Energy Income Limited Partnership II-F (the "Partnership") is entered
into  by  and  between  Geodyne  Resources,   Inc.  ("Resources"),   a  Delaware
corporation,   as  successor  General  Partner,   Geodyne   Depositary   Company
("Depositary"),  a  Delaware  corporation,  as  the  Limited  Partner,  and  all
Substituted Limited Partners admitted to the Partnership.

      WHEREAS, on January 5, 1989, Geodyne Properties,  Inc. ("Properties"),  as
General partner, and Depositary executed and entered into that certain Agreement
and Certificate of Limited Partnership of the Partnership (the "Agreement"); and

      WHEREAS,  on February 25, 1993,  Properties executed and entered into that
certain First Amendment to the Agreement  whereby it changed (i) the name of the
Partnership from "PaineWebber/Geodyne Energy Income Limited Partnership II-F" to
"Geodyne  Energy  Income  Limited  Partnership  II-F",  (ii) the  address of the
Partnership's  principal  place of  business,  and  (iii)  the  address  for the
Partnership's agent for service of process; and

      WHEREAS,  on August 4, 1993,  Properties  executed  and entered  into that
certain Second Amendment to the Agreement whereby it amended certain  provisions
to (i) expedite the method of accepting  transfers of Unit  Holders' (as defined
in the  Agreement)  Units in the  Partnership  and (ii)  provide for an optional
right of repurchase/redemption which may be exercised by the Unit Holders; and

      WHEREAS,  on August 31,  1995,  Properties  executed and entered into that
Third Amendment to the Agreement whereby it amended certain  provisions to allow
transfers  of Units  facilitated  through a matching  service to the extent that
such  transfers   otherwise   comply  with  Internal  Revenue  Service  transfer
regulations  applicable  to  non-permitted  transfers  for  non-publicly  traded
limited partnerships; and

      WHEREAS,  on July  1,  1996,  Resources,  as  successor  via  merger  with
Properties,  executed  and entered  into that  certain  Fourth  Amendment to the
Agreement  whereby it  amended  the  Agreement  to provide  that  Resources,  as
successor via merger with Properties,  is the general partner of the partnership
(the "General Partner") of the Partnership; and

     WHEREAS,  on November  14, 2001,  Resources  executed and entered into that
certain Fifth Amendment to the Agreement whereby the term of the partnership was
extended for an additional two years, until December 31, 2003, and


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      WHEREAS,  Section 2.3 of the Agreement provides that the Partnership shall
continue in full force and effect until  December 31,  2003,  provided  that the
General Partner may extend the term of the Partnership for up to four periods of
two years each if it believes  each such  extension is in the best  interests of
the Unit Holders or until  dissolution  prior thereto pursuant to the provisions
of the Agreement, and

      WHEREAS,  Section 11.1 of the Agreement  provides that the General Partner
may,  without  prior  notice or  consent of any Unit  Holder (as  defined in the
Agreement),  amend any  provision of this  Agreement  if, in its  opinion,  such
amendment does not have a material adverse effect upon the Unit Holders; and

      WHEREAS,  Resources  as General  Partner has elected to extend the life of
the Partnership an additional two years.

      NOW,  THEREFORE,  in  consideration  of  the  covenants,   conditions  and
agreements herein contained, the parties hereto hereby agree as follows:

      Section 2.3. is hereby amended and restated as follows:

                  The  Partnership  shall  continue  in force and  effect  until
            December 31, 2005,  provided that the General Partner may extend the
            term of the Partnership for up to three periods of two years each if
            it believes  such  extension  is in the best  interests  of the Unit
            Holders,   or  until  dissolution  prior  thereto  pursuant  to  the
            provisions hereof.

       IN WITNESS  WHEREOF,  the parties hereto have hereunto set their hands as
of the 18th day of November, 2003.

                                    GEODYNE RESOURCES, INC.,
                                    as General Partner

                                    By://s// Dennis R. Neill
                                    -------------------------
                                          Dennis R. Neill
                                          President

                                    GEODYNE DEPOSITARY COMPANY,
                                    as the Limited Partner

                                    By://s// Dennis R. Neill
                                    -------------------------
                                          Dennis R. Neill
                                          President

                                    GEODYNE RESOURCES, INC.
                                    as Attorney-in-Fact for all
                                    Substituted Limited Partners


                                    By://s// Dennis R. Neill
                                    -------------------------
                                          Dennis R. Neill
                                          President

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