EXHIBIT 4.20

                              Seventh Amendment to
                       Agreement of Limited Partnership of
                 Geodyne Institutional/Pension Energy Income
                             Limited Partnership P-8

      This Seventh  Amendment to  Agreement  of Limited  Partnership  of Geodyne
Institutional/Pension  Energy Income Limited Partnership P-8 (the "Partnership")
is entered into by and between Geodyne Resources, Inc. ("Resources"), a Delaware
corporation,  as successor  General Partner,  Geodyne  Institutional  Depositary
Company ("Depositary"),  a Delaware corporation, as the Limited Partner, and all
Substituted Limited Partners admitted to the Partnership.

      WHEREAS, on February 28, 1992, 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   Institutional/Pension   Energy  Income
Limited Partnership P-8" to "Geodyne Institutional/Pension Energy Income Limited
Partnership  P-8",  (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' 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
certain 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,   Properties  merged  with  and  into  Geodyne  Resources,   Inc.
("Resources"), its parent corporation, effective June 30, 1996; and

      WHEREAS,  on  July  1st,  1996,  Resources  as  successor  via  merger  to
Properties  executed  and entered  into that  certain  Fourth  Amendment  to the
Agreement  whereby it amended the  Agreement to provide that Geodyne  Resources,
Inc., as successor  via merger with  Properties,  is 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 February 28, 2004; and

                                      -1-
<PAGE>



      WHEREAS,  on January 22,  2004,  Resources  executed and entered into that
certain Sixth Amendment to the Agreement whereby the term of the partnership was
extended until December 31, 2005; and

      WHEREAS,  Section 2.3 of the Agreement provides that the Partnership shall
continue in full force and effect until  December 31,  2005,  provided  that the
General Partner may extend the term of the Partnership for an additional 59 days
of the current two year period and for up to three  periods of two years each if
it believes each such extension is in the best interests of the Limited Partners
or until  dissolution prior thereto pursuant to the provisions of the Agreement,
and

      WHEREAS,  Resources  as General  Partner has elected to extend the life of
the Partnership through December 31, 2007.

      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, 2007,  provided that the General Partner may extend the
            term of the Partnership for an additional 59 days of the current two
            year period and for an  additional  two periods of two years each if
            it believes such  extension is in the best  interests of the Limited
            Partners,  or  until  dissolution  prior  thereto  pursuant  to  the
            provisions hereof.


      IN WITNESS WHEREOF, the parties hereto have hereunto set their hands as of
the 27th day of October, 2005.

                                       Geodyne Resources, Inc.
                                       as General Partner

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

                                       Geodyne Institutional 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

                                      -2-