EXHIBIT 4.11

                               Eighth Amendment to
                       Agreement of Limited Partnership of
                 Geodyne Energy Income Limited Partnership III-A

      This Eighth  Amendment  to  Agreement  of Limited  Partnership  of Geodyne
Energy Income Limited  Partnership III-A (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 November 17, 1989, Geodyne Production Company ("Geodyne"),  as
General Partner and Depositary  executed and entered into that certain Agreement
of Limited Partnership of the Partnership (the "Agreement"); and

      WHEREAS,  on February  25,  1993,  Geodyne  executed and entered into that
certain  First  Amendment  to the  Agreement of Limited  Partnership  whereby it
changed (i) the name of the Partnership from "PaineWebber/Geodyne  Energy Income
Partnership III-A" to "Geodyne Energy Income Limited  Partnership  III-A",  (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, Geodyne executed and entered into that certain
Second  Amendment  to the  Agreement  of  Limited  Partnership  in  order 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,  Geodyne  executed  and  entered  into that
certain Third Amendment to the Agreement of Limited  Partnership whereby Section
8.1.A(ii)  of the  Agreement  was deleted in order to allow  transfers  of Units
facilitated  through a matching service to the extent that they otherwise comply
with Internal Revenue Service transfer  regulations  applicable to non-permitted
transfers for non-publicly traded limited partnerships; and

      WHEREAS,  on June 30, 1996,  Geodyne merged into Geodyne  Resources,  Inc.
("Resources"); and

      WHEREAS,  on  July  1,  1996,  Resources,   as  successor  via  merger  to
Properties,  executed and entered into, as General Partner,  that certain Fourth
Amendment  to the  Agreement  of Limited  Partnership  whereby  it  amended  the
Agreement to provide that Resources,  as successor via merger to Geodyne, is the
General Partner of the Partnership; and

     WHEREAS,  on November  15, 1999,  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 November 22, 2001, and

                                      -1-
<PAGE>



     WHEREAS,  on November  14, 2001,  Resources  executed and entered into that
certain Sixth Amendment to the Agreement whereby the term of the partnership was
extended for an additional two years, until November 22, 2003, and

      WHEREAS,  on November 18, 2003,  Resources  executed and entered into that
certain Seventh  Amendment to the Agreement  whereby the term of the partnership
was extended for an additional two years, until November 22, 2005; and

      WHEREAS,  Section 2.3 of the Agreement provides that the Partnership shall
continue  in full  force and effect for a period of ten (10) years from the date
of its  Activation  (as  defined in the  Agreement),  provided  that the General
Partner  may extend  the term of the  Partnership  for up to two  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,  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 November
         22, 2007,  provided that the General Partner may extend the term of the
         Partnership  for up to one  period  of two  years 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
this 27th day of October, 2005.

                                    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

                                      -2-