September 27, 1999




TO:         All Limited Partners in Geodyne I-D, I-E, I-F, III-A,
            III-B and III-C Partnerships

RE:         Election to extend term of Partnership

Dear Limited Partner:

      As previously  described to you, the limited  partnership  agreements (the
"Agreements")   for  the  above   referenced   Geodyne   Energy  Income  Limited
Partnerships  (the  "Partnerships")  provide that each of the Partnerships  will
automatically terminate and dissolve on the following dates:

            I-D......December 31, 1999
            I-E......December 31, 1999
            I-F......December 31, 1999
            III-A....November 28, 1999
            III-B....January 24, 2000
            III-C....February 28, 2000

      The  Agreements  give the General  Partner an option to extend the term of
the  Partnerships  for up to five additional two year terms. The General Partner
is  hereby  notifying  you  that it has  elected  to  extend  each of the  above
referenced  Partnerships' terms for an additional two year period.  Accordingly,
the General  Partner will file amendments to the  Partnerships'  Certificates of
Limited Partnership extending the Partnerships' terms as follows:

            I-D......December 31, 2001
            I-E......December 31, 2001
            I-F......December 31, 2001
            III-A....November 28, 2001
            III-B....January 24, 2002
            III-C....February 28, 2002

      If you have any questions  concerning the  Partnerships'  extension please
contact Geodyne Investor Services at 918-583-1791 or 888-436-3963.


                                  Very truly yours,

                                  GEODYNE RESOURCES, INC.,
                                  General Partner


                                  Dennis R. Neill
                                  President