EXHIBIT 99.1
                                                                    ------------


                      AMENDMENT FOR AN INCREASED COMMITMENT


         This  AMENDMENT  is made as of the  17th day of  November,  2004 by and
among  Chesapeake   Exploration   Limited   Partnership,   an  Oklahoma  limited
partnership ("BORROWER"), Chesapeake Energy Corporation, an Oklahoma corporation
(the "COMPANY"),  Union Bank of California,  N.A., as  administrative  agent and
collateral  agent  ("ADMINISTRATIVE  AGENT"),  and  the  Lenders  listed  on the
attached EXHIBIT A (each a "SUPPLEMENTAL LENDER", and together the "SUPPLEMENTAL
LENDERS").

         Borrower, the Company,  Administrative Agent and certain other Lenders,
as described  therein,  are parties to that certain  Fourth Amended and Restated
Credit Agreement dated as of May 7, 2004 (as amended, supplemented, or restated,
the "CREDIT  AGREEMENT").  All terms used herein and not otherwise defined shall
have the same meaning given to them in the Credit Agreement.

         Pursuant to SECTION  10.6A of the Credit  Agreement,  Borrower  has the
right to increase the aggregate  Revolving  Commitment  by obtaining  additional
Revolving  Commitments upon satisfaction of certain  conditions.  This Amendment
requires  only  the  signature  of  Borrower,   Administrative   Agent  and  the
Supplemental  Lenders so long as the Aggregate Commitment is not increased above
the amount permitted by the Credit Agreement.

         The  Supplemental  Lenders are each either (a) an existing Lender which
is increasing  its  Revolving  Commitment or (b) a new Lender which is a lending
institution  whose identity  Administrative  Agent will approve by its signature
below.

         In consideration of the foregoing,  each Supplemental  Lender, from and
after the date hereof,  shall have the Revolving  Commitment  listed next to its
name on the  attached  EXHIBIT  A,  which  shall  replace  the  prior  Revolving
Commitment of each existing  Supplemental  Lender in effect immediately prior to
this  Amendment,  as listed next to its name on the attached  EXHIBIT A, and any
Supplemental  Lender that is a new Lender  hereby  assumes all of the rights and
obligations of a Lender under the Credit  Agreement.  This  Amendment  shall not
affect the Revolving Commitments of Lenders who are not Supplemental Lenders.

         Borrower has executed and delivered to each  Supplemental  Lender as of
the date hereof, if requested by such Supplemental  Lender, a new or replacement
Note in the form  attached to the Credit  Agreement as EXHIBIT H to evidence the
new or increased Revolving Commitment of such Supplemental Lender.


      [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK. SIGNATURE PAGES FOLLOW.]



         IN WITNESS WHEREOF, Administrative Agent, Borrower and the Supplemental
Lenders have executed this Amendment as of the date shown above.


                                 CHESAPEAKE EXPLORATION LIMITED
                                 PARTNERSHIP

                                 By:    Chesapeake Operating, Inc., its general
                                        partner


                                        By: /S/ MARTHA A. BURGER
                                            -----------------------------------
                                            Name:   Martha A. Burger
                                            Title:  Treasurer and
                                                    Sr. Vice President
                                                    Human Resources


                                 CHESAPEAKE ENERGY CORPORATION


                                        By: /S/ MARTHA A. BURGER
                                            -----------------------------------
                                            Name:   Martha A. Burger
                                            Title:  Treasurer and
                                                    Sr. Vice President
                                                    Human Resources


                                 UNION BANK OF CALIFORNIA, N.A.,
                                 as Administrative Agent


                                        By: /S/ RANDALL OSTERBERG
                                            -----------------------------------
                                            Name:   Randall Osterberg
                                            Title:  Senior Vice President


                                        By: /S/ KIMBERLY CALL
                                            -----------------------------------
                                            Name:   Kimberly Call
                                            Title:  Assistant Vice President



                                                              SIGNATURE PAGE TO
                                              AMENDMENT FOR COMMITMENT INCREASE

                                       2



                                 BNP PARIBAS


                                        By: /S/ DAVID DODD
                                            -----------------------------------
                                            Name:   David Dodd
                                            Title:  Director


                                        By: /S/ POLLY SCHOTT
                                            -----------------------------------
                                            Name:   Polly Schott
                                            Title:  Vice-President



                                                              SIGNATURE PAGE TO
                                              AMENDMENT FOR COMMITMENT INCREASE

                                       3



                                 SUNTRUST BANK

                                        By: /S/ JOE MCCREERY
                                            -----------------------------------
                                            Name:   Joe McCreery
                                            Title:  Vice President



                                                              SIGNATURE PAGE TO
                                              AMENDMENT FOR COMMITMENT INCREASE

                                       4



                                 CALYON NEW YORK BRANCH


                                        By: /S/ OLIVIER AUDEMARD
                                            -----------------------------------
                                            Name:   Olivier Audemard
                                            Title:  Managing Director


                                        By: /S/ ATTILA COACH
                                            -----------------------------------
                                            Name:   Attila Coach
                                            Title:  Managing Director



                                                              SIGNATURE PAGE TO
                                              AMENDMENT FOR COMMITMENT INCREASE

                                       5



                                 BANK OF SCOTLAND


                                        By: /S/ AMENA NABI
                                            -----------------------------------
                                            Name:   Amena Nabi
                                            Title:  Assistant Vice President



                                                               SIGNATURE PAGE TO
                                              AMENDMENT FOR COMMITMENT INCREASE

                                       6



                                 COMERICA BANK


                                        By: /S/ PETER L. SEFZIK
                                            -----------------------------------
                                            Name:   Peter L. Sefzik
                                            Title:  Vice President
                                                    Texas Division



                                                               SIGNATURE PAGE TO
                                              AMENDMENT FOR COMMITMENT INCREASE


                                       7



                                 BANK OF AMERICA, N.A.


                                        By: /S/ RONALD E. MCKAIG
                                            -----------------------------------
                                            Name:   Ronald E. McKaig
                                            Title:  Senior Vice President



                                                               SIGNATURE PAGE TO
                                              AMENDMENT FOR COMMITMENT INCREASE


                                       8



                                 WELLS FARGO BANK, N.A.


                                        By: /S/ DUSTIN S. HANSEN
                                            -----------------------------------
                                            Name:   Dustin S. Hansen
                                            Title:  Assistant Vice President



                                                               SIGNATURE PAGE TO
                                               AMENDMENT FOR COMMITMENT INCREASE


                                       9



                                 NANTEXIS BANQUE POPULAIRE


                                        By: /S/ DONOVAN C. BROUSSARD
                                            -----------------------------------
                                            Name:   Donovan C. Broussard
                                            Title:  Vice President & Manager


                                        By: /S/ LOUIS P. LAVILLE, III
                                            -----------------------------------
                                            Name:   Louis P. Laville, III
                                            Title:  Vice President & Manager



                                                               SIGNATURE PAGE TO
                                               AMENDMENT FOR COMMITMENT INCREASE


                                       10



                                 RZB FINANCE LLC


                                        By: /S/ JUAN M. CSILLAGI
                                            -----------------------------------
                                            Name:   Juan M. Csillagi
                                            Title:  Group Vice President


                                        By: /S/ CHRISTOPH HOEDL
                                            -----------------------------------
                                            Name:   Christoph Hoedl
                                            Title:  Vice President



                                                               SIGNATURE PAGE TO
                                               AMENDMENT FOR COMMITMENT INCREASE

                                       11



                                 ROYAL BANK OF CANADA


                                        By: /S/ LINDA M. STEPHENS
                                            -----------------------------------
                                            Name:   Linda M. Stephens
                                            Title:  Authorized Signatory



                                                               SIGNATURE PAGE TO
                                               AMENDMENT FOR COMMITMENT INCREASE

                                       12



                                    EXHIBIT A
                                    ---------

                                          Prior                   New
                                        Revolving              Revolving
                                        Commitment             Commitment
                                  ---------------------    ------------------

UNION BANK OF CALIFORNIA, N.A.          $45,000,000            $55,000,000
BNP PARIBAS                             $40,000,000            $50,000,000
SUNTRUST BANK                           $40,000,000            $50,000,000
CALYON NEW YORK BRANCH                  $40,000,000            $50,000,000
BANK OF SCOTLAND                        $40,000,000            $50,000,000
COMERICA BANK                           $40,000,000            $50,000,000
BANK OF AMERICA, N.A.                   $40,000,000            $50,000,000
WELLS FARGO BANK, N.A.                  $25,000,000            $35,000,000
NATEXIS BANQUE                          $20,000,000            $25,000,000
RZB FINANCE LLC                         $10,000,000            $15,000,000
ROYAL BANK OF CANADA                        -0-                $10,000,000
                                  ---------------------    -------------------
                                  ---------------------    -------------------


Increase in Aggregate Revolving Commitment          $100,000,000


                                       13