<PAGE>

                                                                   Exhibit 4.9.1

                                 FIFTH AMENDMENT
                                       TO
                  SECOND AMENDED AND RESTATED CREDIT AGREEMENT
                                       AND
                                     CONSENT

     THIS FIFTH AMENDMENT TO SECOND AMENDED AND RESTATED CREDIT AGREEMENT AND
CONSENT (herein called this "Amendment") is dated as of March 3, 2003 (but
effective on the Effective Date, defined below in Section 3.1) by and among
Chesapeake Exploration Limited Partnership, an Oklahoma limited partnership
("Borrower"), Chesapeake Energy Corporation, an Oklahoma corporation
("Company"), Bear Stearns Corporate Lending Inc., as syndication agent
("Syndication Agent"), Union Bank of California, N.A., as administrative agent
and collateral agent ("Administrative Agent"), and the several banks and other
financial institutions or entities parties hereto ("Lenders").

                              W I T N E S S E T H:

     WHEREAS, Borrower, Company, Syndication Agent, Administrative Agent and
Lenders entered into that certain Second Amended and Restated Credit Agreement
dated as of June 11, 2001 (as amended, supplemented, or restated to the date
hereof, the "Original Agreement"), for the purpose and consideration therein
expressed, whereby Lenders became obligated to make loans to Borrower as therein
provided;

     WHEREAS, Company intends to acquire certain oil and gas assets for cash for
a purchase price of $500,000,000 (subject to customary adjustments),
substantially in accordance with the Purchase and Sale Agreement by and between
El Paso Production Company and Noric, L.P., as sellers, and Chesapeake EP
Corporation, as buyer, dated as of February 21, 2003 (the "El Paso
Acquisition");

     WHEREAS, Company intends to issue new senior notes in the aggregate face
amount of up to $350,000,000, providing (a) for an interest rate at the then
prevailing market rate of interest, (b) for a maturity date of not sooner than
seven years from the date of issuance, and (c) for covenants, mandatory
prepayments, defaults, and events of default no more restrictive than those
governing Company's 7-3/4% Senior Notes due 2015 (the "New Notes");

     WHEREAS, prior to or contemporaneously with the issuance of the New Notes,
Company intends to issue new Cumulative Convertible Perpetual Preferred Stock of
the Company in the aggregate face amount of not more than $250,000,000 with a
dividend rate of not more than 7.5% per annum (the "New Preferred Stock") and/or
additional common stock of the Company (the "New Common Stock");

     WHEREAS, Borrower and Company have requested that Administrative Agent and
Lenders consent to the foregoing proposed transactions; and

<PAGE>

     WHEREAS, Borrower, Company, Syndication Agent, Administrative Agent and
Lenders desire to amend the Original Agreement as set forth;

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
and agreements contained herein and in the Original Agreement, in consideration
of the loans which may hereafter be made by Lenders to Borrower, and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto do hereby agree as follows:

                                   ARTICLE I.

                           Definitions and References

     Section 1.1.   Terms Defined in the Original Agreement. Unless the context
otherwise requires or unless otherwise expressly defined herein, the terms
defined in the Original Agreement shall have the same meanings whenever used in
this Amendment.

     Section 1.2.   Other Defined Terms. Unless the context otherwise requires,
the following terms when used in this Amendment shall have the meanings assigned
to them in this Section 1.2.

             "Amendment" means this Fifth Amendment to Second Amended and
     Restated Credit Agreement and Consent.

             "Credit Agreement" means the Original Agreement as amended hereby.

             "Effective Date" has the meaning given to such term in Section 3.1.

                                   ARTICLE II.

                             Amendments and Consents

     Section 2.1.   Defined Terms. The definition of "Indentures" in Section 1.1
of the Original Agreement is hereby amended in its entirety to read as follows:

             " 'Indentures': the collective reference to (i) the 7-7/8% Note
     Indenture, (ii) the 8-1/2% Note Indenture, (iii) the 8-1/8% Note Indenture,
     (iv) the 8-3/8% Note Indenture, and (v) the other Indentures entered into
     from time to time as permitted pursuant to the terms of this Agreement or
     any consent by Majority Lenders hereunder governing Indebtedness of the
     Company and the guarantors thereof."

     Section 2.2.   Restricted Payments. Upon the issuance of not less than
15,000,000 shares of New Common Stock, Paragraph (c) of Section 7.6 of the
Original Agreement is hereby amended to replace the reference to "$25,000,000"
with "$35,000,000."

                                       2

<PAGE>

     Section 2.3.   New Notes. Administrative Agent and Lenders hereby (a)
consent to the issuance of the New Notes, (b) waive any violations of Section
7.2 of the Credit Agreement resulting therefrom, and (c) agree that such New
Notes shall be permitted in addition to the Indebtedness otherwise permitted
pursuant to Section 7.2 of the Credit Agreement; provided that (i) at the time
of the issuance of the New Notes, no Default or Event of Default has occurred
that is continuing, the issuance of the New Notes shall be approved by the Board
of Directors of Company, and the face amount of the New Notes divided by the sum
of (x) the face amount of the New Notes plus (y) the aggregate sales price of
the New Preferred Stock and/or New Common Stock shall not exceed 65%; (ii) the
issuance of the New Notes shall be consummated on or before April 30, 2003;
(iii) the net proceeds of the New Notes shall be used to consummate the El Paso
Acquisition with any remaining funds (or all of such funds should the El Paso
Acquisition fail to close) used to repay outstanding Indebtedness of any Group
Member under the Loan Documents or to pay the purchase price of oil and gas
properties acquired by a Group Member under the Loan Documents or to pay
development costs with respect to oil and gas properties owned by a Group
Member; and (iv) except as otherwise provided herein, nothing in this Amendment
shall allow any Group Member to incur any other new Indebtedness not allowed
pursuant to Section 7.2 of the Credit Agreement.

     Section 2.4.   Acquisition. Administrative Agent and Lenders hereby (a)
consent to the El Paso Acquisition and (b) waive any violations of Section 7.7
of the Credit Agreement resulting therefrom; provided that (i) at the time of
the El Paso Acquisition, no Default or Event of Default has occurred that is
continuing, the El Paso Acquisition shall be approved by the Board of Directors
of Company, and the Company has received proceeds of the New Notes, New
Preferred Stock and/or New Common Stock of at least $350,0000,000, (ii) each
newly formed subsidiary of the Company (the "New Subsidiaries") shall become a
Subsidiary Guarantor under the Credit Agreement pursuant to Section 6.9(b)
thereof or shall be merged into a Subsidiary Guarantor (with such Subsidiary
Guarantor being the continuing or surviving entity), (iii) the initial closing
of the El Paso Acquisition shall be consummated on or before April 30, 2003,
(iv) immediately following the consummation of the El Paso Acquisition, Company
and Borrower shall deliver to Administrative Agent a certificate signed by a
Responsible Officer certifying that after giving effect to the El Paso
Acquisition and the inclusion of the New Subsidiaries as a Subsidiary Guarantor
(x) no Default or Event of Default exists that is continuing and (y) all
representations and warranties contained in Section 4 of the Credit Agreement
are true and correct, and (v) except as otherwise provided herein, nothing in
this Amendment shall allow any Group Member to make any other new Investments
not allowed pursuant to Section 7.7 of the Credit Agreement. The limitations set
forth in this Section shall not be deemed to restrict Investments otherwise
allowed under clause (n) of Section 7.7 of the Credit Agreement.

     Section 2.5.   Preferred Stock Dividends. Administrative Agent and Lenders
hereby (a) consent to the payment of cash dividends in respect of the New
Preferred Stock in the aggregate face amount not to exceed $250,000,000 (the
"New Preferred Dividends"), (b) waive any violations of the Credit Agreement
resulting therefrom, and (c) agree that such New Preferred Dividends shall be
permitted in addition to the Restricted Payments otherwise permitted pursuant to
Section 7.6 of the Credit Agreement; provided that (i) at the time of the
declaration of such New Preferred Dividends, no Default or Event of Default has
occurred which is continuing, (ii) the payment of the New Preferred Dividends
shall be declared by the Board of Directors of

                                       3

<PAGE>

Company, and (iii) nothing in this Amendment shall allow any Person to make any
other new Restricted Payments not allowed pursuant to Section 7.6 of the Credit
Agreement.

                                  ARTICLE III.

                      Conditions of Effectiveness; Closing

     Section 3.1. Effective Date. This Amendment shall become effective on the
date when all of the following conditions precedent have been satisfied (the
"Effective Date"), provided that the Effective Date may occur no later than
April 30, 2003 unless agreed to in writing by Administrative Agent and Borrower.

     (a)   Administrative Agent shall have received, at Administrative Agent's
office, duly executed and delivered and in form and substance satisfactory to
Administrative Agent, all of the following:

           (i)    this Amendment duly executed by Borrower, Company and
     Administrative Agent;

           (ii)   the Consent Agreement attached hereto duly executed by all
     Subsidiary Guarantors;

           (iii)  an "Omnibus Certificate" of the Secretary and of the Chairman
     of the Board or President of the general partner of Borrower, which shall
     contain the names and signatures of the officers of the general partner of
     Borrower authorized to execute Loan Documents and which shall certify to
     the truth, correctness and completeness of the following exhibits attached
     thereto: (1) a copy of resolutions attached thereto duly adopted by the
     Board of Directors of the general partner of Borrower and in full force and
     effect at the time this Amendment is entered into, authorizing the
     execution of this Amendment and the other Loan Documents delivered or to be
     delivered in connection herewith and the consummation of the transactions
     contemplated herein and therein, (2) a copy of the charter documents of
     Borrower and of the general partner of Borrower and all amendments thereto,
     certified by the appropriate official of the Borrower's state and general
     partner's state of organization, and (3) a copy of any bylaws of the
     general partner of Borrower previously delivered to Agent and Lenders in
     connection with the Original Agreement (which may, with respect to any such
     charter documents or bylaws, reference documents previously delivered in
     connection with the Original Agreement);

           (iv)   a "Compliance Certificate" of the Chairman of the Board or
     President and of the chief financial officer of the Company, which shall
     contain (1) a certification by such officers as to the satisfaction of the
     conditions set out in subsections (a), (b), and (c) of Section 5.2 of the
     Original Agreement and (2) the calculations required to determine the
     Senior Debt Limit (along with the supporting documentation described in
     Section 5.2(c) of the Original Agreement);

                                        4

<PAGE>

           (v)  documents similar to those specified in subsection (iii) of this
     Section with respect to each Subsidiary Guarantor (which may, with respect
     to charter documents or bylaws, reference documents previously delivered in
     connection with the Original Agreement); and

           (vi) such other supporting documents as Administrative Agent may
     reasonably request.

     (b)   Borrower shall have paid, in connection with such Loan Documents,
all recording, handling, amendment and other fees required to be paid to
Administrative Agent pursuant to any Loan Documents.

     (c)   Borrower shall have paid, in connection with such Loan Documents, all
other fees and reimbursements to be paid to Administrative Agent pursuant to any
Loan Documents, or otherwise due Administrative Agent and including fees and
disbursements of Administrative Agent's attorneys.

                                   ARTICLE IV.

                         Representations and Warranties

     Section 4.1.   Representations and Warranties of Borrower. In order to
induce each Lender to enter into this Amendment, Borrower represents and
warrants to each Lender that:

     (a)   The representations and warranties contained in Section 4 of the
Original Agreement are true and correct at and as of the time of the
effectiveness hereof, except to the extent that the facts on which such
representations and warranties are based have been changed by the extension of
credit under the Credit Agreement.

     (b)   The Company and Borrower are duly authorized to execute and deliver
this Amendment and are and will continue to be duly authorized to borrow monies
and to perform their respective obligations under the Credit Agreement. The
Company and Borrower have duly taken all corporate or partnership action
necessary to authorize the execution and delivery of this Amendment and to
authorize the performance of the obligations of the Company and Borrower
hereunder.

     (c)   The execution and delivery by the Company and Borrower of this
Amendment, the performance by the Company and Borrower of its obligations
hereunder and the consummation of the transactions contemplated hereby do not
and will not conflict with any provision of law, statute, rule or regulation or
of the certificate of incorporation, bylaws, or agreement of limited partnership
of the Company or Borrower (as applicable), or of any material agreement,
judgment, license, order or permit applicable to or binding upon the Company or
Borrower, or result in the creation of any lien, charge or encumbrance upon any
assets or properties of the Company or Borrower. Except for those which have
been obtained, no consent, approval, authorization or order of any court or
governmental authority or third party is required

                                       5

<PAGE>

in connection with the execution and delivery by the Company and Borrower of
this Amendment or to consummate the transactions contemplated hereby.

     (d)   When duly executed and delivered, each of this Amendment and the
Credit Agreement will be a legal and binding obligation of the Company and
Borrower, enforceable in accordance with its terms, except as limited by
bankruptcy, insolvency or similar laws of general application relating to the
enforcement of creditors' rights and by equitable principles of general
application.

     (e)   The audited annual consolidated financial statements of the Company
dated as of December 31, 2001 and the unaudited quarterly consolidated financial
statements of the Company dated as of September 30, 2002 fairly present the
consolidated financial position at such dates and the consolidated statement of
operations and the changes in consolidated financial position for the periods
ending on such dates for the Company. Copies of such financial statements have
heretofore been delivered to each Lender. Since such dates no material adverse
change has occurred in the financial condition or businesses or in the
consolidated financial condition or businesses of the Company.

                                   ARTICLE V.

                                  Miscellaneous

     Section 5.1. Ratification of Agreements. The Original Agreement as hereby
amended is hereby ratified and confirmed in all respects. Any reference to the
Credit Agreement in any Loan Document shall be deemed to be a reference to the
Original Agreement as hereby amended. The execution, delivery and effectiveness
of this Amendment shall not, except as expressly provided herein, operate as a
waiver of any right, power or remedy of Lenders under the Credit Agreement, the
Notes, or any other Loan Document nor constitute a waiver of any provision of
the Credit Agreement, the Notes or any other Loan Document.

     Section 5.2. Survival of Agreements. All representations, warranties,
covenants and agreements of Borrower herein shall survive the execution and
delivery of this Amendment and the performance hereof, including without
limitation the making or granting of the Loans, and shall further survive until
all of the Obligations are paid in full. All statements and agreements contained
in any certificate or instrument delivered by the Company, Borrower or any
Subsidiary Guarantor hereunder or under the Credit Agreement to any Lender shall
be deemed to constitute representations and warranties by, and/or agreements and
covenants of, such Loan Party under this Amendment and under the Credit
Agreement.

     Section 5.3. Loan Documents. This Amendment is a Loan Document, and all
provisions in the Credit Agreement pertaining to Loan Documents apply hereto.

     Section 5.4. Governing Law. This Amendment shall be governed by and
construed in accordance with the laws of the State of New York and any
applicable laws of the United States of America in all respects, including
construction, validity and performance.

                                       6

<PAGE>

     Section 5.5.   Counterparts; Fax. This Amendment may be separately executed
in counterparts and by the different parties hereto in separate counterparts,
each of which when so executed shall be deemed to constitute one and the same
Amendment. This Amendment may be validly executed by facsimile or other
electronic transmission.

     Section 5.6.   Amendment Fee. In consideration of this Amendment, provided
that Lenders constituting Majority Lenders are signatory to this Amendment on or
before 5:00 p.m., Dallas, Texas time on the date hereof, Borrower will pay to
Administrative Agent, for the account of each such signatory Lender, an
amendment fee determined by multiplying .15% times such Lender's Revolving
Commitment, which shall be due and payable on the date hereof.

     THIS AMENDMENT AND THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT
BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO
UNWRITTEN ORAL AGREEMENTS OF THE PARTIES.

         [The remainder of this page has been intentionally left blank.]

                                       7

<PAGE>

     IN WITNESS WHEREOF, this Amendment is executed as of the date first above
written.

                                          CHESAPEAKE EXPLORATION LIMITED
                                          PARTNERSHIP

                                          By:  Chesapeake Operating, Inc., its
                                               general partner


                                          By:  /s/ Martha A. Burger
                                               ---------------------------------
                                               Martha A. Burger
                                               Treasurer and Sr. Vice President
                                               Human Resources


                                          CHESAPEAKE ENERGY CORPORATION



                                          By:  /s/ Martha A. Burger
                                               ---------------------------------
                                               Martha A. Burger
                                               Treasurer and Sr. Vice President
                                               Human Resources

<PAGE>

                                         UNION BANK OF CALIFORNIA, N.A.
                                         Administrative Agent, Collateral Agent,
                                         Issuing Lender and Lender



                                         By:  /s/ Sean Murphy
                                              ----------------------------------
                                              Name:  Sean Murphy
                                              Title: Vice President

                                         By:  /s/ Carl Stutzman
                                              ----------------------------------
                                              Name:  Carl Stutzman
                                              Title: Senior Vice President and
                                                     Manager

<PAGE>

                                           BANK OF OKLAHOMA, N.A.


                                           By:  /s/ John N. Huff
                                                --------------------------------
                                                Name:  John N. Huff
                                                Title: Vice President

                                           BANK OF SCOTLAND


                                           By:  /s/ Joseph Fratus
                                                --------------------------------
                                                Name:  Joseph Fratus
                                                Title: First Vice President

                                           BEAR STEARNS CORPORATE LENDING INC.


                                           By:  /s/ Victor Bulzacchelli
                                                --------------------------------
                                                Name:  Victor Bulzacchelli
                                                Title: Authorized Agent

                                           BNP PARIBAS


                                           By:  /s/ David Dodd
                                                --------------------------------
                                                Name:  David Dodd
                                                Title: Director


                                           By:  /s/ Polly Schott
                                                --------------------------------
                                                Name:  Polly Schott
                                                Title: Vice President

                                           COMERICA BANK - TEXAS


                                           By:  /s/ Peter L. Sefzik
                                                --------------------------------
                                                Name:  Peter L. Sefzik
                                                Title: Assistant Vice President

<PAGE>

                                    COMPASS BANK


                                    By:  /s/ Kathleen J. Bowen
                                         ---------------------------------------
                                         Name:  Kathleen J. Bowen
                                         Title: Vice President

                                    CREDIT LYONNAIS NEW YORK BRANCH


                                    By:  /s/ Olivier Audemard
                                         ---------------------------------------
                                         Name:  Olivier Audemard
                                         Title: Senior Vice President

                                    CREDIT SUISSE FIRST BOSTON


                                    By:  /s/ James P. Moran
                                         ---------------------------------------
                                         Name:  James P. Moran
                                         Title: Director

                                    By:  /s/ Ian W. Nalitt
                                         ---------------------------------------
                                         Name:  Ian W. Nalitt
                                         Title: Associate

                                    NATEXIS BANQUES POPULAIRES

                                    By:  /s/ Donovan C. Broussard
                                         ---------------------------------------
                                         Name:  Donovan C. Broussard
                                         Title: Vice President


                                    By:  /s/ Louis P. Laville, III
                                         ---------------------------------------
                                         Name:  Louis P. Laville, III
                                         Title: Vice President and Group Manager

                                    PNC BANK, NATIONAL ASSOCIATION

                                    By:  /s/ Doug Clark
                                         ---------------------------------------
                                         Name:  Doug Clark
                                         Title: Vice President

<PAGE>

                                RZB FINANCE LLC


                                By:   /s/ Christoph Hoedl
                                      ------------------------------------------
                                      Name:  Christoph Hoedl
                                      Title: Vice President

                                By:   /s/ Elizabeth Hirst
                                      ------------------------------------------
                                      Name:  Elizabeth Hirst
                                      Title: AVP

                                SUMITOMO MITSUI BANKING
                                CORPORATION


                                By:   /s/ William Ginn
                                      ------------------------------------------
                                      Name:  William Ginn
                                      Title: General Manager

                                TORONTO DOMINION (TEXAS), INC.


                                By:   /s/ Rachel Suiter
                                      ------------------------------------------
                                      Name:  Rachel Suiter
                                      Title: Vice President

                                WASHINGTON MUTUAL BANK, FA


                                By:   /s/ Mark Isensee
                                      ------------------------------------------
                                      Name:  Mark Isensee
                                      Title: Vice President

<PAGE>

   Fifth Amendment to Second Amended and Restated Credit Agreement and Consent


                              CONSENT AND AGREEMENT

     By its execution below, each Guarantor hereby (i) consents to the
provisions of this Amendment and the transactions contemplated herein, (ii)
ratifies and confirms the Guarantee Agreement dated as of June 11, 2001 made by
it for the benefit of Administrative Agent and Lenders (as modified by certain
Assumption Agreements) and the other Loan Documents executed pursuant to the
Credit Agreement (or any prior amendment or supplement to the Credit Agreement),
(iii) agrees that all of its respective obligations and covenants thereunder
shall remain unimpaired by the execution and delivery of this Amendment and the
other documents and instruments executed in connection herewith, and (iv) agrees
that the Guarantee Agreement and such other Loan Documents shall remain in full
force and effect.

CHESAPEAKE ENERGY CORPORATION
CHESAPEAKE OPERATING, INC.


By:  /s/ Martha A. Burger
     -------------------------------
     Martha A. Burger
     Treasurer and Sr. Vice President Human Resources
     of each above corporation

<PAGE>

THE AMES COMPANY, L.L.C.
     (successor to The Ames Company, Inc.)
CARMEN ACQUISITION, L.L.C.
     (successor to Carmen Acquisition Corp.)
CHESAPEAKE ACQUISITION, L.L.C.
     (successor to Chesapeake Acquisition Corporation)
CHESAPEAKE EP CORPORATION
     (formerly known as Chesapeake Beta Corporation)
CHESAPEAKE DELTA CORP.
CHESAPEAKE ENERGY LOUISIANA CORPORATION
CHESAPEAKE ENO ACQUISITION, L.L.C.
     (successor to Chesapeake Eno Acquisition Corp.)
CHESAPEAKE FOCUS, L.L.C.
     (successor to Chesapeake Focus Corp.)
CHESAPEAKE KNAN ACQUISITION, L.L.C.
     (successor to Chesapeake Knan Acquisition Corporation)
CHESAPEAKE MOUNTAIN FRONT, L.L.C.
     (successor to Chesapeake Mountain Front Corp.)
CHESAPEAKE ORC, L.L.C.
CHESAPEAKE ROYALTY, L.L.C.
     (successor to Chesapeake Royalty Company)
GOTHIC ENERGY, L.L.C.
     (successor to Gothic Energy Corporation)
GOTHIC PRODUCTION, L.L.C.
     (successor to Gothic Production Corporation)
NOMAC DRILLING CORPORATION
SAP ACQUISITION, L.L.C.
     (successor to Sap Acquisition Corp.)

By:  /s/ Martha A. Burger
     ----------------------------------------
     Martha A. Burger
     Treasurer of each above corporation

<PAGE>

CHESAPEAKE PANHANDLE LIMITED PARTNERSHIP
CHESAPEAKE-STAGHORN ACQUISITION L.P.
CHESAPEAKE LOUISIANA, L.P.
CHESAPEAKE SIGMA, L.P.

   By:   CHESAPEAKE OPERATING, INC., as General Partner
         of each above limited partnership


   By:   /s/ Martha A. Burger
         ----------------------------------------
         Martha A. Burger
         Treasurer and Sr. Vice President Human Resources