Document:

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                                                                   EXHIBIT 10.15

                             SECOND LEASE AMENDMENT

THIS SECOND LEASE AMENDMENT is made as of September 29, 2000 by and between
Riverside Commerce Center, L.C., a Virginia limited liability company ("Lessor")
and Portfolio Recovery Associates, LLC, a Delaware limited liability company
("Lessee").

                                    RECITALS

A.      By Lease dated February 12, 1999 (the "Lease"), Riverside Investors,
        L.C. leased to Lessee Suite 100 consisting of 35,179 rentable square
        feet (the "Original Premises") in a building commonly known as Riverside
        Commerce Center, Corporate Boulevard, Norfolk, Virginia ("the
        Building"), as more particularly described in said Lease.

B.      By First Lease Amendment dated April 27, 1999, Riverside Investors, L.C.
        and Lessee modified the Building address and Lessors Services.

C.      Riverside Commerce Center, L.C., a Virginia limited liability company is
        successor in interest to Riverside Investors, L.C., a Virginia limited
        liability company.

D.      Lessor and Lessee desire to further modify the terms and conditions of
        the Lease.

NOW, THEREFORE, in consideration of the mutual promises herein contained and
other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, Lessor and Lessee hereby agree as follows:

1.      Expansion Premises: Effective as of November 1, 2000. Lessee shall lease
        an additional 4,503 rentable square feet known as Suite 200 as outlined
        on Exhibit A (the "Expansion Premises") for a total of 39,682 square
        feet (the "Total Premises").

2.      Term: The term for the Expansion Premises shall be for sixty eight (68)
        months commencing on November 1, 2000 and expiring simultaneously with
        the Original Premises on June 30, 2006.

3.      Rent: The monthly rent for the Expansion Premises shall be Five Thousand
        Seven Hundred Seventy Eight and 85/100 Dollars ($5,778.85) payable in
        advance on the first business day of each and every month.

4.      Rent Abatement: The monthly rent for the Expansion Premises only shall
        be abated for the first six (6) months of the Expansion Premises term
        and, therefore, the rent commencement for the Expansion Premises shall
        be May 1, 2001.

5.      Rent Escalation: The monthly rent for the Expansion Premises shall
        increase three percent (3%) per annum simultaneously with the Original
        Premises on July 1, 2001 and on July 1 annually thereafter.

6.      Electricity and Gas: In accordance with paragraph 2 of the First Lease
        Amendment to the Lease, Lessee's electricity and gas to the Expansion
        Premises shall be separately metered and shall be paid directly by
        Lessee.

                                        1

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7.      Tenant Improvements: Lessor shall provide Lessee with an allowance of
        Forty Five Thousand Thirty and No/100 Dollars ($45,030.00) ("Improvement
        Allowance") for tenant improvements to be constructed in accordance with
        the Work Letter Agreement (Exhibit B) attached hereto and incorporated
        herein by reference. The Improvement Allowance shall be due only during
        the initial term of the Lease. All costs in excess of the Improvement
        Allowance shall be at Lessee's cost.

8.      Parking: In addition to the allotment of parking spaces outlined In
        paragraph 12 of the Lease, Lessee shall be entitled to thirty five (35)
        additional unreserved and unassigned vehicle parking spaces.

9.      Right of First Refusal: Paragraph 4 of the Rider No. 1 to the Lease.
        Right of First Refusal, is hereby deleted in its entirety.

10.     All other terms and conditions of the Lease are hereby ratified and
        shall remain in full force and effect. in the event of a conflict
        between the Second Lease Amendment, First Lease Amendment and the Lease,
        this Second Lease Amendment shall prevail.

IN WITNESS WHEREOF, the parties hereto have executed and delivered this
agreement as of the date first written above.

LESSOR:                                 RIVERSIDE INVESTORS, L.C.,
                                        A VIRGINIA LIMITED LIABILITY COMPANY

                                By:     Robinson Development Group, Inc.
                                Its:    Manager

                                By:     /s/ ANTHONY W. SMITH
                                        ----------------------------------------
                                        Anthony W. Smith
                                Its:    Senior Vice President

LESSEE:                                 PORTFOLIO RECOVERY ASSOCIATES, LLC,
                                        A DELAWARE LIMITED LIABILITY COMPANY

                                By:     /s/ STEVEN FREDRICKSON
                                        ----------------------------------------
                                Name:   Steven Fredrickson
                                        ----------------------------------------
                                Its:    President
                                        ----------------------------------------

                                        2<PAGE>

                                                                   Exhibit 4.1.2

                          CHESAPEAKE ENERGY CORPORATION

                                       and

                     the Subsidiary Guarantors named herein

                    ----------------------------------------

                          7 7/8% SENIOR NOTES DUE 2004
                    ----------------------------------------

                               -------------------

                          TENTH SUPPLEMENTAL INDENTURE

                            DATED AS OF June 28, 2002

                               -------------------

                              THE BANK OF NEW YORK

                             as successor Trustee to

                     United States Trust Company of New York

                               -------------------
<PAGE>
      THIS TENTH SUPPLEMENTAL INDENTURE, dated as of June 28, 2002, is among
Chesapeake Energy Corporation, an Oklahoma corporation (the "Company"), each of
the parties identified under the caption "Subsidiary Guarantors" on the
signature page hereto (the "Subsidiary Guarantors") and The Bank of New York, as
successor to United States Trust Company of New York, as Trustee.

                                    RECITALS

      WHEREAS, the Company, the Subsidiary Guarantors a party thereto and the
Trustee entered into an Indenture, dated as of March 15, 1997, as supplemented
prior to the date hereof (the "Indenture"), pursuant to which the Company has
originally issued $150,000,000 in principal amount of 7"% Senior Notes due 2004
(the "Notes"); and

      WHEREAS, Section 9.1(3) of the Indenture provides that the Company, the
Subsidiary Guarantors and the Trustee may amend or supplement the Indenture
without notice to or consent of any Holder to reflect the addition of any
Subsidiary Guarantor, as provided for in the Indenture; and

      WHEREAS, the Board of Directors of the Company has designated Chesapeake
KNAN Acquisition Corporation and Chesapeake Focus Corp. as Restricted
Subsidiaries of the Company and desires to add such entities as Subsidiary
Guarantors under the Indenture; and

      WHEREAS, all acts and things prescribed by the Indenture, by law and by
the charter and the bylaws (or comparable constituent documents) of the Company,
of the Subsidiary Guarantors and of the Trustee necessary to make this Tenth
Supplemental Indenture a valid instrument legally binding on the Company, the
Subsidiary Guarantors and the Trustee, in accordance with its terms, have been
duly done and performed;

      NOW, THEREFORE, to comply with the provisions of the Indenture and in
consideration of the above premises, the Company, the Subsidiary Guarantors and
the Trustee covenant and agree for the equal and proportionate benefit of the
respective Holders of the Notes as follows:

                                    ARTICLE 1

      Section 1.01. This Tenth Supplemental Indenture is supplemental to the
Indenture and does and shall be deemed to form a part of, and shall be construed
in connection with and as part of, the Indenture for any and all purposes.

      Section 1.02. This Tenth Supplemental Indenture shall become effective
immediately upon its execution and delivery by each of the Company, the
Subsidiary Guarantors and the Trustee.

                                    ARTICLE 2

                                      -2-
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      From this date, in accordance with Section 10.3 and by executing this
Tenth Supplemental Indenture, Chesapeake KNAN Acquisition Corporation, an
Oklahoma corporation, and Chesapeake Focus Corp., an Oklahoma corporation, are
subject to the provisions of the Indenture as Subsidiary Guarantors to the
extent provided for in Article X thereunder.

                                    ARTICLE 3

      Section 3.01. Except as specifically modified herein, the Indenture and
the Notes are in all respects ratified and confirmed (mutatis mutandis) and
shall remain in full force and effect in accordance with their terms with all
capitalized terms used herein without definition having the same respective
meanings ascribed to them as in the Indenture.

      Section 3.02. Except as otherwise expressly provided herein, no duties,
responsibilities or liabilities are assumed, or shall be construed to be
assumed, by the Trustee by reason of this Tenth Supplemental Indenture. This
Tenth Supplemental Indenture is executed and accepted by the Trustee subject to
all the terms and conditions set forth in the Indenture with the same force and
effect as if those terms and conditions were repeated at length herein and made
applicable to the Trustee with respect hereto.

      Section 3.03. The Company hereby notifies the Trustee that Chesapeake KNAN
Acquisition Corporation and Chesapeake Focus Corp. have each been designated by
the Board of Directors of the Company as a Restricted Subsidiary (as that term
is defined in the Indenture).

      Section 3.04. THE LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED TO
CONSTRUE AND ENFORCE THIS TENTH SUPPLEMENTAL INDENTURE.

      Section 3.05. The parties may sign any number of copies of this Tenth
Supplemental Indenture. Each signed copy shall be an original, but all of such
executed copies together shall represent the same agreement.

                          [NEXT PAGE IS SIGNATURE PAGE]

                                      -3-
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      IN WITNESS WHEREOF, the parties hereto have caused this Tenth Supplemental
Indenture to be duly executed, all as of the date first written above.

                            COMPANY:

                            CHESAPEAKE ENERGY CORPORATION

                            By  /s/ AUBREY K. MCCLENDON
                              --------------------------------------
                            Name:  Aubrey K. McClendon
                                 -----------------------------------
                            Title: Chief Executive Officer
                                  ----------------------------------

                            SUBSIDIARY GUARANTORS:

                            CARMEN ACQUISITION CORP.
                            CHESAPEAKE ACQUISITION CORPORATION
                            CHESAPEAKE ENERGY LOUISIANA
                            CORPORATION
                            CHESAPEAKE MOUNTAIN FRONT CORP.
                            CHESAPEAKE OPERATING, INC.
                            CHESAPEAKE ROYALTY COMPANY
                            GOTHIC ENERGY CORPORATION
                            GOTHIC PRODUCTION CORPORATION
                            NOMAC DRILLING CORPORATION
                            SAP ACQUISITION CORP.
                            THE AMES COMPANY, INC.
                            CHESAPEAKE KNAN ACQUISITION
                            CORPORATION
                            CHESAPEAKE FOCUS CORP.

                            By /s/ AUBREY K. MCCLENDON
                              --------------------------------------
                            Name:  Aubrey K. McClendon
                                 -----------------------------------
                            Title: Chief Executive Officer
                                  ----------------------------------

                                      -4-
<PAGE>
                            CHESAPEAKE EXPLORATION LIMITED
                            PARTNERSHIP
                            CHESAPEAKE LOUISIANA, L.P.
                            CHESAPEAKE PANHANDLE LIMITED
                            PARTNERSHIP

                            CHESAPEAKE-STAGHORN ACQUISITION L.P.

                                    By:   Chesapeake Operating, Inc. as general
                                          partner of each representative entity

                                     By /s/ Aubrey K. McClendon
                                       -----------------------------
                                     Name:  Aubrey K. McClendon
                                          --------------------------
                                     Title: Chief Executive Officer
                                           -------------------------

                            TRUSTEE:

                            THE BANK OF NEW YORK, as successor to United
                            States Trust Company of New York,
                            as Trustee

                            By /s/ Louis P. Young
                              --------------------------------------
                            Name: Louis P. Young
                                 -----------------------------------
                            Title: Vice President
                                  ----------------------------------

                                      -5-

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