Document:

<PAGE>   1
                                                                    EXHIBIT 10.1

            FOURTH AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT

         This Fourth Amendment to Amended and Restated Credit Agreement (this
"Fourth Amendment") is executed as of the 4th day of May, 2001, to be effective
as of April 1, 2001 (the "Effective Date"), by and among Prize Energy Resources,
L.P., a Delaware limited partnership ("Borrower"), Prize Energy Corp., a
Delaware corporation ("Parent"), Fleet National Bank, a national banking
association, as Administrative Agent ("Administrative Agent"), and the financial
institutions a party hereto as Banks.

                              W I T N E S S E T H:

         WHEREAS, Borrower, Parent, Administrative Agent, First Union National
Bank, as Syndication Agent, CIBC Inc., as Documentation Agent, Bank One, NA,
successor-in-interest to Bank One, Texas, N.A., as Lead Manager, Fleet National
Bank, First Union National Bank, CIBC Inc., Bank One, NA, successor-in-interest
to Bank One, Texas, N.A., Christiania Bank, Bank of Scotland, Comerica
Bank-Texas, Fortis Capital Corp., The Bank of Nova Scotia and The Frost National
Bank (collectively, the "Existing Banks") are parties to that certain Amended
and Restated Credit Agreement dated as of February 8, 2000 (as amended, the
"Credit Agreement") (unless otherwise defined herein, all terms used herein with
their initial letter capitalized shall have the meaning given such terms in the
Credit Agreement); and

         WHEREAS, pursuant to the Credit Agreement, the Existing Banks have made
a revolving credit/term loan to Borrower; and

         WHEREAS, prior to the execution of this Fourth Amendment, certain of
the Existing Banks (herein referred to as "Assigning Banks") have entered into
Assignment and Assumption Agreements with BNP Paribas and U.S. Bank National
Association (herein referred to as "Assignee Banks" and together with the
Existing Banks, collectively, the "Banks"), pursuant to which such Assigning
Banks assigned to such Assignee Banks, and Assignee Banks (a) acquired from such
Assigning Banks (as applicable) a portion of each such Assigning Bank's
Commitments and a portion of the Loans and Letter of Credit Exposure held by
each such Assigning Bank (as applicable) under the Credit Agreement, (b) assumed
and agreed to perform a portion of each such Assigning Bank's (as applicable)
obligations under the Credit Agreement and the other Loan Papers, and (c) became
a party to, and a "Bank" under, the Credit Agreement and the other Loan Papers;
and

         WHEREAS, Schedule 1 attached hereto reflects the Commitments of each
Bank after giving effect to the Assignment and Acceptance Agreements referenced
above, and, pursuant to Section 15.9 of the Credit Agreement, Schedule 1 to the
Credit Agreement is deemed amended and restated in the form of Schedule 1
attached hereto; and

         WHEREAS, Parent and Borrower have requested that the Banks (i) amend
certain terms of the Credit Agreement in certain respects, and (ii) establish a
Borrowing Base of $375,000,000 to be effective as of the Effective Date and
continuing until the next Determination; and

<PAGE>   2

         WHEREAS, subject to the terms and conditions set forth herein, the
Banks have agreed to Parent's and Borrower's requests.

         NOW THEREFORE, for and in consideration of the mutual covenants and
agreements herein contained and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged and confessed, Parent,
Borrower, Administrative Agent and each Bank hereby agree as follows:

         SECTION 1. Amendments. In reliance on the representations, warranties,
covenants and agreements contained in this Fourth Amendment, and subject to the
satisfaction of the conditions precedent set forth in Section 3 hereof, the
Credit Agreement is hereby amended effective as of the Effective Date in the
manner provided in this Section 1.

         1.1.     Amendment to Definitions. The definitions of "Consolidated
Current Assets," "Consolidated Current Liabilities," "Consolidated Net Income,"
"Loan Papers" and "Revolver Conversion Date" contained in Section 2.1 of the
Credit Agreement shall be amended to read in full as follows:

                  "Consolidated Current Assets" means, for any Person at any
         time, the sum of (a) the current assets of such Person and its
         Consolidated Subsidiaries at such time determined in accordance with
         GAAP, plus (b) in the case of Parent and Borrower, and prior to the
         Revolver Conversion Date, the Availability at such time. For purposes
         of this definition, any non-cash gains on any Hedge Agreement resulting
         from the requirements of SFAS 133 for any period of determination shall
         be excluded from the determination of the current assets of such Person
         and its Consolidated Subsidiaries.

                  "Consolidated Current Liabilities" means, for any Person at
         any time, the current liabilities of such Person and its Consolidated
         Subsidiaries at such time determined in accordance with GAAP, but, in
         the case of Parent, excluding CMLTD of Parent and its Consolidated
         Subsidiaries at such time. For purposes of this definition, any
         non-cash losses or charges on any Hedge Agreement resulting from the
         requirements of SFAS 133 for any period of determination shall be
         excluded from the determination of the current liabilities of such
         Person and its Consolidated Subsidiaries.

                  "Consolidated Net Income" means, for any Person as of any
         period, the net income (or loss) of such Person and its Consolidated
         Subsidiaries for such period determined in accordance with GAAP, but
         excluding: (a) the income of any other Person (other than its
         Consolidated Subsidiaries) in which such Person or any of its
         Subsidiaries has an ownership interest, unless received by such Person
         or its Consolidated Subsidiaries in a cash distribution; (b) any
         after-tax gains attributable to asset dispositions; (c) any non-cash
         gains, losses or charges on any Hedge Agreement resulting from the
         requirements of SFAS 133 for that period; (d) to the extent not
         included in clauses (a), (b) and (c) above, any after-tax (i)
         extraordinary gains (net of extraordinary losses) or (ii) non-cash
         nonrecurring gains, and (e) non-cash or non-recurring charges.

                  "Loan Papers" means this Agreement, the First Amendment, the
         Second Amendment, the Third Amendment, the Fourth Amendment, the Notes,
         each Facility

<PAGE>   3

         Guaranty now or hereafter executed (and any ratification thereof), the
         Mortgages, the Assignments and Amendments to Mortgages, each Parent
         Pledge Agreement now or hereafter executed, each Subsidiary Pledge
         Agreement now or hereafter executed, the Borrower Assumption Agreement,
         and all other certificates, documents or instruments delivered in
         connection with this Agreement, as the foregoing may be amended from
         time to time.

                  "Revolver Conversion Date" means June 29, 2004.

         1.2.     Additional Definition. Section 2.1 of the Credit Agreement
shall be amended to add the following definition to such Section:

                  "Hedge Agreements" means, collectively, any agreement,
         instrument, arrangement or schedule or supplement thereto evidencing
         any Hedge Transaction.

         1.3.     New Schedule. Schedule 1 attached to the Credit Agreement
shall be replaced in its entirety by Schedule 1 attached to this Fourth
Amendment.

         SECTION 2. Borrowing Base Effective as of the Effective Date. In
reliance on the representations, warranties, covenants and agreements contained
in this Fourth Amendment, upon the satisfaction of each condition precedent set
forth in Section 3 hereof (evidenced by a written notice to that effect from
Administrative Agent to Borrower), the Borrowing Base shall be increased from
$325,000,000 to $375,000,000 and shall remain at $375,000,000 until the next
Determination thereafter. Parent, Borrower and the Banks agree that the
Determination provided for in this Section 2 shall not be construed or deemed to
be a Special Determination for purposes of Section 5.3 of the Credit Agreement.

         SECTION 3. Conditions Precedent. The effectiveness of (a) the
amendments to the Credit Agreement contained in Section 1 hereof, and (b) the
increase in the Borrowing Base pursuant to Section 2 hereof is subject to the
satisfaction of each of the following conditions precedent on or before the
Effective Date:

         3.1.     Completion of Apache Acquisition. Borrower shall have
completed the acquisition (the "Apache Acquisition") of the Apache Properties
substantially in accordance with the terms of that certain Purchase and Sale
Agreement dated December 29, 2000, by and between Borrower and Apache
Corporation (as amended, the "Apache Acquisition Agreement"). As used herein,
the term "Apache Properties" means the Mineral Interests to be acquired by
Borrower pursuant to the Apache Acquisition Agreement.

         3.2.     Additional Security. To the extent required by Section 6.1 of
the Credit Agreement, Borrower shall execute and deliver to Administrative
Agent, for the ratable benefit of each Bank, Mortgages in form and substance
acceptable to Administrative Agent granting, evidencing and perfecting a first
and prior Lien (subject only to Permitted Encumbrances) covering and encumbering
Proved Mineral Interests owned by Borrower (after giving effect to the Apache
Acquisition) which are not the subject of existing valid, enforceable, and
perfected first priority Liens (subject to Permitted Encumbrances) in favor of
Administrative Agent for the ratable benefit of each Bank (including, without
limitation, the Apache Properties). Borrower shall also deliver to
Administrative Agent such opinions of counsel as Administrative Agent

<PAGE>   4

shall deem necessary or appropriate to verify the validity, perfection and
priority of the Liens created by such Mortgages and such other matters regarding
such Mortgages as Administrative Agent shall reasonably request.

         3.3.     Title Review. Administrative Agent and its counsel shall have
completed a review of title (including opinions of title) to that portion of the
Apache Properties which results in Administrative Agent and its counsel having
reviewed title with respect to the Title Required Reserve Value of all Borrowing
Base Properties (after giving effect to the Apache Acquisition). Such review
shall not have revealed any condition or circumstance which would reflect that
the representations and warranties contained in Section 8.9 of the Credit
Agreement are inaccurate in any respect.

         3.4.     Environmental Review. Administrative Agent and its counsel
shall have been provided with, and shall have completed a review of, such
environmental reports and summaries required by Administrative Agent with
respect to the Apache Properties, and such review shall not have revealed any
condition or circumstance which would reflect that, upon completion of the
Apache Acquisition, the representations and warranties contained in Section 8.16
of the Credit Agreement are inaccurate in any respect.

         3.5.     Material Agreements. Administrative Agent shall have been
provided with a fully executed copy of the Apache Acquisition Agreement and all
other material documents, instruments and agreements executed and/or delivered
by any Credit Party in connection with the Apache Acquisition, together with a
certificate from an Authorized Officer of Borrower certifying that such copies
are accurate and complete and represent the complete understanding and agreement
of the parties with respect to the subject matter thereof.

         3.6.     New Notes. Administrative Agent shall have received a Note
payable to the order of each Bank (as applicable), each in the amount of such
Bank's Commitment as reflected on the new Schedule 1 attached to this Fourth
Amendment.

         3.7.     Borrowing Base Increase Fee. Administrative Agent shall have
received, for the benefit of each Bank (as applicable), all fees due and payable
in connection with the increase in the Borrowing Base pursuant to Section 2
hereof.

         3.8.     Resolutions. Parent and Borrower shall have provided
Administrative Agent with copies of resolutions and comparable authorizations
approving this Fourth Amendment and any other Loan Papers to be executed or
delivered pursuant hereto and authorizing the transactions contemplated by this
Fourth Amendment and any other Loan Papers to be executed or delivered pursuant
hereto, duly adopted by the Board of Directors and partners of Parent and
Borrower (as applicable) accompanied by a certificate of the Secretary or
comparable Authorized Officer or partner of Parent or Borrower (as applicable)
that such copies are true and correct copies of resolutions duly adopted at a
meeting of or (if permitted by applicable Law and, if required by such Law, by
the Bylaws or other charter documents of Parent and Borrower, as applicable) by
the unanimous written consent of the Board of Directors of Parent and Borrower
(as applicable), and that such resolutions constitute all the resolutions
adopted with respect to such transactions, have not been amended, modified or
revoked in any respect, and are in full force and effect as of the date hereof.

<PAGE>   5

         3.9.     Consents of Partners. Borrower shall have provided
Administrative Agent with copies of consents of partners of Borrower (to the
extent required) to the transactions contemplated by this Fourth Amendment and
the other Loan Papers executed in connection herewith, duly executed by each
partner of Borrower required to consent to such transactions, accompanied by
certificates of the Secretary or comparable Authorized Officers or partners of
Borrower that such copies are true and correct copies of all consents of the
partners of Borrower required to be executed and granted pursuant to Borrower's
partnership agreement and all other comparable charter documents of Borrower.

         3.10.    No Default. No Default or Event of Default shall have occurred
which is continuing.

         3.11.    Fees. Borrower shall have paid to Administrative Agent any
fees payable to Administrative Agent or any Affiliate of Administrative Agent
pursuant to this Fourth Amendment and any separate agreement between Borrower,
Administrative Agent or any Affiliate of Administrative Agent in consideration
for providing services in connection with the credit facilities provided by the
Credit Agreement.

         3.12.    Other Documents. Administrative Agent shall have been provided
with such other documents, instruments and agreements, and Parent and Borrower
shall have taken such actions, as Administrative Agent may reasonably require in
connection with this Fourth Amendment and the transactions contemplated hereby.

         SECTION 4. Representations and Warranties of Borrower. To induce the
Banks and Administrative Agent to enter into this Fourth Amendment, Parent and
Borrower hereby jointly and severally represent and warrant to the Banks and
Administrative Agent as follows:

         4.1.     Reaffirm Existing Representations and Warranties. Each
representation and warranty of each Credit Party contained in the Credit
Agreement and the other Loan Papers is true and correct on the date hereof and
will be true and correct after giving effect to the amendments set forth in
Section 1 hereof.

         4.2.     Due Authorization; No Conflict. The execution, delivery and
performance by Parent and Borrower of this Fourth Amendment are within Parent's
and Borrower's corporate and partnership powers (as applicable), have been duly
authorized by all necessary action, require no action by or in respect of, or
filing with, any governmental body, agency or official and do not violate or
constitute a default under any provision of applicable law or any Material
Agreement binding upon Parent or Borrower or any other Credit Party or result in
the creation or imposition of any Lien upon any of the assets of any Credit
Party except Permitted Encumbrances.

         4.3.     Validity and Enforceability; Extension of Liens. This Fourth
Amendment constitutes the valid and binding obligation of Parent and Borrower
enforceable in accordance with its terms, except as (i) the enforceability
thereof may be limited by bankruptcy, insolvency or similar laws affecting
creditor's rights generally, and (ii) the availability of equitable remedies may
be limited by equitable principles of general application.

<PAGE>   6

         4.4.     No Default or Event of Default. No Default or Event of Default
has occurred which is continuing.

         4.5.     Acquisition Documents. No material rights or obligations of
any party to any of the Apache Acquisition Documents have been waived and
neither Parent, Borrower, any other Credit Party, nor, to the best knowledge of
Parent and Borrower, any other party to any of such Apache Acquisition
Documents, is in default of its obligations thereunder. Each of the Apache
Acquisition Documents is a valid, binding and enforceable obligation of the
parties thereto in accordance with its terms and is in full force and effect.
Each representation and warranty made by Parent and Borrower (as applicable),
and to the best knowledge of Parent and Borrower, by the seller in the Apache
Acquisition Documents (a) was true and correct when made, and (b) will be true
and correct on the Effective Date. As used herein, the term "Apache Acquisition
Documents" means the Apache Acquisition Agreement, and all agreements,
assignments, deeds, conveyances, certificates and other documents and
instruments now or hereafter executed and delivered by or between Parent,
Borrower and the seller thereunder pursuant to the Apache Acquisition Agreement,
or in connection with the Apache Acquisition.

         SECTION 5. Miscellaneous.

         5.1.     Reaffirmation of Loan Papers. Any and all of the terms and
provisions of the Credit Agreement and the Loan Papers shall, except as amended
and modified hereby, remain in full force and effect. The amendments
contemplated hereby shall not limit or impair any Liens securing the
Obligations, each of which are hereby ratified, affirmed and extended to secure
the Obligations as they may be increased pursuant hereto.

         5.2.     Parties in Interest. All of the terms and provisions of this
Fourth Amendment shall bind and inure to the benefit of the parties hereto and
their respective successors and assigns.

         5.3.     Legal Expenses. Parent and Borrower hereby jointly and
severally agree to pay on demand all reasonable fees and expenses of counsel to
Administrative Agent incurred by Administrative Agent in connection with the
preparation, negotiation and execution of this Fourth Amendment and all related
documents.

         5.4.     Counterparts. This Fourth Amendment may be executed in
counterparts, and all parties need not execute the same counterpart; however, no
party shall be bound by this Fourth Amendment until all parties have executed a
counterpart. Facsimiles shall be effective as originals.

         5.5.     Complete Agreement. THIS FOURTH AMENDMENT, THE CREDIT
AGREEMENT AND THE OTHER LOAN PAPERS REPRESENT THE FINAL AGREEMENT AMONG THE
PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR
ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN
OR AMONG THE PARTIES.

         5.6.     Headings. The headings, captions and arrangements used in this
Fourth Amendment are, unless specified otherwise, for convenience only and shall
not be deemed to limit, amplify or modify the terms of this Fourth Amendment,
nor affect the meaning thereof.

<PAGE>   7

         5.7.     Effectiveness. This Fourth Amendment shall be effective
automatically and without necessity of any further action by Borrower, Parent,
Administrative Agent or Banks when counterparts hereof have been executed by
Borrower, Parent and all Banks, and all conditions to the effectiveness hereof
set forth herein have been satisfied.

         IN WITNESS WHEREOF, the parties hereto have caused this Fourth
Amendment to be duly executed by their respective Authorized Officers on the
date and year first above written.

                           [Signature pages to follow]

<PAGE>   8

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

PARENT:

PRIZE ENERGY CORP.,
a Delaware corporation

By:      /s/  Lon C. Kile
         ----------------
         Lon C. Kile,
         President

BORROWER:

PRIZE ENERGY RESOURCES, L.P.,
a Delaware limited partnership

By:      Prize Operating Company,
         a Delaware corporation,
         its sole general partner

         By:      /s/  Lon C. Kile
                  ----------------
                  Lon C. Kile,
                  President

                                [Signature Page]

<PAGE>   9

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

ADMINISTRATIVE AGENT:

FLEET NATIONAL BANK,
as Administrative Agent

By:      /s/  Michael Brochetti
         ----------------------
         Michael Brochetti,
         Vice President

FLEET NATIONAL BANK,
as a Bank

By:      /s/  Michael Brochetti
         ----------------------
         Michael Brochetti,
         Vice President

                                [Signature Page]
<PAGE>   10

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

FIRST UNION NATIONAL BANK

By:      /s/  David Humphreys
         --------------------
         David Humphreys,
         Vice President

                                [Signature Page]

<PAGE>   11

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

CIBC INC.

By:      /s/  Nora Catiis
         ----------------
         Nora Q. Catiis,
         Authorized Signature

                                [Signature Page]
<PAGE>   12

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

BANK ONE, NA

By:      /s/  W. Mark Cranmer
         --------------------
         W.  Mark Cranmer,
         Vice President

                                [Signature Page]
<PAGE>   13

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

CHRISTIANIA BANK

By:      /s/  Peter M. Dodge
         -------------------
         Peter M. Dodge,
         Senior Vice President

By:      /s/  William S. Phillips
         ------------------------
         William S. Phillips,
         First Vice President

                                [Signature Page]
<PAGE>   14

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

BANK OF SCOTLAND

By:      /s/  Joseph Fratus
         ------------------
         Joseph Fratus,
         Vice President

                                [Signature Page]
<PAGE>   15

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

COMERICA BANK - TEXAS

By:      /s/  V. Mark Fuqua
         ------------------
         V. Mark Fuqua,
         Senior Vice President

                                [Signature Page]
<PAGE>   16

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

FORTIS CAPITAL CORP.

By:      /s/  Deirdre Sanborn
         --------------------
         Deirdre Sanborn,
         Vice President

By:      /s/  Darrell W. Holley
         ----------------------
         Darrell W. Holley,
         Managing Director

                                [Signature Page]
<PAGE>   17

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

THE BANK OF NOVA SCOTIA

By:      /s/  F.C.H. Ashby
         -----------------
         F.C.H. Ashby,
         Senior Manager Loan Operations

                                [Signature Page]
<PAGE>   18

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

THE FROST NATIONAL BANK

By:      /s/  John s. Warren
         -------------------
         John S. Warren,
         Senior Vice President

                                [Signature Page]
<PAGE>   19

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

BNP PARIBAS

By:      /s/  Betsy Jocher
         -----------------
         Betsy Jocher,
         Vice President

By:      /s/ Larry Robinson
         ------------------
         Larry Robinson,
         Vice President

                                [Signature Page]
<PAGE>   20

                                 SIGNATURE PAGE
                                       TO
                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AGREEMENT BY AND AMONG
                PRIZE ENERGY CORP., PRIZE ENERGY RESOURCES, L.P.,
                  FLEET NATIONAL BANK, AS ADMINISTRATIVE AGENT,
                          AND THE BANKS A PARTY THERETO

U.S. BANK NATIONAL ASSOCIATION

By:      /s/  M. Ward Poizin
         -------------------
         M. Ward Poizin,
         Vice President

                                [Signature Page]<PAGE>   1
                                 TOM BROWN, INC.

                              AMENDED AND RESTATED
                             1993 STOCK OPTION PLAN

                             I. PURPOSE OF THE PLAN

         The Tom Brown, Inc. 1993 Stock Option Plan (the "Plan") is intended to
provide a means whereby certain employees and directors of Tom Brown, Inc., a
Delaware corporation (the "Company"), and its subsidiaries may develop a sense
of proprietorship and personal involvement in the development and financial
success of the Company, and to encourage them to remain with and devote their
best efforts to the business of the Company, thereby advancing the interests of
the Company and its shareholders. Accordingly, the Company may grant to certain
employees and directors ("Optionees") the option ("Option") to purchase shares
of the common stock of the Company ("Stock"), as hereinafter set forth. Options
granted under the Plan shall not be treated as incentive stock options within
the meaning of section 422(b) of the Internal Revenue Code of 1986, as amended
(the "Code").

                               II. ADMINISTRATION

         The Plan shall be administered by a committee (the "Committee")
appointed by the Board of Directors of the Company (the "Board"). The Committee
shall have sole authority to select the Optionees from among those individuals
eligible hereunder and to establish the number of shares which may be issued
under each Option. The Committee is authorized to interpret the Plan and may
from time to time adopt such rules and regulations, consistent with the
provisions of the Plan, as it may deem advisable to carry out the Plan. All
decisions made by the Committee in selecting the Optionees, in establishing the
number of shares which may be issued under each Option and in construing the
provisions of the Plan shall be final.

                             III. OPTION AGREEMENTS

         (a) Each Option shall be evidenced by a written agreement between the
Company and the Optionee ("Option Agreement") which shall contain such terms and
conditions as may be approved by the Committee. The terms and conditions of the
respective Option Agreements need not be identical. Specifically, an Option
Agreement may provide for the payment of the option price, in whole or in part,
by the delivery of a number of shares of Stock (plus cash if necessary) having a
fair market value equal to such option price.

<PAGE>   2

         (b) Each Option and all rights granted thereunder shall not be
transferable other than by will or the laws of descent and distribution, and
shall be exercisable during the Optionee's lifetime only by the Optionee or the
Optionee's guardian or legal representative.

                           IV. ELIGIBILITY OF OPTIONEE

         Options may be granted only to individuals who are employees or
directors of the Company or any parent or subsidiary corporation (as defined in
section 424 of the Code) of the Company at the time the Option is granted.
Options may be granted to the same individual on more than one occasion.

                          V. SHARES SUBJECT TO THE PLAN

         The aggregate number of shares which may be issued under Options
granted under the Plan shall not exceed 4,100,000 shares of Stock. Such shares
may consist of authorized but unissued shares of Stock or previously issued
shares of Stock reacquired by the Company. Any of such shares which remain
unissued and which are not subject to outstanding Options at the termination of
the Plan shall cease to be subject to the Plan, but, until termination of the
Plan, the Company shall at all times make available a sufficient number of
shares to meet the requirements of the Plan. Should any Option hereunder expire
or terminate prior to its exercise in full, the shares theretofore subject to
such Option may again be subject to an Option granted under the Plan. The
aggregate number of shares which may be issued under the Plan shall be subject
to adjustment in the same manner as provided in paragraph VIII hereof with
respect to shares of Stock subject to Options then outstanding. (As amended May
24, 1996, February 19, 1997, May 20, 1998, September 23, 1998, May 20, 1999,
November 18, 1999 and January 12, 2001.)

                                VI. OPTION PRICE

         The purchase price of Stock issued under each Option shall be
determined by the Committee, and may be less than the fair market value of Stock
subject to the Option.

                                VII. TERM OF PLAN

         The Plan shall be effective upon the date of its adoption by the Board.
Except with respect to Options then outstanding, if not sooner terminated under
the provisions of Paragraph IX, the Plan shall terminate upon and no further
Options shall be granted after the expiration of ten years from the date of its
adoption by the Board.

                                      -2-

<PAGE>   3

                    VIII. RECAPITALIZATION OR REORGANIZATION

         (a) The existence of the Plan and the Options granted hereunder shall
not affect in any way the right or power of the Board or the shareholders of the
Company to make or authorize any adjustment, recapitalization, reorganization or
other change in the Company's capital structure or its business, any merger or
consolidation of the Company, any issue of debt or equity securities, the
dissolution or liquidation of the Company or any sale, lease, exchange or other
disposition of all or any part of its assets or business or any other corporate
act or proceeding.

         (b) The shares with respect to which Options may be granted are shares
of Stock as presently constituted, but if, and whenever, prior to the expiration
of an Option theretofore granted, the Company shall effect a subdivision or
consolidation of shares of Stock or the payment of a stock dividend on Stock
without receipt of consideration by the Company, the number of shares of Stock
with respect to which such Option may thereafter be exercised (i) in the event
of an increase in the number of outstanding shares shall be proportionately
increased, and the purchase price per share shall be proportionately reduced,
and (ii) in the event of a reduction in the number of outstanding shares shall
be proportionately reduced, and the purchase price per share shall be
proportionately increased.

         (c) If the Company recapitalizes or otherwise changes its capital
structure, thereafter upon any exercise of an Option theretofore granted the
Optionee shall be entitled to purchase under such Option, in lieu of the number
and class of shares of Stock then covered by such Option, the number and class
of shares of stock and securities to which the Optionee would have been entitled
pursuant to the terms of the recapitalization if, immediately prior to such
recapitalization, the Optionee had been the holder of record of the number of
shares of Stock then covered by such Option. If (i) the Company shall not be the
surviving entity in any merger, consolidation or other reorganization (or
survives only as a subsidiary of an entity other than a previously wholly-owned
subsidiary of the Company), (ii) the Company sells, leases or exchanges all or
substantially all of its assets to any other person or entity (other than a
wholly-owned subsidiary of the Company), (iii) the Company is to be dissolved
and liquidated, (iv) any person or entity, including a "group" as contemplated
by Section 13(d)(3) of the Securities Exchange Act of 1934, acquires or gains
ownership or control (including, without limitation, power to vote) of more than
50% of the outstanding shares of the Company's voting stock (based upon voting
power), or (v) as a result of or in connection with a contested election of
directors, the persons who were directors of the Company before such election
shall cease to constitute a majority of the Board (each such event is referred
to herein as a "Corporate Change"), no later than (a) ten days after the
approval by the shareholders of the Company of such merger, consolidation,
reorganization, sale, lease or exchange of assets or dissolution or such
election of

                                      -3-

<PAGE>   4

directors or (b) thirty days after a change of control of the type described in
clause (iv), the Committee, acting in its sole discretion without the consent or
approval of any Optionee, shall act to effect one or more of the following
alternatives, which may vary among individual Optionees and which may vary among
Options held by any individual Optionee: (1) accelerate the time at which
Options then outstanding may be exercised so that such Options may be exercised
in full for a limited period of time on or before a specified date (before or
after such Corporate Change) fixed by the Committee, after which specified date
all unexercised Options and all rights of Optionees thereunder shall terminate,
(2) require the mandatory surrender to the Company by selected Optionees of some
or all of the outstanding Options held by such Optionees (irrespective of
whether such Options are then exercisable under the provisions of the Plan) as
of a date, before or after such Corporate Change, specified by the Committee, in
which event the Committee shall thereupon cancel such Options and the Company
shall pay to each Optionee an amount of cash per share equal to the excess, if
any, of the amount calculated in Subparagraph (d) below (the "Change of Control
Value") of the shares subject to such Option over the exercise price(s) under
such Options for such shares, (3) make such adjustments to Options then
outstanding as the Committee deems appropriate to reflect such Corporate Change
(provided, however, that the Committee may determine in its sole discretion that
no adjustment is necessary to Options then outstanding) or (4) provide that
thereafter upon any exercise of an Option theretofore granted the Optionee shall
be entitled to purchase under such Option, in lieu of the number of shares of
Stock then covered by such Option the number and class of shares of stock or
other securities or property (including, without limitation, cash) to which the
Optionee would have been entitled pursuant to the terms of the agreement of
merger, consolidation or sale of assets and dissolution if, immediately prior to
such merger, consolidation or sale of assets and dissolution the Optionee had
been the holder of record of the number of shares of Stock then covered by such
Option.

         (d) For the purposes of clause (2) in Subparagraph (c) above, the
"Change of Control Value" shall equal the amount determined in clause (i), (ii)
or (iii), whichever is applicable, as follows: (i) the per share price offered
to shareholders of the Company in any such merger, consolidation,
reorganization, sale of assets or dissolution transaction, (ii) the price per
share offered to shareholders of the Company in any tender offer or exchange
offer whereby a Corporate Change takes place, or (iii) if such Corporate Change
occurs other than pursuant to a tender or exchange offer, the fair market value
per share of the shares into which such Options being surrendered are
exercisable, as determined by the Committee as of the date determined by the
Committee to be the date of cancellation and surrender of such Options. In the
event that the consideration offered to shareholders of the Company in any
transaction described in this Subparagraph (d) or Subparagraph (c) above
consists of anything other than cash, the Committee shall determine the fair
cash equivalent of the portion of the consideration offered which is other than
cash.

                                      -4-

<PAGE>   5

         (e) Any adjustment provided for in Subparagraphs (b) or (c) above shall
be subject to any required shareholder action.

         (f) Except as hereinbefore expressly provided, the issuance by the
Company of shares of stock of any class or securities convertible into shares of
stock of any class, for cash, property, labor or services, upon direct sale,
upon the exercise of rights or warrants to subscribe therefor, or upon
conversion of shares or obligations of the Company convertible into such shares
or other securities, and in any case whether or not for fair value, shall not
affect, and no adjustment by reason thereof shall be made with respect to, the
number of shares of Stock subject to Options theretofore granted or the purchase
price per share.

                    IX. AMENDMENT OR TERMINATION OF THE PLAN

         The Board in its discretion may terminate the Plan at any time with
respect to any shares for which Options have not theretofore been granted. The
Board shall have the right to alter or amend the Plan or any part thereof from
time to time; provided, that no change in any Option theretofore granted may be
made which would impair the rights of the Optionee without the consent of such
Optionee.

                               X. SECURITIES LAWS

         The Company shall not be obligated to issue any Stock pursuant to any
Option granted under the Plan at any time when the offering of the shares
covered by such Option have not been registered under the Securities Act of 1933
and such other state and federal laws, rules or regulations as the Company or
the Committee deems applicable and, in the opinion of legal counsel for the
Company, there is no exemption from the registration requirements of such laws,
rules or regulations available for the offering and sale of such shares.

                                      -5-

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00025-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00025-of-00352.parquet"}]]