<PAGE>   1

                                                                   EXHIBIT 10.6



                                COHO ENERGY, INC.
                              COHO RESOURCES, INC.
                        COHO LOUISIANA PRODUCTION COMPANY
                             COHO EXPLORATION, INC.
                              COHO OIL & GAS, INC.
                         INTERSTATE NATURAL GAS COMPANY

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

                          SECURITIES PURCHASE AGREEMENT

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

                           DATED AS OF MARCH 31, 2000

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

         $72,000,000 15.0% SENIOR SUBORDINATED NOTES DUE MARCH 31, 2007

                 SHARES OF NEW COMMON STOCK OF COHO ENERGY, INC.


<PAGE>   2

                             TABLE OF CONTENTS


<TABLE>
<CAPTION>
                                                                            Page

<S>  <C>                                                                   <C>
1.   PURCHASE AND SALE OF SECURITIES..........................................2

     1.1 Issuance of Securities...............................................2
     1.2 The Closing..........................................................2

2. REPRESENTATIONS AND WARRANTIES OF THE OBLIGORS.............................3

     2.1 Nature of Business...................................................3
     2.2 Sale is Legal and Authorized; Obligations are Enforceable. ..........3
     2.3 Governmental Consent to Sale of Purchased Securities. ...............4
     2.4 No Defaults under Notes and Additional Shares. ......................5
     2.5 Private Offering of Purchased Securities. ...........................5
     2.6 Use of Proceeds......................................................5
     2.7 Credit Facility......................................................6
     2.8 Capitalization. .....................................................6
     2.9 No Placement Fees....................................................6
     2.10 Confirmation Order..................................................7

3.   REPRESENTATIONS AND WARRANTIES OF THE PURCHASERS. .......................7

     3.1 Purchase for Investment..............................................7

4.   CLOSING CONDITIONS.......................................................7

     4.1 Opinions of Counsel..................................................8
     4.2 Representations and Warranties True; Compliance. ....................8
     4.3 Officers' Certificates...............................................8
     4.4 Organic Documents....................................................8
     4.5 Legality.............................................................9
     4.6 Standby Debt Documents...............................................9
     4.7 Legending of Certificates. ..........................................9
     4.8 Credit Facility......................................................9
     4.9 Plan of Reorganization. .............................................9
     4.10 Certain Consents and Agreements. ...................................9
     4.11 Private Placement Numbers...........................................10
     4.12 Certificate as to Representations and Warranties....................10
     4.13 Fees and Expenses...................................................10
     4.14 Proceedings Satisfactory. ..........................................10
     4.15 Registration Rights Agreement.......................................10

5.   INTERPRETATION OF THIS AGREEMENT. .......................................11

     5.1 Terms Defined........................................................11
     5.2 Other Definitions....................................................13
     5.3 Directly or Indirectly...............................................14
     5.4 Section Headings and Table of Contents and Construction..............14
     5.5 Governing Law........................................................14
</TABLE>

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                                        i

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>

                                                                              Page
<S>  <C>                                                                      <C>
6. MISCELLANEOUS................................................................14
     6.1 Notices................................................................14
     6.2 Reproduction of Documents..............................................15
     6.3 Survival. .............................................................15
     6.4 Successors and Assigns. ...............................................15
     6.6 Expenses...............................................................16
     6.7 Waiver of Jury Trial; Consent to Jurisdiction; Etc....................16
     6.8 Indemnification of Each Holder. .......................................17
     6.9 Entire Agreement. .....................................................18
     6.10 Execution in Counterpart..............................................18
</TABLE>

<PAGE>   4

                               COHO ENERGY, INC.
                              COHO RESOURCES, INC.
                       COHO LOUISIANA PRODUCTION COMPANY
                             COHO EXPLORATION, INC.
                              COHO OIL & GAS, INC.
                         INTERSTATE NATURAL GAS COMPANY
                        -------------------------------

                         SECURITIES PURCHASE AGREEMENT

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

         $72,000,000 15.0% SENIOR SUBORDINATED NOTES DUE MARCH 31, 2007

                SHARES OF NEW COMMON STOCK OF COHO ENERGY, INC.

                                                      Dated as of March 31, 2000

PPM America Special Investments Fund, L.P.
PPM America Special Investments CBO II, L.P.
225 West Wacker Drive
Suite 1200
Chicago, Illinois 60606

Appaloosa Investment Limited Partnership I
Palomino Fund Ltd.
Tersk LLC
26 Main Street
Chatham, New Jersey 07928

Pacholder Value Opportunity Fund, L.P.
Pacholder High Yield Fund, Inc.
One Group High Yield Bond Fund
Evangelical Lutheran Church in America Board of Pensions
c/o Pacholder Associates, Inc.
8044 Montgomery Road
Suite 480
Cincinnati, Ohio 45236

AAFES Supplemental Deferred Compensation Plan
AAFES Retiree Medical Dental & Life Insurance Plan
AAFES Retirement Annuity Basis Plan
California State Automobile Association Inter-Insurance Bureau

<PAGE>   5



California State Automobile Association
The California Endowment
Canada Life Insurance Company of America
Canada Life Assurance Company - CDN
Canada Life Assurance Company - USA
Howard Hughes Medical Institute
Hughes Aircraft Company Master Retirement Trust
IBM Retirement Plan - High Yield
International Paper Company
General Board of Pension and Health Benefits of the United Methodist Church
OCM High Yield Fund II, L.P.
OCM High Yield Limited Partnership
OCM High Yield Trust
Pacific Gas & Electric Retirement Plan Master Trust
Pacific Gas & Electric Company Bargained VEBA
RK Mellon Foundation
c/o Oaktree Capital Management, LLC
333 South Grand Avenue
28th Floor
Los Angeles, California 90071

Ladies and Gentlemen:

         COHO ENERGY, INC., a Texas corporation, as debtor-in-possession
(together with any successors and assigns that become such in accordance
herewith, the "Company"); COHO RESOURCES, INC., a Nevada corporation (together
with any successors and assigns that become such in accordance herewith, "CRI");
COHO LOUISIANA PRODUCTION COMPANY, a Delaware corporation (together with its
successors and assigns who become such in accordance herewith, "CLP"); COHO
EXPLORATION, INC., a Delaware corporation (together with any successors and
assigns that become such in accordance herewith, "CEX"); COHO OIL & GAS, INC., a
Delaware corporation (together with any successors and assigns that become such
in accordance herewith, "COG"); and INTERSTATE NATURAL GAS COMPANY, a Delaware
corporation (together with any successors and assigns that become such in
accordance herewith, "INGC") (the Company, CRI, CLP, CEX, COG and INGC,
collectively, the "ISSUERS" or the "OBLIGORS," and, each individually, an
"ISSUER" or "OBLIGOR"), hereby agree with you as set forth below.

1. PURCHASE AND SALE OF SECURITIES.

         1.1 ISSUANCE OF SECURITIES.

                  (a) ISSUANCE OF NOTES. The Issuers will authorize the issuance
of Seventy-Two Million Dollars ($72,000,000) in aggregate principal amount of
their 15.0% Senior Subordinated Notes due March 31, 2007 (all such notes,
whether initially issued, or issued in exchange or substitution for, any such
note, in each case in accordance with the Note Agreement, are referred to
collectively herein as the "NOTES" and individually as a "NOTE"). The Notes
shall be issued

                                       -2-
<PAGE>   6


pursuant to a Note Agreement (as may be amended, restated or otherwise modified
from time to time, the "NOTE AGREEMENT") in the form of Exhibit 1.1(a).

                  (b) ISSUANCE OF ADDITIONAL SHARES. The Company will authorize
the issuance of shares of New Common Stock, as defined in the Plan of
Reorganization pursuant to the Bankruptcy Case (such shares of New Common Stock,
the "Additional Shares") representing fourteen and four-tenths percent (14.4%)
of such New Common Stock on a fully diluted basis after giving effect to the
issuance of the Additional Shares and the Rights Offering (as defined in the
Plan of Reorganization), as such numbers may be adjusted from time to time. The
certificates representing the Additional Shares (the "Additional Share
Certificates") shall be in the form of Exhibit 1.1(b) hereto, and the Additional
Shares shall have the terms provided in the Additional Share Certificates.

                  (c) POST-CLOSING DELIVERY OF ADDITIONAL SHARES. The Company
agrees to issue the Additional Shares in accordance with the Plan of
Reorganization on the earlier to occur of:

                           (i) the closing of the Rights Offering pursuant to
         the Company's Registration Statement on Form S-1 filed with the
         Securities and Exchange Commission, if the Company is able to include
         within that Registration Statement the Additional Shares, if such
         registration of the Additional Shares can comply with all applicable
         laws (including blue sky laws), and if such Registration Statement is
         declared effective by the Securities and Exchange Commission; or

                           (ii) the first business day that is six months after
         the consummation of the Rights Offering made pursuant to the
         Registration Statement described above.,

the Company will deliver to the Purchasers or their successors and assigns, pro
rata as their respective interests may appear, certificates representing the
Additional Shares in accordance with Annex 1 and Annex 1(A) attached hereto and
such number of Additional Shares, if any, as shall be necessary to make the
aggregate number of Additional Shares delivered pursuant to this Agreement equal
to fourteen and four-tenths percent (14.4%) of all shares of New Common Stock
then outstanding after giving effect to the issuance of all shares of New Common
Stock pursuant to the Rights Offering. All certificates representing the
Additional Shares, when issued in accordance with the provisions of this
Agreement shall be affixed with the required legends giving notice of the
restrictions imposed pursuant to the Registration Rights Agreement and any other
applicable agreements related to the Plan of Reorganization, and you shall have
received copies of all such certificates.

         1.2 THE CLOSING.

                  (a) PURCHASE AND SALE OF PURCHASED SECURITIES.

                           (i) The Issuers hereby agree to sell to you and you
         hereby agree to purchase from the Issuers, in accordance with the
         provisions hereof, the aggregate principal amount of Notes set forth
         below your name on Annex 1 and Annex 1A; and

                           (ii) the Company hereby agrees to sell to you and you
         hereby agree to purchase from the Company, in accordance with the
         provisions hereof, the aggregate

                                       -3-

<PAGE>   7


         number and series of Additional Shares in accordance with Annex 1 and
         Annex 1(A) attached hereto,

         for an aggregate purchase price for such Notes and such Additional
         Shares (collectively, the "PURCHASED SECURITIES") equal to one hundred
         percent (100%) of the principal amount of the Notes to be purchased.

                  (b) THE CLOSING. The closing (the "CLOSING") of the sale of
the Notes will be held at 10:00 a.m., local time, on March 31, 2000, or such
other time and date as the Company and you shall agree (the "CLOSING DATE"), at
the offices of Anderson Kill & Olick, P.C., in Chicago, Illinois, or at such
other location in Chicago, Illinois, as the Company and you shall agree. At the
Closing the Issuers will deliver to you one or more Notes (as set forth below
your name on Annex 1 and Annex 1A), in the denominations and series indicated on
Annex 1 and Annex 1A, in the aggregate principal amount of your purchase, dated
the Closing Date and registered in the name of the holder indicated on Annex 1
and Annex 1A against payment by federal funds wire transfer in immediately
available funds of the purchase price therefor to the account described in Annex
2.

2. REPRESENTATIONS AND WARRANTIES OF THE OBLIGORS.

To induce you to enter into this Agreement and to purchase and pay for the
Purchased Securities to be delivered to you at the Closing, the Obligors
represent and warrant as set forth below (except for Section 2.8, which the
Company alone represents and warrants).

         2.1 NATURE OF BUSINESS. The representations and warranties of the
Company set forth in the Credit Facility are true and correct in all material
respects as if they were made by the Company to the Purchasers hereunder as of
the Closing Date.

         2.2 SALE IS LEGAL AND AUTHORIZED; OBLIGATIONS ARE ENFORCEABLE.

                  (a) SALE OF PURCHASED SECURITIES IS LEGAL AND AUTHORIZED.
Based in part on the representations and warranties in Section 3 hereof, each of
the issuance, sale and delivery of the Notes by the Issuers, the execution and
delivery by each Obligor and each Subsidiary of such Obligor of the Standby Debt
Documents to which it is a party, and compliance by each Obligor and each
Subsidiary of such Obligor with all of the provisions of the Standby Debt
Documents to which it is a party:

                           (i) is within the powers of such Obligor and each of
         such Subsidiaries; and

                           (ii) is legal and does not conflict with, result in
         any breach of any of the provisions of, constitute a default under, or
         result in the creation of any Lien upon any Property of any Obligor or
         any such Subsidiary under the provisions of:

                                    (A) any Organic Document of, or any
                  agreement or instrument to which, such Obligor or such
                  Subsidiary is a party or by which such Obligor or such
                  Subsidiary or any of its respective Property may be bound;

                                       -4-

<PAGE>   8


                                    (B) any order, judgment, decree, or ruling
                  of any court, arbitrator or Governmental Authority applicable
                  to such Obligor or such Subsidiary or any of its respective
                  Property; or

                                    (C) any statute or other rule or regulation
                  of any Governmental Authority applicable to such Obligor or
                  such Subsidiary or any of its respective Property;

         except for such conflicts, breaches, defaults or Liens which in the
         aggregate could not be reasonably expected to have a Material Adverse
         Effect.

                  (b) OBLIGATIONS ARE ENFORCEABLE. Each Obligor and each
Subsidiary of each Obligor has duly authorized by all necessary action on its
part including the execution and delivery of each of the Standby Debt Documents
to which it is a party. Each of the Standby Debt Documents to which such Obligor
or any such Subsidiary is a party has been executed and delivered by one or more
duly authorized officers of such Obligor or such Subsidiary, and constitutes a
legal, valid and binding obligation of such Obligor or such Subsidiary,
enforceable in accordance with its terms, except that, in each case, the
enforceability thereof may be:

                           (i) limited by applicable bankruptcy, reorganization,
         arrangement, insolvency, moratorium, or other similar laws affecting
         the enforceability of creditors' rights generally; and

                           (ii) subject to the availability of equitable
         remedies.

         2.3 GOVERNMENTAL CONSENT TO SALE OF PURCHASED SECURITIES.

                  (a) Neither the nature of the Obligors and any Subsidiary of
their Subsidiaries nor of any of their respective businesses or Properties, nor
any relationship between any Obligor or any such Subsidiary and any other
Person, nor any circumstance in connection with the offer, issuance, sale or
delivery of the Notes, the execution and delivery of any Standby Debt Document,
nor the performance of the obligations of any Obligor or any Subsidiary
thereunder, is such as to require a consent, approval or authorization of, or
pre-filing, registration or qualification with, any Governmental Authority on
the part of any Obligor or such Subsidiary as a condition thereto, except for
confirmation of the Plan of Reorganization by the Bankruptcy Court.

                  (b) Each of the issuance and sale of the Notes, the incurrence
of the Indebtedness evidenced by the Standby Debt Documents and the other
obligations represented thereby, the execution and delivery of the Standby Debt
Documents and the performance of the obligations of each Obligor and the
Subsidiaries of each Obligor hereunder and thereunder, by each Obligor and its
Subsidiaries:

                           (i) is not subject to regulation under the Investment
Company Act of 1940, as amended, the Public Utility Holding Company Act of 1935,
as amended, the Transportation Acts of the United States of America (49 U.S.C.),
as amended, or the Federal Power Act, as amended; and

                                       -5-

<PAGE>   9


                           (ii) does not violate any provision of any statute or
other rule or regulation of any Governmental Authority applicable to any Obligor
or any of its Subsidiaries.

         2.4 NO DEFAULTS UNDER NOTES AND ADDITIONAL SHARES.

         No event has occurred and no condition exists that, upon the execution
and delivery of the Standby Debt Documents and the issuance and sale of the
Notes in connection therewith, would constitute a Default or an Event of
Default.

         2.5 PRIVATE OFFERING OF PURCHASED SECURITIES.

         No Obligor nor any Person acting on behalf of any Obligor has offered
any of the Notes or the Additional Shares for sale to, or solicited offers to
buy any thereof from, or otherwise approached or negotiated with respect thereto
with, any prospective purchaser, other than twenty-nine or fewer institutional
"accredited investors" (as defined in Regulation D under the Securities Act)
(including you), each of whom was offered all or a portion of the Notes and the
Additional Shares at private sale for investment.

         2.6 USE OF PROCEEDS.

                  (a) USE OF PROCEEDS. The Obligors shall apply the proceeds
from the sale of the Purchased Securities as contemplated by the Plan of
Reorganization and the Note Agreement.

                  (b) MARGIN REGULATIONS. None of the transactions contemplated
in any of the Standby Debt Documents (including, without limitation, the use of
the proceeds from the sale of the Purchased Securities) violates or will result
in a violation of Section 7 of the Exchange Act, or any regulation issued
pursuant thereto, including, without limitation, Regulation T, Regulation U or
Regulation X of the Board of Governors of the Federal Reserve System, 12 C.F.R.,
Chapter 11.

                  (c) ABSENCE OF FOREIGN OR ENEMY STATUS. Neither the sale of
the Purchased Securities nor the use of proceeds from the sale thereof will
result in a violation of any of the foreign assets control regulations of the
United States Treasury Department (31 CFR, Subtitle B, Chapter V, as amended),
or any ruling issued thereunder or any enabling legislation or Presidential
Executive Order in connection therewith.

         2.7 CREDIT FACILITY.

         Upon consummation of the transactions contemplated by this Agreement,
the Obligors will have duly performed all of their obligations in connection
with the Credit Facility to be performed at or prior to the closing thereunder,
the Loan Documents (as such term is defined in the Credit Facility) thereunder
have all been duly executed and delivered and are in full force and effect, and
no Default or Event of Default (as such terms are defined in the Credit
Facility) has occurred thereunder. The Company has provided to you or your
agents true, correct and complete copies of each of the agreements and
instruments executed and delivered in connection with the Credit Facility, and
there is no other material agreement or understanding between or among any
Obligor and any of the holders of any Senior Indebtedness that has not been so
provided to you.

                                       -6-

<PAGE>   10

         2.8 CAPITALIZATION.

                  (a) CAPITALIZATION. All equity interests in the Company
(including Capital Stock), Rights and other Securities (including all shares of
the New Common Stock) have been duly authorized and validly issued and are fully
paid, non-assessable, free and clear of any Lien.

                  (b) RESTRICTIVE AGREEMENTS. Other than the Registration Rights
Agreement, to the best knowledge of the Responsible Officers of the Obligors,
there is no agreement or understanding between or among the holders of equity
interests in the Company or any Rights in respect of the foregoing, in each case
regarding any of the equity interests, Rights or the holders thereof.

         2.9 NO PLACEMENT FEES.

         No investment banker, placement agent, broker or other intermediary was
employed by any Obligor or its Affiliates in connection with the issuance of the
Purchased Securities or the incurrence or placement of the Indebtedness under
the Credit Facility, and, therefore, no fees or other consideration have been
paid or are payable to any such Persons in connection with such transaction.

         2.10 CONFIRMATION ORDER.

         A Confirmation Order has been duly entered by the Bankruptcy Court, is
in full force and effect and has not been vacated or otherwise modified since
its original entry.

3. REPRESENTATIONS AND WARRANTIES OF THE PURCHASERS.

         Each Purchaser represents and warrants to each of the Issuers that:

         3.1 PURCHASE FOR INVESTMENT.

                  (a) It is an "accredited investor" within the meaning of Rule
501(a) of the Securities Act and it is purchasing the Purchased Securities
listed on Annex 1 and Annex 1A below its name for its own account, or for the
account of one or more separate accounts maintained by it, for investment and
with no present intention of, or view to, distributing such Purchased Securities
or any part thereof except in compliance with the Securities Act, but without
prejudice to its right at all times to:

                           (i) sell or otherwise dispose of all or any part of
         the Purchased Securities under a registration statement filed under the
         Securities Act, or in a transaction exempt from the registration
         requirements of such act, including a transaction pursuant to Rule
         144A; and

                           (ii) have control over the disposition of all of its
         assets to the fullest extent required by any applicable law;

                  (b) the execution, delivery and performance by it of the
Standby Debt Documents to which it is a party, including the purchase of the
Notes and the Additional Shares pursuant

                                       -7-

<PAGE>   11


hereto, are within such Purchaser's corporate powers and have been duly and
validly authorized by all requisite action;

                  (c) the Standby Debt Documents to which it is a party have
been duly executed and delivered by each such Purchaser; and

                  (d) each Standby Debt Document to which it is a party
constitutes a valid and binding agreement of such Purchaser, enforceable in
accordance with its terms.

         It is understood and acknowledged that, in making the representations
contained in Section 2.3(a) and Section 2.5, each Obligor is relying, to the
extent applicable, upon each Purchaser's representation as set forth in Section
3.1(a) above.

4. CLOSING CONDITIONS.

         Your obligations under this Agreement, including, without limitation,
the obligation to purchase and pay for the Purchased Securities to be delivered
to you at the Closing, are subject to the following conditions precedent, and
the failure by the Obligors to satisfy all such conditions shall relieve you, at
your election, of all such obligations.

         4.1 OPINIONS OF COUNSEL.

         You shall have received from Fulbright & Jaworski, L.L.P., counsel to
the Obligors, a closing opinion, dated as of the Closing Date, and substantially
in the form set forth in Exhibit 4.1 and as to such other matters as you may
reasonably request. This Section 4.1 shall constitute direction by the Obligors
to such counsel named in this Section 4.1 to deliver such closing opinion to
you.

         4.2 REPRESENTATIONS AND WARRANTIES TRUE; COMPLIANCE.

                  (a) REPRESENTATIONS AND WARRANTIES TRUE. The representations
and warranties contained in Section 2 shall be true in all material respects on
the Closing Date with the same effect as though made on and as of that date.

                  (b) COMPLIANCE WITH THIS AGREEMENT AND STANDBY DEBT DOCUMENTS.
Each Obligor shall have performed and complied with all agreements and
conditions contained herein and in the other Standby Debt Documents that are
required to be performed or complied with by such Obligor on or prior to the
Closing Date, and such performance and compliance shall remain in effect on the
Closing Date, unless such performance or compliance has been waived by you in
accordance with the terms hereof.

4.3 OFFICERS' CERTIFICATES.

         You shall have received a certificate dated the Closing Date and signed
(on behalf of each Issuer) by the Secretary of each Issuer, substantially in the
form of Exhibit 4.3.

                                       -8-

<PAGE>   12


         4.4 ORGANIC DOCUMENTS.

         You shall have received:

                  (a) GOOD STANDING CERTIFICATES - for each Obligor, a copy of
its certificate of incorporation certified by the Texas, Nevada or Delaware
Secretary of State, as the case may be, and a short-form certificate of good
standing from the Texas, Nevada or Delaware Secretary of State, as the case may
be, certifying the due organization and good standing of such Obligor; and

                  (b) ORGANIC DOCUMENTS - for each Obligor, a copy of its
Organic Documents attached to one of the Certificates provided pursuant to
Section 4.3 above, including such of its Organic Documents as may be certified
by the Texas, Nevada or Delaware Secretary of State, as the case may be.

         4.5 LEGALITY.

         The Notes shall on the Closing Date qualify as a legal investment for
you (if you are an insurance company) under applicable insurance law (without
regard to any "basket" or "leeway" provisions), and in any case, the acquisition
thereof shall not subject you to any penalty or other onerous condition pursuant
to any such law or regulation, and you shall have received such evidence as you
may reasonably request to establish compliance with this condition.

         4.6 STANDBY DEBT DOCUMENTS.

         The Issuers shall have executed and delivered to you the Note
Agreement, in the form of Exhibit 1.1(a), and such Note Agreement shall be in
full force and effect. The Issuers shall have executed, delivered and issued to
you the Notes in the respective amounts set forth below your name on Annex 1 and
Annex 1A.

         4.7 [Reserved]

         4.8 CREDIT FACILITY.

         The Obligors shall have delivered to you or your agent a copy of the
fully executed Credit Facility, which shall be in form and substance
satisfactory to you and your special counsel, certified as true and correct by
an officer of the Company. On the Effective Date, after Closing, the Company
will have at least Fifteen Million Dollars ($15,000,000) in cash and borrowing
availability under the Credit Facility.

         4.9 PLAN OF REORGANIZATION.

         A Confirmation Order shall have been entered by the Bankruptcy Court
and shall be in full force and effect. The Issuers and all other parties to the
Plan of Reorganization shall have performed all of their obligations thereunder
as of the date of this Agreement.

                                       -9-

<PAGE>   13


         4.10 CERTAIN CONSENTS AND AGREEMENTS.

         Each holder of any Indebtedness, equity interests, Rights or other
Securities of any Obligor, and each party to any other contract or other
agreement with any Obligor, the consent of which is, in the reasonable judgment
of you and your special counsel, necessary to permit such Obligor to enter into
the transactions contemplated by this Agreement and to perform its obligations
in respect of the Standby Debt Documents and the Credit Facility, shall have
executed and delivered to you a consent, in form and substance reasonably
acceptable to you and your special counsel, to the transactions contemplated by
the Standby Debt Documents.

         4.11 PRIVATE PLACEMENT NUMBERS. Private placement numbers for each of
the Notes from the CUSIP Service Bureau of Standard & Poor's, a division of the
McGraw-Hill Companies, shall have been obtained by you.

         4.12 [Reserved]

         4.13 FEES AND EXPENSES.

         Subject to Bankruptcy Court approval, the Issuers shall have paid in
full the following fees to and expenses of the Purchasers:

                  (a) Two Hundred Thousand Dollars ($200,000), payable to PPM
America, Inc., as agent, on behalf of itself and the other Purchasers as an
initial deposit (the "Initial Deposit") to be applied against out-of-pocket
costs and expenses of the Purchasers in connection with their due diligence
review and the preparation and negotiation of the commitment letter and loan
documentation; and

                  (b) a fee equal to the greater of One Million Dollars
($1,000,000) or three and one-half percent (3.50%) of the aggregate principal
amount of the Notes purchased; and

                  (c) all fees and disbursements required to be paid pursuant to
Section 6.6 (to the extent not already paid by application of the $200,000
above).

         4.14 PROCEEDINGS SATISFACTORY.

         All proceedings taken in connection with the issuance and sale of the
Notes and all documents and papers relating thereto shall be reasonably
satisfactory to you and your special counsel. You and your special counsel shall
have received copies of such documents and papers as you or they may reasonably
request in connection therewith or in connection with your special counsel's
closing opinion, all in form and substance reasonably satisfactory to you and
your special counsel.

         4.15 REGISTRATION RIGHTS AGREEMENT.

         The Company shall have caused to be executed and delivered a
Registration Rights Agreement, the Registration Rights Agreement to be in the
form attached hereto as Exhibit 4.15.

                                      -10-

<PAGE>   14


The Registration Rights Agreement shall be in full force and effect, and an
executed copy of such Registration Rights Agreement shall have been delivered to
each Purchaser.

5. INTERPRETATION OF THIS AGREEMENT.

         5.1 TERMS DEFINED.

         As used herein, the following terms have the respective meanings set
forth below or set forth in the Section hereof following such term:

         ADDITIONAL SHARE CERTIFICATES - Section 1.1(b).

         ADDITIONAL SHARES -Section 1.1(b).

         AGREEMENT - means this Securities Purchase Agreement, as it may be
amended, restated or otherwise modified from time to time.

         BANKRUPTCY CASE - means, as consolidated for administrative purposes
pursuant to order of the Bankruptcy Court, the cases commenced by each Obligor
under Chapter 11 of the United States Bankruptcy Code on August 23, 1999.

         BANKRUPTCY COURT - means the United States Bankruptcy Court for the
Northern District of Texas.

         CAPITAL STOCK - means any and all shares, interests, participations or
other equivalents (however designated) of capital stock of a corporation, any
and all equivalent ownership interests in a Person (other than a corporation)
and any and all warrants, rights or options to purchase any of the foregoing.

         CLOSING - Section 1.2(b).

         CLOSING DATE - Section 1.2(b).

         CODE - means the Internal Revenue Code of 1986, together with all rules
and regulations promulgated pursuant thereto, as amended from time to time.

         COMPANY - the introductory sentence of this Agreement.

         CONFIRMATION ORDER - means a final, non-appealable order of the
Bankruptcy Court confirming the Plan of Reorganization.

         CREDIT FACILITY - means the Credit Agreement together with the
documents related thereto (including, without limitation, any guaranty
agreements and security documents), in each case as such agreements may be
amended (including any amendment and restatement thereof), supplemented or
otherwise modified from time to time, including any Refinancing Indebtedness.

         ENVIRONMENTAL LAWS - means all laws, rules, regulations, codes,
ordinances, orders, decrees, judgments, injunctions, notices or binding
agreements issued, promulgated or entered into by any Governmental Authority,
relating in any way to the environment, preservation or

                                      -11-

<PAGE>   15


reclamation of natural resources, the management, release or threatened release
of any Hazardous Material or to health and safety matters.

         ERISA - means the Employee Retirement Income Security Act of 1974, as
amended from time to time, and all rules, regulations and interpretations by the
Internal Revenue Service or the Department of Labor thereunder.

         EXCHANGE ACT - means the Securities Exchange Act of 1934, as amended,
together with the rules and regulations of the SEC thereunder.

         GOVERNMENTAL AUTHORITY - means the government of the United States of
America, any other nation or any political subdivision thereof, whether state or
local, and any agency, authority, instrumentality, regulatory body, court,
central bank or other entity exercising executive, legislative, judicial,
taxing, regulatory or administrative powers or functions of or pertaining to
government.

         GOVERNMENTAL RULE - means any statute, law, regulation, ordinance,
rule, judgment, order, decree, permit, concession, grant, franchise, license,
agreement, directive, requirement of, or other governmental restriction or any
similar binding form of decision of or determination by, or any binding
interpretation or administration of any of the foregoing by, any Governmental
Authority, whether now or hereafter in effect.

         ISSUERS - the introductory sentence of this Agreement.

         MATERIAL ADVERSE EFFECT - means a material adverse effect on (a) the
business, assets, operations or condition (financial or otherwise) of the
Company, or of the Company and its Subsidiaries taken as a whole, (b) the
ability of the Company or of any its Subsidiaries to perform any of their
respective obligations under any Standby Debt Document to which it is a party or
(c) the rights of or benefits available to the Purchasers under any Standby Debt
Document.

         NEW COMMON STOCK - See Section 2.47 of the Plan of Reorganization.

         NOTE AGREEMENT - Section 1.1(a).

         NOTES - Section 1.1(a).

         OBLIGORS - the introductory sentence of this Agreement.

         ORGANIC DOCUMENTS - means, relative to any Person, its articles of
organization, formation or incorporation (or comparable document), its by-laws
or operating agreement and all shareholder agreements, partnership agreements,
limited liability company or operating agreements, voting trusts and similar
arrangements applicable to ownership.

         PLAN OF REORGANIZATION - has the meaning set forth in the recitals of
the Credit Agreement.

         PERSON - means any natural person, corporation, limited liability
company, trust, joint venture, association, company, partnership, Governmental
Authority or other entity.

                                      -12-

<PAGE>   16


         PROPERTY - means any interest in any kind of property or asset, whether
real, personal or mixed, and whether tangible or intangible.

         PURCHASED SECURITIES - means the Notes and the Additional Shares to be
purchased by each Purchaser pursuant to Section 1.2 of this Agreement.

         REGISTRATION RIGHTS AGREEMENT - Section 4.15.

         RESPONSIBLE OFFICER - means the president or chief financial officer of
the Company and any senior management officer of any Subsidiary thereof.

         RIGHT - means and includes:

                  (a) any warrant or any option (including, without limitation,
employee stock options) to acquire Capital Stock;

                  (b) any right issued to holders of the Capital Stock of the
Company, or any class thereof, permitting the holders thereof to subscribe to
additional Capital Stock (pursuant to a rights offering or otherwise);

                  (c) any right to acquire Capital Stock pursuant to the
provisions of any Security convertible or exchangeable into Capital Stock; and

                  (d) any similar right permitting the holder thereof to
subscribe for or purchase Capital Stock.

         RIGHTS OFFERING - see section 2.63 of the Plan of Reorganization.

         RULE 144A - means Rule 144A promulgated under the Securities Act, 17
C.F.R. Section 230.144A, as such rule may be amended from time to time.

         SECURITIES ACT - means the Securities Act of 1933, as amended from time
to time.

         SECURITY - means "security" as defined by Section 2(l) of the
Securities Act.

         STANDBY DEBT DOCUMENTS - means and includes this Agreement, the Note
Agreement, the Notes, the Additional Share Certificates and any other
agreements, certificates and instruments to be executed pursuant to the terms of
any of the foregoing, as each may be amended, restated or otherwise modified
from time to time.

         SUBSIDIARY - means any subsidiary of any of the Issuers. For purposes
of the representations and warranties made herein on the Effective Date, the
term "Subsidiary" includes each of the Issuers and their subsidiaries.

         5.2 OTHER DEFINITIONS.

         Except as otherwise provided herein, all capitalized terms as used
herein shall have the respective meanings ascribed to them in the form of Note
Agreement attached hereto.

                                      -13-

<PAGE>   17


         5.3 DIRECTLY OR INDIRECTLY.

         Where any provision herein refers to action to be taken by any Person,
or which such Person is prohibited from taking, such provision shall be
applicable whether such action is taken directly or indirectly by such Person,
including actions taken by or on behalf of any partnership in which such Person
is a general partner.

         5.4 SECTION HEADINGS AND TABLE OF CONTENTS AND CONSTRUCTION.

                  (a) SECTION HEADINGS AND TABLE OF CONTENTS, ETC. The titles of
the Sections of this Agreement and the Table of Contents of this Agreement
appear as a matter of convenience only, do not constitute a part hereof and
shall not affect the construction hereof. The words "herein," "hereof,"
"hereunder" and "hereto" refer to this Agreement as a whole and not to any
particular Section or other subdivision. References to Sections are, unless
otherwise specified, references to Sections of this Agreement. References to
Annexes and Exhibits are, unless otherwise specified, references to Annexes and
Exhibits attached to this Agreement.

                  (b) INDEPENDENT CONSTRUCTION. Each covenant contained herein
shall be construed (absent an express contrary provision herein) as being
independent of each other covenant contained herein, and compliance with any one
covenant shall not (absent such an express contrary provision) be deemed to
excuse compliance with one or more other covenants.

         5.5 GOVERNING LAW.

         THIS AGREEMENT AND THE NOTES SHALL BE GOVERNED BY, AND CONSTRUED AND
ENFORCED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF ILLINOIS. IN
ADDITION, THE PARTIES HERETO SELECT, TO THE EXTENT THEY MAY LAWFULLY DO SO, THE
INTERNAL LAWS OF THE STATE OF ILLINOIS AS THE APPLICABLE INTEREST LAW (AS
DEFINED IN THE NOTE AGREEMENT).

6. MISCELLANEOUS.

         6.1 NOTICES.

                  (a) METHOD; ADDRESS. All notices to be provided hereunder or
under the Notes shall be in writing and shall be delivered either by nationwide
overnight courier or by facsimile transmission (receipt acknowledged by
electronic transmission). Notices to any Issuers shall be addressed as set forth
on Annex 2, or at such other address of which such Issuer shall have notified
each holder of Notes. Notices to the holders of the Notes shall be addressed as
set forth on Annex 1 and Annex 1A by such holder, or at such other address of
which such holder shall have notified the Issuers (and the Issuers shall record
such address in the register for the registration and transfer of Notes
maintained pursuant to Section 2.1 of the Note Agreement).

                  (b) WHEN GIVEN. Any notice addressed and delivered as herein
provided shall be deemed to be received when actually delivered to the address
of the addressee (whether or not delivery is accepted except for the negligence
of the delivering party) or received by the telecopy

                                      -14-

<PAGE>   18

machine of the recipient (assuming evidence of electronic confirmation of
transmission). Any notice not so addressed and delivered shall be ineffective.

                  (c) SERVICE OF PROCESS. Notwithstanding the foregoing
provisions of this Section 6.1, service of process in any suit, action or
proceeding arising out of or relating to this Agreement or any document,
agreement or transaction contemplated hereby, or any action or proceeding to
execute or otherwise enforce any judgment in respect of any breach hereunder or
under any document or agreement contemplated hereby, shall be delivered in the
manner provided in Section 6.7(c).

         6.2 REPRODUCTION OF DOCUMENTS.

         This Agreement and all documents relating hereto, including, without
limitation, consents, waivers and modifications that may hereafter be executed,
documents received by any holder of Notes on the Closing Date (except the Notes
themselves), and financial statements, certificates and other information
previously or hereafter furnished to any holder of Notes, may be reproduced by
any Issuers or any holder of Notes by any photographic, photostatic, microfilm,
micro-card, miniature photographic, digital or other similar process and each
holder of Notes may destroy any original document so reproduced. Any such
reproduction shall be admissible in evidence as the original itself in any
judicial or administrative proceeding (whether or not the original is in
existence and whether or not such reproduction was made by any Issuer or such
holder of Notes in the regular course of business) and any enlargement,
facsimile or further reproduction of such reproduction shall likewise be
admissible in evidence. Nothing in this Section 6.2 shall prohibit any Issuers
or any holder of Notes from contesting the accuracy or validity of any such
reproduction.

         6.3 SURVIVAL.

         All warranties, representations, certifications and covenants made by
the Issuers herein, in the Note Agreement or in any certificate or other
instrument delivered hereunder shall be ordered to have been relied upon by each
holder of Notes and shall survive the delivery of the Notes and the Additional
Shares regardless of any investigation made by or on behalf of any party hereto.
All statements in any certificate or other instrument delivered pursuant to the
terms hereof or of the Note Agreement shall constitute representations and
warranties of the Issuers hereunder. All obligations hereunder (other than
payment of the Notes, but including, without limitation, reimbursement
obligations in respect of costs, expenses and fees) shall survive the payment of
the Notes and the termination hereof.

         6.4 SUCCESSORS AND ASSIGNS.

         This Agreement shall inure to the benefit of and be binding upon the
successors and assigns of each of the parties hereto. The provisions hereof are
intended to be for the benefit of all holders, from time to time, of the Notes,
and shall be enforceable by any such holder whether or not an express assignment
to such holder of rights hereunder shall have been made by any such holder or
its successor or assign. Anything contained in this Section 6.4 notwithstanding,
the Issuers may not assign any of their respective rights, duties or obligations
hereunder or under any of the other Standby Debt Documents without the prior
written consent of all holders of Notes.

                                      -15-

<PAGE>   19


For purposes of the avoidance of doubt, any holder of a Note shall be permitted
to pledge or otherwise grant a Lien in and to such Note (including, without
limitation, pledging such Note to a trustee for the benefit of certain secured
noteholders pursuant to documents relating to the financing of such holder or to
one or more banks or other institutions providing financing in connection with
the purchase by such holder of such Note); provided, however, that any such
pledgee or holder of a Lien shall not be considered a holder hereunder until it
shall have foreclosed upon such Note in accordance with applicable law and
informed the Issuers, in writing, of the same.

         6.5 AMENDMENT AND WAIVER.

         Subject to further limitations set forth in the Note Agreement, this
Agreement may be amended, and the observance of any term hereof may be waived,
with (and only with) the written consent of the Issuers and the Required
Holders.

         6.6 EXPENSES.

                  (a) Amendments and Waivers. The Issuers shall pay when billed
the reasonable out-of-pocket costs and expenses (including reasonable attorneys'
fees) incurred by the holders of the Notes in connection with the consideration,
negotiation, preparation or execution of any amendments, waivers, consents,
standstill agreements and other similar agreements with respect to this
Agreement or any other Standby Debt Document (whether or not any such
amendments, waivers, consents, standstill agreements or other similar agreements
are executed).

                  (b) RESTRUCTURING AND WORKOUT; INSPECTIONS. At any time when
any Issuers and the holders of Notes are conducting restructuring or workout
negotiations in respect hereof, or an Event of Default exists, the Issuers shall
pay when billed the reasonable out-of-pocket costs and expenses (including
reasonable attorneys' fees and the fees of professional advisors) incurred by
the holders of the Notes in connection with the assessment, analysis or
enforcement of any rights or remedies that are or may be available to the
holders of Notes; provided, however, that at all other times inspections will be
at the expense of the inspecting holder of Notes.

                  (c) COLLECTION. If the Issuers shall fail to pay when due any
principal of, or Prepayment Fee (as defined in the Note Agreement) or interest
on, any Note, the Issuers shall pay to each holder of Notes, to the extent
permitted by law, such amounts as shall be sufficient to cover the out-of-pocket
costs and expenses, including but not limited to reasonable attorneys' fees,
incurred by such holder in collecting any sums due on such Note.

         6.7 WAIVER OF JURY TRIAL; CONSENT TO JURISDICTION; ETC.

                  (a) WAIVER OF JURY TRIAL. THE PARTIES HERETO VOLUNTARILY AND
INTENTIONALLY WAIVE ANY RIGHT ANY OF THEM MAY HAVE TO A TRIAL BY JURY IN RESPECT
OF ANY LITIGATION ARISING OUT OF, UNDER OR IN CONNECTION WITH THIS AGREEMENT OR
ANY OF THE DOCUMENTS, AGREEMENTS OR TRANSACTIONS CONTEMPLATED HEREBY.

                  (b) CONSENT TO JURISDICTION. ANY SUIT, ACTION OR PROCEEDING
ARISING OUT OF OR RELATING TO THIS AGREEMENT, OR ANY OF THE

                                      -16-

<PAGE>   20


DOCUMENTS, AGREEMENTS OR TRANSACTIONS CONTEMPLATED HEREBY OR ANY ACTION OR
PROCEEDING TO EXECUTE OR OTHERWISE ENFORCE ANY JUDGMENT IN RESPECT OF ANY BREACH
UNDER THIS AGREEMENT OR ANY DOCUMENT OR AGREEMENT CONTEMPLATED HEREBY, TO THE
FULLEST EXTENT PERMITTED BY APPLICABLE LAW, MAY BE BROUGHT BY SUCH PARTY IN ANY
FEDERAL DISTRICT COURT LOCATED IN CHICAGO, ILLINOIS, OR ANY ILLINOIS STATE COURT
LOCATED IN CHICAGO, ILLINOIS, AS SUCH PARTY MAY IN ITS SOLE DISCRETION ELECT,
AND BY THE EXECUTION AND DELIVERY OF THIS AGREEMENT, THE PARTIES HERETO
IRREVOCABLY AND UNCONDITIONALLY SUBMIT TO THE NONEXCLUSIVE IN PERSONAM
JURISDICTION OF EACH SUCH COURT, AND EACH OF THE PARTIES HERETO IRREVOCABLY
WAIVES AND AGREES NOT TO ASSERT IN ANY PROCEEDING BEFORE ANY TRIBUNAL, BY WAY OF
MOTION, AS A DEFENSE OR OTHERWISE, ANY CLAIM THAT IT IS NOT SUBJECT TO THE IN
PERSONAM JURISDICTION OF ANY SUCH COURT. IN ADDITION, EACH OF THE PARTIES HERETO
IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW, ANY OBJECTION THAT
IT MAY NOW OR HEREAFTER HAVE TO THE LAYING OF VENUE IN ANY SUIT, ACTION OR
PROCEEDING ARISING OUT OF OR RELATING TO THIS AGREEMENT OR ANY DOCUMENT,
AGREEMENT OR TRANSACTION CONTEMPLATED HEREBY BROUGHT IN ANY SUCH COURT, AND
HEREBY IRREVOCABLY WAIVES ANY CLAIM THAT ANY SUCH SUIT, ACTION OR PROCEEDING
BROUGHT IN ANY SUCH COURT HAS BEEN BROUGHT IN AN INCONVENIENT FORUM.

                  (c) SERVICE OF PROCESS. EACH PARTY HERETO IRREVOCABLY AGREES
THAT PROCESS PERSONALLY SERVED OR SERVED BY U.S. REGISTERED MAIL AT THE
ADDRESSES PROVIDED HEREIN FOR NOTICES SHALL CONSTITUTE, TO THE FULLEST EXTENT
PERMITTED BY LAW, ADEQUATE SERVICE OF PROCESS IN ANY SUIT, ACTION OR PROCEEDING
ARISING OUT OF OR RELATING TO THIS AGREEMENT OR ANY DOCUMENT, AGREEMENT OR
TRANSACTION CONTEMPLATED HEREBY, OR ANY ACTION OR PROCEEDING TO EXECUTE OR
OTHERWISE ENFORCE ANY JUDGMENT IN RESPECT OF ANY BREACH HEREUNDER OR UNDER ANY
DOCUMENT OR AGREEMENT CONTEMPLATED HEREBY. RECEIPT OF PROCESS SO SERVED SHALL BE
CONCLUSIVELY PRESUMED AS EVIDENCED BY A DELIVERY RECEIPT FURNISHED BY THE UNITED
STATES POSTAL SERVICE OR ANY COMMERCIAL DELIVERY SERVICE.

                  (d) OTHER FORUMS. NOTHING HEREIN SHALL IN ANY WAY BE DEEMED TO
LIMIT THE ABILITY OF ANY HOLDER OF NOTES TO SERVE ANY WRITS, PROCESSES OR
SUMMONSES IN ANY MANNER PERMITTED BY APPLICABLE LAW OR TO OBTAIN JURISDICTION
OVER THE ISSUER IN SUCH OTHER JURISDICTION, AND IN SUCH OTHER MANNER, AS MAY BE
PERMITTED BY APPLICABLE LAW.

         6.8 INDEMNIFICATION OF EACH HOLDER.

                                      -17-
<PAGE>   21

     From and at all times after the date of this Agreement, and in addition to
all of the holders' other rights and remedies against the Issuers, the Issuers
agree jointly and severally to indemnify and hold harmless each holder of the
Notes and each director, officer, employee, agent, investment advisor and
affiliate of each such holder ("Indemnified Parties") against any and all claims
(whether valid or not), losses, damages, liabilities, costs and expenses of any
kind or nature whatsoever (including, without limitation, reasonable attorneys'
fees, costs and expenses), incurred by or asserted against such Indemnified
Party, from and after the date hereof, as a result of, arising from, or in any
way relating to, whether directly or indirectly, the execution, delivery,
performance or enforcement of this Agreement or the other Standby Debt Documents
or any transactions contemplated herein or therein, or arising out of any breach
of any representation or warranty, covenant or agreement of the Issuers or any
of the Subsidiaries under any Standby Debt Document, including, without
limitation any of the foregoing relating to the violation of any Environmental
Law applicable to the Properties of the Issuers and their Subsidiaries;
provided, however, that no Indemnified Party shall have the right to be
indemnified hereunder for any liability resulting from the willful misconduct or
gross negligence of such Indemnified Party or with respect to liabilities
arising from legal proceedings commenced against such Indemnified Party by a
security holder or creditor of such Indemnified Party based upon alleged rights
afforded to such security holder or creditor solely in its capacity as such. All
of the foregoing losses, damages, costs and expenses of any Indemnified Party
shall be payable as and when incurred upon demand and shall be additional
obligations hereunder, except in the event any such Indemnified Party shall have
been added to such legal proceeding by the Issuer in order to establish the
liability of such Indemnified Party arising from its gross negligence or willful
misconduct. Without limiting the generality of the foregoing, but subject to the
foregoing, each Indemnified Party shall be entitled to collect, and the Issuers
shall be obligated jointly and severally to advance to each Indemnified Party,
to the fullest extent permitted by applicable law, all expenses (including,
without limitations reasonable fees and disbursements of counsel) attendant to
defending against any such claims (whether valid or not), when and as incurred,
regardless of whether any judicial determination of the Indemnified Party's
entitlement to such indemnity has been made, unless a final judicial
determination is made that such Indemnified Party is not entitled to such
indemnity, in which case such Indemnified Party shall promptly repay to the
Issuers, with interest at the applicable statutory rate applicable to judgments
in the relevant jurisdiction, all amounts so advanced by the Issuers. The
obligations of the Issuers and the rights of the Indemnified Parties under this
Section 6.8 shall survive the termination of this Agreement.

     6.9 ENTIRE AGREEMENT.

     This Agreement constitutes the final written expression of all of the terms
hereof and is a complete and exclusive statement of those terms.

     6.10 EXECUTION IN COUNTERPART.

     This Agreement may be executed in one or more counterparts and shall be
effective when at least one counterpart shall have been executed by each party
hereto, and each set of counterparts that, collectively, show execution by each
party hereto shall constitute one duplicate original.

     [Remainder of page intentionally left blank; next page is the signature
page.]

                                      -18-

<PAGE>   22

     If this Agreement is satisfactory to you, please so indicate by signing the
acceptance at the foot of a counterpart hereof and return such counterpart to
each Obligor, whereupon this Agreement shall become binding among us in
accordance with its terms.


                                             COHO ENERGY, INC.



                                             By: /s/  ANNE MARIE O'GORMAN
                                                -------------------------------
                                                Name:  Anne Marie O'Gorman
                                                Title: Senior Vice President


                                             COHO RESOURCES, INC.

                                             By: /s/  ANNE MARIE O'GORMAN
                                                -------------------------------
                                                Name:  Anne Marie O'Gorman
                                                Title: Senior Vice President


                                             COHO LOUISIANA PRODUCTION
                                             COMPANY


                                             By: /s/  ANNE MARIE O'GORMAN
                                                -------------------------------
                                                Name: Anne Marie O'Gorman
                                                Title: Senior Vice President


                                             COHO EXPLORATION, INC.


                                             By: /s/  ANNE MARIE O'GORMAN
                                                -------------------------------
                                                Name:  Anne Marie O'Gorman
                                                Title: Senior Vice President


                                             COHO OIL & GAS, INC.

                                             By: /s/  ANNE MARIE O'GORMAN
                                                -------------------------------
                                                Name:  Anne Marie O'Gorman
                                                Title: Senior Vice President



<PAGE>   23




                                             INTERSTATE NATURAL GAS
                                             COMPANY


                                             By: /s/  ANNE MARIE O'GORMAN
                                                -------------------------------
                                                Name:  Anne Marie O'Gorman
                                                Title: Senior Vice President


<PAGE>   24



PPM AMERICA SPECIAL INVESTMENTS FUND, L.P.

BY: PPM AMERICA, INC., ITS ATTORNEY-IN-FACT

By:    /s/ STUART J. LISSNER
   ----------------------------------------------
Name:  STUART J. LISSNER
Title: Managing Director


PPM AMERICA SPECIAL INVESTMENTS CBO II, L.P.

BY: PPM AMERICA, INC., ITS ATTORNEY-IN-FACT


By:    /s/ STUART J. LISSNER
   ----------------------------------------------
Name:  STUART J. LISSNER
Title: Managing Director


APPALOOSA INVESTMENT LIMITED PARTNERSHIP I

BY: APPALOOSA MANAGEMENT L.P., ITS GENERAL PARTNER

By: Appaloosa Partners Inc., its General Partner

By:      /s/ JAMES E. BOLIN
   ----------------------------------------------
Name:  James E. Bolin
Title: Vice President


PALOMINO FUND LTD.

BY: APPALOOSA MANAGEMENT L.P., ITS GENERAL PARTNER

By:      /s/ JAMES E. BOLIN
   ----------------------------------------------
Name:  James E. Bolin
Title: Vice President



<PAGE>   25

TERSK LLC

BY: APPALOOSA MANAGEMENT L.P., ITS MANAGING MEMBER

By: Appaloosa Management L.P., its General Partner

By: /s/ JAMES E. BOLIN
   ----------------------------------------------
Name:   JAMES E. BOLIN
Title:  VICE PRESIDENT



OAKTREE CAPITAL MANAGEMENT, LLC,
as agent and on behalf of certain funds and accounts

By:
   ----------------------------------------------
Name:
Title:

By:
   ----------------------------------------------
Name:
Title:

PACHOLDER VALUE OPPORTUNITY FUND, L.P.

BY: PACHOLDER ASSOCIATES, INC., ITS ATTORNEY-IN-FACT

By:
   ----------------------------------------------
Name:
Title:



PACHOLDER HIGH YIELD FUND, INC.

BY: PACHOLDER ASSOCIATES, INC., ITS ATTORNEY-IN-FACT

By:
   ----------------------------------------------
Name:
Title:


ONE GROUP HIGH YIELD BOND FUND

BY: PACHOLDER ASSOCIATES, INC., ITS ATTORNEY-IN-FACT

By:
   ----------------------------------------------
Name:
Title:




<PAGE>   26


Agreed to and Accepted by:


PACHOLDER VALUE OPPORTUNITY
FUND, L.P.

BY: PACHOLDER ASSOCIATES, INC., ITS ATTORNEY-
IN-FACT

By: /s/ BRUCE A. FERGUSON
   ----------------------------------------------
Name:  Bruce A. Ferguson
Title: Senior Vice President

Principal Amount of Notes:

$1,500,000.00

Number of Additional Shares:

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



PACHOLDER HIGH YIELD FUND, INC.

BY: PACHOLDER ASSOCIATES, INC., ITS ATTORNEY-
IN-FACT

By: /s/ BRUCE A. FERGUSON
   ----------------------------------------------
Name:  Bruce A. Ferguson
Title: Senior Vice President

Principal Amount of Notes:

$2,000,000.00

Number of Additional Shares:

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


<PAGE>   27


ONE GROUP HIGH YIELD BOND FUND

BY: PACHOLDER ASSOCIATES, INC., ITS ATTORNEY-
IN-FACT

By: /s/ BRUCE A. FERGUSON
   ----------------------------------------------
Name:  Bruce A. Ferguson
Title: Senior Vice President


Principal Amount of Notes:

$2,000,000.00

Number of Additional Shares:

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



EVANGELICAL LUTHERAN CHURCH IN
AMERICA BOARD OF PENSIONS

BY: PACHOLDER ASSOCIATES, INC., ITS ATTORNEY-
IN-FACT

By: /s/ BRUCE A. FERGUSON
   ----------------------------------------------
Name:  Bruce A. Ferguson
Title: Senior Vice President


Principal Amount of Notes:

$1,000,000.00

Number of Additional Shares:

-------------------------------------
<PAGE>   28
Agreed to and Accepted by:

OAKTREE CAPITAL MANAGEMENT, LLC,
as general partner of and investment manager for
those entities set forth on Annex 1 hereto

By: /s/  SHELDON STONE
   ----------------------------------------------
   Sheldon Stone
   Principal

By: /s/ TIMOTHY ANDREWS
   ----------------------------------------------
   Timothy Andrews
   Senior Vice President


Principal Amount of Notes: