<PAGE>   1
                                                                   EXHIBIT 10.55


                          CRUDE OIL PURCHASE AGREEMENT


                              DATED MARCH 14, 2000


                                     BETWEEN



                        SOUTHERN PRODUCER SERVICES, L.P.,
                                   AS "BUYER"

                                       AND

                           TRANSTEXAS GAS CORPORATION,
                                   AS "SELLER"





<PAGE>   2



                          CRUDE OIL PURCHASE AGREEMENT


This CRUDE OIL PURCHASE AGREEMENT (herein called "this Agreement") is entered
into as of March 14, 2000, by and between TransTexas Gas Corporation (herein
called the "Seller") and Southern Producer Services, L.P. (herein called the
"Buyer"), and shall govern the terms and conditions whereby Seller shall sell,
and Buyer shall purchase, certain crude oil and/or condensate (herein
collectively called "Crude Oil"). Buyer and Seller are sometimes referred to
singularly as "Party" and collectively as "Parties". Certain capitalized terms
used herein are defined as set forth in Exhibit A hereto or as otherwise
indicated.

                              W I T N E S S E T H:

         WHEREAS, Seller has heretofore filed for protection under Chapter 11 of
the Bankruptcy Code in Case No. 99-21550 in the United States Bankruptcy Court
(herein called the "Court") for the Southern District of Texas (Corpus Christi
Division), entitled "In re: TransTexas Gas Corporation, et. al." (herein called
the "Bankruptcy Case");

         WHEREAS, pursuant to the Bankruptcy Case, the Court has issued an order
(herein called the "Bankruptcy Order") granting Seller's motion for permission
to (1) sell the Production Payment (as hereinafter defined) and enter into and
deliver to Grantee (as hereinafter defined) the Conveyance (as hereinafter
defined) and other ancillary marketing, transportation and processing agreements
and (2) amend or amend and restate and affirm certain existing marketing,
transportation and processing agreements with third parties in order to
relinquish certain of Seller's capacity under such existing marketing,
transportation and processing agreements as is required for Buyer to market,
transport and/or process the Production Payment hydrocarbons that Buyer and Fund
V (as hereinafter defined) and Fund VI (as hereinafter defined) own or control
and such other volumes of hydrocarbons as Buyer shall purchase from Seller or
other third parties;

         WHEREAS, pursuant to the Bankruptcy Order, Seller and Grantee have
entered into that certain Production Payment Conveyance (herein, as from time to
time amended, restated or otherwise modified, called the "Conveyance"), dated as
of March 14, 2000, from and by Seller, as grantor, and Buyer, TCW Portfolio No.
15555 DR V Sub-Custody Partnership, L.P. (herein called "Fund V") and TCW DR VI
Investment Partnership, L.P. (herein called "Fund VI") (in such capacity, Fund
VI together with Buyer and Fund V, collectively called the "Grantee"), whereby
Seller has granted, bargained, sold, conveyed, assigned, transferred, set over
and delivered to Grantee a term overriding royalty interest (herein called the
"Production Payment") in the Subject Interests (as defined in the Conveyance and
herein so called);

         WHEREAS, pursuant to the terms of the Conveyance, production from the
Subject Interests shall be dedicated to the Grantee as (1) at fifty percent
(50%) from March 1, 2000 until 9:00 a.m., Central Time, on September 1, 2000,
(2) at sixty-two percent (62%) from 9:00 a.m., Central Time, on September 1,
2000 until 9:00 a.m., Central Time, on March 1, 2001 and (3) seventy percent

<PAGE>   3



(70%) from and after 9:00 a.m., Central Time, on March 14, 2001 until the
Termination Time (herein called the "Dedication Percentage");

         WHEREAS, pursuant to the Bankruptcy Order, Seller and Grantee have
entered into that certain Purchase Agreement (herein, as from time to time
amended, restated, supplemented or otherwise modified, called the "Purchase
Agreement"), dated as of March 1, 2000, between Seller and Grantee and TCW Asset
Management Company, as agent on behalf of Fund V and Fund VI (herein called the
"Funds Agent"), whereby Seller has sold the first component of the Production
Payment to Grantee pursuant to the Conveyance, and Grantee has purchased the
same from Seller;

         WHEREAS, the Grantee and Buyer have entered into that certain
Production Sales Agreement (as defined in the Purchase Agreement and herein, as
from time to time amended, restated, supplemented or otherwise modified, called
the "Production Sales Agreement"), dated as of March 14, 2000 pursuant to which
Buyer has agreed to purchase, and Grantee has agreed to sell, Grantee's interest
in the Production Payment hydrocarbons; and

         WHEREAS, subject to the terms and conditions hereinafter set forth,
Buyer desires to purchase certain quantities of Crude Oil from Seller and Seller
desires to sell such quantities of Crude Oil to Buyer;

         NOW, THEREFORE, in consideration of the premises and of the mutual
covenants hereinafter set forth, the Parties hereto covenant and agree as
follows:

1. QUANTITY: Seller agrees to sell and Buyer agrees to purchase, subject to the
other provisions of this Agreement, one hundred percent (100%) of the Crude Oil
that Seller owns, controls or has the authority to sell pursuant to the
Conveyance (as such Exhibit may from time to time be amended, restated,
supplemented or otherwise modified) and that is capable of being transported to
Buyer's Purchaser under contracts with Buyer's Transporters (herein called the
"Marketed Volumes"). Seller hereby agrees to sell to Buyer, and Buyer hereby
agrees to purchase from Seller, upon the terms of this Agreement, all of the
Marketed Volumes.

2. QUALITY: The Marketed Volumes delivered shall meet the Quality Specifications
then in effect for such Crude Oil as established by the Buyer's Transporter
and/or Buyer's Purchaser receiving such Marketed Volumes. Quality, quantity and
gravity of Crude Oil delivered hereunder, shall be determined in accordance with
the terms of the relevant Buyer's Sales Contract or Buyer's Transporter's
contract concerning such Marketed Volumes. In the event that such Buyer's Sales
Contract or Buyer's Transporter's contract fails to specify such terms, quality,
quantity and gravity shall be determined in accordance with generally accepted
industry practices in effect at the time and place of delivery to Buyer, or
Buyer's designee, using the latest A.S.T.M. or A.P.I. test methods, with volumes
being corrected to 60 degrees Fahrenheit temperature in accordance with the
latest A.S.T.M. test methods and the latest edition of A.P.I. volume correction
tables, and full deductions being made for all basic sediment and water and
other impurities. In the event Seller tenders or causes to be tendered Crude Oil
not meeting the Quality Specifications, without prejudice to any

                                        2

<PAGE>   4



other remedy, Buyer may (to the extent it is able to do so under its own sales
and transportation agreements) accept delivery subject to a reduction in Net
Price as provided in the definition of such term to compensate Buyer for the
reasonable charges resulting therefrom, otherwise Buyer, or Buyer's designee,
may elect not to accept delivery.

3. DELIVERY LOCATION: Seller shall sell and deliver or cause to be delivered all
Crude Oil to Buyer, or to Buyer's designee, at Seller's Delivery Point. In the
event Seller delivers or causes to be delivered Crude Oil at any other delivery
point, Buyer may (to the extent it is able to do so under its own sales and
transportation agreements) accept delivery subject to a reduction in Net Price
as provided in the definition of such term to compensate Buyer for the
reasonable charges resulting therefrom, otherwise Buyer, or Buyer's designee,
may elect not to accept delivery.

4. TITLE AND RISK OF LOSS: Title to all Crude Oil sold hereunder shall pass to
Buyer at the Seller's Delivery Point for such Crude Oil described in Paragraph 3
of this Agreement. As between the Parties hereto, Buyer shall be deemed in
possession of and solely liable and responsible for said Crude Oil after its
delivery at the Buyer's Delivery Points and Seller shall be deemed in possession
of and solely liable and responsible for said Crude Oil at all times prior to
such delivery. Each Party shall indemnify and defend the other Party for and
save it harmless from, any and all losses, costs, expenses, damages, injuries,
or liabilities caused by the Crude Oil in its possession to the extent not due
to or contributed to by the negligent act or omission of the other Party. In the
event and to the extent Seller discharges in full, in immediately available
funds, any obligation under the indemnity to Buyer pursuant to this Paragraph 4,
Buyer, to the extent it is able to do so under its own transportation,
processing and sales agreements, agrees to assign to Seller any rights of
indemnification running in favor of Buyer under any such agreement; provided,
however, if Buyer is unable to assign such rights to Seller, Buyer shall,
pursuant to written instructions of Seller and agreement by Seller to reimburse
Buyer for any related costs and expenses therewith, diligently pursue any
remedies running in favor of Buyer at the sole cost and expense of Seller. Buyer
agrees to apply any sums so obtained on behalf of Seller pursuant to any of
Buyer's transportation, processing or sales agreements as an addition to the Net
Price, net of any costs and expenses of Buyer not previously reimbursed by
Seller. The provisions of this Paragraph 4 shall survive the termination of this
Agreement.

5. INDEMNITY:

(a)      In consideration of the execution and delivery of this Agreement by the
         Buyer, the Seller hereby indemnifies, exonerates and holds the Buyer
         and each of its respective officers, directors, employees and agents
         (herein, collectively, called the "Indemnified Parties") free and
         harmless from and against any and all actions, causes of action, suits,
         losses, costs, liabilities, damages and expenses (including, without
         limitation, reasonable attorney's fees and disbursements) incurred in
         connection therewith (irrespective of whether any such Indemnified
         Party is a Party to the action for which indemnification hereunder is
         sought), excluding any portion of such actions, causes of action,
         suits, losses, costs, liabilities, damages and expenses (including,
         without limitation, attorney's fees and disbursements)

                                        3

<PAGE>   5


         resulting from the gross negligence or wilful misconduct of any
         Indemnified Party (herein collectively called the "Indemnified
         Amounts"), incurred by the Indemnified Parties or any of them as a
         result of, or arising out of, or relating to (1) Buyer's Marketing
         Agreements or (2) this Agreement. IT IS UNDERSTOOD BY THE PARTIES
         HERETO THAT THE INDEMNITIES BY SELLER IN FAVOR OF THE BUYER IN THIS
         AGREEMENT SHALL BE APPLICABLE NOTWITHSTANDING THAT ANY INDEMNIFIED
         AMOUNT OTHERWISE COVERED BY THIS AGREEMENT ARE ATTRIBUTABLE TO THE
         NEGLIGENCE (OTHER THAN GROSS NEGLIGENCE OR WILFUL MISCONDUCT) OF BUYER
         (WITHOUT REGARD TO WHETHER SUCH NEGLIGENCE IS SOLE, JOINT, CONCURRENT,
         ACTIVE OR PASSIVE), ANY PRE-EXISTING CONDITION OR DEFECT OR ANY FORM
         OF STRICT LIABILITY.

(b)      In the event that Buyer incurs, owes or is liable for any Indemnified
         Amount under Clause (a) above, Seller shall pay such Indemnified Amount
         by wire transfer of immediately available funds to Buyer within five
         (5) days following Buyer's written demand therefor. In addition to, and
         not in limitation of the foregoing, Buyer is hereby authorized at any
         time and from time to time, without notice to Seller, to setoff and
         apply any and all sums held and any other sums at any time owing to or
         for the credit or the account of Seller against any and all sums owing
         to Buyer (including, without limitation, reasonable attorney's fees and
         disbursements and any Indemnified Amount), together with interest on
         such amounts at the Agreed Rate until paid in full, irrespective of
         whether or not Buyer will have made any demand under this Agreement.
         Buyer agrees promptly to notify Seller after any such setoff and
         application. The rights of the Buyer under this Section are in addition
         to other rights and remedies (including, without limitation, other
         rights of setoff) which Buyer may have. The provisions of Clauses (a)
         and (b) of this Paragraph 5 shall survive the termination of this
         Agreement.

6.       PRICE AND NET PRICE:


(a)      The Price per Barrel of Crude Oil on which the Net Price shall be
         determined shall be the Price per Barrel of Crude Oil paid to Buyer by
         the relevant Buyer's Purchaser for such Crude Oil delivered hereunder
         during each applicable calendar Month from each field listed in Exhibit
         B hereto.

(b)      As described in Paragraph 9 below, Buyer will pay the Net Price to
         Seller for all Marketed Volumes delivered to Buyer and subsequently
         delivered to the relevant Buyer's Purchaser and accepted and paid for
         by such Buyer's Purchaser hereunder.

7.       INVOICES AND ACCOUNTING CORRESPONDENCE: Invoices and any other notices
or documentation shall be mailed or telecopied to the following addresses:

                                        4

<PAGE>   6


SELLER:                                        BUYER:

TransTexas Gas Corporation                     Southern Producer Services, L.P.
1300 North Sam Houston Parkway East            1200 Smith Street
Suite 310                                      Suite 2890
Houston, TX 77032-2949                         Houston, Texas 77251-1188
Attention: Revenue Accounting                  Attention: Ron Franklin
Telephone No.: (281) 987-8600                  Telephone No.: (713) 276-1916
Fax No.: (281) 986-8855                        Fax No.:  (713) 276-1990

8. DELIVERY PERIOD: Subject to the other terms and provisions hereof, deliveries
hereunder shall commence with respect to production from and after 9:00 A.M. on
March 1, 2000, and shall continue for a primary term equal to the greater of (a)
three (3) years or (b) a period equal to the term of the Production Payment
(herein called the "Delivery Period") and Month to Month thereafter until
terminated by Buyer and Seller upon the giving of written notice to the other
Party of its intention to terminate this Agreement at least thirty (30) Days
prior to the end of the primary term or an extension thereof; provided, however,
Buyer may terminate this Agreement, in full or in part, at any time upon the
giving of thirty (30) days notice of such termination to Seller, which
termination shall be effective as of the first Day of the Month following the
expiration of such thirty (30) Day notice period. Conclusion of the Delivery
Period shall not affect the accrued rights and obligations of the Parties.

9. STATEMENTS AND PAYMENT:

(a)      Payment of the Net Price by Buyer to Seller is due no later than two
         (2) Business Days following the twenty-fifth (25th) Day of the Month
         following the Month of delivery via wire transfer in immediately
         available funds to the banks and accounts from time to time specified
         by Seller in writing. As of the date hereof, Buyer shall make payment
         to Seller as follows:

                           Bank of New York
                           48 Wall Street
                           New York, New York
                           ABA #021-000-018
                           For the Account of GMAC Commercial Credit LLC
                           Acct. #809-0653-114
                           For further credit to Account #904200

         Payment shall be made against the following documents: Seller's invoice
         and a copy of Buyer's, or its designee's, carrier's receipt of such
         Crude Oil; provided, however, Buyer is hereby authorized at any time
         and from time to time, without notice to Seller, to setoff and apply
         any and all sums held and any other sums at any time owing to or for
         the credit or the account of Seller against any and all sums owing to
         Buyer (including, without limitation, reasonable attorney's fees and
         disbursements), together with interest on such amounts at the

                                        5

<PAGE>   7



         Agreed Rate until paid in full, irrespective of whether or not Buyer
         will have made any demand under this Agreement. Buyer agrees promptly
         to notify Seller after any such setoff and application. The rights of
         the Buyer under this Section are in addition to other rights and
         remedies (including, without limitation, other rights of setoff) which
         Buyer may have. If the payment due date falls on a Saturday, Sunday,
         Monday or any Day which is a banking holiday in Houston, Texas, Los
         Angeles, California or Atlanta, Georgia, payment will be made on the
         following Business Day.

(b)      Buyer and Seller shall each have the right to examine, at reasonable
         times, and upon five (5) Business Days prior written notice, the books,
         records, charts, and electronic data of the other to the extent
         reasonably necessary to substantiate the accuracy in all material
         respects of any statement, payment, charge or computation made pursuant
         to this Agreement. Subsequent to any statement having been paid, if any
         overpayment or underpayment in any form whatsoever shall be found,
         Seller shall refund the amount of any overpayment received by Seller,
         and Buyer shall pay the amount of any underpayment due Seller, within
         thirty (30) Days after final determination thereof; provided however,
         no retroactive adjustments will be made for any overpayment or
         underpayment beyond (i) with respect to overpayments or underpayments
         arising under or related to any of Buyer's Marketing Agreements, the
         applicable period for retroactive adjustments provided in such Buyer's
         Marketing Agreements and (ii) with respect to overpayments or
         underpayments arising under or related to this Agreement, a period
         twenty-four (24) Months from the date of any such overpayment or
         underpayment, as the case may be. The provisions of this Clause (b)
         shall survive the termination of this Agreement.

10.      FORCE MAJEURE:

(a)      In the event either Party is rendered unable, wholly or in part, by
         force majeure to carry out its obligations under this Agreement, except
         for the obligations to make payments hereunder, it is agreed that the
         obligations of the Parties, so far as they are affected by such force
         majeure, shall be suspended during the continuance of any inability so
         caused, but for no longer period, and such force majeure shall, so far
         as economically possible, be remedied with all reasonable dispatch.
         Each Party shall give notice and reasonably full particulars of such
         force majeure to the other Party, orally as soon as practicable and
         followed in writing or by electronic transmission within a reasonable
         time after the occurrence of the force majeure relied on.

(b)      The term "force majeure", as employed herein, shall mean acts of God;
         strikes, lockouts or other industrial disturbances; acts of the public
         enemy, wars, blockades, insurrections, civil disturbances and riots,
         and epidemics; landslides, lightning, earthquakes, fires, storms,
         hurricanes and threats of hurricanes, floods and washouts; arrests,
         orders, requests, directives, restraints and requirements of the
         government and governmental agencies, either federal or state, civil
         and military; any application of governmental conservation or
         curtailment rules and regulations; outages (including, without
         limitation, planned or

                                        6

<PAGE>   8



         unplanned shutdowns) or failure of any of Buyer's Transporter, Buyer's
         Separator/Stabilizer or Buyer's Purchaser if caused by an event of
         force majeure with respect to such party; explosions, breakage or
         accident to machinery, equipment or lines of pipe; outages (including,
         without limitation, planned or unplanned shutdowns) of equipment,
         machinery or lines of pipe for inspection, maintenance or repair;
         freezing of wells or lines of pipe; premature, partial or entire
         failure of natural gas or crude oil wells, gas or crude oil supply or
         depletion of gas or crude oil reserves; any of the foregoing events or
         circumstances to the extent such event or circumstance affects Seller's
         treating plant, if any or Galveston Bay's Winnie Facility; and other
         causes of a similar nature not reasonably within the control of the
         Party claiming suspension. It is understood and agreed that the
         settlement of strikes or lockouts shall be entirely within the
         discretion of the Party having the difficulty, and that the above
         reasonable dispatch shall not require the settlement of strikes or
         lockouts by acceding to the demand of opposing Party when such course
         is inadvisable or inappropriate in the discretion of the Party having
         the difficulty. Force majeure shall likewise include (i) in those
         instances where either Party hereto is required to obtain servitudes,
         right-of-way grants, permits or licenses to enable such Party to
         fulfill its obligations hereunder, the inability of such Party to
         acquire, or the delays on the part of such Party in acquiring, at
         reasonable cost and after the exercise of reasonable diligence, such
         servitudes, right-of-way grants, permits or licenses; and (ii) in those
         instances where either Party hereto is required to furnish materials
         and supplies for the purpose of constructing or maintaining facilities
         or is required to secure permits or permissions from any governmental
         agency to enable such Party to fulfill its obligations hereunder, the
         inability of such Party to acquire or the delays on the part of such
         Party in acquiring, at reasonable cost and after the exercise of
         reasonable diligence, such materials and supplies, permits and
         permissions.

(c)      The term "force majeure" specifically excludes the following
         occurrences or events: the loss, interruption, or curtailment of
         interruptible transportation on any transporter of Buyer necessary to
         make or take delivery of crude oil hereunder, unless and to the extent
         the same event also curtails firm transportation at the same point; and
         loss of markets. Price changes due to market conditions or economics
         associated with the purchase and sale of crude oil quantities purchased
         and delivered hereunder shall not be considered events of "force
         majeure".

11. WARRANTY: Seller hereby warrants good title to the Crude Oil delivered by
Seller to Buyer and the right to sell the same free and clear from all liens
(excluding liens arising under Section 9.319 of the Uniform Commercial Code as
enacted in the State of Texas, as such may be amended from time to time, and any
successor statute of similar import), encumbrances and adverse claims. Seller
further warrants that Crude Oil delivered shall not be contaminated by chemicals
foreign to virgin Crude Oil (except as required for operational purposes, to the
extent, and only to the extent, permitted under any of Buyer's Marketing
Agreements), including, but not limited to, chlorinated and/or oxygenated
hydrocarbons and lead. Seller agrees to pay, or cause to be paid, or deliver in
kind to the parties entitled thereto all royalties, overriding royalties or like
charges, if any, assessed against the Crude Oil or the value thereof. Seller
shall protect, defend, indemnify and hold

                                        7

<PAGE>   9



Buyer and Buyer's Purchaser harmless from and against all suits, actions, debts,
accounts, damages, costs, losses and expenses (including attorney's fees)
arising from or out of any adverse claims of any nature, including royalty
claims, of any and all persons to or against the Crude Oil. In the event any
adverse claim of any character whatsoever is asserted in respect to any of the
Crude Oil, Buyer may suspend its obligations to pay for Crude Oil hereunder and
suspend payments up to the amount of such claim without interest until such
claim has been finally determined, as security for the performance of Seller's
obligations with respect to such claim, or until Seller shall have furnished a
bond to Buyer, or Buyer's designee, in an amount and with securities
satisfactory to Buyer, or Buyer's designee. The provisions of this Section 11
shall survive the termination of this Agreement.

12. TAXES: The Price under this agreement includes full reimbursement for, and
the Seller is liable for and shall pay, cause to be paid or reimburse Buyer,
Buyer's Transporter, Buyer's Purchaser and Buyer's Separator/Stabilizer, if such
party has paid, any ad valorem, property, occupation, severance, production,
extraction, first use, first or subsequent purchase, conservation, gathering,
pipeline, utility, gross production, gross receipts, gross income, oil revenue,
oil import, privilege, sales, use, consumption, Btu, energy, excise, lease,
transaction and any other taxes, governmental charges, assessments, licenses,
fees or permits, or increase thereon, other than taxes based on net income or
net worth (herein collectively called "Taxes") applicable to the Crude Oil sold
hereunder imposed, assessed or collected at or prior to Buyer's Delivery Point.
Seller shall indemnify, defend and hold Buyer, Buyer's Purchaser, Buyer's
Separator/Stabilizer and Buyer's Transporter harmless from any liability against
all such Taxes. The Price does not include reimbursement for, and the Buyer is
liable for and shall pay, cause to be paid or reimburse Seller if Seller has
paid, any Taxes applicable to the Crude Oil sold hereunder imposed, assessed or
collected after Buyer's Delivery Point. Buyer shall indemnify, defend and hold
Seller harmless from any liability against all such Taxes. Notwithstanding the
foregoing, Buyer, as first purchaser of the Marketed Volumes, shall withhold
from the Net Price payable to Seller for such Marketed Volumes, such amounts
imposed, assessed or owing in respect of severance or gross production taxes or
taxes of similar import assessed against the Crude Oil or the value thereof
(herein collectively called "Severance Taxes") and Buyer shall pay or cause to
be paid on behalf of Seller such Severance Taxes withheld, to the relevant
governmental authority to whom such Severance Taxes are owing. In the event that
Buyer fails to pay when due such sums as are actually withheld by Buyer on
behalf of Seller in respect of Severance Taxes, Buyer hereby indemnifies,
exonerates and holds the Seller and each of its respective officers, directors,
employees and agents (herein called the "Seller Indemnified Parties") free and
harmless from and against any and all actions, causes of action, suits, losses,
costs, liabilities, damages and expenses incurred therewith, excluding any
portion of such actions, causes of action, suits, losses, costs, liabilities,
damages and expenses resulting from the gross negligence or wilful misconduct of
any Seller Indemnified Party and including reasonable attorney's fees and
disbursements, incurred by the Seller Indemnified Parties or any of them as a
result of Buyer's failure to pay such Severance Taxes when due.

Both Parties shall use reasonable efforts to administer this agreement and
implement the provisions thereof in accordance with their intent to minimize or
reduce Taxes. Upon request, a Party shall provide the other Party a certificate
of exemption or other reasonably satisfactory evidence of

                                        8

<PAGE>   10



exemption from any Taxes, and each Party agrees to cooperate with the other
Party in obtaining any such exemption. The provisions of this Section 12 shall
survive the termination of this Agreement; provided, however, the indemnities
running in favor of the Seller Indemnified Parties shall survive the termination
of this Agreement for only three (3) Months.

13. NON-PERFORMANCE:

(a)      In the event that either Party (herein called the "Non-Performing
         Party") shall (i) make an assignment or any general arrangement for the
         benefit of creditors; (ii) file a petition or otherwise commence,
         authorize or acquiesce in the commencement of a proceeding or cause
         under any bankruptcy or similar law for the protection of creditors or
         have such petition filed or proceeding commenced against it; (iii)
         otherwise become bankrupt or insolvent; (iv) be unable to pay its debts
         as they fall due; (v) fail to make, when due, any payment required
         under this Agreement if such failure is not remedied within two (2)
         Business Days after written notice of such failure is given by the
         Party to whom the payment is owed, provided the payment is not the
         subject of a good faith dispute; (vi) fail to perform any covenant set
         forth in this Agreement (other than an obligation to make payment or
         obligations that are otherwise specifically defined herein as a
         separate Default), and such failure is not excused by force majeure or
         cured within fifteen (15) Days after written notice thereof by the
         Party to whom the covenant is owed (herein, collectively, called a
         "Default"), the other Party (herein called the "Performing Party") may
         at its option (without waiving any other remedy for breach hereof): (i)
         immediately suspend the Performing Party's performance of its
         obligations hereunder, (ii) upon three (3) Days' notice in writing to
         the Non-Performing Party specifying wherein the Default has occurred,
         indicate the Non-Performing Party's election to establish a date on
         which this Agreement will terminate (herein called "Early Termination
         Date"), and (iii) withhold any payments due hereunder; provided,
         however, that upon the occurrence of any Default listed in sub-clauses
         (i) - (iv) of this Clause (a) of this Paragraph 13 for any Party, this
         Agreement shall automatically terminate, without notice, as if an Early
         Termination Date has been immediately declared. The Parties agree that
         this contract constitutes a "forward contract" for purposes of Section
         556 of the U.S. Bankruptcy Code.

(b)      Upon the occurrence of a Designated Event (as defined in the Purchase
         Agreement) and the exercise by Grantee, either on its own behalf or
         through any agent or representative, of any remedy pursuant to Section
         4.6 of the Purchase Agreement or Article V of the Conveyance, Buyer
         may, at its option (without waiving any other remedy for breach
         hereof), immediately suspend the performance of its obligations
         hereunder and withhold any payments due hereunder.

(c)      In the case of a Default, notwithstanding the termination of this
         Agreement pursuant to Clause (a) of this Paragraph 13, each Party
         reserves to itself all rights, setoffs, counterclaims, and other
         remedies and/or defenses, consistent with the provision of Paragraph
         14, which such Party is or may be entitled to assert arising from or
         out of this Agreement, and all

                                        9

<PAGE>   11



         obligations to make payments hereunder that are outstanding at the time
         of such default may be off-set against each other, setoff, or recouped
         therefrom.

14. LIABILITIES: NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED HEREIN,
NEITHER PARTY SHALL BE LIABLE OR OTHERWISE RESPONSIBLE TO THE OTHER PARTY FOR
PUNITIVE, SPECIAL, CONSEQUENTIAL, OR INCIDENTAL DAMAGES OR FOR LOST PROFITS
WHICH ARISE OUT OF OR RELATE TO THIS AGREEMENT OR THE PERFORMANCE OR BREACH
THEREOF.

15. ASSIGNMENT: This Agreement shall inure to and be binding upon the successors
and assigns of the assigning Parties. The rights of either party under this
Agreement may be transferred or assigned in whole or in part, but any such
transfer or assignment shall be expressly made subject to the provisions of this
Agreement; provided, further, that (a) no such transfer or assignment shall be
binding on the other Party until the transferring Party has provided to such
other Party a copy of the fully executed instrument of transfer, (b) any such
assignee shall agree in writing to be bound by the terms and conditions hereof,
(c) in the case of an assignment or transfer by Buyer such transfer or
assignment (i) shall relieve the Buyer of responsibility and liability for any
obligations and liabilities arising under the terms of this Agreement after the
effective date of the transfer and (ii) shall be to (X) a Person, the unsecured
long term debt (or if such Person has no outstanding long term debt, its
corporate rating or if such Person has no corporate rating, the long term debt
of such Person's parent or if such Person's parent has no outstanding long term
debt, its parent's corporate rating) of which is rated at least BBB by Standard
& Poor's or Baa2 by Moody's Investors Service, Inc., (Y) a Person who is a
Buyer's Purchaser, or (Z) such Person as Seller shall consent to, which consent
shall not be unreasonably withheld and (d) in the case of Seller, Seller may not
assign or transfer this Agreement without the prior written consent of Buyer,
which consent shall not be unreasonably withheld; provided however, Buyer hereby
consents to the assignment by Seller of Seller's right to money due or to become
due to GMAC Commercial Credit LLC under that certain Third Amended and Restated
Accounts Receivable Management and Security Agreement, dated on or about March
15, 2000, by and between Seller and GMAC Commercial Credit LLC.

16. CHOICE OF LAW: THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED, ENFORCED
AND PERFORMED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS WITHOUT REGARD
TO THE PRINCIPLES OF CONFLICT OF LAWS. THE PARTIES AGREE THAT THIS AGREEMENT
SHALL BE DEEMED TO HAVE BEEN MADE IN TEXAS. THE PARTIES AGREE THAT THE UNITED
NATIONS CONVENTION ON CONTRACTS FOR THE INTERNATIONAL SALE OF GOODS 1980 SHALL
NOT APPLY TO, OR GOVERN, THIS AGREEMENT.

17. WAIVER OF JURY TRIAL: SELLER AND BUYER HEREBY KNOWINGLY, VOLUNTARILY AND
INTENTIONALLY WAIVE THEIR RESPECTIVE RIGHTS TO A TRIAL BY JURY IN RESPECT OF ANY
LITIGATION BASED HEREON, OR ARISING OUT OF, UNDER, OR IN CONNECTION WITH, THIS
AGREEMENT, OR ANY COURSE OF CONDUCT, COURSE OF DEALING, STATEMENTS (WHETHER
VERBAL OR

                                       10

<PAGE>   12


WRITTEN) OR ACTIONS OF THE SELLER OR THE BUYER. EACH OF THE SELLER AND THE BUYER
ACKNOWLEDGES AND AGREES THAT IT HAS RECEIVED FULL AND SUFFICIENT CONSIDERATION
FOR THIS PROVISION AND THAT THIS PROVISION IS A MATERIAL INDUCEMENT FOR SUCH
PARTY'S ENTERING INTO THE PRODUCTION PAYMENT DOCUMENTS AND THIS AGREEMENT.

18.      SUBMISSION TO JURISDICTION:


(a)      ANY LITIGATION BASED HEREON, OR ARISING OUT OF, UNDER, OR IN CONNECTION
         WITH, THIS AGREEMENT, OR ANY COURSE OF CONDUCT, COURSE OF DEALING,
         STATEMENTS (WHETHER VERBAL OR WRITTEN) OR ACTIONS OF THE BUYER OR THE
         SELLER MAY BE BROUGHT AND MAINTAINED IN THE COURTS OF THE STATE OF
         TEXAS OR IN THE UNITED STATES DISTRICT COURT FOR THE SOUTHERN DISTRICT
         OF TEXAS; PROVIDED, HOWEVER, THAT ANY SUIT SEEKING ENFORCEMENT AGAINST
         ANY PROPERTY MAY BE BROUGHT, AT THE BUYER'S OPTION, IN THE COURTS OF
         ANY JURISDICTION WHERE SUCH PROPERTY MAY BE FOUND. THE SELLER HEREBY
         EXPRESSLY AND IRREVOCABLY SUBMITS TO THE JURISDICTION OF THE COURTS OF
         THE STATE OF TEXAS AND OF THE UNITED STATES DISTRICT COURT FOR THE
         SOUTHERN DISTRICT OF TEXAS FOR THE PURPOSE OF ANY SUCH LITIGATION AS
         SET FORTH ABOVE. THE SELLER FURTHER IRREVOCABLY CONSENTS TO THE SERVICE
         OF PROCESS BY REGISTERED MAIL, POSTAGE PREPAID, OR BY PERSONAL SERVICE
         WITHIN OR WITHOUT THE STATE OF TEXAS. THE SELLER HEREBY EXPRESSLY AND
         IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW, ANY
         OBJECTION WHICH IT MAY HAVE OR HEREAFTER MAY HAVE TO THE LAYING OF
         VENUE OF ANY SUCH LITIGATION BROUGHT IN ANY SUCH COURT REFERRED TO
         ABOVE AND ANY CLAIM THAT ANY SUCH LITIGATION HAS BEEN BROUGHT IN AN
         INCONVENIENT FORUM. TO THE EXTENT THAT THE SELLER HAS OR HEREAFTER MAY
         ACQUIRE ANY IMMUNITY FROM JURISDICTION OF ANY COURT OR FROM ANY LEGAL
         PROCESS (WHETHER THROUGH SERVICE OR NOTICE, ATTACHMENT PRIOR TO
         JUDGMENT, ATTACHMENT IN AID OF EXECUTION OR OTHERWISE) WITH RESPECT TO
         ITSELF OR ITS PROPERTY, THE SELLER HEREBY IRREVOCABLY WAIVES SUCH
         IMMUNITY IN RESPECT OF ITS OBLIGATIONS UNDER THIS AGREEMENT.

(b)      The Parties agree that a final judgment by any court in the
         above-designated jurisdiction covered by this Agreement shall be
         conclusive and may be enforced in other jurisdictions in any manner
         provided by law.

(c)      The Parties hereby waive any claim that a judgment obtained in the
         above-designated jurisdiction is invalid or unenforceable.

                                       11

<PAGE>   13


19. No amendment to any Buyer's Marketing Agreement shall be effective for
purposes of this Agreement unless Seller (a) has consented in writing to such
amendment, which consent shall not be unreasonably withheld or (b) is deemed to
have consented to such amendment pursuant to the terms of this Agreement.

20. This Agreement may be executed in any number of counterparts and by
different parties hereto on separate counterparts, each of which when so
executed and delivered shall be deemed to be an original, but all of which shall
taken together constitute one and the same instrument. Any signature delivered
by a party by facsimile transmission shall be deemed to be an original hereto.



                            [Signature pages follow]


                                       12

<PAGE>   14



         IN WITNESS WHEREOF, Buyer and Seller have executed and delivered this
Agreement as of the date first written above.

                                       BUYER:
                                       -----

                                       SOUTHERN PRODUCER SERVICES, L.P.

                                       By:  SC Ashwood Holdings, Inc.,
                                            as its general partner


                                       By:
                                          ------------------------------------
                                       Name:     David W. Stewart
                                       Title:    Vice President

                                       SELLER:
                                       ------

                                       TRANSTEXAS GAS CORPORATION


                                       By:
                                          ------------------------------------
                                       Name:     Ed Donahue
                                       Title:    Vice President

ACKNOWLEDGED AND AGREED TO:

GMAC COMMERCIAL CREDIT LLC


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