PURCHASE AND SALE AGREEMENT

      THIS PURCHASE AND SALE AGREEMENT  ("Agreement") dated as of September ___,
1996  by  and  among  Abraxas  Petroleum   Corporation,   a  Nevada  corporation
("Abraxas"),  Acco, LLC, a Massachusetts  limited  liability  company  ("Acco"),
Massachusetts   Bay   Transportation   Authority   Retirement   Fund   ("MBTA"),
Metropolitan  Life Insurance  Company Separate Account No. 175 ("MetLife"),  The
General Mills, Inc. Master Trust:  Pooled Real Estate Fund ("General Mills" and,
together with MBTA and MetLife,  the "SSR  Investors") and State Street Research
Energy, Inc., a Massachusetts corporation ("State Street").

                             W I T N E S S E T H:

      WHEREAS,  Acco owns a 75% limited partnership interest (the "Interest") in
Portilla - 1996, L.P., a Texas limited partnership (the "Partnership");

      WHEREAS,  the SSR Investors are the holders of (i) promissory notes of the
Partnership dated March 20, 1996 and the date hereof in the aggregate  principal
amount of  $6,451,151.33  (the "Notes") and (ii) options to purchase  overriding
royalty  interests  (the "ORI  Options")  in the  Portilla  Field,  San Patricio
County, Texas ("Portilla"), and the Happy Field, Garza County, Texas ("Happy");

      WHEREAS,  Acco desires to sell the Interest,  the SSR Investors  desire to
sell  the  Notes  and the ORI  Options  and  Abraxas  desires  to  purchase  the
Interests, the Notes and the ORI Options;

      NOW, THEREFORE, IT IS AGREED:



                                  ARTICLE I

                               SALE OF INTEREST

      1.01  Sale of  Interest.  Subject  to the  terms  and  conditions  of this
Agreement,  Acco and the SSR Investors (collectively,  "Sellers") agree to sell,
assign,  transfer  and  deliver to Abraxas on the Closing  Date (as  hereinafter
defined),  and Abraxas  agrees to purchase from Sellers on the Closing Date, the
Interest, the Notes and the ORI Options.

      1.02 Consideration. In consideration for the purchase of the Interest, the
Notes and the ORI Options by Abraxas,  at the Closing,  the  following  payments
shall be made:

            (a) Abraxas shall  purchase the Interest from Acco in  consideration
of the payment of $87,177.67 in cash by certified or bank cashier's check at the
Closing  and  the  assumption  by  Abraxas  of all  of  Acco's  liabilities  and
obligations  pursuant to the loan made to Acco (the "Christiania Loan") pursuant
to that  certain  Credit  Agreement  dated as of March  20,  1996  (the  "Credit
Agreement") by and between Acco and Christiania Bank og

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0135432.01






Kreditkasse  ("Christiania")  including,  but  not  limited  to,  all of  Acco's
obligations under the Loan Papers (as defined in the Credit Agreement) and under
Sections  7.15 and 8.13 of the Credit  Agreement  except as set forth in Section
9.01 hereof;

            (b) Abraxas shall purchase that certain  Promissory Note dated March
20, 1996 in the aggregate  principal amount of $1,000,000 and payable to MBTA as
supplemented by that certain  Promissory Note dated as of the date hereof in the
aggregate  principal  amount of $89,721.51  and payable to MBTA  (together,  the
"MBTA  Note")  in  consideration  of the  payment  of  $1,089.721.51  to MBTA by
certified or bank cashier's check at the Closing;

            (c) Abraxas shall purchase that certain  Promissory Note dated March
20, 1996 in the aggregate  principal amount of $3,920,000 and payable to MetLife
as supplemented  by that certain  Promissory Note dated as of the date hereof in
the aggregate  principal amount of $351,708.31 and payable to MetLife (together,
the "MetLife Note") in  consideration of the payment of $4,271,708.31 to MetLife
by certified or bank cashier's check at the Closing;

            (d) Abraxas shall purchase that certain  Promissory Note dated March
20, 1996 in the aggregate  principal amount of $1,000,000 and payable to General
Mills as  supplemented  by that  certain  Promissory  Note  dated as of the date
hereof in the aggregate  principal  amount of $89,721.51  and payable to General
Mills  (together,  the "General Mills Note") in  consideration of the payment of
$1,089,721.51  to General  Mills by  certified  or bank  cashier's  check at the
Closing;

            (e) Abraxas shall  purchase all right,  title and interest in and to
that  certain  Royalty  Option  dated March 20, 1996 in favor of MBTA (the "MBTA
Option")  in  consideration  of the  payment  of  $64,189.19  to MBTA in cash by
certified or bank cashier's check;

            (f) Abraxas shall  purchase all right,  title and interest in and to
that  certain  Royalty  Option  dated  March 20,  1996 in favor of MetLife  (the
"MetLife  Option") in  consideration of the payment of $251,621.62 to MetLife in
cash by certified or bank cashier's check;

            (g) Abraxas shall  purchase all right,  title and interest in and to
that certain  Royalty Option dated March 20, 1996 in favor of General Mills (the
"General Mills Option") in consideration of the payment of $64,189.19 to General
Mills in cash by certified or bank cashier's check.

      The amounts payable pursuant to paragraphs (e), (f) and (g) above shall be
reduced pro rata by the amount payable to State Street  pursuant to Section 1.05
hereof.

      In the event that the transactions contemplated by this Agreement have not
been consummated on or prior to October 20, 1996, in addition to the payments to
be made to the Sellers  pursuant to this Section  1.02,  Abraxas  shall also pay

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0135432.01







interest  to the Sellers at a rate of 10% per annum on the  principal  amount of
the Notes for the period from October 21, 1996 to the earlier of (i) the Closing
Date or (ii) December 31, 1996. Such interest shall be payable on the earlier of
(i) the Closing Date or (ii) January 15, 1997.

      1.03  Further  Assurances.  Sellers  agree  that,  from  time to time,  at
Abraxas'  request and without  further  consideration,  Sellers will execute and
deliver such  additional  instruments of transfer and take such other actions as
Abraxas may require to more effectively transfer ownership of the Interest,  the
Notes and the ORI Options to Abraxas, as applicable.

      1.04 Closing.  The closing  ("Closing") of the  transactions  contemplated
hereby  shall take place at the  offices  of Cahill,  Gordon & Reindel,  80 Pine
Street,  New  York,  New York  10005 on the date that all of the  conditions  to
Closing set forth in Articles IV and V hereof have been  satisfied  or waived or
such other time and place as the  parties  hereto may agree.  The date,  as thus
determined,  on which  the  Closing  will be held is herein  referred  to as the
"Closing Date".

      1.05  Termination  of Advisory  Agreement.  At the  Closing,  the Advisory
Agreement  between the  Partnership  and State Street shall be  terminated,  and
Abraxas shall pay State Street an amount equal to the expenses incurred by State
Street pursuant to Section 9.01.


                                  ARTICLE II

                  REPRESENTATIONS AND WARRANTIES OF SELLERS

      Each of Acco, MBTA, MetLife, General Mills and State Street, severally for
itself,  and not jointly and  severally,  represents,  warrants  and agrees,  as
follows:

      2.01 Ownership of Interest.  (a) Acco is the lawful owner of the Interest,
free and clear of all liens, encumbrances, restrictions and claims of every kind
other  than  liens,  encumbrances,   restrictions  and  claims  related  to  the
Christiania  Loan. Acco has full legal right,  power and authority to enter into
this Agreement and to sell, assign, transfer and convey the Interest pursuant to
this  Agreement.  The sale by Acco to Abraxas of the  Interest  pursuant  to the
provisions of this Agreement will transfer to Abraxas good, valid and marketable
title  thereto,  free  and  clear  of  all  liens,  encumbrances,  restrictions,
mortgages, pledges, charges or claims of every kind (collectively, "Liens").

      (b) MBTA is the lawful  owner of the MBTA Note and the MBTA  Option,  free
and clear of all liens,  encumbrances,  restrictions  and claims of every  kind.
MBTA has full legal right,  power and authority to enter into this Agreement and
to sell, assign,  transfer and convey the MBTA Note and the MBTA Option pursuant
to this  Agreement.  The sale by MBTA to  Abraxas  of the MBTA Note and the MBTA
Option  pursuant to the  provisions of this  Agreement  will transfer to Abraxas
good, valid and marketable title thereto, free and clear of all Liens.

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0135432.01








      (c)  MetLife  is the  lawful  owner of the  MetLife  Note and the  MetLife
Option,  free and clear of all liens,  encumbrances,  restrictions and claims of
every kind. MetLife has full legal right, power and authority to enter into this
Agreement  and to sell,  assign,  transfer  and convey the MetLife  Note and the
MetLife Option pursuant to this Agreement. The sale by MetLife to Abraxas of the
MetLife Note and the MetLife Option pursuant to the provisions of this Agreement
will transfer to Abraxas good,  valid and  marketable  title  thereto,  free and
clear of all Liens.

      (d) General  Mills is the lawful  owner of the General  Mills Note and the
General Mills Option,  free and clear of all liens,  encumbrances,  restrictions
and  claims  of every  kind.  General  Mills  has full  legal  right,  power and
authority to enter into this Agreement and to sell, assign,  transfer and convey
the General Mills Note and the General Mills Option  pursuant to this Agreement.
The sale by General  Mills to Abraxas of the General  Mills Note and the General
Mills Option  pursuant to the  provisions  of this  Agreement  will  transfer to
Abraxas good, valid and marketable title thereto, free and clear of all Liens.

      2.02  Power  and  Authority.  Acco has the power  and  authority  to make,
execute,  deliver and perform this  Agreement,  and this Agreement has been duly
authorized and approved by all required  action.  State Street has the power and
authority to make, execute, deliver and perform this Agreement on behalf of each
of MBTA,  MetLife and General Mills, and this Agreement has been duly authorized
and approved by all required action of each of MBTA, MetLife and General Mills.

      2.03 Broker's or Finder's Fees. No agent, broker, person or firm acting on
behalf of the Sellers are, or will be, entitled to any commission or broker's or
finder's fees from any of the Sellers.

      2.04  Receipt of  Information.  Acco and State  Street  (acting on its own
behalf and on behalf of the SSR Investors)  acknowledge  the receipt of a letter
dated July 15, 1996 from Abraxas  relating to Portilla and copies of the reserve
report prepared by DeGoyler and MacNaughton relating to Portilla and Happy dated
June 30, 1996.  Each of Acco and State  Street  (acting on its own behalf and on
behalf of the SSR Investors) has had the opportunity to review such  information
and has had the opportunity to ask questions of and receive answers from Abraxas
concerning  the  Partnership,  Portilla  and  Happy  and the  future  plans  and
prospects thereof.  Each of Acco, MBTA, MetLife,  General Mills and State Street
is an  Accredited  Investor  (as  defined  in Rule  501  promulgated  under  the
Securities  Act of 1933, as amended).  Each of Acco and State Street  (acting on
its own behalf and on behalf of the SSR Investors) has engaged such professional
advisers  including,  without limitation,  legal, tax and petroleum  engineering
advisers,   as  it  deemed   necessary  in  connection  with  the   transactions
contemplated hereby.


                                

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0135432.01




                                   ARTICLE III

                           REPRESENTATIONS OF ABRAXAS

      Abraxas represents, warrants and agrees as follows:

      3.01 Existence and Good Standing of Abraxas. Abraxas is a corporation duly
organized,  validly existing and in good standing under the laws of the State of
Nevada.

      3.02 Power and Authority. Abraxas has the corporate power and authority to
make, execute,  deliver and perform this Agreement,  and this Agreement has been
duly authorized and approved by all required corporate action of Abraxas.

      3.03 Broker's or Finder's Fees. No agent, broker, person or firm acting on
behalf of Abraxas  is, or will be,  entitled  to any  commission  or broker's or
finder's fees from Abraxas.

      3.04 No Net Income.  The  Partnership  has not had any net taxable  income
since its inception.


                                  ARTICLE IV

                      CONDITIONS TO ABRAXAS' OBLIGATIONS

      All  obligations  of Abraxas to be discharged  under this Agreement at the
Closing are subject to the fulfillment,  prior to or at the Closing,  of each of
the following conditions, unless waived in writing by Abraxas prior to or at the
Closing:

      4.01 Truth of  Representations  and Warranties.  The  representations  and
warranties  of Acco,  the SSR  Investors  and  State  Street  contained  in this
Agreement  shall be true and correct on and as of the Closing Date with the same
effect as though such  representations and warranties had been made on and as of
such date and Acco, the SSR Investors and State Street shall have each delivered
to Abraxas a certificate, dated the Closing Date, to such effect.

      4.02 No Litigation  Threatened.  No action or proceedings  shall have been
instituted  or, to the best knowledge of Sellers,  threatened  before a court or
other  government body or by any public authority to restrain or prohibit any of
the transactions contemplated hereby.

      4.03  Proceedings.  All  proceedings  to be taken in  connection  with the
transactions  contemplated by this Agreement and all documents  incident thereto
shall be reasonably  satisfactory in form and substance to Abraxas,  and Abraxas
shall have received  copies of all such  documents and other  evidences as it or
its counsel may  reasonably  request in order to establish the  consummation  of
such transactions and the taking of all proceedings in connection therewith.


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      4.04 Mutual Release. Sellers and Abraxas shall have executed and delivered
a  Mutual  Release  in  substantially  the  form  of  Exhibit  "A"  hereto  (the
"Release").

      4.05 Documents and Instruments. Sellers shall have executed such documents
and instruments as may be reasonably  requested by Abraxas to effectively  sell,
transfer,  assign  and  convey the  Interest,  the Notes and the ORI  Options to
Abraxas.

      4.06  Financing.  Abraxas shall have received financing on such terms and
conditions as may be reasonably satisfactory to Abraxas.


                                  ARTICLE V

                     CONDITIONS TO SELLERS'S OBLIGATIONS

      All  obligations  of Sellers to be discharged  under this Agreement at the
Closing are subject to the fulfillment,  prior to or at the Closing,  of each of
the following conditions, unless waived in writing by Sellers prior to or at the
Closing:

      5.01 Truth of  Representations  and Warranties.  The  representations  and
warranties of Abraxas  contained in this Agreement  shall be true and correct on
and as of the Closing  Date with the same effect as though such  representations
and  warranties  had been made on and as of such date,  and  Abraxas  shall have
delivered to Sellers a certificate, dated the Closing Date, to such effect.

      5.02 No Litigation  Threatened.  No action or  proceeding  shall have been
instituted  or, to the best knowledge of Abraxas,  threatened  before a court or
other  government body or by any public authority to restrain or prohibit any of
the transactions contemplated hereby.

      5.03  Proceedings.  All  proceedings  to be taken in  connection  with the
transactions  contemplated by this Agreement and all documents incident thereto,
shall be  reasonably  satisfactory  in form and  substance  to  Sellers  and its
counsel,  and Sellers shall have received copies of all such documents and other
evidences as it or its counsel may reasonably  request in order to establish the
consummation  of  such  transactions  and  the  taking  of  all  proceedings  in
connection therewith.

      5.04 Mutual Release. Sellers and Abraxas shall have executed and delivered
the Release.

      5.05 Documents and Instruments.  Abraxas shall have executed and delivered
such  documents  and  instruments  as may be  reasonably  requested  by  Acco to
effectuate the assumption of the  Christiania  Loan by Abraxas and, in the event
that  Abraxas  does not  repay the  Christiania  Loan and  assume  all of Acco's

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0135432.01







obligations  under the Loan  Papers  except as set forth in Section  9.01 hereof
substantially   simultaneously   with  the   consummation  of  the  transactions
contemplated  hereby,  Abraxas  shall  have  obtained  the  release  of  Acco by
Christiania.


                                  ARTICLE VI

                                  COVENANTS

      6.01 Reasonable Efforts. Abraxas will use its reasonable efforts to obtain
the necessary  financing  through a private  placement of debt  securities to be
closed on or before  September  30,  1996.  If Abraxas is unable to complete the
offering by September 30, 1996, Abraxas agrees to continue to use its reasonable
efforts to pursue alternative  financing  arrangements and, in all events,  will
attempt to complete the purchase of the Interest,  the Notes and the ORI Options
no later than December 31, 1996.

      6.02 Public Announcements.  Upon execution and delivery of this Agreement,
Abraxas  will issue a press  release  reasonably  satisfactory  to  Abraxas  and
Sellers. Otherwise, none of the parties hereto shall, prior to the Closing, make
any public announcement or disclosure relating to the transactions  contemplated
hereby without the prior consent of each other party hereto; provided,  however,
that each party shall consult with the other in advance of making any disclosure
required by law,  but the  agreement  of the other  parties  hereto shall not be
required.

      6.03 Pre-Closing Operations. Prior to the Closing, Abraxas will contribute
to the  Partnership  all monies  necessary  for the  Partnership  (a) to pay its
operating expenses and (b) to make the minimum distributions  necessary for Acco
to make required  payments on the  Christiania  Loan;  provided,  however,  that
Abraxas  shall not be obligated to make  contributions  pursuant to this Section
6.03 after December 31, 1996.


                                 ARTICLE VII

                  TAX MATTERS, DISTRIBUTIONS AND ALLOCATIONS

      7.01 Liquidation and/or Sale of Interest. For federal income tax purposes,
it is the intention of the parties that the purchase and sale of the Interest be
treated as a sale of Acco's interest in the Partnership pursuant to Sections 741
of Subchapter K of the Internal Revenue Code of 1986, as amended.

      7.02  Allocations of Profits and Losses.  Abraxas and Acco agree that Acco
shall be  allocated  its  pro-rata  share (in  accordance  with  Acco's  Capital
Percentage  and  Capital  Ratio,  as  such  terms  are  defined  in the  limited
partnership  agreement  of  the  Partnership)  of the  Partnership's  cumulative
profits  and/or  losses  for the  portion  of the 1996  taxable  year  that were
generated from March 20, 1996 to and including the Closing Date.

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      7.03 Tax Returns and Information Statements.  Abraxas shall be responsible
for the preparation and timely filing of the Partnerships income tax returns for
the 1996 calendar year including, but not limited to, any information statements
related  to the sale  and/or  liquidation  of the  Interest.  Abraxas  agrees to
provide to Acco, in a timely fashion,  any information  reasonably  requested by
Acco in order for Acco to accurately report and reflect the sale of the Interest
on Acco's 1996 income tax return including, but not limited to, the reporting of
Acco's proportionate share of profits and/or losses from the Partnership.


                                 ARTICLE VIII

                   SURVIVAL OF REPRESENTATIONS; INDEMNITY;
                           LIMITATION OF LIABILITY

      8.01 Survival of  Representations.  The  representations and warranties of
each of the  parties  hereto  contained  in this  Agreement  shall  survive  the
purchase and sale of the  Interest,  the Notes and the ORI Options  contemplated
hereby.

      8.02  Indemnification  by  the  Sellers  and  Management.   Sellers  agree
severally,  and not jointly and  severally,  to indemnify and hold Abraxas,  its
directors,  officers,  employees and agents  harmless  from  damages,  losses or
expenses (net of any insurance proceeds)  (collectively,  "Damages") suffered or
paid,  directly  or  indirectly,  by Abraxas as a result of any and all  claims,
demands,  suits,  causes  of  action,  proceedings,  judgments  and  liabilities
(whether   asserted  directly  or  as  a  common  law  or  statutory  claim  for
contribution or indemnity),  including,  without limitation,  reasonable counsel
fees and costs  incurred  in  litigation  or  otherwise,  assessed,  incurred or
sustained  by or  against  any of them with  respect  to or  arising  out of the
failure of any  representation  or warranty made by Sellers in this Agreement to
be true and correct in all respects as of the date of this  Agreement  and as of
the Closing Date or the breach of any covenant made by the Sellers hereunder.

      8.03  Indemnification  by Abraxas.  Abraxas  agrees to indemnify  and hold
Sellers  harmless from Damages  suffered or paid,  directly or indirectly,  as a
result of any and all claims,  demands,  suits,  causes of action,  proceedings,
judgments  and  liabilities,  including  reasonable  counsel  fees  incurred  in
litigation  or otherwise,  assessed,  incurred or sustained by or against any of
them with  respect to or arising  out of the  failure of any  representation  or
warranty  made by  Abraxas  in this  Agreement  to be true  and  correct  in all
respects  as of the date of this  Agreement  and as of the  Closing  Date or the
breach of any covenant made by Abraxas hereunder.

      8.04 Notice of Claim. If indemnification pursuant to Sections 8.02 or 8.03
is sought,  the indemnified party shall give notice to the indemnifying party of
an event giving rise to the  obligation  to  indemnify,  allow the  indemnifying
party to assume and  conduct  the  defense of the claim or action  with  counsel
reasonably  satisfactory  to the  indemnified  party,  and  cooperate  with  the
indemnifying party in the defense thereof; provided,  however, that the omission
to give such notice to the indemnifying party shall not relieve the indemnifying

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party from any liability which it may have to the indemnified  party,  except to
the extent that the indemnifying party is prejudiced by the failure to give such
notice. The indemnified party shall have the right to employ separate counsel to
represent the indemnified  party if the indemnified  party is advised by counsel
that a conflict of interest makes it advisable for the  indemnified  party to be
represented  by separate  counsel and the  reasonable  expenses and fees of such
separate counsel shall be paid by the indemnifying party. If the party obligated
to  indemnify  and hold the other  harmless  wrongfully  refuses  to assume  the
defense of the party seeking  indemnification,  the party  refusing to indemnify
shall be  responsible,  for all legal and other  expenses  incurred by the other
party in connection  with the  investigation  or defense of such claim or action
including, without limitation, expenses incurred in enforcing such obligation to
indemnify.


                                  ARTICLE IX

                                MISCELLANEOUS

      9.01  Expenses.  The parties  hereto  shall pay all of their own  expenses
relating to the transactions contemplated by this Agreement,  including, without
limitation,  the fees and  expenses of their  respective  counsel and  financial
advisers; provided, however, Abraxas shall pay all filing and recording fees and
expenses in connection with the purchase and sale of the Interest, the Notes and
the ORI  Options.  Notwithstanding  anything to the  contrary  set forth in this
Agreement,  Acco shall be responsible for the fees and expenses,  including fees
and expenses of counsel,  of Christiania  incurred in connection with the Credit
Agreement and the transactions  contemplated  hereby up to a maximum of $25,000;
provided,  however,  that if Christiania's fees and expenses exceed $25,000, the
parties  hereto agree to negotiate  in good faith  regarding  the payment of the
fees and expenses in excess of $25,000.

      9.02 Governing Law. The interpretation and construction of this Agreement,
and all matters relating  hereto,  shall be governed by the laws of the State of
Texas.

      9.03  Captions.  The  Article  and  Section  captions  used herein are for
reference  purposes  only,  and  shall  not in any way  affect  the  meaning  or
interpretation of this Agreement.

      9.04  Notices.  Any notice or other  communications  required or permitted
hereunder  shall  be  sufficiently  given  if  delivered  in  person  or sent by
registered or certified mail, postage prepaid, if to:

      If to Abraxas:

            Abraxas Petroleum Corporation
            500 North Loop 1604 East, Suite 100
            San Antonio, Texas  78232

                                     9


0135432.01






            Attention:  Robert L. G. Watson

      With a copy to:

            Cox & Smith Incorporated
            112 E. Pecan Street, Suite 1800
            San Antonio, Texas  78205
            Attention:  Steven R. Jacobs

      If to Sellers:

            State Street Research Energy, Inc.
            One Financial Center
            31st Floor
            Boston, MA  02109
            Attention:  Tom Moore

      With a copy to:

            Mintz, Levin, Cohen, Ferris, Glovsky and Popeo, P.C.
            One Financial Center
            Boston, Massachusetts  02111
            Attention:  Thomas J. Kelly

            and

            Baker & Botts, L.L.P.
            One Shell Plaza
            910 Louisiana
            Houston, Texas  77002-4995
            Attention:  Frank W. R. Hubert, Jr.

or such other  address as shall be furnished  in writing by any such party,  and
such notice or  communication  shall be deemed to have been given as of the date
so delivered or mailed.

      9.05 Parties in Interest. This Agreement may not be transferred, assigned,
pledged or hypothecated by any party hereto other than by operation of law. This
Agreement  shall be binding  upon and shall  inure to the benefit of the parties
hereto and their respective  heirs,  executors,  administrators,  successors and
assigns.

      9.06  Counterparts.  This  Agreement  may  be  executed  in  two  or  more
counterparts, all of which taken together shall constitute one instrument.

      9.07 Entire  Agreement.  This  Agreement,  including  the other  documents
referred to herein which form a part hereof or any other written agreements that

                                     10


0135432.01







the parties enter into pursuant to or relating to the transactions  contemplated
by this Agreement,  contains the entire understanding of the parties hereto with
respect to the subject  matter  contained  herein and  therein.  This  Agreement
supersedes  all prior  agreements  and  understandings  between the parties with
respect to such subject  matter.  All exhibits and schedules  referred to herein
and attached hereto are incorporated herein by reference.

      9.08 Amendments.  This Agreement may not be changed orally, but only by an
agreement in writing signed by all of the parties hereto.

      9.09  Severability.  In case any provision in this Agreement shall be held
invalid, illegal or unenforceable,  the validity, legality and enforceability of
the  remaining  provisions  hereof  will not in any way be  affected or impaired
thereby.

      9.10 Third  Party  Beneficiaries.  Each  party  hereto  intends  that this
Agreement  shall not  benefit  or  create  any right or cause of action in or on
behalf of any person other than the parties hereto.

      9.11   Arbitration.   The  parties   hereto   agree  that  all   disputes,
controversies  or claims that may arise among them  (including  their agents and
employees)  including,  without  limitation,  any dispute,  controversy or claim
arising out of or  relating to this  Agreement  or any other  agreement,  or the
breach,  termination  or  invalidity  thereof,  whether  entered into or arising
prior,  on or  subsequent  to the  date  hereof,  shall  be  submitted  to,  and
determined  by,  binding  arbitration.  Such  arbitration  shall be conducted in
accordance  with the terms of Section 12.9 of the  Partnership  Agreement of the
Partnership.

      IN WITNESS WHEREOF,  the parties hereto have executed this Agreement to be
effective as of the day and year first above written.


                              ABRAXAS PETROLEUM CORPORATION



                              By:
                              Robert L. G. Watson,
                               Chairman of the Board, President
                               and Chief Executive Officer



                              




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                              ACCO, LLC

                              By:
                              Title:



                              STATE STREET RESEARCH ENERGY, INC.,
                                 Creditors Representative of Massachusetts
                                 Bay Transportation Authority Retirement
                                 Fund, Metropolitan Life Insurance Company
                                 Separate Account No. 175 and The General
                                 Mills, Inc. Master Trust: Pooled Real Estate
                                 Fund


                              By:
                              Title:


                              STATE STREET RESEARCH ENERGY, INC.
   

                              By:
                              Title:























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0135432.01