EXHIBIT 10.65.1

                               FIRST AMENDMENT TO

                           JOINT DEVELOPMENT AGREEMENT

     This First Amendment (the  "Amendment")  to that certain Joint  Development
Agreement  (the  "Agreement")  entered  into dated  effective as of February 10,
1999, by and between BRIGHAM OIL & GAS, L.P.  ("Brigham")  and ASPECT  RESOURCES
LLC  ("Aspect")   (Brigham  and  Aspect  being  sometimes   referred  to  herein
individually as a "Party" and collectively as the "Parties"), is dated effective
as of May 1, 1999.

                                       I.
                                  DEFINED TERMS

     Unless a term is specifically  defined in this  Amendment,  all capitalized
terms shall have the defined meaning set forth in the Agreement.

                                       II.
                        AMENDMENT TO EXPAND SUBJECT LANDS

     The Parties  hereby agree that Exhibit A to the  Agreement is replaced with
Exhibit A which is attached hereto and incorporated herein for all purposes.

                                      III.
                       AMENDMENT TO PROVIDE FOR AVO COSTS

     In addition  to and without  limitation  of its other  funding  obligations
under  the  Agreement,  Aspect  hereby  agrees  to pay  Brigham  for the  actual
third-party  costs that are  incurred to  purchase  processed  amplitude  versus
offset ("AVO") data covering approximately 65.64 square miles of land within the
Subject Lands which is generally outlined on Exhibit B attached hereto.  Brigham
shall not be required to reimburse Aspect for any of the costs described in this
Article III,  regardless of whether or not Brigham exercises its partial payback
election which is set forth in Article II of the Agreement.

     The Parties  estimate that the AVO processing and analysis costs will total
approximately  $400 per square mile.  Following  Aspect's  receipt of an invoice
from  Brigham,  Aspect  shall  promptly  reimburse  Brigham  for the total costs
incurred to acquire the AVO data,  but in any event such  payment  shall be made
within 30 days of Aspect's receipt of the invoice.

     In return for Aspect funding the above-described  AVO costs,  Brigham shall
interpret the resulting AVO data and, subject to the restrictions that have been
imposed by the seismic  contractor or other party  licensing the seismic data to
Brigham, Brigham shall immediately share the results of such interpretation with
Aspect during the AMI Term.


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     ASPECT  UNDERSTANDS  AND AGREES THAT BRIGHAM  MAKES NO  REPRESENTATIONS  OR
WARRANTIES  OF ANY  KIND  AS TO THE  AVO  DATA OR  INTERPRETATIONS  THAT  MAY BE
PROVIDED TO ASPECT BY BRIGHAM, INCLUDING WITHOUT LIMITATION, THEIR FITNESS FOR A
PARTICULAR  PURPOSE,  MERCHANTABILITY OR ACCURACY,  AND BRIGHAM HEREBY DISCLAIMS
ANY AND ALL SUCH REPRESENTATIONS OR WARRANTIES,  AND ANY USE OF SUCH AVO DATA OR
INTERPRETATIONS  BY ASPECT,  OR ANY ACTION TAKEN BY ASPECT SHALL BE BASED SOLELY
ON THEIR OWN JUDGMENT, AND NEITHER BRIGHAM , OR ITS SUCCESSORS OR ASSIGNS, SHALL
BE LIABLE OR  RESPONSIBLE  TO ASPECT OR ITS  SUCCESSOR  OR ASSIGNS FOR ANY LOSS,
COST,  DAMAGES,  OR EXPENSE  WHATSOEVER,  INCLUDING  INCIDENTAL OR CONSEQUENTIAL
DAMAGES,  INCURRED OR SUSTAINED AS A RESULT OF THE USE OF OR RELIANCE  UPON SUCH
AVO DATA OR  INTERPRETATIONS,  REGARDLESS  OF WHETHER  OR NOT SUCH  LOSS,  COST,
DAMAGE  OR  EXPENSE  IS FOUND  TO  RESULT  IN WHOLE OR IN PART  FROM THE SOLE OR
CONCURRENT NEGLIGENCE OR OTHER FAULT OF BRIGHAM.

                                       IV.
                                  MISCELLANEOUS

     Except as  expressly  modified  herein,  all other  terms,  conditions  and
provisions of the Agreement shall remain in full force and effect.

     This  Amendment  may be executed in  multiple  counterparts,  each of which
shall be binding  upon the signing  Party or Parties  thereto as fully as if all
Parties  had  executed  one  instrument,  and  all of  such  counterparts  shall
constitute one and the same  instrument.  If  counterparts of this Amendment are
executed,  the signatures of the Parties,  as affixed hereto, may be combined in
and treated and given effect for all purposes as a single  instrument.  However,
anything to the contrary contained herein notwithstanding,  this Amendment shall
not be binding upon any Party hereto  unless and until all of the Parties sign a
counterpart thereof.

     IN WITNESS  WHEREOF this  Amendment is executed by the Parties on the dates
set forth opposite their  respective  signatures  below but is effective for all
purposes as of the date first set forth above.


BRIGHAM OIL & GAS, L.P.                     ASPECT RESOURCES LLC
by Brigham, Inc.                            by Aspect Management Corporation
its Managing General Partner                its Manager


By: /s/ Ben M. Brigham                      By:  /s/ Alex Campbell
    -------------------------------------      ---------------------------------
Ben M. Brigham, President                   Alex Campbell, Vice President

Date:          9/28/99                      Date:          9/30/99
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