Document:

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.

<PAGE>

     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
      -----------------------------------        -------------------------------ACQUISITION AND PARTICIPATION AGREEMENT

     This Acquisition and Participation Agreement (this "Agreement") is executed
as of the 21st day of  October,  1999,  by Brigham Oil & Gas,  L.P.  ("BOG") and
Aspect Resources LLC ("Aspect") (BOG and Aspect are herein  collectively  called
"Parties"   or   "Participants"   and   individually   called  a  "Party"  or  a
"Participant").

                                    Recitals:

(a) BOG currently owns  interests in and to the oil and gas leases  described in
Exhibit A hereto (such leases, insofar only as they cover the lands described in
Exhibit A hereto,  and further as  heretofore  amended or  extended,  are herein
called the "BOG Leases") and proprietary  interpretations  of certain geological
and/or geophysical information relating to the AMI Lands, as hereinafter defined
(the "G & G Data").

(b) Aspect  desires to acquire from BOG,  and BOG agrees to assign to Aspect,  a
share of the  undivided  interest  of BOG in the BOG Leases and the right to use
the G & G Data, all upon and subject to the terms and conditions hereof.

(c) BOG and  Aspect  further  desire to  establish  an area of  mutual  interest
covering  all of the AMI  Lands,  and  agree  upon a scheme  of joint  operation
thereof, all upon and subject to the terms and conditions hereof.

                                 Defined Terms:

     "Acquired Interest" shall have the meaning assigned to it in Section 2.2.

     "Affiliate" means (a) any Person directly or indirectly owning, controlling
or holding with power to vote 50% or more of the outstanding  voting  securities
of any other  Person,  (b) any  Person 50% or more of whose  outstanding  voting
securities  are directly or indirectly  owned,  controlled or held with power to
vote by any other Person,  (c) any Person  directly or  indirectly  controlling,
controlled  by or under  common  control  with  any  other  Person,  and (d) any
officer,  director,  partner or  sanguinal or affinal kin of any other Person or
any  Person  described  in  subsection  (c) of this  paragraph;  as used in this
definition,  the term "Person" means an individual, an estate, a corporation,  a
partnership, an association, a joint stock company, a limited liability company,
a joint venture, a trust and any other legally recognized entity.

     "AMI" shall have the meaning assigned to it in Section 2.1(a).

     "AMI Lands" shall mean the lands described in Exhibit A hereto.

     "AMI Party" and "AMI Parties" shall have the meaning(s) assigned to them in
Article II.

     "AMI Term" shall have the meaning assigned to it in Section 2.1(b).

                                       1
<PAGE>

     "BOG Leases" has the meaning assigned to it in the Recitals.

     "BOG/Aspect  Assignment"  shall have the meaning  assigned to it in Section
3.1.

     "Business Days" means all days of the week, other than Saturday,  Sunday or
any legal holiday on which commercial banks in Texas are closed for business.

     "Code" shall have the meaning assigned to it in Section 1.1.

     "Dickson Prospect" has the meaning assigned to it in Section 4.1.

     "Effective  Date" shall have the meaning  assigned to it in the  BOG/Aspect
Assignment.

     "Farm-In"  means a farm-in  or any other  agreement,  other than a Lease or
Option,  that  affords  the  holder  the right to earn or  otherwise  acquire an
interest  in oil,  gas or  other  minerals,  whether  leasehold,  fee,  royalty,
overriding royalty or otherwise.

     "G & G Data" has the meaning assigned to it in the Recitals.

     "Initial Well" means,  as to any  particular  Prospect Area, the first well
drilled hereunder in such Prospect Area.

     "JOA" means an  Operating  Agreement  in  substantially  the form  attached
hereto as Exhibit E, with each Prospect Area to be covered by a separate JOA.

     "Lease"  means an oil, gas and/or  mineral  lease,  fee interest or mineral
servitude  affording  the holder the right to explore  for,  develop and produce
oil, gas and/or other minerals.

     "Option"  means an agreement  affording  the holder an option,  exercisable
upon certain circumstances, to acquire a Lease.

     "Ownership Interest Share" or "Participation Share" shall mean, relative to
any particular Prospect Area and unless expressly provided otherwise herein, the
respective  interests  set out for each of BOG and  Aspect in  Exhibit C hereto;
provided  that,  in the  event  fewer  than  all of the  AMI  Parties  elect  to
participate  in any  particular  Acquired  Interest  within a Prospect Area, the
Ownership Interest Shares and Participation  Shares shall be adjusted as to such
Acquired Interest as more particularly described in Article II, below.

     "Participant(s)"  shall have the meaning assigned to it in the introductory
paragraph.

     "Party"  shall  have  the  meaning  assigned  to  it  in  the  introductory
paragraph.

     "Prospect Areas" means all of the lands described in Parts One through Four
of  Exhibit  A  hereto,  with the lands  described  in any one of such  parts of
Exhibit A being individually called a "Prospect Area".

                                       2
<PAGE>

     "Subsequent Well" means, relative to any particular Prospect Area, any well
drilled hereunder after the drilling of the Initial Well for such Prospect Area.

                                    ARTICLE I
                             Relationship of Parties

     Section 1.1. Several Liability. The liabilities, covenants and undertakings
of the Parties are  several,  not joint or  collective.  Under no  circumstances
shall any Party be  considered a fiduciary  to any other Party,  nor shall there
otherwise be a  confidential,  special or other  relationship  of trust  created
between any one or more Parties under or by virtue of this Agreement.

     Section  1.2. No  Partnership.  It is not the  intention  of the Parties to
create,  nor shall this  Agreement  be deemed as  creating a joint  venture or a
mining,  tax or other  partnership  or  association  or to otherwise  render the
Parties liable as co-venturers or partners.  However,  if for federal income tax
purposes,  this  Agreement  and  the  operations  hereunder  are  regarded  as a
partnership,  each  Party  thereby  affected  elects  to be  excluded  from  the
application of all of the provisions of Subchapter "K," Chapter 1, Subtitle "A,"
of the Internal Revenue Code of 1986, as amended (hereinafter referred to as the
"Code"),  as  permitted  and  authorized  by  Section  761 of the  Code  and the
regulations  promulgated  thereunder.  Should there be any requirement that each
Party hereby  affected give further  evidence of this election,  each such Party
shall execute such  documents and furnish such other evidence as may be required
by the federal  Internal Revenue Service or as may be necessary to evidence this
election.  No Party shall give any notice or take any other action  inconsistent
with the election  made hereby.  In making the  foregoing  election,  each Party
states that the income  derived by such Party from  operations  hereunder can be
adequately determined without the computation of partnership taxable income.

                                   ARTICLE II
                             Area of Mutual Interest

     Section 2.1. Establishing an Area of Mutual Interest.

     (a) BOG and Aspect  hereby  establish  an area of mutual  interest  ("AMI")
which shall  encompass the AMI Lands (as used in this Article II, BOG and Aspect
are herein collectively called the "AMI Parties" and individually called an "AMI
Party").

     (b) The AMI shall remain in force for a term of three years,  unless sooner
terminated by mutual agreement of the Parties (the "AMI Term ").

                                       3
<PAGE>

     Section 2.2.  Notification and Response  Procedures.  In the event that any
AMI Party  acquires or proposes to acquire,  at any time during the AMI Term, by
purchase,  exchange,  gift or otherwise,  a Lease,  Option or a Farm-In covering
lands,  any part of which are located  within the AMI (such Leases,  Options and
Farm-Ins,  insofar  and only  insofar as they cover  lands  within the AMI,  are
herein called  "Acquired  Interests"),  such AMI Party (the  "Acquiring  Party")
shall notify the other AMI Parties (the "Notified Parties"), in writing, of such
acquisition or proposed acquisition and the initial  consideration paid or to be
paid for the Acquired  Interest.  Each Notified Party shall,  within thirty (30)
days  after  receipt  of such a notice  from the  Acquiring  Party,  notify  the
Acquiring  Party,  in  writing,   whether  it  wishes  to  participate  in  such
acquisition;  provided that failure to respond within the time and in the manner
set forth above shall be deemed to be an  election  to not  participate  in such
acquisition.   However,  if  a  Notified  Party  reasonably  desires  additional
information  with respect to an Acquired  Interest  before it makes its election
whether or not to participate in the acquisition of an Acquired  Interest,  such
Notified  Party may notify the Acquiring  Party in writing  within  fifteen (15)
days of its receipt of the Acquiring Party's notice, detailing in such notice to
the  Acquiring  Party the  additional  information  reasonably  desired  by such
Notified  Party,  and such Notified  Party shall have fifteen (15) days from the
date of its receipt of the additional  information  it has reasonably  requested
from the Acquiring Party in which to make its election whether to participate in
the acquisition of the Acquired  Interest.  Payment for a Participating  Party's
share of an  Acquired  Interest  is due within 30 days  after the  participation
election  was due.  Failure to timely make any portion of such payment as is not
in good faith dispute  shall result in a forfeiture of the right to  participate
in same. In the event a rig is drilling  within one mile of the Prospect Area to
which any  particular  Acquired  Interest  relates,  the period  within which an
election  must be made shall be reduced from 30 days to 48 hours  (exclusive  of
weekends and legal  holidays).  Notice of the 48-hour election data shall be set
out in the election  notification  notice.  Anything to the  contrary  contained
herein notwithstanding,  a sale, exchange, gift or other disposition of any part
of an AMI Party's  interest in any Leases,  Options or Farm-Ins to any other AMI
Party hereto shall not be deemed to be an Acquired Interest for purposes of this
Section 2.2,  and this  Section 2.2 shall not apply to any such sale,  exchange,
gift or other disposition.

     Section 2.3. Effect of a Party's Election Regarding  Participation.  Should
all of the AMI Parties elect to  participate  in an  acquisition  of an Acquired
Interest,  upon payment of its Ownership Interest Share of the acquisition costs
(or to the extent not yet due, upon  agreement to pay when due),  each AMI Party
shall be entitled to its Ownership Interest Share of the Acquired Interest,  and
the  Acquiring  Party shall execute an  Assignment,  in  substantially  the form
attached hereto as Exhibit B, in favor of the Notified Parties. If any AMI Party
elects not to  participate in any particular  Acquired  Interest,  the Ownership
Interest Share for each AMI Party electing to participate  shall,  unless all of
the  Parties  electing  to  participate  agree  otherwise,   be  the  percentage
determined by dividing, for each participating AMI Party, the Ownership Interest
Share  otherwise   applicable  (if  all  Parties  had   participated)   to  such
participating  AMI  Party  by  the  total  Ownership   Interest  Share  for  all
participating  AMI Parties;  the Acquiring  Party shall then execute in favor of
those Notified  Parties  electing to  participate  in such Acquired  Interest an
Assignment,  in  substantially  the form  attached  hereto  as  Exhibit  B, with
appropriate adjustments for relative quantum of interest being transferred.  The
AMI Parties  that  acquire  part of a  non-participating  AMI Party's  Ownership
Interest Share in an Acquired  Interest shall be responsible for a proportionate
share of such  non-participating AMI Party's share of the costs of such Acquired
Interest. An Acquired Interest shall be subject to one or more JOA's,  depending
upon the Prospect Area(s) within which such Acquired  Interest is situated,  all
as more  particularly  described  in Section  2.5,  below.  Notwithstanding  any
provision hereof to the contrary,  in the event an Acquired Interest also covers
lands  outside the AMI,  the  Acquiring  Party shall be  obligated  to offer the
Notified  Parties  the right to  participate  in the  subject  acquisition  only
insofar as it relates to the Acquired  Interest  (i.e., as limited to the extent
it covers lands in the AMI). In the event the Acquiring Party voluntarily elects
to  authorize  a  Notified  Party  or  Parties  to  participate  in  the  entire
acquisition  (i.e.,  insofar as it covers lands within and without the AMI), any
lands outside the AMI shall not become a part of the AMI and shall not otherwise
be subject to the provisions of the Agreement.

                                       4
<PAGE>

     Section  2.4.  Election as to  Participation  in  Maintenance  or Extension
Costs. In the event  maintenance or extension costs are incurred with respect to
an Acquired  Interest,  each AMI Party that owns an Ownership  Interest Share in
such  Lease,  Option  or  Farm-In  shall  have the  right to  elect  whether  to
participate  in such  maintenance  or  extension  cost for the Lease,  Option or
Farm-In,  utilizing the same  procedures set forth in Sections 2.2 and 2.3 above
for Acquired Interests;  provided,  however, that in the event that an AMI Party
elects not to  participate in a maintenance  or extension  cost,  such AMI Party
shall promptly  relinquish and assign to the AMI Parties  participating  in such
maintenance  or  extension  cost  (in  proportion  to their  relative  Ownership
Interest Shares) all of such  non-participating  AMI Party's Ownership  Interest
Share in the Acquired  Interest that would have been relinquished or lost if the
maintenance or extension cost had not been paid.

     Section 2.5. JOA's.  Immediately upon execution hereof,  each Prospect Area
within which both AMI Parties own a Lease,  Option and/or Farm-In interest shall
be deemed subject to a separate JOA in substantially the form attached hereto as
Exhibit E. Within  thirty (30) days after  written  request by either AMI Party,
the other AMI Party shall  formally  execute a JOA covering  any  Prospect  Area
within which both AMI Parties own a Lease,  Option or Farm-In  interest.  Aspect
agrees  that BOG shall be named as the  Operator  under  each JOA.  In the event
there is any  irreconcilable  conflict between the terms hereof and the terms of
any JOA, the terms hereof shall control.

                                   ARTICLE III
     Acquisition by Aspect of Interest in BOG Leases and Use of G & G Data.

     Section 3.1.  Conveyance  and Payment of  Consideration.  Immediately  upon
execution of this Agreement,  BOG shall execute in favor of Aspect an Assignment
in  substantially  the  form  attached  hereto  as  Exhibit  D (the  "BOG/Aspect
Assignment"),  and  Aspect  shall pay over to BOG the sum of  $397,890,  as full
consideration for the properties  covered thereby (herein and therein called the
"Interests").  For a period of thirty (30) days from and after the date  hereof,
BOG shall,  at its sole  discretion,  have the right to remove the Prospect Area
described  in Part Four of Exhibit A hereto  ("Saenz  Prospect  Area")  from the
operation of this Agreement;  failure to affirmatively so elect removal shall be
deemed an election to maintain the Saenz  Prospect Area under  operation of this
Agreement.  If BOG elects to remove the Saenz  Prospect  Area from  operation of
this  Agreement,  (a) Aspect shall  reassign to BOG all of its right,  title and
interest that was acquired pursuant hereto in the Saenz Prospect Area,  together
with its right to review  and use any G & G Data  related  thereto,  and (b) BOG
shall immediately  refund to Aspect the sum of $46,800 (being the portion of the
consideration  allocable  to the Saenz  Prospect  Area and its  allocable  G & G
Data), and thereafter the Saenz Prospect Area shall no longer be included in the
AMI Lands or otherwise subject to this Agreement. The Prospect Area described in
Part Two of Exhibit A hereto (the Geissen  Prospect  Area") was  prepared  based
upon the best  information  currently  available to BOG. In the event,  however,
that the Geissen  Prospect Area is reconfigured  under the terms of that certain
Geophysical Exploration Agreement, SW Danbury Project, dated as of July 1, 1996,
such that BOG and Aspect are  collectively  entitled  to less than a 40% working
interest in the Initial Well to be drilled in the Geissen Prospect Area,  Aspect
shall have the right to remove the Geissen  Prospect  Area from the operation of
this Agreement;  failure to  affirmatively so elect removal within 10 days after
the date the prospect  designation becomes effective shall be deemed an election
to maintain the Geissen Prospect Area under this Agreement.  If Aspect elects to
remove the Geissen  Prospect Area from operation of this  Agreement,  (a) Aspect
shall  reassign  to BOG all of its  right,  title and  interest  in the  Geissen
Prospect  Area that was acquired by Aspect  pursuant  hereto,  together with its
right  to  review  and use any G & G Data  related  thereto,  and (b) BOG  shall
immediately  refund to Aspect  the sum of  $132,490  (being  the  portion of the
consideration  allocable to the Geissen  Prospect  Area and its  allocable G & G
Data),  and thereafter the Geissen  Prospect Area shall no longer be included in
the AMI Lands or otherwise subject to this Agreement.

                                       5
<PAGE>

     Section 3.2 Seismic  Licenses.Notwithstanding  any provision  hereof to the
contrary, neither this Agreement in general nor the defined term "G & G Data" in
particular  is intended to or shall be construed to cover any seismic or related
data that is covered by a license or similar agreement in favor of BOG, it being
recognized that  interpretations of such data created by or on behalf of BOG are
not covered by any such license or similar agreement and thus are covered hereby
and expressly included in the defined term "G & G Data".

     Section 3.3 G & G Data. With respect to any G & G Data covered hereby,  the
following provisions shall apply:

     (a)  During  the term of this  Agreement,  Aspect  shall  have the right to
review and use the G & G Data for its own  purposes in  evaluating  the Prospect
Areas; legal ownership of such G & G Data,  however,  shall remain solely vested
in BOG.

     (b) Aspect shall keep and maintain the G & G Data strictly confidential and
shall not  disclose  any G & G Data to any third  party,  except (i)  employees,
officers or directors  of any such Party or  employees,  officers,  directors or
consultants  of any  lender  or  other  supplier  of  material  debt or  similar
proceeds,  (ii) any third parties (including without limitation any governmental
authority)  to whom such G & G Data must be  disclosed  pursuant  to  applicable
laws,  rules,  orders and/or  regulations,  (iii) third parties  engaged in bona
fide, good faith  negotiations with any such Party to (A) acquire or be acquired
by such Party(by merger, consolidation or stock acquisition), (B) acquire all or
substantially all of the assets of such Party, including all of its interests in
the AMI  Lands,  (C)  participate  with  such  Party in the  exploration  and/or
development  of the  AMI  Lands,  (D)  acquire  all or a part  of  such  Party's
interests under this Agreement and in the AMI Lands, (E) consult with such Party
in order to aid in  analyzing  or  interpreting  the G & G Data or in  preparing
reserve estimates, (F) invest in such Party by acquiring a material part of such
Party's stock (or by having a material part of such third party's stock acquired
by such Party) or by  advancing  material  loan funds or some other form of debt
proceeds,  and/or (G)  farm-out  or  otherwise  transfer  to such Party all or a
portion of the third party's interest in the AMI Lands;  provided that, prior to
any such  disclosure,  the disclosee  must execute a  Confidentiality  Agreement
wherein it expressly  recognizes  and agrees to be bound by the  confidentiality
provisions hereof.

     (c) Aspect hereby releases BOG from any liability or obligations arising in
relation  to the G & G Data  (or  the  processing  or  interpretation  thereof),
WHETHER  OR NOT ANY SUCH  LIABILITY  OR  OBLIGATIONS  AROSE  OR ARISE  OUT OF OR
OTHERWISE  IN  RELATION  TO  BOG'S  SOLE  OR  CONCURRENT  NEGLIGENCE  OR  STRICT
LIABILITY.

                                       6
<PAGE>

     (d) THE PARTIES  UNDERSTAND  THAT NONE OF BOG AND ITS OFFICERS,  EMPLOYEES,
AGENTS,  CONSULTANTS AND SHAREHOLDERS  (hereinafter  collectively referred to as
the "BOG GROUP") MAKE ANY  REPRESENTATIONS OR WARRANTIES OF ANY KIND AS TO THE G
& G DATA,  INCLUDING WITHOUT  LIMITATION,  ITS FITNESS FOR A PARTICULAR PURPOSE,
MERCHANTABILITY OR ACCURACY, AND THE BOG GROUP HEREBY DISCLAIMS ANY AND ALL SUCH
REPRESENTATIONS  OR WARRANTIES,  AND ANY USE OF THE G & G DATA BY THE PARTIES OR
THEIR  SUCCESSORS  OR  ASSIGNS,  OR ANY  ACTION  TAKEN BY THE  PARTIES  OR THEIR
SUCCESSORS OR ASSIGNS SHALL BE BASED SOLELY ON THEIR OWN JUDGMENT, AND NO MEMBER
OF THE BOG GROUP SHALL BE LIABLE OR  RESPONSIBLE  TO THE OTHER  PARTIES OR THEIR
SUCCESSORS  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 THE G & G DATA, 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 ANY MEMBER OF THE BOG GROUP.
Each Party hereto waives all of the provisions of any applicable Deceptive Trade
Practices or Consumer Protection Act ("DTPA"),  other than Section 17.555 of the
Texas DTPA,  and  expressly  agrees and  acknowledges  that it (i) has assets of
twenty-five  million  dollars or more,  and (ii) has knowledge and experience in
financial  and business  matters that enable it to evaluate the merits and risks
of the transaction and operations contemplated by this Agreement, (iii) has been
represented  by  counsel  of its  choosing,  and (iv) is not in a  significantly
disparate  bargaining  position  relative to each other Party to this Agreement,
but has agreed to this  provision in  negotiations  involving real choice on the
part of each Party.

                                   ARTICLE IV
                             Participation in Wells

     Section 4.1.  Limitation  on Well  Proposals.  BOG and Aspect  hereby agree
that, until December 31, 1999, and  notwithstanding  any provision of any JOA to
the  contrary,  Aspect  shall not be  authorized  to propose the drilling of any
Initial Well or  Subsequent  Well,  except for the Initial Well to be drilled on
the  Prospect  Area  described  in Part One of  Exhibit A hereto  (the  "Dickson
Prospect").

     Section 4.2 Elections.

     (i) Initial  Wells.  In the event that a Party elects not to participate in
the drilling of the Initial Well proposed and then actually  drilled  within any
particular  Prospect Area,  anything to the contrary  contained herein or in the
applicable JOA to the contrary,  such Party (A) must permanently  relinquish and
assign (without  reimbursement for costs) all of its right, title,  interest and
properties  (whether  legal or  equitable,  vested  or  contingent  and  whether
real/immovable,  personal/movable  or  mixed),  other than the G & G Data in the
case of BOG, in the applicable Prospect Area to the Parties participating in the
drilling of such well (in the ratio that each  participating  Party's  leasehold
working  interest in the acreage included within the Prospect Area for such well
bears to the total of the  leasehold  working  interests  of all of the  Parties
hereto  participating in the operation),  (B) shall no longer (as of the date it
elects not to  participate in the drilling of the well) be deemed a party to the
applicable  JOA,  and  (C)  shall  not  own  or  acquire,  whether  directly  or
indirectly,  itself or through any Affiliate,  representative,  agent or broker,
any Lease,  Option,  Farm-In or other interest in oil, gas and/or other minerals
within such  Prospect Area for a period of three (3) years from the date of this
Agreement.

                                       7
<PAGE>

     (ii) Subsequent  Wells. In the event a Party that elected to participate in
the Initial Well drilled within any particular Prospect Area,  thereafter elects
not to participate in any Subsequent  Well proposed and then drilled within such
Prospect Area,  anything to the contrary  contained  herein or in the applicable
JOA to the  contrary,  such  Party (A) must  permanently  relinquish  and assign
(without  reimbursement  for costs) all of its right,  title,  and  interest and
properties  (whether  legal or  equitable,  vested  or  contingent  and  whether
real/immovable,  personal/movable  or mixed) in the  wellbore of the  Subsequent
Well and a sufficient interest in the Leases,  Options and Farm-Ins allocable to
such Subsequent Well to afford the relinquishing  party its full allowable share
of production from the Subsequent Well (the "Subsequent Well Interests"), to the
Parties participating in the drilling of such Subsequent Well (in the ratio that
each  participating  Party's  leasehold working interest in the acreage included
within  the  Prospect  Area for such well  bears to the  total of the  leasehold
working interests of all of the Parties hereto  participating in the operation),
(B) shall no longer (as of the date it elects not to participate in the drilling
of the  Subsequent  Well) be deemed a party to the  applicable JOA insofar as it
pertains to the  Subsequent  Well  Interests,  and (C) shall not own or acquire,
whether directly or indirectly, itself or through any Affiliate, representative,
agent or broker, any Lease,  Option,  Farm-In,  Permit or other interest in oil,
gas and/or other minerals directly relating to the Subsequent Well Interests for
a period of three (3) years from the date of this Agreement.

     (iii) Completion  Elections.  In the event that a Party has participated in
the  drilling of the Initial  Well in any  particular  Prospect  Area,  and then
elects not to participate in a completion operation proposed for such well, such
Party (A) must  permanently  relinquish  (without  reimbursement  for costs) and
assign  all of its right,  title,  interest  and  properties  (whether  legal or
equitable, vested or contingent and whether real/immovable,  personal/movable or
mixed) in the  completed  formation,  insofar as it can be  produced  out of the
wellbore  of such well,  (B) shall  relinquish  (as of the date it elects not to
participate in the completion  operation) all of its rights and interests  under
the JOA, insofar as it covers the relinquished  completed formation,  insofar as
such  completed  formation can be produced out of the wellbore of such well, and
(C) shall not, for a period of three (3) years from the date of this  Agreement,
own or acquire, whether directly or indirectly, itself or through any Affiliate,
representative,  agent or broker, any Lease, Option,  Farm-In, or other interest
in oil,  gas and/or  other  minerals  located  within the  completed  formation,
insofar as such completed  formation can be produced out of the wellbore of such
well. In each of the foregoing cases, such  relinquishment  and assignment is to
be made to the Parties  participating  in such completion in the ratio that each
participating  Party's leasehold working interest in the acreage included within
the Prospect for such well bears to the total of the leasehold working interests
of all  of  the  Parties  hereto  participating  in  the  operation.  Where  the
completion  election  relates to a Subsequent  Well in such Drilling  Unit,  the
non-consent  and other  operative  provisions of the applicable JOA shall govern
completion  point  elections.  If a Party  has  elected  to  participate  in the
drilling of a well and then elects not to participate  in a proposed  completion
operation within the well, but then subsequently  participates in the completion
of another  formation  within the same well, such Party will be obligated to pay
for its  proportionate  share  of the  completion  operation  costs  which  were
previously  incurred in completing  the other  formation in accordance  with the
drilling  footage  ratio  method set forth in COPAS  Bulletin No. 2 in paragraph
B.1(b) for intangible costs and in paragraphs B.1 and B.2 for tangible costs.

                                       8
<PAGE>

     (iv) Any well  drilled to  replace a well  drilled  within a Prospect  Area
because of drilling or mechanical  difficulties incurred in the drilling of such
well shall be deemed to be the same well for purposes of the  relinquishment and
assignment  provisions  of this Section 4.2;  provided,  however,  that only the
Parties that  participated  in the original  drilling of the well shall have the
right to participate in the drilling of a replacement well for such well.

     (iv)  In the  event  of  any  required  relinquishment  and  assignment  of
interests  as  provided  in this  Section  4.2,  the  relinquishing  Party shall
promptly  execute  all  conveyance  instruments  necessary  to  effectuate  such
relinquishment and assignment.

                                   ARTICLE V.
                                  Miscellaneous

     Section 5.1. Assignments. This Agreement shall be binding upon and inure to
the benefit of the Parties hereto and their  respective  successors and assigns;
provided,  however,  that the  conveyance,  assignment  or other  instrument  of
transfer vesting such transferee with all or part of such rights,  interests and
unaccrued obligations must expressly provide that the assignment,  conveyance or
other  instrument  of  transfer  is made  subject  to the terms  and  conditions
contained  in this  Agreement  and in the  absence  of such  language  any  such
attempted  transfer shall be void and of no legal force and effect. In addition,
in any  such  assignment,  conveyance  or  other  instrument  of  transfer,  the
transferee   shall  expressly  agree  to  assume  and  be  responsible  for  any
liabilities,  damages,  obligations,  covenants and agreements  arising from and
after the date of such  assignment,  conveyance or other instrument of transfer,
in relation to or otherwise out of the properties, rights and interests that are
the  subject of this  Agreement  and/or  such  assignment,  conveyance  or other
instrument of transfer,  and the transferor shall remain  responsible for any of
the foregoing arising prior to the date of such assignment,  conveyance or other
instrument of transfer and in the absence of such  language,  any such attempted
transfer shall be void and of no force and effect.  Any  subsequent  assignment,
conveyance  or other  instrument  of transfer  shall  likewise  contain  express
language so allocating responsibility as between transferor and transferee,  and
in the absence of such language any such attempted transfer shall be void and of
no force and effect.

     Section 5.2. Termination.  This Agreement shall terminate at the expiration
of the AMI Term except as to any Prospect Area covered or deemed covered at such
time by a JOA between the Parties,  and as to each such  Prospect Area the terms
hereof,  other than those set out in Sections 2.1 through  2.4,  shall remain in
force and effect for so long as the applicable JOA remains in force and effect.

     Section  5.3.  Notices.  All notices and other  communications  required or
permitted  under  this  Agreement  shall be in  writing,  and  unless  otherwise
specifically provided, shall be delivered personally,  or by mail, telecopier or
delivery  service,  to the  addresses set forth  opposite the  signatures of the
Parties below, and shall be considered delivered upon the date of receipt.  Each
Party may specify its proper address or any other post office address within the
continental  limits of the United States by giving notice to other  Parties,  in
the  manner  provided  in this  section,  at least  ten (10)  days  prior to the
effective date of such change of address.

                                       9
<PAGE>

     Section  5.4.  Merger.  This  Agreement  supersedes  any and all  prior and
existing agreements, whether oral or in writing, between the Parties hereto with
respect to the subject  matter  hereof and  contains  all of the  covenants  and
agreements  between the Parties with respect to the subject matter hereof.  Each
Party acknowledges that no Party to this Agreement or anyone on their behalf has
made  any  representations,  inducements,  promises  or  agreements,  orally  or
otherwise,  relating  to the  subject  matter  of this  Agreement  that  are not
embodied herein.

     Section  5.5.  Counterparts.  This  Agreement  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 Agreement 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  Agreement  shall not be binding upon any Party hereto unless and until all
of the Parties sign a counterpart thereof.

     Section 5.6.  CHOICE OF LAW/VENUE.  THIS AGREEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE  WITH THE LAWS OF THE STATE OF TEXAS,  WITHOUT REGARD TO
PRINCIPLES OF CONFLICTS OF LAW.

     This  Agreement  is executed  by the  Parties the dates set forth  opposite
their respective signatures below but is effective for all purposes as on of the
date first set forth above.

Address:                                    BRIGHAM OIL & GAS, L.P.

6300 Bridge Point Parkway                   By:   Brigham, Inc., its
Building 2, Suite 500                             Managing General Partner
Austin, Texas  78730
(512)  427-3300
Fax: (512) 427-3400                         By:  /s/ Karen E. Lynch
                                                 --------------------
                                            Name:  Karen E. Lynch
Dated:  October 21, 1999                    Title:  Vice President

Address:                                    ASPECT RESOURCES LLC

511 16th Street, Suite 300
Denver, Colorado   80202
(303) 573-7011                              By:  /s/ Alex B. Campbell
                                                 ---------------------
Fax: (303) 573-7340                         Name:   Alex B. Campbell
                                                 ---------------------
                                            Title:  Vice President

Dated:  October 18, 1999

                                       10

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