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                                                                 EXHIBIT 10.6(b)

                        ASSIGNMENT OF RIGHTS AGREEMENT

  This Agreement (the "Agreement") is entered into effective as of October 27,
1999, by and between Atlantic Richfield Company, a Delaware corporation
("Assignor"), and Vastar Resources, Inc., a Delaware corporation ("Assignee"),
each individually a "Party" and collectively the "Parties."

WITNESSETH:

WHEREAS, Assignor and Assignee have previously entered into technical services
agreements (the "AEPT Technical Services Agreement" effective as of October 1,
1993, and the "AEPT/Vastar Miscellaneous Software Transfer Agreement" dated
February 29, 1996, here collectively referred to as the "Technical Services
Agreement") pertaining to the provision by Assignor of certain Services and IT
Services to Assignee.  All defined terms used herein shall have the meanings
ascribed to them in the Technical Services Agreement unless otherwise stated in
this Agreement; and

WHEREAS, since October 1, 1993, Assignor has performed various Services and IT
Services for Assignee pursuant to said Technical Services Agreement, which
performance of Services and IT Services culminated in business information and
data important to Assignee, hereinafter termed "Results."  The Results of said
Services and IT Services only pertain to those projects specifically described
in the attached Exhibit "A" and may include certain intellectual property here
defined as covering confidential information, trade secrets, information, data
and all copyright rights in such information or data (the "Intellectual Property
in Results"); and

WHEREAS, on or before March 31, 2000, BP Amoco Corporation will likely acquire
all of Assignor's outstanding shares; and

WHEREAS, in recognition of such anticipated stock sale or exchange, the Parties
believe it is in their respective best interests to enter into an agreement
which confirms Assignee's ownership of the Results and Intellectual Property in
Results, including Assignee's right to possession and use of same.

NOW, THEREFORE, in consideration of the premises and mutual covenants of this
Agreement, the Parties agree as follows:

1.   TRANSFER OF COPYRIGHT OWNERSHIP

Assignor hereby assigns to Assignee all rights, title and interest of every kind
and character in perpetuity throughout the world in and to the Results and
Intellectual Property in Results arising from Assignor's Services and IT
Services under the Technical Services Agreement. Said Results and Intellectual
Property in Results shall be deemed to be works made for hire specially
commissioned by Assignee, but this assignment is effective whether or not such
Results and Intellectual Property in Results are considered works made for hire.
Said Results do not include any software licensed by Assignor to Assignee under
that certain Software License Agreement entered into between the Parties
effective as of October 27, 1999, or any other license agreement between the
Parties predating this Agreement.  Assignee shall have the right to adapt,
change, revise, delete

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from, add to or rearrange the Results and Intellectual Property in Results,
including the right to assign to any assignee the right to utilize all or any
part of the Results and Intellectual Property in Results. Assignee shall have
and own all right to use and further develop the Results and Intellectual
Property in Results, including the right to develop derivative works from the
Results and Intellectual Property in Results. Without limiting the generality of
the foregoing, Assignee shall have the right to exhibit, distribute, reproduce,
broadcast and otherwise exploit the Results and Intellectual Property in Results
in any and all manners now known or hereafter devised, in perpetuity throughout
the world, and Assignor hereby waives all moral rights of authors or similar
rights under any law or jurisdiction. Assignor acknowledges that it has no
separation of rights with respect to the Results and Intellectual Property in
Results. Assignor agrees to execute and deliver to Assignee or its designee such
additional documents as Assignee or its designee may request or require to
effectuate or evidence the purpose of this Agreement.

2.  POSSESSION

Assignor hereby grants to Assignee the right to possess the Results and
Intellectual Property in Results which are the subject of this Agreement as
specified in Exhibit "A" hereto.  Where Assignee is not already in possession of
the Results and Intellectual Property in Results, Assignor shall, within thirty
(30) days of the execution of this Agreement, provide such possession of the
Results and Intellectual Property in Results to Assignee in such form as
Assignee shall reasonably request.

3.  WARRANTIES

The Results are furnished to Assignee on an "as is" basis.  Assignor makes no
other express warranties and disclaims all implied warranties as to any matter
whatsoever, including, without limitation, the condition of the Results, their
merchantability, or their fitness for any particular purpose, or the correctness
of the Results.

4.  NOTICES

Any notice required to be given pursuant to this Agreement shall be in writing
and mailed by certified or registered mail, return receipt requested, or
delivered by a national overnight express service. Assignor's and Assignee's
addresses for notice purposes will be as follows:

To Assignor: Atlantic Richfield Company
    2300 West Plano Parkway
    Plano, Texas 75075
    Attention: ________________

To Assignee: Vastar Resources, Inc.
    15375 Memorial Drive
    Houston, Texas 77079
    Attention: Gary Charlson

Either Party may change the address to which notice is to be sent by written
notice to the other Party

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pursuant to the provisions of this paragraph.

5.  JURISDICTION AND DISPUTES

This Agreement shall be governed by the laws of the state of Texas and
applicable Federal copyright law.  All disputes hereunder shall be resolved in
the applicable state or federal court of Texas.  The Parties consent to the
exclusive jurisdiction of such courts, agree to accept service of process by
mail, and waive any jurisdictional or venue defenses otherwise available.

6.  AGREEMENT BINDING ON SUCCESSORS AND ASSIGNS

This Agreement shall be binding on and shall inure to the benefit of the Parties
hereto, and their successors and assigns.

7.  SEVERABILITY

If any provision hereof is held invalid or unenforceable by a court of competent
jurisdiction, such invalidity shall not affect the validity or operation of any
other provision and such invalid provision shall be deemed to be severed from
the Agreement.

8.   INTEGRATION

As to the ownership and use of the Results and Intellectual Property in Results,
this Agreement constitutes the entire understanding of the Parties and is
intended as a final expression of their agreement.  It shall not be modified or
amended except in writing signed by the Parties hereto and specifically
referring to this Agreement.  As to the ownership and use of the Results and
Intellectual Property in Results, this Agreement shall control over any other
precedent document that may be in conflict with the provisions contained herein.

IN WITNESS WHEREOF, the Parties hereto, intending to be legally bound hereby,
have each executed this Agreement effective as of the date first above written.


ATLANTIC RICHFIELD COMPANY            VASTAR RESOURCES, INC.


By: /s/ Stephen G. Suellentrop        By: /s/ Phillip A. Gobe
    -------------------------             -------------------------------------

Title: Vice President                 Title:  Senior Vice President, Production
       ----------------------                 ---------------------------------

Date: 11/18/99                        Date: 11/1/99
      -----------------------               -----------------------------------

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                                   Exhibit A


1. The work (lab, reports, notes, any interpretations, etc.) of Andy Spence on
   Fruitland core floods with peroxide and bleach, including cat scans, etc.
   done on Coal Bed Methane cores.

2. Interpretations for Coal Bed Methane by the Plano Petrophysical Group for the
   Fruitland Coal Field in Colorado and Northern New Mexico.

3. Analyses and interpretations done for Vastar's deepwater prospects in Mirage
   and Horn Mountain.

4. Interpretations and analyses, as well as derived reservoir characterizations
   done for Vastar in the Deepwater (King, Mirage, Horn Mountain).

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