Document:

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                                                                    EXHIBIT 10.5

                         SPECIAL AMENDMENT TO CERTAIN
                         VASTAR RESOURCES, INC. PLANS

         Vastar Resources, Inc. Amended and Restated Executive Deferral Plan;
         Vastar Resources, Inc. Comprehensive Medical Plan;
         Vastar Resources, Inc. Executive Medical Plan;
         Vastar Resources, Inc. Deferral Plan for Outside Directors

     Pursuant to the power of amendment reserved in each of the Vastar
Resources, Inc. Amended and Restated Executive Deferral Plan; Vastar Resources,
Inc. Comprehensive Medical Plan; Vastar Resources, Inc. Executive Medical Plan;
and Vastar Resources, Inc. Deferral Plan for Outside Directors (the "Vastar
Plans"), each Vastar Plan is amended effective May 24, 2000, as follows:

     1.  A new section, consecutively numbered as appropriate, is hereby added
at the end of each Vastar Plan:

          "The Vice President, Human Resources is authorized to make
     administrative amendments to the Plan as may be necessary to implement the
     purpose and intent of provisions of the Plan providing for benefits to be
     paid as a result of, or upon a Termination of Employment after, a
     Subsequent Change of Control during the Benefit Trigger Window, as such
     terms are defined in the Plan.  The term "administrative amendments" means
     such amendments or changes which do not result in additional cost or
     expense to the Company or its successors, other than costs or expenses
     which, in the judgment of the Vice President, Human Resources,  are de
     minimus.  An administrative amendment to the Plan shall become effective
     upon the execution of the amendment by the Vice President, Human Resources.
     No approval of the Board of Directors of Vastar is necessary for any
     administrative amendment to the Plan, provided however, that no amendment
     made pursuant to this provision shall be effective without the consent of
     the Special Plan Administrator."
<PAGE>

     Executed this 6th day of July, 2000.

                              VASTAR RESOURCES, INC.

ATTEST:                       By:   /s/  JEFFREY M. BENDER
                                    --------------------------------------
                                    Jeffrey M. Bender
                                    Vice President, Human Resources

By: /s/  ANTHONY S. NOONAN
    ----------------------------------
         Anthony S. Noonan
Name: ________________________________
         General Tax Officer
Title: _______________________________

Approved as to Form:

WACHOVIA BANK, N.A.

By:  /s/  PETER D. QUINN
     ---------------------------------

Name:     Peter D. Quinn
      --------------------------------

Title:    Senior Vice President
       -------------------------------

                                      -2-<PAGE>

                                                                    EXHIBIT 10.6

                            VASTAR RESOURCES, INC.
                              SECOND AMENDMENT TO
                            EXECUTIVE DEFERRAL PLAN

     Pursuant to the power of amendment reserved therein, Vastar Resources, Inc.
Amended and Restated Executive Deferral Plan, which was effective March 24,
1999, and amended by the First Amendment to such plan executed August 12, 1999,
is hereby amended effective May 24, 2000, as follows:

     1.   Section 2.5(b) is amended to replace the subsection with the
          following:

          "A Participant's Deferral Commitments shall not terminate upon a
     Change of Control triggered by the Merger.  Further, except as provided
     below, Deferral Commitments shall not terminate upon a Subsequent Change of
     Control.  If a Subsequent Change of Control occurs on or before June 30,
     2001, Deferral Commitments shall terminate as of June 30, 2001.
     Notwithstanding the foregoing, any Deferral Commitments relating to Awards
     and ESSP benefits which a Participant is or becomes entitled to on or prior
     to June 30, 2001, shall remain binding."

     Executed this 6th day of July, 2000.

                              VASTAR RESOURCES, INC.

                                   /s/  JEFFREY M. BENDER
ATTEST:                       By: ----------------------------------
                                    Jeffrey M. Bender
                                    Vice President, Human Resources
    /s/  ANTHONY S. NOONAN
By: -------------------------------
         Anthony S. Noonan
Name: -----------------------------
         General Tax Officer
Title: ----------------------------

Approved as to Form:

WACHOVIA BANK, N.A.

    /s/  PETER D. QUINN
By: ------------------------------
         Peter D. Quinn
Name: ----------------------------
         Senior Vice President
Title: ---------------------------<PAGE>

                                                                    EXHIBIT 10.7

                            VASTAR RESOURCES, INC.
                              FIRST AMENDMENT TO
                            VASTAR RESOURCES, INC.
                     RETIREMENT PLAN FOR OUTSIDE DIRECTORS

     Pursuant to the power of amendment reserved therein, the Vastar Resources,
Inc. Retirement Plan for Outside Directors, effective June 26, 1994 (the
"Plan"), is hereby amended as follows:

     1.  Article I, Section 1.7, is amended in its entirety and shall now read
as follows:

     "Director means a member of the Board who is not an employee of the Company
or its affiliates.  For the purposes of this definition, an affiliate means any
person or entity that, directly or indirectly, controls, or is controlled by, or
is under common control with, the Company."

     2.  Except as amended hereby, the Plan remains unchanged and in full force
and effect.

     Executed as of the 1st day of December, 1999, but effective as of October
20, 1999.

     ATTEST:                                VASTAR RESOURCES, INC.

          /s/  JONATHAN D. EDELFELT              /s/  JEFFREY M. BENDER
     By: ------------------------------     By: ------------------------------
           Jonathan D. Edelfelt                  Jeffrey M. Bender
           Associate Secretary                   Vice President, Human Resources<PAGE>

                                                                    EXHIBIT 10.8

                            VASTAR RESOURCES, INC.
                              SECOND AMENDMENT TO
                            EXECUTIVE MEDICAL PLAN

     Pursuant to the power of amendment reserved therein, Vastar Resources, Inc.
Executive Medical Plan (the "Plan") is hereby amended effective May 24, 2000, as
follows:

     1.  Paragraph 5 is amended in its entirety and shall now read as follows:

          5.   Retiree Medical Coverage.

               A Retiree (as hereafter defined) may continue participation in
          the Plan.  The term "Retiree" shall mean any Participant who was
          participating in the Plan and who while participating in the Plan:

          (a) Terminated employment and, at such time, was entitled to an
          immediate retirement allowance from a qualified retirement plan of the
          Company; or

          (b) Terminated employment after attainment of age 53 years plus six
          months and ten or more years of Membership Service, as defined in the
          Vastar Resources, Inc. Retirement Plan and is eligible for an
          allowance under the Vastar Resources, Inc. Special Termination
          Allowance Plan.  A Participant described in this subparagraph (b)
          shall become a Retiree upon the date the Participant becomes eligible
          to receive an immediate monthly retirement allowance from a qualified
          retirement plan of the Company; or

          (c) Terminated employment in accordance with the terms and conditions
          of a written agreement between the Company and the Employee, which
          grants the Employee Retiree status.  The applicable provisions of such
          written agreement are incorporated by reference as a provision of the
          Plan; or

          (d) Has a termination of employment as described in Paragraph 2(b)(i)
          of the Plan during a Benefit Trigger Window and the Participant, as of
          the date of the Participant's termination of employment, (A) has
          attained the age of 48 years plus six months or more and (B) as of the
          date of the Participant's termination of employment, has five or more
          years of Membership Service, as defined under the Vastar Resources,
          Inc. Retirement Plan and is eligible for an allowance under the Vastar
          Resources, Inc. Special Termination Allowance Plan.  A Participant
          described in this subparagraph (d) shall become a Retiree on the
          earlier of the 19th month  after such Participant's termination of
          employment or the date the Participant becomes eligible to receive an
          immediate monthly retirement allowance under the Vastar Resources,
          Inc. Retirement Plan.
<PAGE>

     Executed this 6th day of July, 2000.

                              VASTAR RESOURCES, INC.

                                   /s/  JEFFREY M. BENDER
ATTEST:                       By: ----------------------------------
                                    Jeffrey M. Bender
                                    Vice President, Human Resources
     /s/  ANTHONY S. NOONAN
By: --------------------------------
          Anthony S. Noonan
Name:_______________________________
          General Tax Officer
Title:________________________________

Approved as to Form:

WACHOVIA BANK N.A.

     /s/  PETER D. QUINN
By: --------------------------------
          Peter D. Quinn
Name:_______________________________
          Senior Vice President
Title:________________________________

                                      -2-

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