Exhibit 10.15
Apache Corporation 401(k) Savings Plan

First Amendment Not Covered by the 2010 Determination Letter
Apache Corporation (“Apache”) sponsors the Apache Corporation 401(k) Savings
Plan (the “Plan”). In section 10.4 of the Plan, Apache reserved the right to
amend the Plan from time to time. Apache hereby exercises that right, as
follows.
1. Sections 6.5(a) and 6.5(b) of the Plan shall be replaced with the following,
effective as of November 10, 2010.

  (a)   Withdrawals for Employees Age 591/2 or Older. An Employee who has
attained age 591/2 may at any time thereafter withdraw any portion of his
Participant Contributions Account and any vested portion of his Company
Contributions Account. If the Employee is not fully vested in his Company
Contributions Account at the time of a withdrawal under this subsection, the
rules of subparagraph
5.4(c)(ii)(A) shall be applied when determining the vested portion of the
Company Contributions Account at any time thereafter.     (b)   Rollover
Account. An Employee may withdraw all or any portion of his Rollover Account at
any time.

2. Section 7.4 of the Plan shall be replaced in its entirety with the following,
effective as of the date this amendment is signed.
7.4 Interest
Each loan shall bear a reasonable rate of interest, which shall remain fixed for
the duration of the loan. The Committee or its agent shall determine the
reasonable rate of interest on the date the loan documents are prepared. The
Committee shall have the authority to establish procedures from time to time for
determining the rate of interest.
3. The following shall be added as the last row in the table in Appendix A,
effective as of November 10, 2010.

          Apache Deepwater LLC   November 10, 2010   N/A

4. The last row in the table in Appendix C regarding Mariner Energy, Inc. shall
be revised as follows, effective as of November 10, 2010, and an additional row
regarding BP, p.l.c. shall be added to the table in Appendix C, effective as of
the date of each asset acquisition from BP, p.l.c. and related companies in
2010.

     
Mariner Energy Inc. (“Mariner”)
  All individuals who became Covered Employees on the date of the merger between
Apache and Mariner are New Employees. The amount of a New Employee’s pre-Apache
service with Mariner shall be equal to his service credited under the Mariner
Energy, Inc. Employee Capital Accumulation Plan (or the service that would have
been credited under such plan if the New Employee had been a participant in it).
A New Employee shall be eligible to make Participant Contributions from
Compensation paid after the date of the merger. See Appendix E for additional
provisions related to the merger of the Mariner Energy Inc. Employee Capital
Accumulation Plan into this Plan.

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BP, p.l.c. (“BP”)
  The New Employees are those who were hired by Apache in connection with
property acquisitions from BP during 2010.

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5. The following new Appendix E shall be added to the Plan, effective as of
November 10, 2010.
APPENDIX E
Mariner Energy, Inc.
Introduction
Through a merger effective as of November 10, 2010 (the “Closing Date”), Apache
acquired Mariner Energy, Inc., (“Mariner”) which sponsored the Mariner Energy,
Inc. Employee Capital Accumulation Plan (“Mariner’s 401(k) Plan”). Mariner’s
401(k) Plan is merged into this Plan as of November 16, 2010. This Appendix
describes the special rules that apply to amounts transferred from Mariner’s
401(k) Plan to this Plan, and also describes how the match is calculated for
2010 in this Plan.
Capitalized terms in this Appendix have the same meanings as those given to them
in the Plan. The regular terms of the Plan shall apply, except as provided
below.
Match
The Company Matching Contribution for 2010 shall be determined pursuant to
section 3.2 of the Plan, based on the Participant Contributions and Compensation
paid to a Covered Employee after the date of the merger, except as provided in
the next sentence. If a Covered Employee’s Participant Contributions to this
Plan and his contributions to Mariner’s 401(k) Plan that are subject to the
limits of Code §402(g) are $16,500 or (because of catch-up contributions) more
during 2010, his Company Matching Contribution for 2010 will be the greater of
(a) the aggregate matching contributions he would have received in both this
Plan and Mariner’s 401(k) Plan had equal salary deferrals of $16,500 in the
aggregate been withheld from each regular paycheck during 2010, minus the match
allocated to him for 2010 in Mariner’s 401(k) Plan, or (b) the amount described
in the preceding sentence.
The Company Matching Contribution shall vest pursuant to the usual rules in
Article V. See Appendix C for additional (pre-Apache) service that is taken into
account for vesting purposes.
Incoming Assets
A participant in Mariner’s 401(k) Plan may have as many as seven different types
of accounts in that plan. The following distribution rules apply to those
incoming accounts (the “Old Mariner Accounts”).
1. Accounts.

  (a)   Employee Deferrals. Any Old Mariner Account that is subject to Code
§401(k) shall be transferred to the Participant Contribution Account. No special
distribution rules apply to such amounts.     (b)   Regular Match. Matching
contributions to Mariner’s 401(k) Plan and the earnings thereon shall be
transferred to a separate subaccount of the Company Contributions Account in
this Plan. These amounts vest 33% when his Period of Service is one year, 66%
when his Period of Service is two years, and 100% when his Period of Service is
three years or more. These amounts are subject to the distribution rules that
apply to Company Contributions Accounts, except as noted below in section 2
below.     (c)   Discretionary Company Contribution. Discretionary employer
contributions to Mariner’s 401(k) Plan and the earnings thereon that were
subject to a 6-year vesting schedule shall be transferred to a separate
subaccount of the Company Contribution Account in this Plan that is subject to
the regular 5-year vesting schedule described in Article V. The additional
vesting shall apply to this subaccount on the date of the merger of the plans,
even to those subaccounts of individuals who are no longer employees. This
subaccount is subject to the distribution rules that apply to Company
Contributions Accounts, except as noted in section 2 below.

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  (d)   Pre-Tax Rollover Account. Pre-tax rollovers contributions to Mariner’s
401(k) Plan and the earnings thereon shall be transferred to the Rollover
Account. No special distribution rules apply to such amounts.     (e)  
After-Tax Rollover Account. After-tax rollovers contributions to Mariner’s
401(k) Plan and the earnings thereon shall be transferred to a separate, fully
vested, subaccount of the Rollover Account in this Plan. No special distribution
rules apply to this subaccount.     (f)   After-Tax Account. A participant’s
after-tax contributions to Mariner’s 401(k) Plan and the earnings thereon shall
be transferred to a separate, fully vested, subaccount of the Participant
Contributions Account in this Plan. The same distribution rules that apply to
the Rollover Account will apply to this subaccount.     (g)   FERI Accounts.
Both matching and discretionary employer contributions to a plan sponsored by
Forest Oil and transferred to Mariner’s 401(k) Plan and the earnings thereon
shall be transferred to separate, fully vested, subaccounts of the Company
Contributions Account in this Plan. These subaccounts are subject to the
distribution rules that apply to Company Contributions Accounts, except as noted
in section 2 below.

2. Special Distribution Rules.

  (a)   Installments. Except as provided in the next sentence, in subsection
6.4(b) of the Plan (relating to in-service withdrawals and installments to
beneficiaries), and in subsection 13.9(f) of the Plan (relating to QDROs), all
distributions shall be in the form of a lump sum of the Account Owner’s entire
vested account balance in the Plan. Any Account Owner who elected installment
payments from the Old Mariner Accounts before the merger of Mariner’s 401(k)
Plan and this Plan shall be paid the installments in the amount and on the
schedule he had elected.     (b)   Hardship Withdrawals. A Participant may take
an in-service hardship withdrawal that meets the requirements of paragraphs
6.5(c)(i) and 6.5(c)(ii) of the Plan from the subaccounts of the Company
Contribution Account that were established in subsections 1(b), 1(c), and 1(g)
of this Appendix, to the extent such subaccounts are vested.     (c)   Two-Year
Rule. Once the funds have actually been in either the Plan or Mariner’s 401(k)
Plan for 24 months, a Participant may take an in-service withdrawal from the
vested portion of the subaccounts of the Company Contribution Account that were
established in subsections 1(b), 1(c), and 1(g) of this Appendix.     (d)  
Five-Year Rule. Once a Participant has been a Participant in this Plan and
Mariner’s 401(k) Plan for 60 months, the Participant may take an in-service
withdrawal from the vested portion of the subaccounts of the Company
Contribution Account that were established in subsections 1(b), 1(c), and 1(g)
of this Appendix.

3. Investments.

  The Plan may accept an in-kind transfer of assets from Mariner’s 401(k) Plan,
as determined by the Committee.

4. Loans.

  Loans in Mariner’s 401(k) Plan will be transferred to the Plan. The repayment
schedule of the loans may be modified to accommodate the Borrower’s new pay
schedule. Participants cannot borrow from the Plan again until all prior loans
have been repaid.

5. Enrollment.

  Individuals who were employed by Mariner or related companies and become
Covered Employees on the Closing Date will be deemed to have elected to make
Participant Contributions to this Plan at the same rate that they had been
making similar contributions to Mariner’s 401(k) Plan immediately before the
plans’ merger. If any such individual was not contributing to Mariner’s 401(k)
Plan when the plan merger occurred,

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  he will not be automatically enrolled in the Plan, even if he was hired by
Mariner as recently as one day before the plans’ merger.

6. Vesting.

  If (a) the Participant was an employee of Mariner on the Closing Date, (b) his
severance from employment occurs on or before June 30, 2011, (c) Apache decided
to terminate the Participant or the Participant decided not to accept Apache’s
offer of employment, and (d) the Participant’s termination is not for cause,
then the Participant’s Old Mariner Accounts shall become fully vested upon his
severance from employment.

— END OF APPENDIX E —
EXECUTED this 30 day of December, 2010.

            APACHE CORPORATION
      By:   /s/ Margery M. Harris         Margery Harris        Vice President,
Human Resources     

Prepared October 17, 2010

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