Document:

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                                                                    Exhibit 10.5

                              AMENDED AND RESTATED

                            TAX ALLOCATION AGREEMENT

                                 by and between

                              PLAINS RESOURCES INC.

                                       and

                     PLAINS EXPLORATION & PRODUCTION COMPANY

                                 October 2, 2002

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                               TABLE OF CONTENTS

                                                                        Page

1.       Spinco Group .................................................  2
2.       Tax Returns ..................................................  2
3.       Obligation for Payment of Taxes ..............................  4
4.       No Plains Tax Payments .......................................  5
5.       Spinco Tax Payments ..........................................  5
6.       Tax Benefits Before Spin-Off; Deferred Intercompany Gains ....  7
7.       Spinco Tax Benefits After Spin-Off; No Payment by Spinco .....  8
8.       Tax Audits ...................................................  8
9.       Proposed Adjustments .........................................  8
10.      Notice of Settlement or Compromise ...........................  9
11.      Spinco's Right to Contest ....................................  9
12.      Subsequent Adjustments or Refunds ............................ 10
13.      Spinco Spin-Off Tax Indemnity ................................ 11
14.      Future Actions ............................................... 12
15.      Combined, Consolidated or Unitary Basis Returns .............. 13
16.      Earnings and Profits Information ............................. 13
17.      Tax Interpretation ........................................... 14
18.      Consistent Tax Treatment ..................................... 14
19.      Retention of Records ......................................... 14
20.      Post Spin-Off Period Taxes ................................... 15
21.      Expenses ..................................................... 15
22.      Definitions .................................................. 15
         (a)      "After-Tax Basis" ................................... 15
         (b)      "Agreed Rate" ....................................... 15
         (c)      "Code" .............................................. 15
         (d)      "Distribution Agreement" ............................ 16
         (e)      "Items of Loss or Tax Benefit" ...................... 16
         (f)      "Interim Period" .................................... 16
         (g)      "Plains" ............................................ 16
         (h)      "Plains Group" ...................................... 16

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                               TABLE OF CONTENTS
                                  (continued)

         (i)      "Returns" ........................................... 16
         (j)      "Ruling" ............................................ 16
         (k)      "Short Period" .....................................  16
         (l)      "Spinco" ............................................ 16
         (m)      "Spinco Group" ...................................... 16
         (n)      "Spin-Off" .......................................... 16
         (o)      "Spin-Off Date" ..................................... 16
         (p)      "Spin-Off Tax" ...................................... 16
         (q)      "Tax Authority" ..................................... 17
         (r)      "Taxes" ............................................. 17
         (s)      "Transfer Tax" ...................................... 17

23.      Notices ...................................................... 17
24.      Binding Effect; Successors ................................... 18
25.      Severability ................................................. 18
26.      Entire Agreement ............................................. 19
27.      Governing Law ................................................ 19
28.      Arbitration .................................................. 20

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                              AMENDED AND RESTATED
                            TAX ALLOCATION AGREEMENT

     THIS AMENDED AND RESTATED TAX ALLOCATION AGREEMENT, made and entered into
as of the 2nd day of October, 2002, by and between Plains Resources Inc., a
Delaware corporation ("Plains"), and Plains Exploration & Production Company, a
Delaware corporation ("Spinco").

                              W I T N E S S E T H:

     WHEREAS, Plains is the common parent of an affiliated group of corporations
(hereinafter referred to as the "Plains Group") within the meaning of Section
1504(a) of the Internal Revenue Code of 1986, as amended (the "Code"), and the
members of the Plains Group have heretofore joined in filing consolidated
Federal income Tax Returns;

     WHEREAS, on or about July 3, 2002, certain assets associated with the
upstream business conducted by the Plains Group, including the stock of certain
subsidiaries included in the Plains Group and engaged in the upstream business,
were contributed to the capital of Spinco or otherwise acquired by Spinco or one
or more of its subsidiaries;

     WHEREAS, on September 18, 2002, Spinco (1) converted from a California
limited partnership to a Delaware limited partnership and immediately thereafter
(2) converted from a Delaware limited partnership to a Delaware corporation;

     WHEREAS, Plains, on a date to be determined by Plains (the "Spin-Off
Date"), will distribute to its stockholders all of the outstanding stock of
Spinco that it then holds (the "Spin-Off"), and thereafter Spinco and its
subsidiaries will no longer be members of the Plains Group for Federal income
Tax purposes;

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     WHEREAS, on July 3, 2002, the parties entered into the Tax Allocation
Agreement to provide for the sharing of the Federal, state, local and foreign
income Tax liabilities and benefits accrued prior to the Spin-Off between Plains
and its subsidiaries and Spinco and its subsidiaries;

     WHEREAS, the parties now desire to amend and restate the Tax Allocation
Agreement to determine, under the Tax Allocation Agreement, Spinco's potential
liability to Plains for Spinco's use of the Tax benefits of the Plains Group
prior to the Spin-Off;

     NOW, THEREFORE, the parties hereto agree as follows:

     1. Spinco Group. For purposes of this Agreement, the "Spinco Group" shall
mean (i) Spinco, (ii) Spinco's subsidiaries, and (iii) those corporations and
other entities whose stock or ownership interests will be contributed to Spinco
prior to the Spin-Off Date, all of such subsidiaries of Spinco and such
corporations and other entities being listed on Exhibit A attached hereto.
Unless otherwise specified, whenever Items of Loss or Tax Benefit (as defined
below) of Spinco are referred to in this Agreement the reference shall be to the
collective amounts of such items for the Spinco Group. For purposes of this
Agreement, items of income, gain, loss, deduction, credit, or other Tax
attributes are referred to as "Items of Loss or Tax Benefit".

     2. Tax Returns. Plains shall prepare and file or cause to be prepared and
filed timely all appropriate Returns in respect of Spinco and the other members
of the Spinco Group that (i) are required to be filed on or before the Spin-Off
Date; or (ii) are required to be filed after the Spin-Off Date that (A) are
required to include, on a consolidated, combined or unitary basis, the
operations of Spinco or any other member of the Spinco Group for any Tax period
or portion thereof ending on or before the Spin-Off Date; or (B) are required to
be filed by Spinco or any other member of the Spinco Group on a separate return
basis for any Tax period ending on or before the Spin-Off Date. To the extent
requested by Plains, Spinco shall participate in the filing

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of and shall file any required Returns with respect to any Tax period that ends
on or before the Spin-Off Date. Spinco shall prepare or cause to be prepared the
schedules in respect of Spinco and other members of the Spinco Group containing
the information necessary for Plains to prepare any consolidated, combined or
unitary Returns. If Plains, after consulting with Spinco, files any such
consolidated, combined or unitary Return using information with respect to
Spinco and the other members of the Spinco Group that is different from the
information prepared and furnished by Spinco, and Plains and Spinco thereafter
are unable to resolve such difference, such difference shall constitute a claim
for purposes of Paragraph 28 of this Agreement. Spinco shall also prepare or
cause to be prepared and shall file or cause to be filed all other Returns
required of Spinco or any other members of the Spinco Group, or in respect of
its or any of their activities, for any Tax period ending after the Spin-Off
Date that includes the operations of Spinco or any other member of the Spinco
Group prior to the Spin-Off Date. The parties hereto will, to the extent
permitted by applicable law, elect with the relevant Tax Authority to treat for
all purposes the Spin-Off Date as the last day of a Tax period of Spinco and the
other members of the Spinco Group, and such period shall be treated as a "Short
Period" for purposes of this Agreement. In any case where applicable law does
not permit Spinco to treat the Spin-Off Date as the last day of a Short Period,
then for purposes of this Agreement, the portion of such Taxes that is
attributable to the operations of Spinco and the other members of the Spinco
Group for such Interim Period (as defined below) shall be (i) in the case of
Taxes that are not based in whole or in part on income or gross receipts, the
total amount of such Taxes for the period in question multiplied by a fraction,
the numerator of which is the number of days in the Interim Period, and the
denominator of which is the total number of days in the entire period in
question, and (ii) in the case of Taxes that are based in whole or in part on
income or gross receipts, the

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Taxes that would be due with respect to the Interim Period, if such Interim
Period were a Short Period. "Interim Period" means with respect to any Taxes
imposed on Spinco or any other members of the Spinco Group for which the
Spin-Off Date is not the last day of a Short Period, the period of time
beginning on the first day of the actual Tax period that includes (but does not
end on) the Spin-Off Date and ending on and including the Spin-Off Date. Any
franchise Tax shall be allocated to the Tax period or portion thereof during
which the right to do business obtained by the payment of such franchise Tax
relates, regardless of whether such franchise Tax is measured by income,
operations, assets or capital relating to another Tax period.

     3. Obligation for Payment of Taxes. Plains shall be entitled to receive
from Spinco amounts calculated in accordance with Paragraphs 2, 3, 5, 12 and 13
hereof. Except as otherwise provided in Paragraph 5, the amounts, if any, that
Spinco shall be obligated to pay Plains pursuant to Paragraph 5, with respect to
Tax periods of the Plains Group ending on or prior to the Spin-Off Date, shall
be paid (i) within 30 days after the Spin-Off Date where the Taxes were paid by
Plains on or before the Spin-Off Date and shall include interest thereon
calculated for the period from the Spin-Off Date to the date of payment at a per
annum rate of interest (computed on the basis of the actual number of days
elapsed (including the Spin-Off Date but excluding the payment date) over a year
of 365 or 366 days, as the case may be) equal to the underpayment rate under
Section 6601 of the Code, or (ii) within 30 days after the date of payment where
the Taxes are paid by Plains after the Spin-Off Date. This initial settlement
shall be based on the Returns as they have been filed and shall include any
amendments of or adjustments to such Returns that have been finally settled.
Except as otherwise provided in Paragraph 5, any amounts that Spinco shall be
obligated to pay Plains pursuant to Paragraph 5 with respect to Tax periods of
the Plains Group ending after the Spin-Off Date shall be paid within 30 days
after

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filing of the Returns for such Tax periods. In the event of an adjustment to the
amount of payment for any Tax period as determined under Paragraph 12, Plains
shall be entitled to receive from Spinco such payment within 30 days after
payment of a deficiency to or receipt of a refund from the Tax Authority. In the
event of an adjustment under Paragraph 12 resulting in no additional payment to
or receipt of a refund from the Tax Authority, settlement shall be made within
30 days after filing of the amended Return or final settlement of the
adjustment. In the event that Spinco is delinquent in paying to Plains any
amount due pursuant to this Paragraph 3, including any interest accrued thereon
pursuant to this Paragraph 3, such unpaid amount shall bear interest from the
original due date until paid at a per annum rate equal to the lesser of (a) 18
percent and (b) the maximum lawful non-usurious rate of interest, if any, which
under applicable law Plains is permitted to charge Spinco thereon from time to
time.

     4. No Plains Tax Payments. Notwithstanding any other provision of this
Agreement to the contrary, Plains shall not be obligated to pay Spinco for any
Items of Loss or Tax Benefit of the Spinco Group used by the Plains Group to
reduce its Federal income Tax liability or Federal taxable income for any Tax
period ending on or before the Spin-Off Date. For purposes of these
computations, the allocation of Tax attributes to the Spinco Group and
absorption thereof by the Plains Group for each Tax period shall be determined
in accordance with the Treasury Regulations under ss. 1502 of the Code, applied
in a manner consistent with practices and methods followed in reporting the
Federal income Tax liability of the Plains Group for such Tax periods. In any
instance where a Tax attribute must be characterized, the characterization
prescribed by the aforementioned Treasury Regulations will control.

     5. Spinco Tax Payments. For each Tax period included in a consolidated
Federal income Tax return of the Plains Group which includes income of the
Spinco Group, Spinco shall

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be obligated to pay Plains an amount equal to the product of (i) the net taxable
income of the Spinco Group included in the consolidated Federal income Tax
Return of the Plains Group for such period, multiplied by (ii) the highest
marginal statutory Federal corporate income Tax rate applicable to such income
for such period; provided, however, that no payment shall be required pursuant
to this Paragraph 5 to the extent such payments have previously been made by the
Spinco Group to members of the Plains Group other than the Spinco Group under
any Tax sharing agreement or arrangement (whether written or oral) or any other
similar system of payments with respect to Federal income Taxes of the Plains
Group in existence prior to the Spin-Off Date, including, but not limited to,
any estimated Tax payments. For purposes of these computations, the allocation
of Tax attributes to the Plains Group and absorption thereof by the Spinco Group
for each Tax period shall be determined in accordance with the Treasury
Regulations under ss.1502 of the Code, applied in a manner consistent with
practices and methods followed in reporting the Federal income Tax liability of
the Plains Group for such Tax periods. In any instance where a Tax attribute
must be characterized, the characterization prescribed by the aforementioned
Treasury Regulations will control. To the extent, if any, that the amount of
Taxes Plains is required to pay for a Tax period that includes any net taxable
income of the Spinco Group is less than the amount calculated as owed by Spinco
to Plains under this Paragraph 5, the amount owed by Spinco to Plains shall be
(i) reduced to the extent that such difference is attributable to Items of Loss
or Tax Benefit of the Plains Group used which would have otherwise expired
unused but for the fact that the Spinco Group had net taxable income for such
Tax period, or (ii) deferred to the extent such difference is attributable to
Items of Loss or Tax Benefit of the Plains Group used which would have otherwise
carried forward to a subsequent year or years of the Plains Group but for the
fact that the Spinco Group had net

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taxable income for such Tax period. In the event an amount otherwise payable by
Spinco to Plains is deferred pursuant to clause (ii) of the immediately
preceding sentence, such amount shall be paid by Spinco to Plains within 30 days
after the filing of the Tax Return for the Tax period in which such Items of
Loss or Tax Benefit of the Plains Group previously used by the Spinco Group
would have been used by the Plains Group. In no event shall the aggregate
amounts payable by Spinco to Plains pursuant to the immediately preceding
sentence (including the aggregate amounts of any state, local or foreign Taxes
similarly deferred) exceed $3 million. Any interest that would otherwise be
added to any such amount pursuant to Paragraph 3 or otherwise shall be added to
such amounts notwithstanding that such addition causes the aggregate amounts to
exceed $3 million.

     The parties acknowledge that certain state, local or foreign income Tax
Returns may be filed on a combined, consolidated, separate or unitary basis. In
any such event, the parties intend that the required calculations for
determining which party owes Taxes to the other with respect thereto be made in
accordance with the principles referred to Paragraph 15.

     The parties further acknowledge that all Taxes shown on any Tax Return
prepared and filed on a separate return basis (notwithstanding who may be
obligated to prepare and file any such Tax Return) shall be the sole liability
of, and shall be paid by, the entity reflected as the taxpayer thereon.

     6. Tax Benefits Before Spin-Off; Deferred Intercompany Gains. For purposes
of the calculations under Paragraphs 5, 12 and 13 of this Agreement, any loss of
or decrease in any Items of Loss or Tax Benefit of the Plains Group resulting
from or attributable to the transfer of assets to Spinco or any other member of
the Spinco Group in connection with the Spin-Off (under the Treasury Regulations
governing Federal consolidated returns) shall be ignored and all

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calculations shall be made as though all such Items of Loss or Tax Benefit were
available for use by the Plains Group. In the event any deferred intercompany
gain attributable to assets transferred to Spinco or any other members of the
Spinco Group by other members of the Plains Group is recognized by the Plains
Group by reason of the Spin-Off, such deferred intercompany gain, if any, shall
be deemed to be a gain of the Spinco Group for its taxable year ending on the
Spin-Off Date for purposes of all calculations under this Agreement, including
the calculation of Taxes owed by Spinco to Plains pursuant to Paragraphs 2, 3,
5, 12 and 13 hereof. Notwithstanding anything in this Agreement to the contrary,
with respect to any items of income or gain resulting from an acceleration of an
excess loss account prior to or on the Spin-Off Date, Spinco shall not be liable
to Plains for Taxes or the use of Items of Loss or Tax Benefit resulting from
those items of income or gain.

     7. Spinco Tax Benefits After Spin-Off; No Payment by Spinco.
Notwithstanding anything in this Agreement to the contrary, with respect to
Items of Loss or Tax Benefit apportioned to and carried over by the Spinco Group
after the Spin-Off (under the Treasury Regulations governing Federal
consolidated income Tax Returns) and regardless of whether such Items of Loss or
Tax Benefit (x) are used by the Spinco Group to reduce its Federal income Tax
liability after the Spin-Off or (y) expire unused by the Spinco Group, Spinco
shall not have any obligation to pay Plains for any such item of loss or other
Tax benefit.

     8. Tax Audits. In the event of an audit by any Tax Authority of a Return
filed by Plains for any Tax period ending prior to or on the Spin-Off Date (or
any Tax period thereafter in which a carryforward of the Spinco Group's Items of
Loss or Tax Benefit is used), Plains shall give Spinco timely and reasonable
notice of such audit proceedings and Spinco shall have the right to participate
in any such audit; provided, however, that Plains shall have the full power and

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authority to control such audit. In connection with any such audit,
Spinco will provide all necessary information and other assistance reasonably
requested by Plains with respect to issues concerning the activities of the
Spinco Group. All communications with any such Tax Authority and its employees
concerning any such audit will be made by Plains unless otherwise agreed between
the parties hereto. In connection with its participation in any audit, Spinco
shall be given reasonable notice of all material meetings, investigations, field
examinations and similar events and copies of all relevant material
correspondence between the Tax Authority conducting the audit and Plains.

     9. Proposed Adjustments. Plains shall give prompt notice to Spinco of any
adjustment or adjustments proposed by any Tax Authority relating to the
activities of the Spinco Group for any Tax period ending prior to or on the
Spin-Off Date. After consulting with Spinco, Plains shall determine in its sole
discretion the nature of all action to be taken to contest such proposed
adjustment, including whether any such action shall initially be contested by
way of judicial or administrative proceedings, or both, whether any such
proposed adjustment shall be contested by resisting payment thereof or by paying
the same and seeking a refund thereof, and if Plains shall undertake to contest
such proposed adjustment, the court or other judicial body before which such
action will be commenced. Plains shall have full control over any contest or
administrative proceeding pursuant to this Paragraph, but Spinco, at its expense
and subject to approval by Plains, which approval shall not be unreasonably
withheld, may participate in any proceedings contesting any proposed adjustment
relating to the activities of the Spinco Group.

     10. Notice of Settlement or Compromise. Plains shall give prompt notice to
Spinco of any proposal made to it at the time of an audit or otherwise, to
settle or compromise issues relating to the Tax liabilities of the Spinco Group
for any Tax period ending prior to or on the

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Spin-Off Date. Plains will not accept or offer any settlement or compromise
of such issues without the consent of Spinco, and such consent shall not be
unreasonably withheld. If, in Plains' opinion, Spinco unreasonably withholds
such consent, Plains shall have the right to settle or compromise such issues on
the basis contained in the notice to Spinco. If Spinco thereafter desires to
dispute such settlement or compromise, Spinco's claim with respect thereto shall
constitute a claim for purposes of Paragraph 28 of this Agreement.

     11. Spinco's Right to Contest. Should Plains decline or cease to contest
any proposed adjustment relating to the activities of the Spinco Group for any
Tax period ending prior to or on the Spin-Off Date, Plains shall so notify
Spinco. Spinco, at its expense and upon providing reasonable assurances to
Plains of Spinco's ability to pay any Taxes resulting from any such proposed
adjustment, may contest such proposed adjustment; but in no event shall Spinco
be permitted to accept or offer any settlement or compromise that would require
the settlement or compromise of issues relating to the Tax liabilities of
members of the Plains Group other than the Spinco Group.

     12. Subsequent Adjustments or Refunds. With respect to any Tax period of
the Plains Group after December 31, 2001, for which Plains received (or would be
entitled to receive) from Spinco a payment pursuant to Paragraph 5 or this
Paragraph 12, if the filing of an amended income Tax Return, final determination
of any adjustment made by any Tax Authority or the receipt of a refund by Plains
occurs with respect to such period and such event would cause a difference in
the amount of payment required for such period as previously calculated pursuant
to Paragraph 5 or this Paragraph 12, Plains shall give Spinco prompt notice of
such difference and Plains shall be obligated to pay or entitled to receive from
Spinco the amount of such difference. Any amount required to be paid pursuant to
this Paragraph 12 shall include any

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interest imposed by or received from the Tax Authority if the adjustment results
in the payment of Tax to or receipt of Tax from the Tax Authority.

     In addition, Plains and Spinco acknowledge and agree that the tax sharing
agreement in effect for the Plains Group as of December 31, 2001, shall be
negated and canceled as of the Spin-Off Date. Plains and Spinco further agree
that there are no claims or causes of action under such tax sharing agreement as
of December 31, 2001, for periods ending on or before December 31, 2001, by
either of them or any member of their respective group against the other or any
member of the other's group, and they release each other from any and all such
claims. With respect to Taxes for periods ending after December 31, 2001, Plains
and Spinco agree that this Agreement shall control. Spinco agrees that it will
have no right to request that Plains file an amended return or a claim for
refund for any reason, unless Spinco agrees to pay any Tax liability shown
thereon or therein and Plains, in its absolute discretion (which may be withheld
for any reason), agrees. In the event Spinco generates net operating losses or
other Items of Loss or Tax Benefit after the Spin-Off Date that may otherwise be
carried back to the taxable income or Tax liability of the Plains Group prior to
the Spin-Off Date, Spinco agrees to relinquish the entire carry back period with
respect to each such net operating loss or other Items of Loss or Tax Benefit
under Section 172(b)(3) or other appropriate sections and to carry forward any
such losses and other items.

     13. Spinco Spin-Off Tax Indemnity. Notwithstanding any other provision of
this Agreement to the contrary, Spinco shall be liable for, shall pay and shall
indemnify and hold Plains and the other members of the Plains Group harmless, on
an After-Tax Basis, against (A) any Transfer Taxes and other Taxes which may be
imposed or assessed as a result of the contribution by Plains to the capital of
Spinco or the acquisition (by sale or purchase or

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otherwise) by Spinco or one or more of the other members of the Spinco Group of
assets associated with the upstream business conducted by the Plains Group,
including the stock of certain subsidiaries included in the Plains Group and
engaged in the exploration and production business, (B) any Taxes resulting from
the recognition of deferred intercompany gains as contemplated by Paragraph 6
hereof, and (C) any Spin-Off Tax. In determining the amount of, and the time of
payment of, any such Transfer Taxes, other Taxes or Spin-Off Tax owed by Spinco
to Plains, the principles set forth in Paragraph 5 shall apply.

     In addition, Spinco shall be liable, and shall indemnify Plains, for 50
percent of any Tax to which Plains or any member of the Plains Group is subject
as a result of the application of any provision of the Code to the Spin-Off,
including without limitation, Section 311(b), Section 355(c)(2), Section 355(e)
or Section 361(c)(2) of the Code (or any corresponding or similar provision of
state, local or foreign law), other than (i) any Spin-Off Tax, which is provided
for in the immediately preceding paragraph, or (ii) any such Tax which results
(x) solely from the fact that one or more persons acquire after the Spin-Off
Date directly or indirectly stock representing a 50-percent or greater interest
in Plains and such acquisition is subject to Section 355(e) of the Code, (y)
from the failure of Plains or any other member of the Plains Group (other than
Spinco or any other member of the Spinco Group) to comply with the covenants,
agreements and representations in the Ruling, except to the extent that any of
the covenants, agreements or representations require compliance by Spinco or any
other member of the Spinco Group after the Spin-Off, or (z) from any action by,
or failure to take an action on the part of, Plains or any other member of the
Plains Group (other than Spinco or any other member of the Spinco Group).

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     14. Future Actions. Spinco agrees that, during the three-year period
following the Spin-Off, it will not engage in any transaction that could
adversely affect the tax treatment of the Spin-Off without the prior written
consent of Plains, which consent may be withheld only if reasonable, unless (i)
Spinco delivers to Plains a supplemental ruling from the Internal Revenue
Service or a tax opinion acceptable to Plains of nationally recognized tax
counsel to the effect that the proposed transaction would not adversely affect
the tax treatment of the Spin-Off, or (ii) Spinco or another person or entity
acceptable to Plains provides to, or for the benefit of, Plains a cash escrow,
letter of credit or other comparable security acceptable to Plains in an amount
equal to the Taxes and accrued interest thereon (which accrued interest shall be
increased over time until such Taxes are paid or determined not to be payable)
that Plains reasonably calculates would be payable if the Spin-Off were
determined to be a taxable event for Tax purposes, with the terms and conditions
of any such cash escrow, letter of credit or other security being mutually
acceptable to Plains and Spinco or such other person or entity, as the case may
be. Plains agrees to cooperate with and provide reasonable assistance to Spinco
in the event that Spinco requests a supplemental ruling from the Internal
Revenue Service.

     15. Combined, Consolidated or Unitary Basis Returns. The parties
acknowledge that certain state, local or foreign Tax Authorities may require, or
one of the parties may desire, to file amended or original state, local or
foreign income Tax Returns on a combined, consolidated or unitary basis. In this
regard, Spinco agrees that it will have no right to request that Plains file an
amended return or a claim for refund for any reason, unless Spinco agrees to pay
any Tax liability shown thereon or therein and Plains, in its absolute
discretion (which may be withheld for any reason), agrees. Such filing may
result in an aggregate decrease in the state, local or foreign income Tax of
both parties; however, one party may suffer a Tax increase compared to

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its state, local or foreign income Tax liability calculated on a separate
company basis, while the other party enjoys a Tax decrease. In any such event,
the parties intend that the required calculations for determining which party
owes Taxes to the other with respect thereto be made by utilizing the principles
set forth in Paragraphs 2, 3, 5, 12 and 13 hereof.

     16. Earnings and Profits Information. The parties agree to share such
information as is necessary to allocate properly the earnings and profits of the
Spinco Group in accordance with the Code and Treasury Regulations for Tax
periods prior to or ending on the Spin-Off Date. After the Spin-Off, Plains
agrees to provide Spinco and Spinco's independent auditors with such information
as is necessary to verify amounts received or receivable or paid or payable by
Spinco under this Agreement. Spinco agrees to make available to Plains, upon
request, all Federal, state, local and foreign Tax Returns, work papers and
other documents pertaining to the activities of the Spinco Group prior to the
Spin-Off.

     17. Tax Interpretation. For all Tax purposes and notwithstanding any other
provision of this Agreement, to the extent permitted by applicable law, the
parties hereto shall treat any payment made pursuant to this Agreement as a
capital contribution or dividend distribution, as the case may be, immediately
prior to the Spin-Off Date and, accordingly, as not includible in the taxable
income of the recipient. If it is finally determined that the receipt or accrual
of any payment made under this Agreement is taxable to the recipient, the payor
shall pay to the recipient, on an After-Tax Basis, an amount equal to any
increase in the Taxes of the recipient as a result of receiving the payment from
the payor.

     18. Consistent Tax Treatment. To the extent that assets are assigned, sold,
transferred or conveyed by a member of the Plains Group to Spinco or another
member of the Spinco Group in contemplation of the Separation (as defined in the
Distribution Agreement) or the Spin-Off

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and any such transaction is treated as a sale for Tax purposes, the
aggregate purchase price shall be allocated among the assets assigned, sold,
transferred or conveyed as determined by Plains in its sole discretion. Each of
Plains and Spinco agrees to report and, where applicable, to cause the members
of their respective groups to report, the purchase prices of such assets as
determined by Plains.

     19. Retention of Records. Each party hereto agrees, to the extent
potentially relevant to the other party, to (1) retain, in accordance with
Plains' record retention policies in effect on the date of this Agreement, all
records, documents, accounting and other information (including computer data)
necessary for the preparation and filing of all Returns or the audit of such
Returns, and (2) give to the other party reasonable access to such records,
documents, accounting data, Returns and related books and records and other
information (including computer data) and to its personnel (insuring their
cooperation) and premises, for purposes of the review or audit of such Returns
to the extent relevant to an obligation or liability of a party under this
Agreement.

     20. Post Spin-Off Period Taxes. Except as otherwise provided to the
contrary in this Agreement, (i) Plains and the other members of the Plains Group
(which, for this purpose, shall not include Spinco and the other members of the
Spinco Group) shall be solely responsible for all Taxes of the Plains Group
(which, for this purpose, shall not include Spinco and the other members of the
Spinco Group) arising in Tax periods beginning after the Spin-Off Date, and (ii)
Spinco and the other members of the Spinco Group shall be solely responsible for
all Taxes of the Spinco Group arising in Tax periods beginning after the
Spin-Off Date.

     21. Expenses. Each party will bear its own expenses in complying with this
Agreement, including but not limited to the cost of employee work hours. The
sharing of fees

                                       15

<PAGE>

and expenses of nonemployees and independent contractors mutually engaged by the
parties shall be agreed upon before such persons are engaged.

     22. Definitions.

          (a) "After-Tax Basis" means, with respect to any payment, an amount
calculated by taking into account the Tax consequences of the receipt of such
payment, as well as any Tax benefit associated with the liability giving rise to
the payment, in each case calculated on a present value basis using the Agreed
Rate.

          (b) "Agreed Rate" means the annual rate of interest quoted, from time
to time, by JPMorgan Chase Bank in Houston, Texas as its prime rate of interest
for the purpose of determining the interest rates charged by it for United
States dollar commercial loans made in the United States.

          (c) "Code" has the meaning set forth in the first recital hereof.

          (d) "Distribution Agreement" means that certain Master Separation
Agreement dated as of the date hereof, by and between Plains and Spinco, as the
same may be amended or otherwise modified from time to time pursuant to the
terms thereof.

          (e) "Items of Loss or Tax Benefit" has the meaning set forth in
Paragraph 1 hereof.

          (f) "Interim Period" has the meaning set forth in Paragraph 2 hereof.

          (g) "Plains" has the meaning set forth in the preamble hereto.

          (h) "Plains Group" has the meaning set forth in the first recital
hereto.

          (i) "Returns" means all returns, declarations, reports, statements and
other documents required to be filed in respect of Taxes, and the term "Return"
means any one of the foregoing Returns.

                                       16

<PAGE>

          (j) "Ruling" means that certain private letter ruling issued by the
Internal Revenue Service on May 22, 2002, with respect to the Spin-Off and
relating to the tax consequences associated with the distribution of all
outstanding shares of Spinco common stock, as the same may be amended,
supplemented or otherwise modified or added to by the Internal Revenue Service
on or before the Spin-Off Date.

          (k) "Short Period" has the meaning set forth in Paragraph 2 hereof

          (l) "Spinco" has the meaning set forth in the preamble hereof.

          (m) "Spinco Group" has the meaning set forth in Paragraph 1 hereof.

          (n) "Spin-Off" has the meaning set forth in the fourth recital hereof.

          (o) "Spin-Off Date" has the meaning set forth in the fourth recital
hereof.

          (p) "Spin-Off Tax" means any Tax to which Plains or any member of the
Plains Group is subject as a result of the application of any provision of the
Code to the Spin-Off, including without limitation, Section 311(b), Section
355(c)(2), Section 355(e) or Section 361(c)(2) of the Code (or any corresponding
or similar provision of state, local or foreign law), which results (i) solely
from the fact that one or more persons acquire after the Spin-Off Date directly
or indirectly stock representing a 50-percent or greater interest in Spinco and
such acquisition is subject to Section 355(e) of the Code; (ii) from the failure
of Spinco or any other member of the Spinco Group to comply with the covenants,
agreements and representations in the Ruling; (iii) from any action by, or
failure to take an action on the part of, Spinco or any other member of the
Spinco Group, or (iv) from any combination of (i) through (iii) above.

          (q) "Tax Authority" means the United States Internal Revenue Service
or any other comparable state, local or foreign governmental authority.

                                       17

<PAGE>

          (r) "Taxes" means all federal, state, local, foreign and other taxes,
duties, levies, imposts, customs or other assessments, including, without
limitation, all net income, alternative minimum, gross income, gross receipts,
sales, use, ad valorem, transfer, franchise, profits, profit share, license,
value added, withholding, payroll, employment, excise, estimated, severance,
stamp, occupation, premium, property, windfall profits, or other taxes, of any
kind whatsoever, together with any interest, penalties, additions to tax, fines
or other additional amounts imposed thereon or related thereto, and the term
"Tax" means any one of the foregoing Taxes.

          (s) "Transfer Tax" means any excise, sales, use, transfer,
documentary, filing, recordation or other similar tax or fee, together with any
interest, additions or penalties with respect thereto and any interest in
respect of such additions or penalties.

     23. Notices. All notices and other communications to be given or made
hereunder shall be in writing and shall be (a) personally delivered with signed
receipt obtained acknowledging delivery; (b) transmitted by postage prepaid
registered mail, return receipt requested (air mail if international); or (c)
transmitted by facsimile; to a party at the address set out below (or at such
other address as it may have provided notification for the purposes hereof to
the other party hereto in accordance with this Section).

                  If to Spinco:   Plains Exploration & Production Company
                                  500 Dallas Street, Suite 700
                                  Houston, Texas 77002
                                  Fax number:   713-654-4915
                                  Attention:    General Counsel

                  If to Plains:   Plains Resources Inc.
                                  500 Dallas Street, Suite 700
                                  Houston, Texas 77002
                                  Fax number:   (713) 654-4915
                                  Attention:    Chief Executive Officer

                                       18

<PAGE>

     24. Binding Effect; Successors. This Agreement shall be binding upon and
inure to the benefit of and be enforceable by the parties hereto and any
successor, by merger, acquisition of substantially all of a party's assets or
otherwise, to either of the parties hereto (including but not limited to any
successor of Plains or Spinco succeeding to the Tax attributes of Plains or
Spinco under Section 381 of the Code), to the same extent as if such successor
had been an original party to this Agreement. In addition, in the event of an
acquisition of substantially all of the assets of Spinco in which gain or loss
is not recognized, in whole or in part, for Federal income Tax purposes, Spinco
shall ensure that any purchaser of such assets shall assume the obligations set
forth in this Agreement.

     25. Severability. Any provision of this Agreement that is determined by
arbitration as provided herein or a court of competent jurisdiction to be
invalid, illegal or unenforceable shall be ineffective to the extent of such
invalidity, illegality or unenforceability, without affecting in any way the
remaining provisions hereof in such jurisdiction or rendering that or any other
provision of this Agreement invalid, illegal or unenforceable, so long as the
material purposes of this Agreement can be determined and effectuated. Should
any provision of this Agreement be so declared invalid, illegal or
unenforceable, the parties shall agree on a valid provision to substitute for
it.

     26. Entire Agreement. This Agreement, including the exhibit and other
writings referred to herein or delivered pursuant hereto and the Distribution
Agreement, as well as the other agreements entered into by and between Plains
and Spinco in connection with the transactions contemplated by the Distribution
Agreement, constitutes the entire agreement between Plains and Spinco with
respect to the subject matter hereof and supersedes all other

<PAGE>

agreements, representations, warranties, statements, promises and undertakings,
whether oral or written, with respect to the subject matter hereof, including,
without limitation, any and all Tax sharing agreements or arrangements (whether
oral or written) between Plains and the other members of the Plains Group (other
than the Spinco Group) on the one hand and Spinco and the other members of the
Spinco Group on the other hand, that require payments or indemnities to be made
with respect to Taxes. This Agreement may not be amended, altered or modified
except by a writing signed by duly authorized officers of Plains and Spinco.

     27. Governing Law. All questions arising out of this Agreement and the
rights and obligations created herein, or its validity, existence,
interpretation, performance or breach, shall be governed by and construed in
accordance with the internal laws of the State of Texas, without regard to or
the application of the rules of conflicts of laws set forth in such laws.

     28. Arbitration. The parties agree that any claim arising out of or related
to this Agreement shall be governed by the dispute resolution, arbitration and
choice of forum provisions set forth in Article VIII of the Distribution
Agreement.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the date first written above.

                              PLAINS RESOURCES INC.

                              By:      /s/  James C. Flores
                                       -----------------------------------------
                                       Chairman and Chief Executive Officer

                              PLAINS EXPLORATION & PRODUCTION
                              COMPANY

                              By:      /s/  John T. Raymond
                                       -----------------------------------------
                                       President

                                       20<PAGE>

                                                                    EXHIBIT 10.6

                               FIRST AMENDMENT TO
                              PLAINS RESOURCES INC.
                            2001 STOCK INCENTIVE PLAN

     Plains Resources Inc. (the "Company"), having previously adopted the Plains
Resources Inc. 2001 Stock Incentive Plan (the "Plan"), and in accord with the
powers granted to the board of directors of the Company (the "Board") pursuant
to Section 15 of the Plan, does hereby amend the Plan, effective as of September
10, 2002, as follows:

     Section 6.4(a) of the Plan is hereby amended and replaced in its entirety
by the following:

     "(a) Except as otherwise provided by the Board, if an Optionee's service as
     a Director terminates for any reason other than Disability, death or Cause,
     the Optionee may for a period of three (3) months after such termination
     exercise his or her Option to the extent, and only to the extent, that such
     Option or portion thereof was vested and exercisable as of the date the
     Optionee's service as a Director terminated, after which time the Option
     shall automatically terminate in full."

     This amended Section 6.4(a) shall apply to Options outstanding on the date
hereof and to Options granted in the future pursuant to the terms of the Plan
(as amended). Agreements with respect to Options outstanding on the date hereof
shall be amended as necessary to provide for this amendment.

     The first paragraph of Section 6.4 of the Plan is hereby amended and
replaced in its entirety by the following:

     "Duration. Subject to Section 7.4, each Formula Option shall terminate on
     the date which is the tenth anniversary of the date of grant (or if later,
     the first anniversary of the date of the Director's death if such death
     occurs prior to such tenth anniversary), unless terminated earlier as
     follows:"

     This amended first paragraph of Section 6.4 shall apply to Options granted
in the future pursuant to the terms of the Plan (as amended).

     Adopted by the Board on September 10, 2002.

                                       1

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