SECOND AMENDMENT TO TAX SHARING AGREEMENT EFFECTIVE JANUARY 1, 1997 This SECOND AMENDMENT TO THE TAX SHARING AGREEMENT (this "Second Amendment") is made and entered into as of January 1, 1997 by and among ATLANTIC RICHFIELD COMPANY, a Delaware corporation ("ARCO"), VASTAR RESOURCES, INC., a Delaware corporation ("VRI"), and the Subsidiaries of VRI that are signatories hereto. WHEREAS, ARCO and VRI entered into a Tax Sharing Agreement effective as of October 1, 1993 and to a First Amendment effective as of June 1, 1995 to provide for the sharing of income tax liability, including specifically credits provided under section 29 of the Internal Revenue Code of 1986 (the "Basic Agreement as Amended"). WHEREAS, the parties wish to enter into an agreement to modify the Basic Agreement as Amended to allow Vastar to realize more immediately benefits from section 29 credits that it generates and that are utilized by the ARCO Group, and to fairly compensate ARCO for earlier payment. NOW THEREFORE, in consideration of the premises and the mutual covenants and agreements contained herein, the parties agree as follows: 1. DEFINITIONS. Any capitalized term not otherwise defined herein shall have the meaning given to such term in Section 1 of the Basic Agreement as Amended. 2. AMENDMENTS TO BASIC AGREEMENT AS AMENDED. The Basic Agreement as Amended shall be further amended as follows: a. Section 1(k) is deleted and a new Section 1(k) is hereby added to read as follows: (k) DESIGNATED CREDIT shall mean (i) in the case of income tax credits described in section 29 of the Code ("section 29 credits") that do not constitute Refundable Designated Credits, as defined below, the product of the amount of such credits multiplied by 96.75%, (ii) Refundable Designated Credits and (iii) income tax credits described in section 43 of the Code ("section 43 credits"), provided that all of such credits are generated by any member of the VRI Group (1) in the ordinary course of its trade or business of exploration, development, production and marketing of natural resources and (2) from interests in properties that are acquired by any Member of the VRI Group in the ordinary course of its trade or business. All determinations of whether a Designated Credit was generated or whether a property was acquired by a Member of the VRI Group in the ordinary course of its trade or business shall be made by ARCO in its sole and absolute discretion. Upon request from ARCO, Vastar shall provide certifications relating to the facts associated with the generation or acquisition of such credits and shall furnish such additional data or information as ARCO may require in order to make such determinations. b. The third sentence of Section 4(a) shall be amended by deleting the phrase "prepared in accordance with subsections (b) and (c) of this Section 4" and by inserting the phrase "prepared in accordance with subsections (b), (c) and (h) of this Section 4". c. The preamble to Section 4(h) and Section 4(h)(i) shall be deleted. New Section 4(h)(i) is hereby added to read and provide as follows: (i) USE OF DESIGNATED CREDITS IN CURRENT TAXABLE YEAR. Amounts of Designated Credits generated in a Taxable Year may be applied to reduce the VRI Group Consolidated Tax Liability for the Taxable Year in the same manner as if the Pro Forma VRI Return were an actual return. In addition, Designated Credits may further reduce the VRI Group Consolidated Tax Liability (including 2 a reduction below zero which will result in a negative amount that is refundable to VRI to the extent provided herein), without regard to the impact of any statutory or income limitations but only if and to the extent that such Designated Credits reduce the ARCO Group Consolidated Tax Liability for such Taxable Year (or in the case of carryover Designated Credits, a prior Taxable Year). Notwithstanding the foregoing, (A) the refund, if any, that VRI is permitted to receive with respect to any Taxable Year that is attributable to the utilization of Refundable Designated Credits pursuant to this Section 4(h) (including credits utilized pursuant to the carryover provisions of Sections 4(h)(iv) and 4(h)(v) of this Agreement) may not exceed $15 million, and (B) VRI will not be permitted to receive a refund that is attributable to the use of section 43 credits. Refundable Designated Credits that are utilized pursuant to the carryover provisions of Sections 4(h)(iv) and 4(h)(v) shall be applied against the $15 million limitation in the year that they are utilized. In the event that the amount of VRI's refund that is attributable to its use of Refundable Designated Credits pursuant to this Section 4(h) with respect to a Taxable Year is less than $15 million, such shortfall shall not increase the $15 million limitation in any subsequent Taxable Year. ARCO shall refund in cash to VRI the tax benefit associated with the Designated Credits that are permitted to be refunded pursuant to this Section 4(h) within 60 days of the actual reduction in the ARCO Group Consolidated Tax Liability (or, in the case of Refundable Designated Credits that are utilized pursuant to Section 4(h)(v), within 60 days of Completion date) for such Taxable Year. For purposes of this Section 4(h)(i), the actual reduction in the ARCO Group Consolidated Tax Liability occurs when credits are either applied on the ARCO Group's Consolidated Return for a Taxable Year or used to reduce the ARCO Group's estimated income tax payments for such year (as determined by ARCO). To the extent that VRI has received a refund pursuant to Section 4(h) with respect to Designated Credits, the amount of carryovers on the Pro Forma VRI Return shall be correspondingly reduced (adjustments shall also be made to reflect subsequent adjustments pursuant to this Section 4(h) or Section 8). If VRI has received a refund from ARCO pursuant to this Section 4(h)(i) with respect to a Taxable Year as a result of any Designated Credit and (A) ARCO determines that such credits did not reduce the ARCO Group Consolidated Tax Liability for such year (or, if applicable, for a prior Taxable Year) or (B) if the amount of Designated Credits for which VRI has received a refund with 3 respect to a Taxable Year exceeds the amount of section 29 credits from Members of the VRI Group that are eligible to be treated as Designated Credits in such year and utilized under this Section 4(h) in such year, then VRI shall reimburse ARCO for any payment received within 60 days of receiving from ARCO a schedule setting forth ARCO's calculation of VRI's reimbursement obligations pursuant to this sentence. ARCO shall make such calculation within 30 days of the Completion date for such Taxable Year; HOWEVER, any failure by ARCO to redetermine the amount of credits that reduce the ARCO Group Consolidated Tax Liability or to reconcile the amount of Designated Credits utilized within the 30-day period set forth in the preceding sentence shall not prevent ARCO, in its sole and absolute discretion, from making subsequent calculations of VRI's refund obligations contemplated by the preceding sentence, as circumstances warrant, within the applicable statute of limitations (determined as if the Pro Forma VRI Return were an actual return that is subject to any extensions that have been granted by ARCO with respect to the Consolidated Return). d. Section 4(h)(ii) shall be deleted. References to Section 4(h)(ii) in the Basic Agreement As Amended shall be deemed to be references to Section 4(h)(i). e. The first sentence of Section 4(h)(iii) is amended by deleting the phrase "(z) cannot be utilized under Section 4(h)(i) solely because of the limitation contained therein that prevents Designated Credits from reducing the VRI Group Tax Liability below zero." f. The first sentence of Section 4(h)(iv) is amended by deleting the phrase ", in the case of Refundable Designated Credits,". g. Section 4(h)(v) shall be deleted, and new Section 4(h)(v) is hereby added to read and provide as follows: (v) DESIGNATED CREDITS PREVIOUSLY UTILIZED BY THE ARCO GROUP. Amounts of Designated Credits that have been applied to reduce the ARCO Group Consolidated Tax 4 Liability in a prior Taxable Year, but which have not been applied to reduce the VRI Group Tax Liability under Section 4(h)(i) solely because of (A) the limitation contained in Section 4(h)(i) that prevents Designated Credits described in section 43 of the Code from reducing the VRI Group Tax Liability below zero or (B) the limitation contained in Section 4(h)(i) that limits refunds with respect to Refundable Designated Credits, may be applied to reduce the VRI Group Consolidated Tax Liability in any subsequent Taxable Year, including a reduction below zero, notwithstanding any statutory or income limitations. For purposes of the preceding sentence, the provisions of Sections 4(h)(i) and 4(h)(iii) shall apply to Refundable Designated Credits carried over pursuant to this Section 4(h)(v) as if such credits were generated by sales of production from the well in the Taxable Year to which they are carried. The preceding sentence is not intended to affect the application of the ordering rule contained in the first sentence of Section 4(h)(vi) of this Agreement. h. Section 4(h)(viii) shall be deleted and new Section 4(h)(viii) is hereby added to read and provide as follows: (viii) DISPLACED CREDITS. If VRI has reduced the VRI Group Consolidated Tax Liability or received a refund pursuant to this Section 4(h) for any Taxable Year pursuant to this Section 4(h) as a result of any Designated Credit of any Member of the VRI Group, and such Designated Credit is subsequently displaced by another attribute of the ARCO Group in a situation where Section 4(h)(vii) does not apply, VRI shall reimburse ARCO for any amount by which VRI's liability to ARCO was reduced as a result of the use of the displaced Designated Credit or repay to ARCO the amount of the refund from ARCO that was attributable to the use of the displaced Designated Credit. For purposes of this Section 4(h)(viii), Refundable Designated Credits shall be deemed to be displaced prior to Designated Credits. A Designated Credit that is displaced may be carried forward pursuant to Section 4(h)(iv) thereafter, or, with the consent of ARCO, carried back if ARCO determines that the circumstances giving rise to such displacement will allow it 5 to utilize a greater amount of Designated Credits in a prior Taxable Year than it would have utilized absent such circumstances. i. Section 7(b) of the Basic Agreement As Amended is amended by deleting the following phrase "(other than Designated Credits (including carryovers) that reduced the VRI Group Tax Liability for any Taxable Year pursuant to Section 4(h) of this Agreement or Refundable Designated Credits (including carryovers) with respect to which VRI has received a refund from ARCO pursuant to Section 4(h) of this Agreement)" in the 10th and 19th lines of that section and by substituting in its place the following phrase "(other than Designated Credits (including carryovers) that reduced the VRI Group Consolidated Tax Liability or with respect to which VRI has received a refund from ARCO for any Taxable Year pursuant to Section 4(h) of this Agreement)". 3. EFFECTIVE DATE AND PAYMENT FOR CARRY FORWARD DESIGNATED CREDITS. The effective date for this Second Amendment shall be January 1, 1997. ARCO shall pay $59,382,000 to VRI within 2 days after the execution date of this Second Amendment to compensate VRI for all Designated Credits that were (i) generated by the VRI Group prior to January 1, 1997 and (ii) with respect to which VRI is not entitled to compensation under the Basic Agreement as Amended in any Taxable Year ending prior to the effective date of this 6 Second Amendment. The amount of the carryovers on the Pro Forma VRI Return shall be reduced by the full amount of the Designated Credits for which VRI received compensation, notwithstanding the fact that the payment was calculated by reference to 96.75% of the statutory credit amount for certain of such credits. The amount of, and payment for, such credits shall continue to be subject to adjustments as provided in the Basic Agreement as Amended, including without limitation, Sections 4(h)(vii), 4(h)(viii) and 8; PROVIDED HOWEVER, that to the extent that the adjustment affects the calculation of credits described in the first sentence of this Section 3, the amount of such adjustment shall be calculated at 96.75% of the statutory credit amount. 4. GOVERNING LAW. THIS SECOND AMENDMENT SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS, WITHOUT GIVING EFFECT TO THE PRINCIPLES OF CONFLICT OF LAWS. 5. CONTINUATION OF BASIC AGREEMENT AS AMENDED. The Basic Agreement as Amended continues in full force and effect, except as expressly amended herein. IN WITNESS WHEREOF, the parties hereto have caused their names to be subscribed and executed by their respective authorized officers on the dates indicated, effective as of January 1, 1997. ATLANTIC RICHFIELD COMPANY By:/s/ PATRICK J. ELLINGSWORTH Date: 3/20/97 --------------------------- ------- Patrick J. Ellingsworth Associate General Tax Officer 7 VASTAR RESOURCES, INC. By: /s/ A. SHAWN NOONAN Date: 3/18/97 ------------------- ------- A. Shawn Noonan General Tax Officer F&H PIPELINE COMPANY By: /s/ A. SHAWN NOONAN Date: 3/18/97 ------------------- ------- A. Shawn Noonan Assistant Secretary GRANT GATHERING COMPANY By: /s/ A. SHAWN NOONAN Date: 3/18/97 ------------------- ------- A. Shawn Noonan Assistant Secretary WILBURTON HUB, INC. By: /s/ A. SHAWN NOONAN Date: 3/18/97 ------------------- ------- A. Shawn Noonan Assistant Secretary VASTAR GAS MARKETING, INC. By: /s/ A. SHAWN NOONAN Date: 3/18/97 ------------------- ------- A. Shawn Noonan Assistant Secretary VASTAR HOLDINGS, INC. By: /s/ A. SHAWN NOONAN Date: 3/18/97 ------------------- ------- A. Shawn Noonan Assistant Secretary VASTAR POWER MARKETING, INC. By: /s/ A. SHAWN NOONAN Date: 3/18/97 ------------------- ------- A. Shawn Noonan Assistant Secretary 8