Execution Version
TAX SHARING AGREEMENT
BY AND AMONG
ANADARKO PETROLEUM CORPORATION
AND
WESTERN GAS PARTNERS, LP
May 14, 2008

 

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TABLE OF CONTENTS
ARTICLE I
Definitions

             
1.1
  Definitions     1  
 
            ARTICLE II
Preparation and Filing of Tax Returns

 
           
2.1
  Manner of Filing     3  
2.2
  Franchise Tax Taxable Period     4  
 
            ARTICLE III
Allocation of Taxes

 
           
3.1
  Liability of the Partnership Group for Combined Taxes     4  
3.2
  Partnership Group Combined Tax Liability     4  
3.3
  Preparation and Delivery of Pro Forma Tax Returns     5  
3.4
  Payment of Tax     5  
3.5
  Subsequent Changes in Treatment of Tax Items     5  
 
            ARTICLE IV
Control of Tax Proceedings; Cooperation and Exchange of Information

 
           
4.1
  Control of Proceedings     5  
4.2
  Cooperation and Exchange of Information     6  
 
            ARTICLE V
Warranties and Representations; Payment Obligations

 
           
5.1
  Warranties and Representations Relating to Actions of        
 
  Anadarko and the Partnership     6  
5.2
  Calculation of Payment Obligations     7  
5.3
  Prompt Performance     7  
5.4
  Interest     7  
5.5
  Tax Records     8  
5.6
  Continuing Covenants     8  
 
            ARTICLE VI
Miscellaneous Provisions

 
           
6.1
  Notice     8  
6.2
  Required Payments     8  
6.3
  Injunctions     9  
6.4
  Further Assurances     9  
6.5
  Parties in Interest     9  
6.6
  Setoff     9  
6.7
  Change of Law     9  
6.8
  Termination and Survival     9  
6.9
  Amendments; No Waivers     9  
6.10
  Governing Law and Interpretation     10  

 

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6.11
  Resolution of Certain Disputes     10  
6.12
  Confidentiality     10  
6.13
  Costs, Expenses and Attorneys’ Fees     10  
6.14
  Counterparts     11  
6.15
  Severability     11  
6.16
  Entire Agreement.     11  
6.17
  Assignment     11  
6.18
  Fair Meaning     12  
6.19
  Titles and Headings     12  
6.20
  Construction     12  

 

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TAX SHARING AGREEMENT
BY AND AMONG
ANADARKO PETROLEUM CORPORATION AND
WESTERN GAS PARTNERS, LP
     Tax Sharing Agreement (the “Agreement”), dated this 14th day of May, 2008,
by and among ANADARKO PETROLEUM CORPORATION (“Anadarko”), a Delaware
corporation, and WESTERN GAS PARTNERS, LP (the “Partnership”), a Delaware
limited partnership.
RECITALS
     WHEREAS, Anadarko is the common parent of an affiliated group of
corporations within the meaning of Section 1504(a) of the Code (as defined
below), which currently files a consolidated federal income tax return;
     WHEREAS, the Partnership Group (as defined below) includes various entities
that may be required to join with Anadarko in the filing of a consolidated,
combined or unitary state tax return;
     WHEREAS, the Parties (as defined below) wish to set forth the general
principles under which they will allocate and share various Taxes (as defined
below) and related liabilities;
     WHEREAS, Anadarko, on behalf of itself and its present and future
subsidiaries other than the Partnership Group (“Anadarko Group”), and the
Partnership, on behalf of itself and its present and future subsidiaries (the
“Partnership Group”), are entering into this Agreement to provide for the
allocation among the Anadarko Group and the Partnership Group of all
responsibilities, liabilities and benefits relating to any Tax for which a
Combined Return (as defined below) is filed for a taxable period including or
beginning on or after the Effective Date (as defined below) and to provide for
certain other matters;
     NOW, THEREFORE, in consideration of the mutual agreements, provisions and
covenants contained in this Agreement, and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
Parties hereby agree as follows:
ARTICLE I
Definitions
     1.1 Definitions. The following terms shall have the following meanings
(such meanings to be equally applicable to both the singular and the plural
forms of the terms defined):
     “Accounting Referee” is defined in Section 6.11 herein.
     “Anadarko Group” is defined in the Recitals to this Agreement.
     “Code” means the Internal Revenue Code of 1986, as amended, or any
successor thereto, as in effect for the taxable period in question.

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     “Combined Group” means a group of corporations or other entities that files
a Combined Return.
     “Combined Return” means any Tax Return (other than a Tax Return for U.S.
federal income taxes) filed on a consolidated, combined (including nexus
combination, worldwide combination, domestic combination, line of business
combination or any other form of combination) or unitary basis that includes
activities of any member of the Anadarko Group and any member of the Partnership
Group.
     “Effective Date” means 7:00 a.m., Central time, on May 14, 2008.
     “Final Determination” means the final resolution of any Tax (or other
matter) for a taxable period, including related interest or penalties, that,
under applicable law, is not subject to further appeal, review or modification
through proceedings or otherwise, including (i) by the expiration of a statute
of limitations or a period for the filing of claims for refunds, amending Tax
Returns, appealing from adverse determinations or recovering any refund
(including by offset), (ii) by a decision, judgment, decree or other order by a
court of competent jurisdiction, which has become final and unappealable,
(iii) by a closing agreement, an accepted offer in compromise or a comparable
agreement under laws of the particular Tax Authority, (iv) by execution of a
form under the laws of a Tax Authority that is comparable to an Internal Revenue
Service Form 870 or 870-AD (excluding, however, with respect to a particular Tax
Item for a particular taxable period any such form that reserves (whether by its
terms or by operation of law) the right of the taxpayer to file a claim for
refund and/or the right of the Tax Authority to assert a further deficiency with
respect to such Tax Item for such period) or (v) by any allowance of a refund or
credit, but only after the expiration of all periods during which such refund
may be adjusted.
     “Notice” is defined in Section 6.1 herein.
     “Partnership Group” is defined in the recitals to this Agreement.
     “Partnership Group Combined Tax Liability” means, with respect to any Tax,
the Partnership Group’s liability for such Tax owed with respect to a Combined
Return for a taxable period, as determined under Section 3.2 of this Agreement.
     “Partnership Group Deposit” is defined in Section 3.4 herein.
     “Partnership Group Members” means those entities included in the
Partnership Group.
     “Partnership Group Pro Forma Combined Return” means a pro forma Combined
Return or other schedule prepared pursuant to Section 3.2 of this Agreement.
     “Party” means each of Anadarko and the Partnership, and solely for purposes
of this definition, “Anadarko” includes the Anadarko Group and the “Partnership”
includes the Partnership Group. Each of Anadarko and the Partnership shall cause
the Anadarko Group and the Partnership Group, respectively, to comply with this
Agreement.

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     “Tax Attribute” means a Tax Item of a member of the Partnership Group
reflected on a Combined Return that is comparable to one or more of the
following attributes with respect to a U.S. federal income tax consolidated tax
return: a net operating loss, a net capital loss, an unused investment credit,
an unused foreign tax credit, an excess charitable contribution, a U.S. federal
minimum tax credit or a U.S. federal general business credit (but not tax basis
or earnings and profits).
     “Tax Authority” means a domestic governmental authority (other than the
United States) or any subdivision, agency, commission or authority thereof or
any quasi-governmental or private body having jurisdiction over the assessment,
determination, collection or imposition of any Tax (excluding the U.S. Internal
Revenue Service).
     “Tax Controversy” means any audit, examination, dispute, suit, action,
litigation or other judicial or administrative proceeding initiated by Anadarko
or the Partnership or any Tax Authority.
     “Tax Item” means any item of income, gain, loss, deduction or credit, or
other item reflected on a Tax Return or any Tax Attribute.
     “Tax Return” means any return, report, certificate, form or similar
statement or document (including any related or supporting information or
schedule attached thereto and any information return, amended Tax Return, claim
for refund or declaration of estimated tax) required to be supplied to, or filed
with, a Tax Authority in connection with the determination, assessment or
collection of any Tax or the administration of any laws, regulations or
administrative requirements relating to any Tax.
     “Taxes” means all forms of taxation, whenever created or imposed, and
whether imposed by a domestic, local, municipal, governmental, state, federation
or other body, but excluding taxes imposed by the United States, and without
limiting the generality of the foregoing, shall include net income, alternative
or add-on minimum, gross income, sales, use, ad valorem, gross receipts, value
added, franchise, profits, license, transfer, recording, withholding, payroll,
employment, excise, severance, stamp, occupation, premium, property, windfall
profit, custom duty or other tax, governmental fee or like assessment or charge
of any kind whatsoever, together with any related interest, penalties or other
additions to tax, or additional amounts imposed by any such Tax Authority.
     Any term used but not capitalized herein that is defined in the Code or in
the Treasury Regulations thereunder shall, to the extent required by the context
of the provision at issue, have the meaning assigned to it in the Code or such
regulation.
ARTICLE II
Preparation and Filing of Tax Returns
     2.1 Manner of Filing.
          (a) For periods that include the Effective Date and periods after the
Effective Date, Anadarko shall have the sole and exclusive responsibility for
the preparation and filing of, and shall prepare and file, all Combined Returns
or cause to be prepared and filed all Combined

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Returns. Anadarko shall be authorized to take any and all action necessary or
incidental to the preparation and filing of a Combined Return, including,
without limitation, (i) making elections and adopting accounting methods,
(ii) filing all extensions of time, including extensions of time for payment of
tax, (iii) filing claims for refund or credit or (iv) giving waivers or bonds.
          (b) For periods that include the Effective Date and periods after the
Effective Date, the Partnership Group shall have the sole and exclusive
responsibility for the preparation and filing of, and shall prepare and file or
cause to be prepared and filed, all Tax Returns of the Partnership Group Members
that are not Combined Returns.
          (c) Anadarko shall have sole discretion to include, or cause to be
included, in a Combined Return for any Tax any member of the Partnership Group
for which inclusion in such Combined Return is elective; provided, however, that
the Partnership Group Combined Tax Liability for any period shall not exceed the
aggregate of (x) each such elective Partnership Group Member’s liability for
such Tax for such period, computed as if such Partnership Group Member were not
included in such Combined Return and (y) the Partnership Group Combined Tax
Liability calculated for the Partnership Group Members for which inclusion is
not elective. Anadarko shall provide pro forma Tax Returns pursuant to
Section 3.5 of this Agreement to support the calculation of the amount of any
decrease in the Partnership Group Combined Tax Liability pursuant to this
Section 2.1(c).
     2.2 Franchise Tax Taxable Period. References to “taxable period” for any
franchise or other doing business Tax shall mean the taxable period during which
the income, operations, assets or capital comprising the base of such Tax is
measured, regardless of whether the right to do business for another taxable
period is obtained by the payment of such franchise Tax.
ARTICLE III
Allocation of Taxes
     3.1 Liability of the Partnership Group for Combined Taxes. For each Tax for
each taxable period that includes or begins on or after the Effective Date and
for which a Combined Return is filed, the Partnership Group Members included in
such Combined Return shall be liable to Anadarko for an amount equal to the
Partnership Group Combined Tax Liability in respect of such Tax.
     3.2 Partnership Group Combined Tax Liability. With respect to each Tax for
each taxable period that includes or begins on or after the Effective Date and
for which a member of the Partnership Group is included in a Combined Return,
the Partnership Group Combined Tax Liability for such Tax for such taxable
period shall be the Tax for such taxable period as determined on a Partnership
Group Pro Forma Combined Return prepared:
          (a) by including only the Tax Items of the members of the Partnership
Group that are included in the Combined Return and computing the liability of
the Partnership Group Members for such Tax as if such Partnership Group Members
were included in a separate consolidated or unitary group;
          (b) except as provided in Section 3.2(e) hereof, using all elections,
accounting methods and conventions used on the Combined Return for such period;

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          (c) applying the Tax rate in effect for the Combined Return of the
Combined Group for such taxable period;
          (d) assuming that the Partnership Group elects not to carry back any
net operating losses and
          (e) assuming that the Partnership Group’s utilization of any Tax
Attribute carryforward or carryback is limited to the Tax Attributes of the
Partnership Group that would be available if the Partnership Group Combined Tax
Liability for each taxable period ending after January 1, 2008 were determined
in accordance with this Section 3.2.
     3.3 Preparation and Delivery of Pro Forma Tax Returns. Not later than
90 days following the date on which a Combined Return is filed with the
appropriate Tax Authority, Anadarko shall prepare and deliver to the Partnership
the related Partnership Group Pro Forma Combined Return calculating the
Partnership Group Combined Tax Liability attributable to the period covered by
such filed Combined Return.
     3.4 Payment of Tax. Anadarko shall timely pay (or shall cause to be timely
paid) any Tax reflected on a Combined Return and hold the Partnership harmless
for all liability for such Tax. In the event Anadarko is required to make an
estimated payment or deposit of any Tax of any Combined Group which includes any
member of the Partnership Group, Anadarko shall calculate the portion, if any,
of such estimated payment or deposit attributable to the Partnership Group using
a methodology similar to that described in Section 3.2 (the “Partnership Group
Deposit”) and shall present such calculation to the Partnership. Within 5 days
thereafter, the Partnership shall pay the Partnership Group Deposit to Anadarko.
Within 30 days after delivery by Anadarko of a Partnership Group Pro Forma
Combined Return to the Partnership calculating the Partnership Group Combined
Tax Liability with respect to a Combined Return, the Partnership shall pay to
Anadarko such Partnership Group Combined Tax Liability less the amount of any
Partnership Group Deposit relating to the same Combined Return.
     3.5 Subsequent Changes in Treatment of Tax Items. With respect to any
Combined Return for any taxable period beginning on or after the Effective Date,
in the event of a change in the treatment of any Tax Item of any member of a
Combined Group as a result of a Final Determination, within 30 days following
such Final Determination (i) Anadarko shall calculate the change, if any, to the
Partnership Group Combined Tax Liability resulting from such change,
(ii) Anadarko shall pay any decrease in the Partnership Group Combined Tax
Liability to the Partnership and (iii) the Partnership shall pay any increase in
the Partnership Group Combined Tax Liability to Anadarko.
ARTICLE IV
Control of Tax Proceedings; Cooperation and Exchange of Information
     4.1 Control of Proceedings. Except as provided in this Article IV, Anadarko
shall have full responsibility and discretion in handling, settling or
contesting any Tax Controversy involving a Tax Return for which it has filing
responsibility under this Agreement as well as all Tax Returns for all taxable
periods ending before the Effective Date. The Partnership shall have full
responsibility and discretion in handling, settling or contesting any Tax
Controversy

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involving a Tax Return for which it has filing responsibility under this
Agreement. Except as otherwise provided in this Article IV, any costs incurred
in handling, settling or contesting any Tax Controversy shall be borne by the
Party having full responsibility and discretion thereof.
     4.2 Cooperation and Exchange of Information.
          (a) Each Party shall cooperate fully at such time and to the extent
reasonably requested by any other Party in connection with the preparation and
filing of any Tax Return or claim for refund, or the conduct of any audit,
dispute, proceeding, suit or action concerning any issues or other matters
considered in this Agreement. Such cooperation shall include, without
limitation, the following: (i) the retention and provision on demand of Tax
Returns, books, records (including those concerning ownership and Tax basis of
property which a Party may possess), documentation or other information relating
to the Tax Returns, including accompanying schedules, related workpapers and
documents relating to rulings or other determinations by Taxing Authorities,
until the expiration of the applicable statute of limitations (giving effect to
any extension, waiver or mitigation thereof); (ii) the provision of additional
information, including an explanation of material provided under clause (i) of
this Section 4.2(a), to the extent such information is necessary or reasonably
helpful in connection with the foregoing; (iii) the execution of any document
that may be necessary or reasonably helpful in connection with the filing of a
Tax Return by Anadarko, the Partnership or of their respective subsidiaries, or
in connection with any audit, dispute, proceeding, suit or action and (iv) such
Party’s commercially reasonable efforts to obtain any documentation from a
governmental authority or a third party that may be necessary or reasonably
helpful in connection with any of the foregoing.
          (b) Each Party shall make its employees and facilities available on a
reasonable and mutually convenient basis in connection with any of the foregoing
matters.
          (c) If any Party fails to provide any information requested pursuant
to Section 4.2 hereof within a reasonable period, as determined in good faith by
the Party requesting the information, then the requesting Party shall have the
right to engage a public accounting firm to gather such information, provided
that 30 days’ prior written notice is given to the unresponsive Party. If the
unresponsive Party fails to provide the requested information within 30 days of
receipt of such notice, then such unresponsive Party shall permit the requesting
Party’s public accounting firm full access to all appropriate records or other
information as reasonably necessary to comply with this Section 4.2 and shall
reimburse the requesting Party or pay directly all costs connected with the
requesting Party’s engagement of the public accounting firm.
ARTICLE V
Warranties and Representations; Payment Obligations
     5.1 Warranties and Representations Relating to Actions of Anadarko and the
Partnership. Each of Anadarko and the Partnership warrants and represents to the
other that:

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          (a) in the case of Anadarko, it is a corporation duly organized,
validly existing and in good standing under the laws of the State of Delaware
and has all requisite power to carry out the transactions contemplated by this
Agreement;
          (b) in the case of the Partnership, it is a limited partnership duly
organized, validly existing and in good standing under the laws of the State of
Delaware and has all requisite power to carry out the transactions contemplated
by this Agreement;
          (c) it has duly and validly taken all action necessary to authorize
the execution, delivery and performance of this Agreement and the consummation
of the transactions contemplated hereby;
          (d) this Agreement has been duly executed and delivered by it and
constitutes its legal, valid and binding obligation enforceable in accordance
with its terms subject, as to the enforcement of remedies, to (i) applicable
bankruptcy, reorganization, insolvency, moratorium or other similar laws
affecting the enforcement of creditors’ rights generally from time to time in
effect and (ii) general principles of equity, whether enforcement is sought in a
proceeding at law or in equity and
          (e) the execution and delivery of this Agreement, the consummation of
the transactions contemplated hereby or the compliance with any of the
provisions of this Agreement will not (i) conflict with or result in a breach of
any provision of its certificate of incorporation, by-laws, certificate of
limited partnership, limited partnership agreement or general partnership
agreement, as the case may be, (ii) breach, violate or result in a default under
any of the terms of any agreement or other instrument or obligation to which it
is a party or by which it or any of its properties or assets may be bound or
(iii) violate any order, writ, injunction, decree, statute, rule or regulation
applicable to it or affecting any of its properties or assets.
     5.2 Calculation of Payment Obligations. Except as otherwise provided under
this Agreement, to the extent that the payor Party has a payment obligation to
the payee Party pursuant to this Agreement, the payee Party shall provide the
payor Party with its calculation of the amount of such obligation. The
documentation of such calculation shall provide sufficient detail to permit the
payor Party to reasonably understand the calculation. All payment obligations
shall be made to the payee Party or to the appropriate Tax Authority as
specified by the payee Party within 30 days after delivery by the payee Party to
the payor Party of written notice of a payment obligation. Any disputes with
respect to payment obligations shall be resolved in accordance with Section 6.11
below.
     5.3 Prompt Performance. All actions required to be taken by any Party under
this Agreement shall be performed within the time prescribed for performance in
this Agreement or if no period is prescribed, such actions shall be performed
promptly.
     5.4 Interest. Payments pursuant to this Agreement that are not made within
the period prescribed therefor in this Agreement shall bear interest (compounded
daily) from and including the date immediately following the last date of such
period through and including the date of payment at a rate equal to the U.S.
federal short-term rate or rates established pursuant to Section 6621 of the
Code for the period during which such payment is due but unpaid.

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     5.5 Tax Records. The Parties to this Agreement hereby agree to retain and
provide on proper demand by any Tax Authority (subject to any applicable
privileges) the books, records, documentation and other information relating to
any Tax Return until the later of (i) the expiration of the applicable statute
of limitations (giving effect to any extension, waiver or mitigation thereof),
(ii) the date specified in an applicable records retention agreement entered
into with a Tax Authority, (iii) a Final Determination made with respect to such
Tax Return and (iv) the final resolution of any claim made under this Agreement
for which such information is relevant.
     5.6 Continuing Covenants. Each Party agrees (i) not to take any action
reasonably expected to result in a new or changed Tax Item that is detrimental
to any other Party and (ii) to take any action reasonably requested by any other
Party that would reasonably be expected to result in a new or changed Tax Item
that produces a benefit or avoids a detriment to such other Party; provided that
such action does not result in any additional cost not fully compensated for by
the requesting Party. The Parties hereby acknowledge that the preceding sentence
is not intended to limit, and therefore shall not apply to, the rights of the
Parties with respect to matters otherwise covered by this Agreement.
ARTICLE VI
Miscellaneous Provisions
     6.1 Notice. Any notice, demand, claim or other communication required or
permitted to be given under this Agreement (a “Notice”) shall be in writing and
may be personally served provided a receipt is obtained therefor, or may be sent
by certified mail return receipt requested postage prepaid, to the Parties at
the following addresses (or at such other address as one Party may specify by
notice to any other Party):

     
Anadarko at:
  Anadarko Petroleum Corporation
 
  1201 Lake Robbins Drive
 
  The Woodlands, Texas 77380
 
  Attention: General Counsel
 
  Fax: 832-636-3214
 
   
Partnership at:
  Western Gas Partners, LP
 
  c/o Western Gas Holdings, LLC
 
  1201 Lake Robbins Drive
 
  The Woodlands, Texas 77380
 
  Attention: President
 
  Fax: 832-636-6001

     A Notice which is delivered personally shall be deemed given as of the date
specified on the written receipt therefor. A Notice mailed as provided herein
shall be deemed given on the third business day following the date so mailed.
Notification of a change of address may be given by any Party to another in the
manner provided in this Section 6.1 for providing a Notice.
     6.2 Required Payments. Unless otherwise provided in this Agreement, any
payment of Tax required shall be due within 30 days of a Final Determination of
the amount of such Tax.

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     6.3 Injunctions. The Parties acknowledge that irreparable damage would
occur in the event that any of the provisions of this Agreement were not
performed in accordance with its specific terms or were otherwise breached. The
Parties hereto shall be entitled to an injunction or injunctions to prevent
breaches of the provisions of this Agreement and to enforce specifically the
terms and provisions of this Agreement in any court having jurisdiction, such
remedy being in addition to any other remedy to which they may be entitled at
law or in equity.
     6.4 Further Assurances. Subject to the provisions hereof, the Parties
hereto shall make, execute, acknowledge and deliver such other instruments and
documents, and take all such other actions, as may be reasonably required in
order to effectuate the purposes of this Agreement and to consummate the
transactions contemplated hereby. Subject to the provisions hereof, each of the
Parties shall, in connection with entering into this Agreement, perform its
obligations hereunder and take any and all actions relating hereto, comply with
all applicable laws, regulations, orders and decrees, obtain all required
consents and approvals and make all required filings with any governmental
agency, other regulatory or administrative agency, commission or similar
authority and promptly provide the other Parties with all such information as
such Parties may reasonably request in order to be able to comply with the
provisions of this sentence.
     6.5 Parties in Interest. Except as herein otherwise specifically provided,
nothing in this Agreement expressed or implied is intended to confer any right
or benefit upon any person, firm or corporation other than the Parties and their
respective successors and permitted assigns.
     6.6 Setoff. Except as provided by Section 2.1(c) of this Agreement, all
payments to be made under this Agreement shall be made without setoff,
counterclaim or withholding, all of which are expressly waived.
     6.7 Change of Law. If, due to any change in applicable law or regulations
or the interpretation thereof by any court of law or other governing body having
jurisdiction subsequent to the date of this Agreement, performance of any
provision of this Agreement or any transaction contemplated hereby shall become
impracticable or impossible, the Parties hereto shall use their best efforts to
find and employ an alternative means to achieve the same or substantially the
same result as that contemplated by such provision.
     6.8 Termination and Survival. Notwithstanding anything in this Agreement to
the contrary, this Agreement shall remain in effect and its provisions shall
survive for the full period of all applicable statutes of limitation (giving
effect to any extension, waiver or mitigation thereof) or until otherwise agreed
to in writing by Anadarko and the Partnership, or their successors.
     6.9 Amendments; No Waivers.
          (a) Any provision of this Agreement may be amended or waived if, and
only if, such amendment or waiver is in writing and signed, in the case of an
amendment, by Anadarko and the Partnership, or in the case of a waiver, by the
Party against whom the waiver is to be effective.

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          (b) No failure or delay by any Party in exercising any right, power or
privilege hereunder shall operate as a waiver thereof nor shall any single or
partial exercise thereof preclude any other or further exercise thereof or the
exercise of any other right, power or privilege.
     6.10 Governing Law and Interpretation. This Agreement shall be governed by
and construed in accordance with the laws of the State of Delaware applicable to
agreements made and to be performed in the State of Delaware.
     6.11 Resolution of Certain Disputes. Any disagreement between the Parties
with respect to any matter that is the subject of this Agreement, including,
without limitation, any disagreement with respect to any calculation or other
determinations by Anadarko hereunder, which is not resolved by mutual agreement
of the Parties, shall be resolved by a nationally recognized independent
accounting firm chosen by and mutually acceptable to the Parties hereto (an
“Accounting Referee”). Such Accounting Referee shall be chosen by the Parties
within fifteen (15) business days from the date on which one Party serves
written notice on another Party requesting the appointment of an Accounting
Referee, provided that such notice specifically describes the calculations to be
considered and resolved by the Accounting Referee. In the event the Parties
cannot agree on the selection of an Accounting Referee, then the Accounting
Referee shall be any office or branch of the public accounting firm of KPMG LLP.
The Accounting Referee shall resolve any such disagreements as specified in the
notice within 30 days of appointment; provided, however, that no Party shall be
required to deliver any document or take any other action pursuant to this
Section 6.11 if it determines that such action would result in the waiver of any
legal privilege or any detriment to its business. Any resolution of an issue
submitted to the Accounting Referee shall be final and binding on the Parties
hereto without further recourse. The Parties shall share the costs and fees of
the Accounting Referee equally.
     6.12 Confidentiality. Except to the extent required to protect a Party’s
interests in a Tax Controversy, each Party shall hold and shall cause its
consultants and advisors to hold in strict confidence, unless compelled to
disclose by judicial or administrative process or, in the opinion of its
counsel, by other requirements of law, all information (other than any such
information relating solely to the business or affairs of such Party) concerning
another Party or its representatives pursuant to this Agreement (except to the
extent that such information can be shown to have been (i) previously known by
the Party to which it was furnished, (ii) in the public domain through no fault
of such Party or (iii) later lawfully acquired from other sources by the Party
to which it was furnished), and each Party shall not release or disclose such
information to any other person, except its auditors, attorneys, financial
advisors, bankers and other consultants and advisors who shall be advised of the
provisions of this Agreement. Each Party shall be deemed to have satisfied its
obligation to hold confidential information concerning or supplied by another
Party if it exercises the same care as it takes to preserve confidentiality for
its own similar information.
     6.13 Costs, Expenses and Attorneys’ Fees. Except as expressly set forth in
this Agreement, each Party shall bear its own costs and expenses incurred
pursuant to this Agreement. In the event a Party to this Agreement brings an
action or proceeding for the breach or enforcement of this Agreement, the
prevailing party in such action, proceeding or appeal,

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whether or not such action, proceeding or appeal proceeds to final judgment,
shall be entitled to recover as an element of its costs, and not as damages,
such reasonable attorneys’ fees as may be awarded in the action, proceeding or
appeal in addition to whatever other relief the prevailing party may be
entitled. For purposes of this Section 6.13, the “prevailing party” shall be the
Party who is entitled to recover its costs; a Party not entitled to recover its
costs shall not recover attorneys’ fees. No sum for attorneys’ fees shall be
counted in calculating the amount of the judgment for purposes of determining
whether a Party is entitled to recover its costs or attorneys’ fees.
     6.14 Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original, but all of which
together shall constitute one and the same instrument.
     6.15 Severability. The Parties hereby agree that, if any provision of this
Agreement should be adjudicated to be invalid or unenforceable, such provision
shall be deemed deleted herefrom with respect, and only with respect, to the
operation of such provision in the particular jurisdiction in which such
adjudication was made, and only to the extent of the invalidity, and any such
invalidity or unenforceability in a particular jurisdiction shall not invalidate
or render unenforceable such provision in any other jurisdiction. All other
remaining provisions of this Agreement shall remain in full force and effect for
the particular jurisdiction and all other jurisdictions.
     6.16 Entire Agreement.
          (a) This Agreement contains the entire agreement between the Parties
with respect to the subject matter hereof and supersedes all other agreements,
whether or not written, in respect of any Tax between the Anadarko Group and the
Partnership Group.
          (b) In the event of any conflict or inconsistency between the
provisions of this Agreement and the provisions of any other agreement between
the Anadarko Group and the Partnership Group, the provisions of this Agreement
shall take precedence and to such extent shall be deemed to supersede such
conflicting provisions under the other agreement.
     6.17 Assignment. This Agreement is being entered into by Anadarko and the
Partnership on behalf of themselves and each member of the Anadarko Group and
the Partnership Group. This Agreement shall constitute a direct obligation of
each such member and shall be deemed to have been readopted and affirmed on
behalf of any entity that becomes a member of the Anadarko Group or the
Partnership Group in the future. Each of Anadarko and the Partnership hereby
guarantee the performance of all actions, agreements and obligations provided
for under this Agreement of each member of the Anadarko Group and the
Partnership Group, respectively. Each of Anadarko and the Partnership shall,
upon the written request of the other, cause any of their respective group
members to formally execute this Agreement. This Agreement shall be binding
upon, and shall inure to the benefit of, the successors, assigns and persons
controlling any of the entities bound hereby for so long as such successors,
assigns or controlling persons are members of the Anadarko Group or the
Partnership Group or their successors and assigns.

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     6.18 Fair Meaning. This Agreement shall be construed in accordance with its
fair meaning and shall not be construed strictly against the drafter.
     6.19 Titles and Headings. Titles and headings to sections herein are
inserted for the convenience of reference only and are not intended to be a part
of or to affect the meaning or interpretation of this Agreement.
     6.20 Construction. In this Agreement, unless the context otherwise
requires, the terms “herein,” “hereof” and “hereunder” refer to this Agreement.

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     IN WITNESS WHEREOF, the Parties hereto have executed and delivered this
Agreement as of the day and year first above written.

                  ANADARKO PETROLEUM CORPORATION    
 
           
 
  By:   /s/ James T. Hackett
 
   
 
  Name:   James T. Hackett    
 
  Title:   Chairman, President and Chief Executive Officer    
 
                WESTERN GAS PARTNERS, LP    
 
           
 
  By:   Western Gas Holdings, LLC,
its general partner    
 
           
 
  By:   /s/ Robert G. Gwin    
 
           
 
      Robert G. Gwin    
 
      President and Chief Executive Officer    

Signature Page to Tax Sharing Agreement