OMNIBUS AGREEMENT
BY AND AMONG
WESTERN GAS PARTNERS, LP
WESTERN GAS HOLDINGS, LLC
AND
ANADARKO PETROLEUM CORPORATION

 

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Table of Contents

         
ARTICLE I
Definitions
1.1 Definitions
    1  
ARTICLE II
Indemnification
2.1 Indemnification by Anadarko
    5  
2.2 Indemnification by the Partnership Entities
    6  
2.3 Limitations Regarding Indemnification
    6  
2.4 Indemnification Procedures
    7  
ARTICLE III
Reimbursement Obligations
3.1 Reimbursement for Allocated General and Administrative Expenses; Limitations
on Reimbursement
    8  
3.2 Reimbursement for Publicly Traded Partnership Expenses
    9  
3.3 Reimbursement for Insurance
    9  
3.4 Reimbursement for Allocated Commitment Fee
    9  
3.5 Reimbursement Procedures
    9  
ARTICLE IV
Miscellaneous
4.1 Accuracy of Recitals
    10  
4.2 Choice of Law; Submission to Jurisdiction
    10  
4.3 Notices
    10  
4.4 Further Assurances
    10  
4.5 Agreement
    11  
4.6 Termination
    11  
4.7 Effect of Waiver or Consent
    11  
4.8 Amendment or Modification
    11  
4.9 Assignment; Third-Party Beneficiaries
    11  
4.10 Counterparts
    11  
4.11 Severability
    11  
4.12 Interpretation
    12  
4.13 Titles and Headings
    12  
4.14 Relationship of the Parties
    12  
4.15 Binding Effect
    12  
4.16 Time of the Essence
    12  
4.17 Delay or Partial Exercise Not Waiver
    12  
4.18 Withholding or Granting of Consent
    12  
4.19 Laws and Regulations
    13  
4.20 Negation of Rights of Limited Partners, Assignees and Third Parties
    13  
4.21 No Recourse Against Officers or Directors
    13  
4.22 Signatories Duly Authorized
    13  
4.23 Incorporation of Exhibits by References
    13  

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OMNIBUS AGREEMENT
     This Omnibus Agreement (“Agreement”) is entered into on, and effective as
of, the Closing Date (as defined herein), and is by and among Western Gas
Partners, LP, a Delaware limited partnership (the “Partnership”), Western Gas
Holdings, LLC, a Delaware limited liability company (“General Partner”), and
Anadarko Petroleum Corporation, a Delaware corporation (“Anadarko”). The
above-named entities are sometimes referred to in this Agreement each as a
“Party” and collectively as the “Parties.”
R E C I T A L S:
     The Parties desire by their execution of this Agreement to evidence their
understanding, as more fully set forth in Article II and Article III of this
Agreement, with respect to certain indemnification and reimbursement obligations
of the Parties.
     In consideration of the premises and the covenants, conditions, and
agreements contained herein, and for 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. (a) Capitalized terms used herein but not defined shall
have the meanings given them in the Partnership Agreement.
     (b) As used in this Agreement, the following terms shall have the
respective meanings set forth below:
     “Affiliate” means, with respect to any Person, (a) any other Person
directly or indirectly controlling, controlled by or under common control with
such Person, (b) any Person owning or controlling fifty percent (50%) or more of
the voting interests of such Person, (c) any officer or director of such Person,
or (d) any Person who is the officer, director, trustee, or holder of fifty
percent (50%) or more of the voting interest of any Person described in clauses
(a) through (c). For purposes of this definition, the term “controls,” “is
controlled by” or “is under common control with” shall mean the possession,
direct or indirect, of the power to direct or cause the direction of the
management and policies of a Person, whether through the ownership of voting
securities, by contract or otherwise.
     “Agreement” means this Omnibus Agreement, as it may be amended, modified or
supplemented from time to time in accordance with the terms hereof.
     “Anadarko” is defined in the preamble to this Agreement.
     “Anadarko Entities” means Anadarko and any other Person controlled by
Anadarko other than the Partnership Entities. For purposes of this definition,
“control” means the possession, direct or indirect, of the power to direct or
cause the direction of the management and policies of a Person, whether through
ownership of Voting Securities, by contract or otherwise.

 

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     “Change of Control” means, with respect to any Person (the “Applicable
Person”), any of the following events: (i) any sale, lease, exchange or other
transfer (in one transaction or a series of related transactions) of all or
substantially all of the Applicable Person’s assets to any other Person, unless
immediately following such sale, lease, exchange or other transfer such assets
are owned, directly or indirectly, by the Applicable Person; (ii) the
dissolution or liquidation of the Applicable Person; (iii) the consolidation or
merger of the Applicable Person with or into another Person pursuant to a
transaction in which the outstanding Voting Securities of the Applicable Person
are changed into or exchanged for cash, securities or other property, other than
any such transaction where (A) the outstanding Voting Securities of the
Applicable Person are changed into or exchanged for Voting Securities of the
surviving Person or its parent and (B) the holders of the Voting Securities of
the Applicable Person immediately prior to such transaction own, directly or
indirectly, not less than a majority of the outstanding Voting Securities of the
surviving Person or its parent immediately after such transaction; and (iv) a
“person” or “group” (within the meaning of Sections 13(d) or 14(d)(2) of the
Exchange Act) other than Anadarko or any Affiliate of Anadarko becomes the
“beneficial owner” (as defined in Rules 13d-3 and 13d-5 under the Exchange Act)
of more than 50% of all of the then outstanding Voting Securities of the
Applicable Person, other than in a merger or consolidation which would not
constitute a Change of Control under clause (iii) above.
     “Closing Date” means the date of the closing of the initial public offering
of Common Units.
     “Covered Environmental Losses” means all Environmental Losses by reason of
or arising out of any violation, event, circumstance, action, omission or
condition associated with the operation of the Partnership Assets occurring on
or before the Closing Date, but only to the extent such violation, event
circumstance, action, omission or condition occurs on or before the Closing
Date.
     “Credit Agreement” means that certain Revolving Credit Agreement, dated as
of March 4, 2008, by and among Anadarko Petroleum Corporation, Western Gas
Partners, LP, JP Morgan Chase Bank, N.A., The Royal Bank of Scotland, PLC, BNP
Paribas, Bank of America, N.A., BMO Capital Markets Financing, Inc., The Bank of
Tokyo-Mitsubishi UFJ, LTD., and each of the Lenders named therein.
     “CP Index” is defined in Section 3.1(c).
     “Environmental Activity” shall mean any investigation, study, assessment,
evaluation, sampling, testing, monitoring, containment, removal, disposal,
closure, corrective action, remediation (regardless of whether active or
passive), natural attenuation, restoration, bioremediation, response, repair,
corrective measure, cleanup or abatement that is required or necessary under any
applicable Environmental Law, including, without limitation, institutional or
engineering controls or participation in a governmental voluntary cleanup
program to conduct voluntary investigatory and remedial actions for the
clean-up, removal or remediation of Hazardous Substances that exceed actionable
levels established pursuant to Environmental Laws, or participation in a
supplemental environmental project in partial or whole mitigation of a fine or
penalty.

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     “Environmental Laws” means all federal, state, and local laws, statutes,
rules, regulations, orders, judgments, ordinances, codes, injunctions, decrees,
Environmental Permits and other legally enforceable requirements and rules of
common law relating to (i) pollution or protection of the environment or natural
resources, (ii) any Release or threatened Release of, or any exposure of any
Person or property to, any Hazardous Substances or (iii) the generation,
manufacture, processing, distribution, use, treatment, storage, transport or
handling of any Hazardous Substances; including, without limitation, the federal
Comprehensive Environmental Response, Compensation and Liability Act, the
Superfund Amendments and Reauthorization Act, the Resource Conservation and
Recovery Act, the Clean Air Act, the Clean Water Act, the Safe Drinking Water
Act, the Toxic Substances Control Act, the Oil Pollution Act of 1990, the
Federal Hazardous Materials Transportation Law, the Occupational Safety and
Health Act, the Marine Mammal Protection Act, the Endangered Species Act, the
National Environmental Policy Act and other environmental conservation and
protection laws, each as amended through the Closing Date.
     “Environmental Losses” means all Losses (including, without limitation, the
costs and expenses of any Environmental Activity or of any environmental or
toxic tort pre-trial, trial or appellate legal or litigation work), by reason of
or arising out of:
     (i) any violation of or cost to correct a of violation of any Environmental
Laws;
     (ii) any Environmental Activity to address a Release of Hazardous
Substances; or
     (iii) any event, omission or condition associated with ownership or
operation of the Partnership Assets that results in a violation of any
Environmental Law (including, without limitation, the exposure to or presence of
Hazardous Substances on, under, about or migrating to or from the Partnership
Assets or the exposure to or Release of Hazardous Substances arising out of
operation of the Partnership Assets at non-Partnership Asset locations).
     “Environmental Permit” means any permit, approval, identification number,
license, registration, certification, consent, exemption, variance or other
authorization required under or issued pursuant to any applicable Environmental
Law.
     “Exchange Act” means the Securities Exchange Act of 1934, as amended.
     “G&A Expenses Limit” is defined in Section 3.1(c).
     “General Partner” is defined in the preamble to this Agreement.
     “Hazardous Substance” means (i) any substance that is designated, defined
or classified under any Environmental Law as a hazardous waste, solid waste,
hazardous material, pollutant, contaminant or toxic or hazardous substance, or
terms of similar meaning, or that is otherwise regulated under any Environmental
Law, including, without limitation, any hazardous substance as defined under the
Comprehensive Environmental Response, Compensation and Liability Act, as
amended, (ii) oil as defined in the Oil Pollution Act of 1990, as amended,
including, without limitation, oil, gasoline, natural gas, fuel oil, motor oil,
waste oil, diesel fuel, jet fuel and other refined petroleum hydrocarbons and
petroleum products and (iii) radioactive materials, asbestos containing
materials or polychlorinated biphenyls.

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     “Indemnified Party” means each Person entitled to indemnification in
accordance with Article II.
     “Indemnifying Party” means each Person from whom indemnification may be
required in accordance with Article II.
     “Losses” means any losses, damages, liabilities, claims, demands, causes of
action, judgments, settlements, fines, penalties, sanctions, costs and expenses
(including, without limitation, court costs and reasonable attorney’s and
experts’ fees) of any and every kind or character.
     “Partnership” is defined in the preamble to this Agreement.
     “Partnership Agreement” means the First Amended and Restated Agreement of
Limited Partnership of the Partnership, dated as of the Closing Date, as such
agreement is in effect on the Closing Date, to which reference is hereby made
for all purposes of this Agreement. An amendment or modification to the
Partnership Agreement subsequent to the Closing Date shall be given effect for
the purposes of this Agreement only if it has received the approval of the
Special Committee that would be required, if any, pursuant to Section 4.8 hereof
if such amendment or modification were an amendment or modification of this
Agreement.
     “Partnership Assets” means the gathering pipelines, compressors, treating
facilities, transportation pipelines or related equipment or assets, or portions
thereof, conveyed, contributed or otherwise transferred or intended to be
conveyed, contributed or otherwise transferred to any member of the Partnership
Group, or owned by, leased by or necessary for the operation of the business,
properties or assets of any member of the Partnership Group, prior to or as of
the Closing Date.
     “Partnership Entities” means the General Partner and each member of the
Partnership Group.
     “Partnership Group” means the Partnership and its Subsidiaries treated as a
single consolidated entity.
     “Partnership Group Member” means any member of the Partnership Group.
     “Party” and “Parties” are defined in the preamble to this Agreement.
     “Person” means an individual, corporation, partnership, joint venture,
trust, limited liability company, unincorporated organization or any other
entity.
     “Release” means any depositing, spilling, leaking, pumping, pouring,
placing, emitting, discarding, abandoning, emptying, discharging, migrating,
injecting, escaping, leaching, dumping or disposing into the environment.
     “Services” is defined in Section 3.1(a).

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     “Subsidiary” means, with respect to any Person, (i) a corporation of which
more than 50% of the voting power of shares entitled (without regard to the
occurrence of any contingency) to vote in the election of directors or other
governing body of such corporation is owned, directly or indirectly, at the date
of determination, by such Person, by one or more Subsidiaries of such Person or
a combination thereof, (ii) a partnership (whether general or limited) in which
more than 50% of the partnership interests (considering all of the partnership
interests of the partnership as a single class) is owned, directly or
indirectly, at the date of determination, by such Person, by one or more
Subsidiaries of such Person, or a combination thereof, or (iii) any other Person
(other than a corporation or a partnership) in which such Person, one or more
Subsidiaries of such Person, or a combination thereof, directly or indirectly,
at the date of determination, has (A) at least a majority ownership interest or
(B) the power to elect or direct the election of a majority of the directors or
other governing body of such Person.
     “Voting Securities” means securities of any class of a Person entitling the
holders thereof to vote in the election of, or to appoint, members of the board
of directors or other similar governing body of the Person.
ARTICLE II
Indemnification
     2.1 Indemnification by Anadarko
          (a) Environmental Indemnification. Subject to the provisions of
Section 2.3 and Section 2.4, Anadarko shall indemnify, defend and hold harmless
the Partnership Entities from and against any Covered Environmental Losses
suffered or incurred by the Partnership Entities and arising from or relating to
the Partnership Assets for a period of three (3) years from the Closing Date.
          (b) Additional Indemnification. Subject to the provisions of
Section 2.3 and Section 2.4, Anadarko shall indemnify, defend and hold harmless
the Partnership Entities from and against any Losses suffered or incurred by the
Partnership Entities by reason of or arising from:

  (i)   the failure of the Partnership Entities to be the owner of valid and
indefeasible easement rights, leasehold and/or fee ownership interests in and to
the lands on which are located any Partnership Assets, and such failure renders
the Partnership Entities liable to a third party or unable to use or operate the
Partnership Assets in substantially the same manner that the Partnership Assets
were used and operated by the Anadarko Entities immediately prior to the Closing
Date;     (ii)   the failure of the Partnership Entities to have on the Closing
Date any consent or governmental permit necessary to allow (A) the transfer of
any of the Partnership Assets to the Partnership Group on the Closing Date or
(B) the Partnership Entities to use or operate the Partnership Assets in
substantially the same manner that the Partnership Assets were used and operated
by the Anadarko Entities immediately prior to the Closing Date;

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  (iii)   all federal, state and local income tax liabilities (A) attributable
to the ownership or operation of the Partnership Assets prior to the Closing
Date, (B) of the Anadarko Entities that may result from the consummation of the
formation transactions for the Partnership Entities, (C) of the Partnership
Entities that may arise after the Closing Date and which have been specifically
assumed by Anadarko or (D) arising under Treasury Regulation Section 1.1502-6
and any similar provision of state, local or foreign applicable law, by
contract, as successor or transferee or otherwise and which income tax is
attributable to having been a member of any consolidated, combined or unitary
group prior to the Closing Date;     (iv)   all liabilities, other than Covered
Environmental Losses and other than liabilities incurred in the ordinary course
of business conducted in compliance with applicable laws, that arise out of the
Partnership Assets prior to the Closing Date; and     (v)   all liabilities
attributable to any assets or liabilities retained by the Anadarko Entities;

provided, however, that, in the case of clauses (i), (ii) and (iv) above, such
indemnification obligations shall survive for three (3) years from the Closing
Date; and in the case of clauses (iii) and (v) above, such indemnification
obligations shall survive until 12:01 a.m. of the first day after the expiration
of any applicable statute of limitations.
     2.2 Indemnification by the Partnership Entities. In addition to and not in
limitation of the indemnification provided under the Partnership Agreement, the
Partnership Entities shall indemnify, defend and hold harmless the Anadarko
Entities from and against any Losses (excluding Environmental Losses) suffered
or incurred by the Anadarko Entities by reason of or arising out of events and
conditions associated with the operation of the Partnership Assets and occurring
on or after the Closing Date, unless in any such case indemnification would not
be permitted under the Partnership Agreement by reason of one of the provisos
contained in Section 7.7 of the Partnership Agreement.
     2.3 Limitations Regarding Indemnification.
          (a) Notwithstanding anything herein to the contrary, in no event shall
the Indemnifying Party have any indemnification obligations under this Agreement
for claims made as a result of additions to or modifications of Environmental
Laws promulgated after the Closing Date.
          (b) Notwithstanding anything herein to the contrary, the liability of
the Indemnifying Party for any indemnification obligations under this Agreement
will be subject to reduction for (i) any insurance proceeds realized by the
Indemnified Party with respect to the indemnified party and (ii) any amounts
recovered by the Indemnified Party under contractual indemnities from third
parties. The Partnership hereby agrees to use commercially reasonable efforts to
realize any applicable insurance proceeds and amounts recoverable under such
contractual indemnities.

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          (c) The liability of the Indemnifying Party for any indemnification
obligations under this Agreement will be reduced by any amounts reserved or
accrued for such Losses on the consolidated balance sheet of the Partnership
Entities as of December 31, 2007.
     2.4 Indemnification Procedures.
          (a) The Indemnified Party agrees that within thirty (30) days after it
becomes aware of facts giving rise to a claim for indemnification pursuant to
this Article II, it will provide notice thereof in writing to the Indemnifying
Party specifying the nature of and specific basis for such claim; provided,
however, that the Indemnified Party shall not submit claims more frequently than
once a calendar quarter (or twice in the case of the last calendar quarter prior
to the expiration of the applicable indemnity coverage under this Agreement).
Notwithstanding the foregoing, the Indemnified Party’s failure to provide notice
under this Section 2.4 will not relieve the Indemnifying Party from liability
hereunder with respect to such matter except in the event and only to the extent
that the Indemnifying Party is materially prejudiced by such failure or delay.
          (b) The Indemnifying Party shall have the right to control all aspects
of the defense of (and any counterclaims with respect to) any claims brought
against the Indemnified Party that are covered by the indemnification set forth
in this Article II, including, without limitation, the selection of counsel
(provided that if such claim involves Covered Environmental Losses, such counsel
shall be reasonably acceptable to the Indemnified Party), determination of
whether to appeal any decision of any court and the settling of any such matter
or any issues relating thereto; provided, however, that no such settlement shall
be entered into without the consent (which consent shall not be unreasonably
withheld, conditioned or delayed) of the Indemnified Party unless it includes a
full release of the Indemnified Party from such matter or issues, as the case
may be.
          (c) The Indemnified Party agrees to cooperate fully with the
Indemnifying Party with respect to all aspects of the defense of any claims
covered by the indemnification set forth in this Article II, including, without
limitation, the prompt furnishing to the Indemnifying Party of any
correspondence or other notice relating thereto that the Indemnified Party may
receive, permitting the names of the Indemnified Party to be utilized in
connection with such defense, the making available to the Indemnifying Party of
any files, records or other information of the Indemnified Party that the
Indemnifying Party considers relevant to such defense and the making available
to the Indemnifying Party of any employees of the Indemnified Party; provided,
however, that in connection therewith the Indemnifying Party agrees to use
reasonable efforts to minimize the impact thereof on the operations of the
Indemnified Party and further agrees to maintain the confidentiality of all
files, records and other information furnished by the Indemnified Party pursuant
to this Section 2.4, unless otherwise required by law or the listing standards
of the New York Stock Exchange. In no event shall the obligation of the
Indemnified Party to cooperate with the Indemnifying Party as set forth in the
immediately preceding sentence be construed as imposing upon the Indemnified
Party an obligation to hire and pay for counsel in connection with the defense
of any claims covered by the indemnification set forth in this Article II;
provided, however, that the Indemnified Party may, at its own option, cost and
expense, hire and pay for counsel in connection with any such defense. The
Indemnifying Party agrees to keep any such counsel hired by the Indemnified
Party reasonably informed as to the

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status of any such defense, but the Indemnifying Party shall have the right to
retain sole control over such defense.
          (d) The indemnification obligations under this Article II shall
continue with respect to any claim for indemnification pursuant to this
Article II that is pending as of the end of the applicable survival period
notwithstanding the expiration of such survival period.
ARTICLE III
Reimbursement Obligations
     3.1 Reimbursement for Allocated General and Administrative Expenses;
Limitations on Reimbursement.
          (a) Anadarko hereby agrees to cause the Anadarko Entities to continue
to provide the Partnership Entities with certain general and administrative
services, such as legal, accounting, treasury, cash management, insurance,
administrative and claims processing, risk management, health, safety and
environmental, information technology, human resources, credit, payroll,
internal audit, tax, marketing and midstream. These general and administrative
services shall be substantially identical in nature and quality to the services
of such type previously provided by the Anadarko Entities in connection with
their management and operation of the Partnership Assets prior to their
acquisition by the Partnership Group. In the event that the Partnership Group
makes any acquisitions of assets or businesses from any of the Anadarko Entities
during the first three years following the date of this Agreement, Anadarko will
cause the Anadarko Entities to similarly provide general and administrative
services that are substantially identical in nature and quality to the services
of such type previously provided by the Anadarko Entities in connection with
their management and operation of such assets or businesses prior to their
acquisition by the Partnership Group. In addition, in the event that the
Partnership Group makes any acquisition of assets or businesses from any third
party during the first three years following the date of this Agreement,
Anadarko will cause the Anadarko Entities to provide general and administrative
services that are substantially identical in nature and quality to the services
of such type previously provided by the Anadarko Entities in connection with
their management and operation of similar assets or businesses.
          (b) Subject to the provisions of Section 3.1(c) below, the Partnership
Group hereby agrees to reimburse Anadarko for all cash expenses and expenditures
that the Anadarko Entities incur or payments they make on behalf of the
Partnership Entities for these general and administrative services provided for
in Section 3.1(a).
          (c) Subject to the provisions of this Section 3.1(c), the amount for
which Anadarko shall be entitled to reimbursement from the Partnership Entities
pursuant to Section 3.1(b) for general and administrative expenses shall not
exceed $6.0 million annually from the date of this Agreement through
December 31, 2009 (the “G&A Expenses Limit”). On January 1, 2009, the G&A
Expenses Limit shall be increased by the percentage increase in the Consumer
Price Index – All Urban Consumers, U.S. City Average, Not Seasonally Adjusted
(the “CP Index”). In making such adjustment, the G&A Expenses Limit shall be
increased by the CP Index for the prior year period based on the most recent
information available from the U.S. Department of Labor. If after the Closing
the Partnership Group completes any acquisition of

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assets or businesses or the business of the Partnership Group otherwise expands
from the date of this Agreement through December 31, 2009, then the G&A Expenses
Limit shall be appropriately increased in order to account for adjustments in
the nature and extent of the general and administrative services provided by the
Anadarko Entities to the Partnership Entities, with any such increase in the G&A
Expenses Limit (i) to remain in effect (subject to adjustment, if any, as
provided in the immediately preceding sentence or for any subsequent
acquisition(s)) for the period from the completion of any such acquisition
through December 31, 2009 and (ii) to be subject to the prior approval of the
Special Committee. After December 31, 2009, the G&A Expenses Limit will no
longer apply and the General Partner will determine the amount of general and
administrative expenses that will be properly allocated to the Partnership Group
in accordance with the terms of the Partnership Agreement. The G&A Expenses
Limit shall not apply to reimbursement for publicly traded partnership expenses
of the Partnership Group as provided in Section 3.3 or the reimbursement of
allocable commitment fees as provided in Section 3.4, including those publicly
traded partnership expenses and allocable commitment fees incurred on or before
the Closing Date by the Anadarko Entities on behalf of the Partnership Entities.
     3.2 Reimbursement for Publicly Traded Partnership Expenses.
          (a) The Partnership Entities hereby agree to reimburse Anadarko for
all expenses and expenditures that the Anadarko Entities incur or payments that
they make as a result of the Partnership becoming a publicly traded partnership,
including (but not limited to) expenses associated with annual and quarterly
reporting; tax return and Schedule K-1 preparation and distribution expenses;
Sarbanes-Oxley compliance expenses; expenses associated with listing on the New
York Stock Exchange; independent auditor fees; legal fees; investor relations
expenses; and registrar and transfer agent fees. Furthermore, the Partnership
Entities agree to reimburse Anadarko for these expenses incurred on or before
the Closing Date by the Anadarko Entities on behalf of the Partnership Entities.
          (b) The obligation of the Partnership Entities to reimburse Anadarko
pursuant to this Section 3.2 shall not be subject to any monetary limitation,
including the G&A Expenses Limit contained in Section 3.1.
     3.3 Reimbursement for Insurance. The Partnership Entities hereby agree to
reimburse Anadarko for all expenses that the Anadarko Entities incur or payments
that they make on behalf of the Partnership Entities for insurance coverage with
respect to the Partnership Assets.
     3.4 Reimbursement for Allocated Commitment Fee. The Partnership Entities
hereby agree to reimburse Anadarko for their allocable portion of commitment
fees that Anadarko incurs or pays under the Credit Agreement equal to an annual
amount of 0.11% of the Partnership’s committed and available borrowing capacity
thereunder.
     3.5 Reimbursement Procedures. On or before the fifth business day of each
month, Anadarko shall send an invoice to the General Partner for that amount of
money associated with all expenses or expenditures incurred or payments made by
the Anadarko Entities during the preceding month that are to be reimbursed by
the Partnership Entities pursuant to Sections 3.1,

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3.2, 3.3 and 3.4 hereof. Where it is not reasonably practicable to determine the
cost of such an expense, expenditure or payment, Anadarko or the applicable
Anadarko entity may make a good faith reasonable estimate of such expense,
expenditure or payment (and provided that any such estimates, other than with
respect to benefit load, are is “trued up” within 10 days of the end of each
quarter based on the actual amount of the expenses, expenditures or payments in
respect of which estimates were made in the immediately preceding quarter).
Subject to the parenthetical clause in the immediately preceding sentence, the
Partnership Entities shall accept any estimate or benefit load described in this
paragraph, provided that such estimate is reasonable and made in good faith. The
Partnership Entities shall pay such invoice, subject to any adjustment imposed
by Section 3.1(c) hereof, within 30 days of receipt.
ARTICLE IV
Miscellaneous
     4.1 Accuracy of Recitals. The paragraphs contained in the recitals to this
Agreement are incorporated in this Agreement by this reference, and the Parties
to this Agreement acknowledge the accuracy thereof.
     4.2 Choice of Law; Submission to Jurisdiction. This Agreement shall be
subject to and governed by the laws of the State of Texas. Each Party hereby
submits to the jurisdiction of the state and federal courts in the State of
Texas and to venue in Houston, Texas.
     4.3 Notices. Any notice, demand, or communication required or permitted
under this Agreement shall be in writing and delivered personally, by reputable
courier, or by telecopier, and shall be deemed to have been duly given as of the
date and time reflected on the delivery receipt if delivered personally or sent
by reputable courier service, or on the automatic telecopier receipt if sent by
telecopier, addressed as follows:
Anadarko Petroleum Corporation
1201 Lake Robbins Drive
The Woodlands, Texas 77380
Attn: General Counsel
Fax: 832-636-3214
Western Gas Holdings, LLC
1201 Lake Robbins Drive
The Woodlands, Texas 77380
Attn: President
Fax: 832-636-6001
A Party may change its address for the purposes of notices hereunder by giving
notice to the other Party specifying such changed address in the manner
specified in this Section 6.2.
     4.4 Further Assurances. The Parties agree to execute such additional
instruments, agreements and documents, and to take such other actions, as may be
necessary to effect the purposes of this Agreement.

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     4.5 Agreement. This Agreement constitutes the entire agreement of the
Parties relating to the matters contained herein, superseding all prior
contracts or agreements, whether oral or written, relating to the matters
contained herein.
     4.6 Termination. This Agreement, other than the provisions set forth in
Article II hereof, shall terminate upon a Change of Control of the General
Partner or the Partnership, other than any Change of Control of the General
Partner or the Partnership that may be deemed to have occurred pursuant to
clause (iv) of the definition of Change of Control solely as a result of a
Change of Control of Anadarko. Notwithstanding any other provision of this
Agreement, if the General Partner is removed as general partner of the
Partnership under circumstances where Cause does not exist and Common Units held
by the General Partner and its Affiliates are not voted in favor of such
removal, this Agreement may immediately thereupon be terminated by Anadarko.
     4.7 Effect of Waiver or Consent. No waiver or consent, express or implied,
by any Party to or of any breach or default by any Person in the performance by
such Person of its obligations hereunder shall be deemed or construed to be a
consent or waiver to or of any other breach or default in the performance by
such Person of the same or any other obligations of such Person hereunder.
Failure on the part of a Party to complain of any act of any Person or to
declare any Person in default, irrespective of how long such failure continues,
shall not constitute a waiver by such Party of its rights hereunder until the
applicable statute of limitations period has run.
     4.8 Amendment or Modification. This Agreement may be amended or modified
from time to time only by the written agreement of all the Parties; provided,
however, that the Partnership may not, without the prior approval of the Special
Committee, agree to any amendment or modification of this Agreement that, in the
reasonable discretion of the General Partner, will have an adverse effect on the
holders of Common Units. Each such instrument shall be reduced to writing and
shall be designated on its face an “Amendment” or an “Addendum” to this
Agreement.
     4.9 Assignment; Third-Party Beneficiaries. No Party shall have the right to
assign its rights or obligations under this Agreement without the prior written
consent of the other Parties. Each of the Parties hereto specifically intends
that each entity comprising the Anadarko Entities and the Partnership Entities,
as applicable, whether or not a Party to this Agreement, shall be entitled to
assert rights and remedies hereunder as third-party beneficiaries hereto with
respect to those provisions of this Agreement affording a right, benefit or
privilege to any such entity.
     4.10 Counterparts. This Agreement may be executed in any number of
counterparts with the same effect as if all signatory Parties had signed the
same document. All counterparts shall be construed together and shall constitute
one and the same instrument.
     4.11 Severability. If any provision of this Agreement or the application
thereof to any Person or circumstance shall be held invalid or unenforceable to
any extent, the remainder of this Agreement and the application of such
provision to other Persons or circumstances shall not be affected thereby and
shall be enforced to the greatest extent permitted by law.

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     4.12 Interpretation. In this Agreement, unless a clear contrary intention
appears: (a) the singular includes the plural and vice versa; (b) reference to
any Person includes such Person’s successors and assigns but, in the case of
Party, only if such successors and assigns are permitted by this Agreement, and
reference to a Person in a particular capacity excludes such Person in any other
capacity; (c) reference to any gender includes each other gender; (d) reference
to any agreement (including this Agreement), document or instrument means such
agreement, document, or instrument as amended or modified and in effect from
time to time in accordance with the terms thereof and, if applicable, the terms
of this Agreement; (e) reference to any Section means such Section of this
Agreement, and references in any Section or definition to any clause means such
clause of such Section or definition; (f) “hereunder,” “hereof,” “hereto” and
words of similar import will be deemed references to this Agreement as a whole
and not to any particular Section or other provision hereof or thereof; (g)
“including” (and with correlative meaning “include”) means including without
limiting the generality of any description preceding such term; and (h) relative
to the determination of any period of time, “from” means “from and including,”
“to” means “to but excluding” and “through” means “through and including.”
     4.13 Titles and Headings. Section titles and headings in this Agreement are
inserted for convenience of reference only and are not intended to be a part of,
or to affect the meaning or interpretation of, this Agreement.
     4.14 Relationship of the Parties.
          (a) Nothing in this Agreement shall cause any of the Anadarko Entities
or the Partnership Entities to become members of any other partnership, joint
venture, association, syndicate or other entity. Nothing in this Agreement shall
cause any Partnership Entity to be considered an Anadarko Entity, and vice
versa.
          (b) For purposes of this Agreement, no Partnership Entity shall be
deemed to be an Affiliate of the Anadarko Entities nor shall any Anadarko Entity
be deemed to be an Affiliate of any the Partnership Entities.
     4.15 Binding Effect. This Agreement will be binding upon, and will inure to
the benefit of, the Parties and their respective successors, permitted assigns
and legal representatives.
     4.16 Time of the Essence. Time is of the essence in the performance of this
Agreement.
     4.17 Delay or Partial Exercise Not Waiver. No failure or delay on the part
of any Party to exercise any right or remedy under this Agreement will operate
as a waiver thereof; nor shall any single or partial exercise of any right or
remedy under this Agreement preclude any other or further exercise thereof or
the exercise of any other right or remedy granted hereby or any related
document. The waiver by either Party of a breach of any provisions of this
Agreement will not constitute a waiver of a similar breach in the future or of
any other breach or nullify the effectiveness of such provision.
     4.18 Withholding or Granting of Consent. Unless otherwise provided in this
Agreement, each Party may, with respect to any consent or approval that it is
entitled to grant pursuant to this Agreement, grant or withhold such consent or
approval in its sole and

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uncontrolled discretion, with or without cause, and subject to such conditions
as it shall deem appropriate.
     4.19 Laws and Regulations. Notwithstanding any provision of this Agreement
to the contrary, no Party shall be required to take any act, or fail to take any
act, under this Agreement if the effect thereof would be to cause such Party to
be in violation of any applicable law, statute, rule or regulation.
     4.20 Negation of Rights of Limited Partners, Assignees and Third Parties.
Except as set forth in Section 4.9, the provisions of this Agreement are
enforceable solely by the Parties, and no limited partner, member, or assignee
of Anadarko or the Partnership or other Person shall have the right, separate
and apart from Anadarko or the Partnership, to enforce any provision of this
Agreement or to compel any Party to comply with the terms of this Agreement.
     4.21 No Recourse Against Officers or Directors. For the avoidance of doubt,
the provisions of this Agreement shall not give rise to any right of recourse
against any officer or director of any Anadarko Entity or any Partnership
Entity.
     4.22 Signatories Duly Authorized. Each of the signatories to this Agreement
represents that he is duly authorized to execute this Agreement on behalf of the
Party for which he is signing, and that such signature is sufficient to bind the
Party purportedly represented.
     4.23 Incorporation of Exhibits by References. Any reference herein to any
exhibit to this Agreement will incorporate it herein, as if it were set out in
full in the text of this Agreement.
[Signature page follows]

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     IN WITNESS WHEREOF, the Parties have executed this Agreement on, and
effective as of, the Closing Date.

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

Signature Page to Omnibus Agreement