WESTERN GAS RESOURCES INC
EXHIBIT 10.27
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<P ALIGN="RIGHT"><FONT SIZE=2><A
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<BR></FONT><FONT SIZE=2><B>Exhibit 10.27    <BR>  </B></FONT></P>

<P ALIGN="CENTER"><FONT SIZE=2><B>LETTER AMENDMENT NO. 6<BR>
TO<BR>
SECOND AMENDED AND RESTATED MASTER SHELF AGREEMENT  </B></FONT></P>

<P ALIGN="CENTER"><FONT SIZE=2>March&nbsp;1,
2002 </FONT></P>

<P><FONT SIZE=2>The
Prudential Insurance Company of America<BR>
Pruco Life Insurance Company<BR>
c/o Prudential Capital Group<BR>
2200 Ross Avenue, Suite&nbsp;4200E<BR>
Dallas, Texas 75201 </FONT></P>

<P><FONT SIZE=2>Ladies
and Gentlemen: </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
refer to the Second Amended and Restated Master Shelf Agreement dated as of December&nbsp;19, 1991 (effective January&nbsp;31, 1996), as amended by Letter Amendment No.&nbsp;1
dated November&nbsp;21, 1997, Letter Amendment No.&nbsp;2 dated March&nbsp;31, 1999, Limited Waiver, Consent, Release and Amendment No.&nbsp;3 dated June&nbsp;1, 1999, Limited Waiver,
Consent, Release and Amendment No.&nbsp;4 dated August&nbsp;25, 2000 and Letter Amendment No.&nbsp;5 dated March&nbsp;30, 2001 (as amended, the
"</FONT><FONT SIZE=2><B>Agreement</B></FONT><FONT SIZE=2>") among the undersigned, Western Gas Resources,&nbsp;Inc. (the "</FONT><FONT SIZE=2><B>Company</B></FONT><FONT SIZE=2>") and you. Unless
otherwise defined herein, the terms defined in the Agreement shall be used herein as therein defined. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;It
is hereby agreed by you and us as follows: </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
Agreement is, effective the date first above written, hereby amended as follows: </FONT></P>


<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a)&nbsp;&nbsp;</FONT><FONT
SIZE=2><B>Paragraph&nbsp;6A(3). Total Debt Maintenance.</B></FONT><FONT SIZE=2> Paragraph&nbsp;6A(3) of the Agreement is amended in its entirety to
read as follows: </FONT></P>

<UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"</FONT><FONT
SIZE=2><B>6A(3). Total Debt Maintenance.</B></FONT><FONT SIZE=2> The sum of Adjusted Consolidated Debt plus Excess Lease Payments at any time to exceed (i)&nbsp;from
October&nbsp;1, 1998 through December&nbsp;31, 2001, 60% of the sum of Consolidated Net Tangible Assets plus Excess Lease Payments and (ii)&nbsp;from and after January&nbsp;1, 2002, 55% of the
sum of Consolidated Net Tangible Assets plus Excess Lease Payments. In any event, for purposes of determining compliance with this paragraph&nbsp;6A(3), Adjusted Consolidated Debt shall include
without duplication and without limitation all indebtedness included in determining compliance with the similar covenant in the NCNB Agreement." </FONT></P>

</UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b)&nbsp;&nbsp;</FONT><FONT
SIZE=2><B>Paragraph&nbsp;6A(4). Senior Debt Maintenance.</B></FONT><FONT SIZE=2> Paragraph&nbsp;6A(4) of the Agreement is amended in its entirety to
read as follows: </FONT></P>

<UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"</FONT><FONT
SIZE=2><B>6A(4). Senior Debt Maintenance.</B></FONT><FONT SIZE=2> The sum of Adjusted Consolidated Senior Debt plus Excess Lease Payments at any time to exceed
(i)&nbsp;from January&nbsp;1, 1999 until the completion of the 1999 Action Plan, 60% of the sum of Consolidated Net Tangible Assets plus Excess Lease Payments, (ii)&nbsp;from and after
completion of the 1999 Action Plan through March&nbsp;31, 2002, 40% of the sum of Consolidated Net Tangible Assets plus Excess Lease Payments and (iii)&nbsp;from and after April&nbsp;1, 2002,
35% of the sum of Consolidated Net Tangible Assets plus Excess Lease Payments. In any event, for purposes of determining compliance with this paragraph&nbsp;6A(4), Adjusted Consolidated Senior Debt
shall include without duplication and without limitation all indebtedness included in determining compliance with the similar covenant in the NCNB Agreement." </FONT></P>

</UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c)&nbsp;&nbsp;</FONT><FONT
SIZE=2><B>Paragraph&nbsp;6A(7). Senior Debt to EBITDA.</B></FONT><FONT SIZE=2> Paragraph&nbsp;6A(7) of the Agreement is amended in its entirety to read
as follows: </FONT></P>

<UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"</FONT><FONT
SIZE=2><B>6A(7). Senior Debt to EBITDA</B></FONT><FONT SIZE=2>. As of any date of determination (i)&nbsp;from the date on which the 1999 Action Plan is completed through
December&nbsp;31, 1999, the ratio of the sum of Senior Debt plus Excess Lease Payments to EBITDA for the period of four fiscal quarters most recently ended to be greater than 4.50 to 1.00 and
(ii)&nbsp;from and after January&nbsp;1, 2000, the ratio of the sum
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of Senior Debt plus Excess Lease Payments to EBITDA for the period of four fiscal quarters most recently ended to be greater than 4.00 to 1.00." </FONT></P>

</UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d)&nbsp;&nbsp;</FONT><FONT
SIZE=2><B>Paragraph&nbsp;6C(6). Lease Rentals.</B></FONT><FONT SIZE=2> Paragraph&nbsp;6C(6)&nbsp;of the Agreement is amended in its entirety to read
as follows: </FONT></P>

<UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"</FONT><FONT
SIZE=2><B>6C(6). Lease Rentals.</B></FONT><FONT SIZE=2> Except for oil, gas and mineral leases, real estate leases for office space used by the Company, and except for
leases for transportation equipment, including over-the-road trucks and tankers, data processing and other office equipment used in the ordinary course of business, enter into
or permit to remain in effect, any agreements to rent or lease (as lessee) any real or personal property if after giving effect thereto the aggregate amount of all sums payable by the Company and all
Subsidiaries over the remaining lives of all such Leases in the aggregate would exceed $75,000,000." </FONT></P>

</UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(e)&nbsp;&nbsp;</FONT><FONT
SIZE=2><B>Paragraph&nbsp;10B. Other Terms.</B></FONT><FONT SIZE=2> Paragraph&nbsp;10B of the Agreement is amended by adding thereto in alphabetical
order the following definitions: </FONT></P>

<UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"</FONT><FONT
SIZE=2><B>Excess Lease Payments</B></FONT><FONT SIZE=2>' shall mean all amounts payable under leases, throughout the life of such leases, whether or not such payments are
capitalized in accordance with GAAP, to the extent such payments exceed $35,000,000 in the aggregate, excluding obligations arising under oil and gas leases, real estate leases for office space used
by the Company or any Subsidiary, and leases for vehicles, office equipment and data processing equipment." </FONT></P>

</UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(f)&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT
SIZE=2><B>Schedule&nbsp;6C(3). Joint Ventures.</B></FONT><FONT SIZE=2> Schedule&nbsp;6C(3)&nbsp;of the Agreement is hereby amended in its entirety to
read as set forth on Schedule&nbsp;6C(3)&nbsp;attached hereto: </FONT></P>

<UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;On
and after the effective date of this Letter Amendment, each reference in the Agreement to "this Agreement", "hereunder", "hereof", or words of like import referring to the Agreement,
and each reference in the Notes to "the Agreement", "thereunder", "thereof", or words of like import referring to the Agreement, shall mean the Agreement as amended by this Letter Amendment. The
Agreement, as amended by this Letter Amendment, is and shall continue to be in full force and effect and is hereby in all respects ratified and confirmed. The execution, delivery and effectiveness of
this Letter Amendment shall not, except as expressly provided herein, operate as a waiver of any right, power or remedy under the Agreement nor constitute a waiver of any provision of the Agreement. </FONT></P>

</UL>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This
Letter Amendment may be executed in any number of counterparts and by any combination of the parties hereto in separate counterparts, each of which counterparts shall be an original
and all of which taken together shall constitute one and the same Letter Amendment. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
you agree to the terms and provisions hereof, please evidence your agreement by executing and returning at least a counterpart of this Letter Amendment to the Company at its address
at 12200 N. Pecos Street, Denver, CO 80234, Attention of Chief Financial Officer. This Letter Amendment shall become effective as of the date first above written when and if counterparts of this
Letter Amendment shall have been executed by us and you and the consent attached hereto shall have been executed by the Guarantors. </FONT></P>

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Very truly yours,</FONT></TD>
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&nbsp;</FONT></TD>
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WESTERN GAS RESOURCES,&nbsp;INC.</FONT></TD>
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&nbsp;</FONT></TD>
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By:</FONT></TD>
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<TD WIDTH="45%"><BR><HR NOSHADE><FONT SIZE=2> Title:</FONT></TD>
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<P><FONT SIZE=2>Agreed
as of the date first above written: </FONT></P>

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THE PRUDENTIAL INSURANCE COMPANY OF AMERICA</FONT></TD>
<TD WIDTH="3%" VALIGN="TOP"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
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&nbsp;</FONT></TD>
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By:</FONT></TD>
<TD WIDTH="1%"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD WIDTH="45%"><BR><HR NOSHADE><FONT SIZE=2> Vice President</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
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&nbsp;</FONT></TD>
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PRUCO LIFE INSURANCE COMPANY</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
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&nbsp;</FONT></TD>
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By:</FONT></TD>
<TD WIDTH="1%"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD WIDTH="45%"><BR><HR NOSHADE><FONT SIZE=2> Vice President</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
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&nbsp;</FONT></TD>
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<P ALIGN="CENTER"><FONT SIZE=2><B>CONSENT  </B></FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Each of the undersigned is a Guarantor ("</FONT><FONT SIZE=2><B>Guarantor</B></FONT><FONT SIZE=2>" and, collectively
"</FONT><FONT SIZE=2><B>Guarantors</B></FONT><FONT SIZE=2>") under separate guaranties (each being a "</FONT><FONT SIZE=2><B>Guaranty</B></FONT><FONT SIZE=2>") in favor of The Prudential Insurance
Company of America and Pruco Life Insurance Company (together, "</FONT><FONT SIZE=2><B>Prudential</B></FONT><FONT SIZE=2>") with respect to the obligations of Western Gas Resources,&nbsp;Inc. (the
"</FONT><FONT SIZE=2><B>Company</B></FONT><FONT SIZE=2>") under that certain Second Amended and Restated Master Shelf Agreement dated as of December&nbsp;19, 1991 (effective January&nbsp;31,
1996) as amended by Letter Amendment No.&nbsp;1 dated November&nbsp;21, 1997, Letter Amendment No.&nbsp;2 dated March&nbsp;31, 1999, Limited Waiver, Consent, Release and Amendment No.&nbsp;3
dated June&nbsp;1, 1999, Limited Waiver, Consent, Release and Amendment No.&nbsp;4 dated August&nbsp;25, 2000 and Letter Amendment No.&nbsp;5 dated March&nbsp;30, 2001 (as amended, the
"</FONT><FONT SIZE=2><B>Agreement</B></FONT><FONT SIZE=2>"). Prudential and the Company are entering into that certain Letter Amendment No.&nbsp;6 to Second Amended and Restated Master Shelf
Agreement, dated as of March&nbsp;1, 2002 (the "</FONT><FONT SIZE=2><B>Amendment</B></FONT><FONT SIZE=2>"). Each of the undersigned hereby consents to the Amendment and each hereby confirms and
agrees that its Guaranty is, and shall continue to be, in full force and effect and is hereby confirmed and ratified in all respects except that, upon the effectiveness of, and on and after the date
of this consent, all words of like import referring to the Agreement shall mean the Agreement as amended by the Amendment, as the same may be further amended or modified from time to time. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Dated
as of March&nbsp;1, 2002 </FONT></P>

<P><FONT SIZE=2><B>LANCE OIL&nbsp;&amp; GAS COMPANY,&nbsp;INC.<BR>
MGTC,&nbsp;INC.<BR>
MIGC,&nbsp;INC.<BR>
MOUNTAIN GAS RESOURCES,&nbsp;INC.<BR>
WESTERN GAS RESOURCES&#151;TEXAS,&nbsp;INC.<BR>
WESTERN GAS WYOMING, L.L.C.  </B></FONT></P>

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<TD WIDTH="5%"><BR><FONT SIZE=2>By:</FONT></TD>
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<TD WIDTH="45%"><BR><HR NOSHADE><FONT SIZE=2> William J. Krysiak, as Chief Financial Officer of each of the above-named companies.</FONT></TD>
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