Document:

<PAGE>

                                                                   Exhibit 10.27

                       AMENDMENT TO EMPLOYMENT AGREEMENT

         THIS AMENDMENT (hereinafter referred to as "Amendment") to that certain
Employment Agreement (hereinafter referred to as "Agreement") effective October
1, 1999 by and between WESTERN GAS RESOURCES, INC., a Delaware corporation,
(hereinafter referred to as the "Corporation"), and LANNY F. OUTLAW (hereinafter
referred to as the "Employee") is made effective as of the 18/th/ day of May
2001.

                               R E C I T A L S:

         a.   The Corporation desires to extend the term of its retention of
              Employee on an exclusive basis to the Corporation in connection
              with its business activities as the Chief Executive Officer and
              President under the terms and conditions of the Agreement, except
              as amended herein, for the duration of this Agreement, as amended.

         b.   The parties have reached agreement with respect to the terms of
              such extension of the term of Employee's retention under the
              Agreement, as amended herein.

         NOW THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged by the parties and for the mutual
promises exchanged herein, the parties agree to the following Amendment to the
Agreement:

         Paragraph 2 of the Agreement shall be amended as follows:

         2. Compensation and Bonus. For all of the services rendered by Employee
            ----------------------
         pursuant to this Agreement, the Corporation shall pay the Employee a
         minimum monthly compensation of Thirty Five Thousand Four Hundred
         Sixteen Dollars and Sixty-Seven Cents ($35,416.67) (hereinafter
         referred to as "Compensation"), payable in accordance with the
         Corporation's normal pay practices during the term of Employee's
         employment. Except for the Change of Control bonus described in
         paragraph 13 of Agreement, as amended herein, which is
         non-discretionary, the Corporation shall pay Employee such additional
         bonus, if any, as may be determined appropriate by the Corporation's
         Board of Directors from time to time in its sole and absolute
         discretion.

         Paragraph 5 of the Agreement shall be amended as follows:

         5. Employee and Director Benefits. During the term of Employee's
            ------------------------------
         employment he shall be eligible to participate in all of the employee
         benefit plans provided by the Corporation, from time to time, in
         accordance with the provisions of such plans, including but not limited
         to the Corporation's qualified retirement plans, the
<PAGE>

         Corporation's Incentive Stock Option Plan For Key Employees, and the
         Corporation's loan plan to acquire stock pursuant to the Agreement to
         Provide Loan(s) to Exercise Key Employees' Stock Options between the
         Corporation and Employee, as amended of even date herewith. The
         Employee hereby agrees and acknowledges that nothing in this Agreement
         guarantees him the right to any additional stock under any Stock Option
         Plan, or loan under the loan plan, but that such determination is made
         by the Board of Directors, in its sole and absolute discretion, in
         accordance with the terms of such plans. Upon termination without cause
         or Termination Date, Employee shall be eligible to participate in the
         Corporation's Directors' Medical Insurance Plan (hereinafter "Director
         Plan") as if Employee was a director of the Corporation on the
         effective date of the Director Plan, in accordance with the terms of
         the Director Plan.

         Paragraph 9 (a) of the Agreement shall be deleted in its entirety and
         replaced with the following:

         9 (a)  November 30, 2001 ("Termination Date")

         Paragraph 10(a) of the Agreement shall be amended as follows:

         Paragraph 10 (a) Employee's Right to Compensation and Benefits.
                          ---------------------------------------------
         Employee shall be entitled to the Compensation and employee benefits
         through the Termination Date of the Agreement, as amended, due to
         Employee's death or disability. In the event of disability, Employee
         shall be eligible to participate in Director Plan as if Employee was a
         director of the Corporation on the effective date of the Director Plan,
         in accordance with the terms of the Director Plan. Except for the
         Change of Control bonus described in paragraph 13 of Agreement, as
         amended herein, which is non-discretionary, Employee shall only be
         entitled to such additional bonus, if any, which as been previously
         authorized by the Board of Directors, but has not been paid as of the
         date of Employee's death or disability.

         Paragraph 11(a) of the Agreement shall be amended as follows:

         11 (a) Severance Pay. In the event Employee is terminated with or
                -------------
         without cause, Employee shall be entitled to severance pay of the
         Compensation, as specified in Paragraph 2 of this Agreement through the
         Termination Date of the Agreement, as amended. Such severance pay shall
         be payable in a lump sum payment on January 1, of the year following
         the date of termination less any and all applicable taxes. In the event
         Employee is terminated without cause and such termination is not due to
         a Change of Control of the Corporation (as hereinafter defined),
         Employee's stock options which have not yet vested upon termination
         without cause, shall continue to vest under the terms granted to
         Employee for each vesting period which naturally occurs for so long as
         Employee continues to serve as a director of the Corporation's Board of
         Directors.
<PAGE>

         Notwithstanding anything else contained herein, in the event Employee's
         employment is terminated without cause due to a Change of Control of
         the Corporation prior to the Termination Date of Employee, then
         Employee shall receive either of the following for unvested stock
         options previously granted to Employee:

                  i)  in the event of a Change of Control in which the
                  Corporation is acquired in a cash purchase, then Employee
                  shall receive a lump sum payment constituting the positive
                  difference between the exercise price of unvested stock
                  options previously granted to Employee and the transaction
                  price of common stock; or

                  ii) in the event of a Change of Control in which the
                  Corporation is acquired in a stock purchase, then Employee's
                  stock options which have not vested prior to termination
                  without cause shall be converted to an amount of unqualified
                  vested options of the acquiring corporation's stock at the
                  original grant price to Employee based upon the conversion
                  rate of the acquiring corporation's stock on the acquisition
                  date.

         Paragraph 11(b) of the Agreement shall be amended as follows:

         11  (b) Employee's Right to Compensation and Benefits. Employee shall
                 ---------------------------------------------
         be entitled to the Compensation and employee benefits through the
         Termination Date of the Agreement, as amended. In the event Employee is
         terminated without cause, Employee shall be eligible to participate in
         the Director Plan as if Employee was a director of the Corporation on
         the effective date of the Director Plan, in accordance with the terms
         of the Director Plan. In the event Employee is terminated without
         cause, and except for the Change of Control bonus described in
         paragraph 13 of the Agreement, as amended herein, which is non-
         discretionary, Employee shall only be entitled to such additional
         bonus, if any, which as been previously authorized by the Board of
         Directors, but has not been paid as of the date of Employee's
         termination of employment.

         Paragraph 13 of the Agreement shall be amended as follows:

         13. Employee's Rights and Obligations Upon Termination Date of
             ----------------------------------------------------------
         Employment. Upon the Termination Date of Employee's employment,
         ----------
         Employee shall be entitled to the pro-rata share of Compensation and
         employee benefits, if any, which have been earned but not paid through
         the Termination Date. Upon the Termination Date, Employee shall be
         eligible to participate in the Director Plan as if Employee was a
         director of the Corporation on the effective date of the Director Plan,
         in accordance with the terms of the Director Plan. Except for the
         Change of Control bonus described herein, which is non-discretionary,
         Employee shall only be entitled to such additional bonus, if any, which
         as been previously authorized by the Board of Directors, but has not
         been paid as of the
<PAGE>

         Termination Date of employment. Employee's stock options which have not
         yet vested upon the Termination Date, shall continue to vest under the
         terms granted to Employee for each vesting period which naturally
         occurs for so long as Employee continues to serve as a director of the
         Corporation's Board of Directors. In the event a Change of Control is
         commenced prior to Employee's Termination Date and such Change of
         Control results in the acquisition of the Corporation after Employee's
         Termination Date, then Employee shall receive a bonus of Two Hundred
         and Twelve Thousand and Five Hundred Dollars ($212,500.00) less any and
         all applicable taxes within thirty (30) days of the acquisition date of
         the Corporation. Notwithstanding such Termination Date, Employee shall
         remain bound by the provisions of paragraphs 4, 6, 7 and 8 hereof.

         Except for the foregoing amendments herein, all other provisions of the
         Agreement remain unchanged.

         IN WITNESS WHEREOF, The parties have hereunto set their hands as of the
         date of this Amendment.

         WESTERN GAS RESOURCES, INC.,
         a Delaware corporation

         By:______________________________
               John C. Walter
               Executive Vice President

         EMPLOYEE

         _________________________________
               Lanny F. Outlaw<PAGE>

                                                                   EXHIBIT 10.17

May 9, 2001

Eric J. Keller
Executive Vice President, Chief Financial Officer

Dear Eric:

This confirms the agreement reached today between you and Corio, Inc. (the
"Company") regarding your employment with the Company. Effective July 30, 2001,
you will resign as the Company's Chief Financial Officer. Commencing on August
1, 2001 and continuing through and until the earlier of: (a) January 31, 2002,
or (b) the date you begin full time employment with another company (the
"Termination Date"), whichever applies, Corio will retain you as a part-time
employee in an Executive Advisor role. During this "Transition Period," you will
be available to provide services to Corio as requested, not to exceed 40 hours a
month. Corio will provide you a monthly salary during the Transition Period of
$18,333.33 through September 30, 2001 and $9,166.67 thereafter, less all
applicable withholdings. In addition, Corio will continue to provide you all
other employee benefits that you are currently eligible to receive during the
Transition Period, with the following exceptions: after July 30, 2001, you will
not be eligible to participate in the accrual of flexible time off hours and in
any bonus plans for the Company. Your Stock Options will continue to vest up
through the Termination Date.

Please indicate your agreement with the above terms by signing below.

Sincerely,

/s/ George Kadifa
George Kadifa
Chief Executive Officer

I have read, understand and agree to the terms set forth above.
/s/ Eric J. Keller                    May 10, 2001
------------------                    ------------
Eric J. Keller                        Date

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00028-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00028-of-00352.parquet"}]]