EXHIBIT 10.21

                        PIONEER NATURAL RESOURCES COMPANY
                               SEVERANCE AGREEMENT


     This  Severance  Agreement  (this  "Agreement")  is entered into  effective
December 1, 1999,  between  Pioneer  Natural  Resources  Company  ("Parent"),  a
Delaware  corporation,  and Thomas C. Halbouty (the "Officer").  As used in this
Agreement,  the term "Company"  shall be deemed to include Parent and its direct
or indirect wholly-owned subsidiaries.

                                    Recitals

     A.  Company  acknowledges  that  Officer is a  significant  employee of the
Company,  possessing skills and knowledge instrumental to the successful conduct
of the  Company's  business.  Company  is  willing  to  enter  into a  severance
arrangement  with  Officer  in order to better  ensure  itself of the  continued
management  services of Officer for itself and its subsidiaries and, in part, to
induce  Officer to continue to provide  those  services  and subject  himself to
certain restrictions regarding the use of Company information.

     B.  Officer is willing to  subject  himself to the  restrictions  mentioned
above in part to induce  Company to enter into a compensation  arrangement  that
provides  for,  among other  things,  the payment of certain  benefits  upon the
termination of Officer's employment under certain circumstances.

     Now,  therefore,  for and in  consideration  of the  mutual  covenants  and
agreements set forth herein and for other good and valuable  consideration,  the
receipt and  sufficiency of which are hereby  acknowledged,  the parties to this
Agreement hereby agree as follows:

     1.  Position and Duties.  Officer  shall  initially  serve  Company as Vice
President  - Chief  Information  Officer,  and,  in so  doing,  shall  report to
Company's Board of Directors (the "Board"),  Company's  Chief Executive  Officer
(the "Chief Executive  Officer") or such officers of Company as is prescribed by
Company's  bylaws,  by  resolutions  of the Board or by  direction  of the Chief
Executive  Officer.  Officer  shall  have  supervision  and  control  over,  and
responsibility  for, such  management and  operational  functions of the Company
currently  assigned  to such  position,  and shall have such other or  different
functions,  powers,  duties  and  responsibilities  (including  holding  officer
positions with one or more subsidiaries of Parent),  as may from time to time be
prescribed  by the Board or the Chief  Executive  Officer,  or any other Company
officer to whom Officer  reports,  so long as such functions,  powers and duties
are reasonable and customary for a Vice  President - Chief  Information  Officer
serving an enterprise  comparable to Company.  Employee's  failure to accept and
perform such other or different  functions,  powers or duties shall be deemed to
be a Termination  of Employment by voluntary  action of Employee,  and shall not
constitute a Termination for Good Reason.

     2.  Devotion of  Efforts.  So long as Officer is serving the Company in the
capacities  described in Section 1, he/she shall devote his/her full time, skill
and  attention  and his/her best efforts  during  normal  business  hours to the
business  and  affairs  of the  Company  to the extent  necessary  to  discharge
faithfully  and  efficiently  his/her  duties and  responsibilities,  except for
usual,  ordinary and customary periods of vacation and absence due to illness or
other  disability  or such  periods of leave as are  approved  in writing by the
Board or the Chief Executive  Officer.  The provisions of this Section shall not
be construed to prevent Officer from making  investments in other  businesses or
enterprises,  so long as such investments do not violate the Company's  conflict
of interest  policies or require  the  provision  of services by Officer to such
businesses  or  enterprises  to an extent that would  interfere  in any material
respect with the  performance of Officer's  duties and  responsibilities  to the
Company.

     3. Compensation.

        (a) Base Salary. As compensation for Officer's services, the
Company shall pay Officer an annualized base salary of a specified amount per
annum (the "Base Salary"). The Base Salary shall be payable in substantially
equal semi-monthly installments. The Compensation Committee of the Board (the
"Compensation Committee") may review the Base Salary periodically and may grant

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such increases, or effect such reductions, in the Base Salary as the
Compensation Committee considers appropriate in accordance with such
compensation guidelines and policies as it may establish from time to time. The
Base Salary applicable from time to time for any period of Officer's employment
with the Company, commencing on the effective date of this Agreement, shall be
identified on Schedule A attached hereto, which shall be amended periodically to
reflect any increases or reductions effected by the Compensation Committee.

        (b) Bonuses. Officer shall be entitled to receive (in addition
to the Base Salary) such annual or other periodic bonus as the Compensation
Committee may award in accordance with such compensation guidelines and policies
as it may establish from time to time.

        (c) Other Benefits. Officer shall be entitled to participate
in, or receive benefits under, any employee benefit plan or other arrangement
made available now or in the future by the Company to the officers of Company (a
"Benefit Plan"), subject to the terms, conditions and overall administration of
such Benefit Plan. Officer's participation in, or receipt of benefits under, any
Benefit Plan shall be in addition to (and not in lieu of) the Base Salary.

        (d) Vacations and Holidays. Officer shall be entitled to the
number of paid vacation days in each calendar year determined by Company from
time to time for its officers and shall be entitled to all paid holidays given
by the Company to its employees in general.

     4.  Relocation.  Officer  shall  initially  be required to perform  his/her
duties and  responsibilities  hereunder at Company's  offices located in Irving,
Texas.  If  the  Company   requires   Officer  to  perform  his/her  duties  and
responsibilities  at any  location  that is more than 50 miles from the  nearest
border of Irving,  Texas (a "New  Location") and, within 30 days after receiving
notice thereof,  Officer accepts such relocation rather than terminating his/her
employment  with the Company  pursuant to Section 5(a), the Company shall pay to
Officer,  or shall reimburse Officer for (upon submission of reasonably detailed
evidence thereof), such sums as are provided for under the Relocation Policy for
Exempt  Employees as  established by Company.  Officer's  failure to accept such
relocation within 30 days after receiving notice thereof,  shall be deemed to be
a  Termination  of  Employment  by  voluntary  action of Officer,  and shall not
constitute a Termination for Good Reason.

     5. Termination of Employment.

        (a) Right to Terminate. Officer's employment with the Company
(including his/her officer position with Company) shall be terminated upon the
death, Disability (as defined in subsection (f)(3) of this Section) or Normal
Retirement (as defined in subsection (f)(5) of this Section) of Officer. In
addition, Officer's employment with the Company (including his/her officer
position with Company) may be terminated at any time and for any reason as a
result of a dismissal by the Company or as a result of a voluntary action by
Officer. Any such termination of employment is referred to herein as a
"Termination of Employment."

        (b) Notice of Termination.

            (1) Any Termination of Employment that is the result of Officer's
         Disability shall be communicated by the Company to Officer in a written
         notice thereof. Such notice shall state that, in the opinion of the
         Board, Officer is suffering from a Disability and such Disability is
         the reason for the Termination of Employment.

            (2) Any Termination of Employment that is the result of Officer's
         Normal Retirement shall be communicated by Officer to Company by a
         written notice thereof. Such notice shall state that Officer is
         retiring and shall specify the date of such Termination of Employment,
         which shall be not less than 30 days following the date such notice is
         received by Company.

            (3) Any Termination of Employment that is the result of a dismissal
         by the Company (but is not the result of Officer's Disability) shall be
         communicated by the Company to Officer by a written notice thereof.
         Such notice shall state whether or not (in the Company's opinion) the
         Termination of Employment constitutes a Termination for Cause (as

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         defined in subsection (f)(6) of this Section) and, if so, shall set
         forth in reasonable detail facts and circumstances constituting a basis
         for such Termination for Cause.

            (4) Any Termination of Employment that is the result of a voluntary
         action by Officer (but is not the result of Officer's Normal
         Retirement) shall be communicated by Officer to Company by written
         notice thereof. Such notice shall state whether or not (in Officer's
         opinion) the Termination of Employment constitutes a Termination for
         Good Reason (as defined in subsection (f)(7) of this Section) and, if
         so, shall set forth in reasonable detail the facts and circumstances
         claimed as the basis for such Termination for Good Reason. Such notice
         shall also specify the date of such Termination of Employment, which
         (if the Termination of Employment does not constitute a Termination for
         Good Reason) shall be not less than 30 days following the date such
         notice is received by Company.

        (c) Date of Termination of Employment. For purposes of this
Agreement, the date of a Termination of Employment shall be (1) if the
Termination of Employment is the result of Officer's death, the date of such
death, (2) if the Termination of Employment is the result of Officer's
Disability, the date on which the notice described in subsection (b)(1) of this
Section is received by Officer, (3) if the Termination of Employment is the
result of Officer's Normal Retirement, the date specified in the notice
described in subsection (b)(2) of this Section, (4) if the Termination of
Employment is the result of a dismissal by the Company (but is not the result of
Officer's Disability), the date on which the notice described in subsection
(b)(3) of this Section is received by the Officer, or such later date as may be
specified by the Company in such notice, and (5) if the Termination of
Employment is the result of a voluntary action by Officer (but is not the result
of Officer's Normal Retirement), the date specified in the notice described in
subsection (b)(4) of this Section, or such earlier date as the Company may
specify, provided that if such date specified by Company is less than 30 days
following the date Company received notice from Employee, then Company agrees to
pay officer an amount equal to one-twelfth (1/12) of Officer's Base Salary,
which amount shall be paid in cash on the date of such Termination of
Employment.

        (d) Payments Due Upon Termination of Employment. The
provisions of subsections (d)(1) and (d)(3) of this Section shall apply to any
Termination of Employment, whether occurring prior to, at the time of or at any
time following a Change in Control (as defined in subsection (f)(2) of this
Section); and the provisions of subsection (d)(2) of this Section shall apply
only to any Termination of Employment prior to a Change in Control.

            (1) Death, Disability or Normal Retirement. If the
         Termination of Employment is the result of Officer's death, Disability
         or Normal Retirement, the Company shall pay the following amounts to
         Officer (or his/her estate or personal representative):

                       (A) The Base Salary (at the rate in effect
                  on the date of such Termination of Employment, as identified
                  on Schedule A) pro-rated through and including the date of
                  such Termination of Employment, to the extent not already
                  paid, which amount shall be paid in cash on the first normal
                  semi-monthly Base Salary payment date immediately succeeding
                  the date of such Termination of Employment;

                       (B) Any amounts arising from Officer's
                  participation in, or benefits under, any Benefit Plan through
                  and including the date of such Termination of Employment,
                  which amounts shall be payable in accordance with the terms
                  and conditions of such Benefit Plan; and

                       (C) An amount equal to one full year's Base
                  Salary (at the rate in effect on the date of such Termination
                  of Employment, as identified on Schedule A), which amount
                  shall be paid in cash within 30 days following the date of
                  such Termination of Employment.

            (2) Termination for Good Reason or Not for Cause. If
         the Termination of Employment (i) is the result of a dismissal by the
         Company (but is not the result of Officer's Disability) and does not
         constitute a Termination for Cause or (ii) is the result of a voluntary

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         action by Officer (but is not the result of Officer's Normal
         Retirement) and constitutes a Termination for Good Reason, the Company
         shall pay the following amounts, and provide the following benefits to
         Officer:

                       (A) The Base Salary (at the rate in effect
                  on the date of such Termination of Employment, as identified
                  on Schedule A) pro-rated through and including the date of
                  such Termination of Employment, to the extent not already
                  paid, which amount shall be paid in cash on the date of such
                  Termination of Employment;

                       (B) Any amount arising from Officer's
                  participation in, or benefits under, any Benefit Plan through
                  and including the date of such Termination of Employment,
                  which amounts shall be payable in accordance with the terms
                  and conditions of such Benefit Plan;

                       (C) A lump sum amount equal to one full
                  year's Base Salary (at the rate in effect on the date of such
                  Termination of Employment, as identified on Schedule A), which
                  amount shall be paid in cash on the date of such Termination
                  of Employment;

                       (D) For a period of one year following the
                  date of such Termination of Employment, a continuation of all
                  health insurance coverage applicable at the time of such
                  Termination of Employment to Officer and Officer's immediate
                  family under any Benefit Plan; and

                       (E) With respect to a Termination of
                  Employment described in subsection (d)(2)(i) of this Section,
                  if the date of Termination of Employment is less than thirty
                  (30) days after the date of notice thereof, an amount equal to
                  one-twelfth (1/12) of the Officer's Base Salary, which amount
                  shall be paid in cash on the date of such Termination of
                  Employment.

            (3) Termination for Cause or Not for Good Reason. If
         the Termination of Employment (i) is the result of a dismissal by the
         Company (but is not the result of Officer's Disability) and constitutes
         a Termination for Cause or (ii) is the result of a voluntary action by
         Officer (but is not the result of Officer's Normal Retirement) and does
         not constitute a Termination for Good Reason, the Company shall pay the
         following amounts to Officer:

                       (A) The Base Salary (at the rate in effect
                  on the date of such Termination of Employment, as identified
                  on Schedule A) pro-rated through and including the date of
                  such Termination of Employment, to the extent not already
                  paid, which amount shall be paid in cash on the first normal
                  semi-monthly Base Salary payment date immediately succeeding
                  the date of such Termination of Employment; and

                       (B) Any amounts arising from Officer's
                  participation in, or benefits under, any Benefit Plan through
                  and including the date of such Termination of Employment,
                  which amounts shall be payable in accordance with the terms
                  and conditions of such Benefit Plan.

            (4) Payment Contingent on Release. If Officer's
         Termination of Employment is prior to a Change in Control (and only in
         that event), and Officer is otherwise entitled to the payment provided
         in subsection (d)(2) of this Section, then such payment shall be
         subject to, and contingent upon, Officer's execution of a General
         Release Agreement in favor of the Company in substantially the form and
         substance as the one attached hereto as Schedule B.

        (e) Additional Provisions Applicable Upon Termination of
Employment Concurrent with or Following Change in Control. The following
provisions shall apply to any Termination of Employment occurring at the time
of, or at any time within one year following, a Change in Control.

            (1) Termination for Good Reason or Not for Cause. If
         the Termination of Employment (i) is the result of a dismissal by the
         Company (but is not the result of Officer's Disability) and does not
         constitute a Termination for Cause, or (ii) is the result of a

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         voluntary action by Officer (but is not the result of Officer's Normal
         Retirement) and constitutes a Termination for Good Reason, the Company
         shall pay the following amounts, and provide the following benefits, to
         Officer:

                       (A) The Base Salary (at the rate in effect
                  on the date of such Termination of Employment, as identified
                  on Schedule A) pro-rated through and including the date of
                  such Termination of Employment, to the extent not already
                  paid, which amount shall be paid in cash on the date of such
                  Termination of Employment;

                       (B) A lump sum in cash equal to 2.99 times
                  the sum of (i) Officer's Base Salary (at the rate in effect on
                  the date of such Termination of Employment, as identified on
                  Schedule A), plus (ii) the greater of the then current year's
                  targeted bonus or actual bonus award (if applicable) for
                  Officer, which amount shall be paid in cash on the date of
                  such Termination of Employment;

                       (C) Any amount arising from Officer's
                  participation in, or benefits under, any employee Benefit Plan
                  or other arrangement made available now or in the future by
                  the Company to its employees, through and including the date
                  of such Termination of Employment, which amounts shall be
                  payable in accordance with the terms and conditions of such
                  Benefit Plan;

                       (D) For a period of one year following the
                  date of such Termination of Employment, a continuation of all
                  health insurance coverage applicable at the time of such
                  Termination of Employment to Officer and his/her immediate
                  family under any Benefit Plan; and

                       (E) With respect to a Termination of
                  Employment described in subsection (e)(1)(i) of this Section,
                  if the date of Termination of Employment is less than thirty
                  (30) days after the date of notice thereof, an amount equal to
                  one-twelfth (1/12) of the Officer's Base Salary, which amount
                  shall be paid in cash on the date of such Termination of
                  Employment.

            (2) Voluntary Termination Not for Good Reason or for
         Failure to Relocate. Notwithstanding any other provision of this
         subsection (e) to the contrary, if the Termination of Employment (i) is
         the result of a voluntary action by Officer, does not constitute a
         Termination for Good Reason, and occurs at least six months, but not
         more than one year, following a Change in Control, or (ii) whether
         voluntary or involuntary, occurs at the time of, or at any time within
         one year following, a Change in Control and following the Company's
         requiring the Officer to perform his/her duties and responsibilities
         hereunder at a New Location, which relocation is not accepted by
         Officer within 30 days after receiving notice thereof, then the Company
         shall pay to Officer all amounts that would be payable pursuant to
         subsection (d)(2) of this Section had such Termination of Employment
         occurred prior to the Change in Control and constituted a Termination
         for Good Reason.

            (3) Excise Tax and Gross-Up Payment.

                       (A) If any portion of such compensation
                  constitutes a parachute payment (a "Payment") and is subject
                  to the Excise Tax (hereinafter defined), then Company shall,
                  in addition to providing such compensation, pay the Gross-Up
                  Payment (hereinafter defined) to Officer in the manner
                  described below. For purposes of this Agreement, (i) "Excise
                  Tax" shall mean the tax imposed pursuant to section 4999 of
                  the Code and any interest or penalties incurred by the Officer
                  with respect to such Excise Tax, and (ii) "Gross-Up Payment"
                  shall mean, with respect to any compensation provided to the
                  Officer by Company (including without limitation the payments
                  provided for under this Agreement and any payments to the
                  Officer under any employee benefit plan, including without
                  limitation the Company's Long-term Incentive Plan, or other
                  arrangement) that is subject to the Excise Tax, an amount

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                  that, after reduction of the amount of such Gross-Up Payment
                  for all federal, state, and local tax (including any interest
                  or penalties imposed with respect to such taxes) to which the
                  Gross-Up Payment is subject (including the Excise Tax to which
                  the Gross-Up Payment is subject), is equal to the amount of
                  the Excise Tax to which such compensation is subject. For
                  purposes of determining the amount of any Gross-Up Payment,
                  Officer shall be deemed to pay federal income taxes at the
                  highest marginal rate of taxation and state and local taxes,
                  if applicable, at the highest marginal rate of taxation in the
                  state and locality of residence of the Officer on the Date of
                  Termination, net of the maximum reduction in federal income
                  taxes that could be obtained from deduction of such state and
                  local taxes, if any.

                       (B) Subject to the provisions of subsection
                  5(e)(3)(C), all determinations required to be made under this
                  subsection 5(e)(3), including whether and when a Gross-Up
                  Payment is required, the amount of such Gross-Up Payment and
                  the assumptions to be utilized in arriving at such
                  determination, shall be made by the accounting firm which
                  performed the audit of the Company for the year preceding the
                  year in which the Change in Control occurred (the "Accounting
                  Firm") which shall provide detailed supporting calculations
                  both to the Company and the Officer within 15 business days of
                  the receipt of notice from the Officer that there has been a
                  Payment, or such earlier time as is requested by the Company.
                  In the event that the Accounting Firm is serving as accountant
                  or auditor for the individual, entity or group effecting the
                  Change in Control, the Officer shall appoint another
                  nationally recognized accounting firm to make the
                  determinations required hereunder (which accounting firm shall
                  then be referred to as the Accounting Firm hereunder). All
                  fees and expenses of the Accounting Firm shall be borne solely
                  by the Company. Any Gross-Up Payment, as determined pursuant
                  to this subsection 5(e)(3), shall be paid by the Company to
                  the Officer within five days of the receipt of the Accounting
                  Firm's determination. If the Accounting Firm determines that
                  no Excise Tax is payable by the Officer, it shall furnish the
                  Officer with a written opinion that failure to report the
                  Excise Tax on the Officer's applicable federal income or
                  excise tax return would not result in the imposition of a
                  negligence or similar penalty. Any determination by the
                  Accounting Firm shall be binding upon the Company and the
                  Officer.

                       (C) The Officer shall notify the Company in
                  writing of any claim by the Internal Revenue Service that, if
                  successful, would require the payment by the Company of the
                  Gross-Up Payment. Such notification shall be given no later
                  than ten business days after the Officer is informed in
                  writing of such claim. The Officer shall not pay such claim
                  prior to the expiration of the 30-day period following the
                  date on which it gives such notice to the Company (or such
                  shorter period ending on the date that any payment of taxes
                  with respect to such claim is due). If the Company notifies
                  the Officer in writing prior to the expiration of such period
                  that it desires to contest such claim, (i) the Officer shall
                  accept legal representation with respect to such claim by an
                  attorney reasonably selected by the Company, (ii) cooperate
                  with the Company in good faith in order to effectively contest
                  such claim, and (iii) permit the Company to participate in any
                  proceedings relating to such claim; provided, however, the
                  Company shall bear and pay directly all costs and expenses
                  (including legal and accounting fees and additional interest
                  and penalties) incurred in connection with such contest and
                  shall indemnify and hold the Officer harmless, on an after-tax
                  basis, for any Excise Tax or income tax (including interest
                  and penalties with respect thereto) imposed as a result of
                  such representation and payment of costs and expenses. The
                  Company shall control all proceedings taken in connection with
                  such contest to the extent relating to issues impacting
                  whether a Gross-Up Payment is payable hereunder. The Officer
                  shall be entitled to settle or contest, as the case may be,
                  any other issue raised by the Internal Revenue Service or any
                  other taxing authority in connection with such contest.

                       (D) If any such claim referred to in
                  subsection 5(e)(3)(C) is made by the Internal Revenue Service
                  and the Company does not request the Officer to contest the
                  claim within the 30-day period following notice of the claim,
                  the Company shall pay to the Officer the amount of any
                  Gross-Up Payment owed to the Officer, but not previously paid
                  pursuant to subsection 5(e)(3)(B), immediately upon the
                  expiration of such 30-day period. If any such claim is made by
                  the Internal Revenue Service and the Company requests the
                  Officer to contest such claim, the Company shall pay to the
                  Officer the amount of any Gross-Up Payment owed to the

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                  Officer, but not previously paid under the provisions of
                  subsection 5(e)(3)(B), within five days of a Final
                  Determination of the liability of the Officer for such Excise
                  Tax. For purposes of this Agreement, a "Final Determination"
                  shall be deemed to occur with respect to a claim when (i)
                  there is a decision, judgment, decree or other order by any
                  court of competent jurisdiction, which decision, judgment,
                  decree or other order has become final, i.e., all allowable
                  appeals have been exhausted by either party to the action,
                  (ii) there is a closing agreement made under Section 7121 of
                  the Code, or (iii) the time for instituting a claim for refund
                  has expired, or if a claim was filed, the time for instituting
                  suit with respect thereto has expired.

            (4) Letter of Credit. Following a Change in Control,
         Parent (within 10 days following receipt of Officer's written request
         therefor), at its sole cost and expense, shall post an irrevocable
         letter of credit with a banking institution reasonably acceptable to
         Officer in an amount equal to the maximum amount of the aggregate cash
         payments that would be made to Officer pursuant to the provisions of
         paragraph (1) of this subsection if the provisions of paragraph (1) of
         this subsection were to become applicable. Such letter of credit shall
         contain provisions making the funds available thereunder to Officer by
         Officer's drafts drawn at sight at any time and from time to time. Such
         provisions shall permit Officer to present drafts (including drafts for
         partial draws) drawn at sight by presentation by Officer to the
         applicable banking institution of a written statement to the effect
         that the Company is in default on a payment to be made to Officer
         pursuant to the terms of this Agreement (setting forth the amount of
         such payment in default) and that Officer is not in default under, and
         has not breached the terms of, this Agreement. Parent shall continue to
         keep such letter of credit in place until the expiration of at least 60
         days following the date of a Termination of Employment occurring after
         the Change in Control.

            (5) Retirement Benefits Funded. Upon a Change in Control, any
         accrued but unfunded retirement benefit obligations to Officer under
         any then existing retirement plan shall be fully funded to a Rabbi
         Trust for the benefit of such Officer, which amount shall be paid in
         cash on the date of such Change in Control.

        (f) Certain Definitions. As used in the Section and elsewhere
in this Agreement, the following terms shall have the respective meanings
indicated:

            (1) "Across-the-Board Salary Reduction" shall mean a
         reduction in the Base Salary that is a part of, and is at a rate
         consistent with, a reduction in the base salaries paid to substantially
         all officers of Company.

            (2) "Change in Control" shall mean the occurrence,
         following the Effective Date hereof, of either of the following events:
         (i) an event that would constitute a Change in control as that term is
         defined in the Company's Long-Term Incentive Plan, or any successor
         plan thereto, or (ii) Consummation of a Business Combination not
         otherwise constituting a Change in Control but, pursuant to which the
         Person serving as Chief Executive Officer at the time of the execution
         of the initial agreement is removed from, or replaced in, such capacity
         with respect to the corporation resulting from such Business
         Combination.

            (3) "Disability" shall mean Officer's physical or
         mental impairment or incapacity of sufficient severity that, in the
         opinion of the Board, either (A) Officer is unable to continue to
         perform his/her duties and responsibilities hereunder or (B) Officer's
         condition entitles him to disability benefits under any Benefit Plan
         providing for the payment thereof.

            (4) "Excessive Salary Reduction" shall mean (A) a
         reduction in the Base Salary that is not an Across-the-Board Salary
         Reduction (as defined in paragraph (1) of this subsection) and that,
         when combined with the net effect of all prior increases and reductions

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         in the Base Salary (other than prior reductions that were
         Across-the-Board Salary Reductions), results in the Base Salary being
         less than 80% of the highest Base Salary to which Officer has ever been
         subject pursuant to this Agreement (as identified on Schedule A) or (B)
         a reduction in the Base Salary (whether or nor an Across-the-Board
         Salary Reduction) that, when combined with the net effect of all prior
         increases and reductions in the Base Salary (whether or not
         Across-the-Board Salary Reductions), results in the Base Salary being
         less than 65% of the highest Base Salary to which Officer has ever been
         subject pursuant to this Agreement (as identified on Schedule A).

            (5) "Normal  Retirement"  shall have the meaning  given to such term
         in Section  1.29 of the  Long-term Incentive Plan.

            (6) "Termination for Cause" shall mean a Termination of Employment
         as a result of a dismissal by the Company following (A) Officer's
         continued failure to substantially perform his/her duties and
         responsibilities other than any such failure resulting from Officer's
         physical or mental impairment or incapacity) after written demand for
         substantial performance is delivered by the Company specifically
         identifying the manner in which the Company believes Officer has not
         substantially performed his/her duties and responsibilities, (B)
         Officer's engaging in fraud or other misconduct that is injurious to
         the Company, monetarily or otherwise, (C) Officer's engaging in
         insubordination, (D) Officer's violation of, or failure to comply with,
         any written policy, guideline, rule or regulation of the Company which
         specifically provides that Officer may be dismissed (or his/her
         employment terminated) as a consequence of any such violation or
         failure to comply, (E) Officer's conviction of (or plea of guilty or
         nolo contendere to a charge of) any felony, or any crime or misdemeanor
         involving moral turpitude or financial misconduct, or (F) a material
         violation by Officer of the provisions of Section 6. For purposes of
         clause (B) above, an act, or failure to act, on Officer's part shall be
         considered "misconduct" if done, or omitted, by Officer not in good
         faith and without reasonable belief that such act, or failure to act,
         was in the best interest of the Company.

            (7) "Termination for Good Reason" shall mean a Termination of
         Employment as a result of voluntary action by Officer within 30 days
         after receiving notice of (A) the demotion of the Officer to an officer
         position junior to the officer position specified in Section 1 or to a
         non-officer position, (B) an Excessive Salary Reduction (as defined in
         paragraph (4) of this subsection), or (C) the failure by Parent to
         obtain the assumption agreement described in Section 7(h) on or prior
         to a succession described in Section 7(h).

     6.  Nonpublic Information.

        (a) Officer hereby acknowledges that, in connection with
his/her employment with the Company, he has received, and will continue to
receive, various information regarding the Company and its business, operations
and affairs. All such information, to the extent not publicly available other
than as a result of a disclosure by Officer in violation of this Agreement, is
referred to herein as the "Nonpublic Information."

        (b) Officer hereby agrees that, from and after the date hereof
and continuing until three (3) years following a Termination of Employment, he
will keep all Nonpublic Information confidential and will not, without the prior
written consent of the Board or the Chief Executive Officer, disclose any
Nonpublic Information in any manner whatsoever or use any Nonpublic Information
other than in connection with the performance of his/her services to the Company
hereunder; provided, however, that the provisions of this subsection shall not
prevent Officer from (1) disclosing any Nonpublic Information to any other
employee of the Company or to any representative or agent of the Company (such
as an independent accountant, engineer, attorney or financial advisor) when such
disclosure is reasonably necessary or appropriate (in Officer's judgment) in
connection with the performance by Officer of his/her duties and
responsibilities hereunder or (2) disclosing any Nonpublic Information as
required by applicable law, rule, regulation or legal process (but only after
compliance with the provisions of subsection (c) of this Section).


                                                                         /s/ TCH
                                                                        --------
                                                                        initials
                                      -8-





        (c) If Officer is requested pursuant to, or required by,
applicable law, rule, regulation or legal process to disclose any Nonpublic
Information, Officer will notify Parent promptly so that the Company may seek a
protective order or other appropriate remedy or, in the Company's sole
discretion, waive compliance with the terms of this Section, and Officer will
fully cooperate in any attempt by the Company to obtain any such protective
order or other remedy. If no such protective order or other remedy is obtained,
or the Company waives compliance with the terms of this Section, Officer will
furnish or disclose only that portion of the Nonpublic Information as is legally
required and will exercise all reasonable efforts to obtain reliable assurance
that confidential treatment will be accorded the Nonpublic Information that is
so disclosed.

     7.   Miscellaneous Provisions.

        (a) Mitigation. Officer shall not be required to mitigate the
amount of any payment provided for in this Agreement by seeking other employment
or otherwise, and the amount of any payment provided for in this Agreement shall
not be reduced by any compensation earned by Officer as the result of employment
by another employer after the date of any Termination of Employment or
otherwise.

        (b) Interest. Until paid, all past due amounts required to be
paid by the Company to Officer under any provision of this Agreement shall bear
interest at the per annum rate equal to the higher of (1) twelve percent (12%),
or (2) the prime rate announced from time to time by the Company's primary bank
lender, plus three percent (3%).

        (c) Equitable Relief Available. Officer acknowledges that
remedies at law may be inadequate to protect the Company against any actual or
threatened breach of the provisions of Section 6 by Officer. Accordingly,
without prejudice to any other rights or remedies otherwise available to the
Company, Officer agrees that the Company shall have the right to equitable and
injunctive relief to prevent any breach of the provisions of Section 6, as well
as to such damages or other relief as may be available to the Company by reason
of any such breach as does occur.

        (d) At-Will Employment. Officer acknowledges that his/her
employment with the Company is strictly "at-will", and that nothing contained in
this Agreement shall confer upon Officer the right to continue in the employ of
the Company, or interfere in any way with the rights of the Company to terminate
his/her employment at any time for any reason. Officer further acknowledges that
this Agreement is not an "employment agreement" or "employment contract"
(written or otherwise), as either term is used or defined in, or contemplated by
or under, (i) the Company's Long-Term Incentive Plan, (ii) any other plan or
agreement to which the Company is a party, or (iii) applicable statutory, common
or case law.

        (e) Breach Not a Defense. The representations and covenants on
the part of Officer contained in Section 6 shall be construed as ancillary to
and independent of any other provision of this Agreement, and the existence of
any claim or cause of action of Officer against the Company or any officer,
director, stockholder or representative of the Company, whether predicated on
this Agreement or otherwise, shall not constitute a defense to the enforcement
by the Company of the covenants on the part of Officer contained in Section 6.

        (f) Notices. Any notice or other communication called for by
the terms of this Agreement shall be in writing and either delivered personally
or by registered or certified mail (postage prepaid and return receipt
requested) and shall be deemed given when received at the following addresses
(or at such other address for a party as shall be specified by like notice):

            (1) If to Parent or the Company,  1400 Williams  Square West,  5205
         North  O'Connor  Boulevard,  Irving,  Texas 75039,  Attention: General
         Counsel.

            (2) If to Officer, the address of Officer set forth below Officer's
         signature on the signature page of this Agreement.

        (g) Assumption by Successor of Parent. Parent shall require
any successor (whether direct or indirect) to all or substantially all of the

                                                                         /s/ TCH
                                                                        --------
                                                                        initials
                                      -9-






business or assets of Parent (whether by purchase of securities, merger,
consolidation, sale of assets or otherwise), by a written agreement in form and
substance satisfactory to Officer, to expressly assume and agree to perform the
obligations to be performed by Parent or the Company under this Agreement in the
same manner and to the same extent that Parent or the Company would be required
to perform if no such succession had taken place.

        (h)  Assignment.

            (1) Except pursuant to an assumption by a successor
         described in subsection (h) of this Section, the rights and obligations
         of the Company pursuant to this Agreement may not be assigned, in whole
         or in part, by the Company to any other person or entity without the
         express written consent of Officer.

            (2) The rights and obligations of Officer pursuant to
         this Agreement may not be assigned, in whole or in part, by Officer to
         any other person or entity without the express written consent of the
         Board.

        (i) Successors. This Agreement shall be binding on, and shall
inure to the benefit of, the Company, Officer and their respective successors,
permitted assigns, personal and legal representatives, executors,
administrators, heirs, distributees, devisees and legatees, as applicable.

        (j) Amendment and Waivers. Except as hereinafter provided, no
provision of this Agreement may be amended or otherwise modified, and no right
of any party to this Agreement may be waived, unless such amendment,
modification or waiver is agreed to in a written instrument signed by Officer
and Parent (and any dated and signed Schedule A, as described in subsection (p)
of this Section, shall constitute such an instrument). Unless a Change of
Control shall have occurred or be pending or under consideration, Parent may
amend, modify, or waive any provision of, or terminate, this Agreement upon
sixty (60) days notice without the consent of Officer; provided that any such
amendment, modification, waiver or termination shall be made to all severance
agreements of Parent covering all officers of Parent similarly situated to
Officer. No waiver by either party hereto of, or compliance with, any condition
or provision of this Agreement to be performed by the other party hereto shall
be deemed a waiver of similar or dissimilar provisions or conditions at the same
or at any prior or subsequent time.

        (k) Complete Agreement. This Agreement replaces and supersedes
all prior agreements, if any, among the parties with respect to the subject
matter hereof, and the provisions of this Agreement constitute the complete
understanding and agreement among the parties with respect to the subject matter
hereof, and no agreements or representations, oral or otherwise, express or
implied, with respect to the subject matter hereof have been made by either
party which are not set forth expressly in this Agreement.

        (l) Governing Law. THIS AGREEMENT IS BEING MADE AND EXECUTED
IN, AND IS INTENDED TO BE PERFORMED IN, THE STATE OF TEXAS AND SHALL BE
GOVERNED, CONSTRUED, INTERPRETED AND ENFORCED IN ACCORDANCE WITH THE SUBSTANTIVE
LAWS OF THE STATE OF TEXAS.

        (m) Attorney Fees. All legal fees and other costs incurred by
Officer in connection with the resolution of any dispute or controversy under or
in connection with this Agreement shall be reimbursed by the Company to Officer,
if such dispute or controversy is resolved in favor of Officer. The Company
shall be responsible for, and shall pay, all legal fees and other costs incurred
by the Company in connection with the resolution of any dispute or controversy
under or in connection with this Agreement, regardless of whether such dispute
or controversy is resolved in favor of the Company or Officer.

        (n) Counterparts. This Agreement may be executed in several
counterparts, each of which shall be deemed to be an original, but all of which
together will constitute one and the same agreement.

        (o) Construction. The captions of the Sections, subsections
and paragraphs of this Agreement have been inserted as a matter of convenience

                                                                         /s/ TCH
                                                                        --------
                                                                        initials
                                      -10-





of reference only and shall not affect the meaning or construction of any of the
terms or provisions of this Agreement. Unless otherwise specified, references in
this Agreement to a "Section," "subsection," "paragraph," "subparagraph" or
"Schedule" shall be considered to be references to the appropriate Section,
subsection, paragraph, subparagraph or Schedule, respectively, of this
Agreement. Unless the context otherwise requires, all words used in this
Agreement in any gender shall include the masculine, feminine and neuter gender,
all singular words shall include the plural and all plural words shall include
the singular. As used in this Agreement, the term "including" shall mean
"including, but not limited to."

        (p) Schedule A. Schedule A may be replaced at any time and
from time to time to reflect a change in the Base Salary; provided, however,
that no Schedule A attached hereto shall be effective unless it contains a date
and bears a signature of approval on behalf of Officer and a signature of
approval on behalf of Company; and provided further, however, that if at any
time two or more dated and signed copies of Schedule A conflict with each other,
the later dated of such copies shall control.

        (q) Validity and Severability. If any term or provision of
this Agreement is held to be illegal, invalid or unenforceable under the present
or future laws effective during the term of this Agreement, (1) such term or
provision shall be fully severable, (2) this Agreement shall be construed and
enforced as if such term or provision had never comprised a part of this
Agreement and (3) the remaining terms and provisions of this Agreement shall
remain in full force and effect and shall not be affected by the illegal,
invalid or unenforceable term or provision or by its severance from this
Agreement. Furthermore, in lieu of such illegal, invalid or unenforceable term
or provision, there shall be added automatically as a part of this Agreement, a
term or provision as similar to such illegal, invalid or unenforceable term or
provision as may be possible and be legal, valid and enforceable.

        (r) Execution by Company. The execution of this Agreement by
Company shall constitute an acceptance of, and an agreement to be bound by, the
terms and provisions of this Agreement by Company and each of its direct and
indirect wholly-owned subsidiaries, and Company hereby agrees to cause each of
its direct and indirect wholly-owned subsidiaries, now and in the future, to
fully comply with all obligations applicable to the Company pursuant to the
terms of this Agreement.




                            (SIGNATURE PAGE ATTACHED)

                                                                         /s/ TCH
                                                                        --------
                                                                        initials

                                      -11-








     In witness whereof,  the parties have executed this Agreement  effective as
of the date first written above.

                        PIONEER NATURAL RESOURCES COMPANY




                        By:   /s/ Mark. L. Withrow
                            -------------------------------
                        Name:  Mark L. Withrow
                        Title: Executive Vice President




                        OFFICER:



                           /s/ Thomas C. Halbouty
                        -----------------------------------
                        Thomas C. Halbouty

                        Address:


                        -----------------------------------

                        -----------------------------------










                                   Schedule A

                     Attached to Severance Agreement between
                      Pioneer Natural Resources Company and
                               Thomas C. Halbouty





BASE Salary:

         Effective Date                                    Amount

         January 1, 2005                                   $231,000.00





















Dated and Approved as of _______________:

PIONEER NATURAL RESOURCES COMPANY                OFFICER:


By:    /s/ Scott D. Sheffield                      /s/ Thomas C. Halbouty
    ---------------------------------------      ------------------------------
Name:  Scott D. Sheffield                          Thomas C. Halbouty
Title: Chief Executive Officer and Chairman












                                   Schedule B

                            GENERAL RELEASE AGREEMENT


NOTICE:  Various  state and federal  laws and  regulations  prohibit  employment
discrimination  based on age,  race,  color,  religion,  sex,  national  origin,
disability,  citizenship,  and  membership or  application  for  membership in a
uniformed  service.  These  laws  are  enforced  through  the  Equal  Employment
Opportunity  Commission,  U.S.  Department of Labor,  Texas  Commission on Human
Rights,  and other federal and state  agencies.  You are advised to discuss this
release  with your  attorney.  In any event,  you should  thoroughly  review and
understand the effect of this document before signing it. Therefore, please take
this General Release Agreement home and carefully  consider it for at least five
days before signing it. In accordance with the requirements of the Older Workers
Benefit  Protection  Act, you are allowed at least 45 days from the date of your
receipt of this document and the accompanying explanatory letter to consider the
offer  made to you and to  return  an  executed  copy of this  form to the  Vice
President Administration.  Additionally,  after you have executed this form, you
have seven days to reconsider and revoke your agreement.

GENERAL RELEASE:  In consideration of my acceptance of the payments and benefits
offered to me under  Section  5(d)(2)(C) of the  Severance  Agreement,  I hereby
release and discharge Pioneer Natural Resources Company and its subsidiaries and
affiliates (the  "Company"),  and the officers,  directors,  employees,  agents,
successors,  and assigns of such entities  (collectively the "Released Parties")
from any and all claims,  liabilities,  demands,  and causes of action, known or
unknown, fixed or contingent,  which I have or claim against them as a result of
the  termination of my  employment,  including but not limited to claims arising
under  federal,  state,  or local laws  prohibiting  employment  discrimination,
including the Age Discrimination in Employment Act, or claims growing out of any
legal  restrictions,  contractual  or  otherwise,  on  the  Company's  right  to
terminate the employment of its  employees,  and I do hereby agree not to file a
lawsuit to assert such claims. I further acknowledge and agree that by accepting
the  Severance  Agreement  benefits,  I have  given  up my  right  to  file  any
complaint,  lawsuit,  or other legal action against any of the Released  Parties
growing out of,  connected  with, or relating in any way to my employment or the
termination of my employment with the Company.  Further in  consideration of the
payments and benefits offered to me under the Severance Agreement, I acknowledge
and agree that the  Released  Parties  may recover  from me any loss,  including
attorney's  fees and costs of  defending  against any claim  brought by me, that
they may suffer arising out of my breach of this General Release Agreement.

     I understand that this General Release Agreement is final and binding,  and
I  agree  not  to  challenge   its   enforceability.   If  I  do  challenge  the
enforceability of this General Release Agreement, I agree initially to tender to
the Company all money received pursuant to the Severance  Agreement,  and invite
the  Company  to retain  such  money and agree  with me to cancel  this  General
Release  Agreement.  In the event the Company  accepts  this offer,  the Company
shall retain such money and this General Release  Agreement will be void. In the
event the Company  does not accept such offer,  the Company  shall so notify me,
and shall place such money in an  interest-bearing  escrow  account  pending the
resolution of any dispute as to whether this General Release  Agreement shall be
set aside and/or otherwise be rendered unenforceable.

     I acknowledge and agree that the Company has no legal obligation to provide
the payment offered to me under Section  5(d)(2)(C) of the Severance  Agreement,
and my  acceptance  of the  obligations  and  attendant  additional  payment  as
described therein constitutes my agreement to all terms and conditions set forth
in this General Release Agreement,  and are in consideration of the promises and
undertakings  of the Company  pursuant  to the  Severance  Agreement.  I further
acknowledge and agree that for unemployment  compensation purposes, the payments
I receive under the Severance Agreement shall be considered  additional wages in
lieu  of  notice;  and  that,  accordingly,  I  may  be  ineligible  to  receive
unemployment compensation benefits for an equivalent period of time.

     This General Release  Agreement does not have any effect on any claim I may
have against the Released Parties  unrelated to the termination of my employment
or with  respect  to any  rights  or claims  that may arise  after the date this
General Release Agreement is executed.

     I have  carefully  read and fully  understand all of the provisions of this
General Release.  I further  acknowledge that entering into this General Release
Agreement is knowing and voluntary on my part, that I have had a reasonable time
to deliberate regarding its terms, and that I have had the right to consult with
an attorney if I so desired.




Date signed:
             ----------------------        -----------------------------------
                                             Signature of Officer

Date signed:
             ----------------------        -----------------------------------
                                             Signature of Officer