<PAGE>

                                                                    Exhibit 10.1

                           OFFICER SEVERANCE AGREEMENT

     This Officer Severance Agreement ("Agreement") is made and entered into as
of this 16th day of May, 2002, by and between Pure Resources, Inc., a Delaware
corporation (the "Company"), and Jack Harper, an individual currently residing
in Midland, Texas ("Officer").

                                    RECITALS

     The Board of Directors of the Company (the "Board") has determined that it
is in the best interest of the Company to assure that the Company will have the
continued dedication of Officer, notwithstanding the possibility, threat or
occurrence of a Company Change of Control or Unocal Change of Control. The Board
believes it is imperative to diminish the inevitable distraction of Officer by
virtue of the personal uncertainties and risks created by a pending or
threatened Company Change of Control or Unocal Change of Control, to encourage
Officer's full attention and dedication to the Company currently and in the
event of any threatened or pending Company Change of Control or Unocal Change of
Control, and to provide Officer with compensation and benefit arrangements upon
a Company Change of Control or Unocal Change of Control which ensures that such
compensation and benefits are competitive with other corporations.

                                    AGREEMENT

     Now, therefore, in consideration of Officer's continued employment by the
Company or an affiliate of the Company, as well as the promises, covenants and
obligations contained herein, the Company and Officer agree as follows:

     1.   Severance and Other Benefits.

          (a)  Severance Payment. Upon the occurrence of a Termination Event (as
     defined in Section 2):

               (i)   within 30 days following such Termination Event, upon
          Officer's execution of a General Release materially in the form
          attached hereto as Exhibit A (the "General Release"), the Company or
          its successor (or an affiliate of the Company or any successor
          thereto) shall pay Officer an amount equal to Officer's Annual Base
          Salary (as defined in Section 2) multiplied by 1, payable as a lump
          sum cash payment;

               (ii)  if Officer was participating in a life insurance and/or
          disability benefit plan maintained by an Employer as of his or her
          Termination Date, such coverage will be continued at the same cost, if
          any, charged to similarly situated active employees under such plans
          for a period of eighteen months following the Termination Date or, if
          earlier, the date as of which Officer obtains other employment.
          Officer shall immediately notify the Company upon obtaining other
          employment;

               (iii) if Officer was participating in a hospital, surgical,
          medical or dental benefit plan maintained by an Employer as of his or
          her Termination Date and if Officer elects to continue such coverage
          under the Consolidated Omnibus Budget Reconciliation Act of 1985
          ("COBRA"), Officer will be reimbursed the premiums paid to continue
          such coverage under COBRA until the date as of which Officer obtains
          other employment. Officer shall immediately notify the Company upon
          obtaining other employment;

               (iv)  all restricted stock, options or other rights with respect
          to equity interests in the Company and/or its affiliates granted to
          Officer on or before such Termination Date shall immediately vest as
          of the Termination Date; and

<PAGE>

               (v)  the Company or any successor thereto (or an affiliate of the
          Company or any successor thereto) shall take all such action as may be
          necessary or appropriate to amend any option to purchase the Company's
          Common Stock held by Officer to provide that such option will not
          terminate as a result of or in connection with Officer's termination
          of employment with the Company or any successor thereto (or an
          affiliate of the Company or any successor thereto), but may continue
          to be exercised following such termination of employment until the
          date on which such options otherwise would expire.

     2.   Definitions.

          (a)  "Annual Base Salary," as determined on the Termination Date shall
     be equal to the sum of (i) the annual base salary payable to Officer by the
     Company or any successor thereto (or any affiliate of the Company or a
     successor thereto) as of the Termination Date plus (ii) an amount equal to
     the greater of (A) the bonus earned by Officer for the calendar year
     immediately preceding the Termination Date or (B) the average annual bonus
     earned by Officer during the three calendar years immediately preceding the
     Termination Date.

          (b)  "Cause" as used herein with respect to Officer's termination of
     employment shall include any of the following: (A) Officer's conviction of,
     or plea of nolo contendere to, any felony of theft, fraud, embezzlement or
     violent crime causing substantial harm to the Company or its affiliates;
     (B) the willful and continued failure by Officer to substantially perform
     Officer's duties with the Company (or an affiliate of the Company or any
     successor thereto) (other than such failure resulting from Officer's
     incapacity due to physical or mental illness), after a written demand for
     substantial performance is delivered to Officer by the Chief Executive
     Officer of the Company and the Board, which specifically identifies the
     manner in which the Chief Executive Officer and the Board believes that
     Officer has not substantially performed Officer's duties or (C) the willful
     engaging by Officer in misconduct which is materially injurious to the
     interests of the Company or any successor thereto (or any affiliate of the
     Company or a successor thereto). For purposes of this Section, no act, or
     failure to act, on Officer's part shall be considered "willful" unless
     done, or omitted to be done, by Officer not in good faith and without
     reasonable belief that Officer's action or omission was in the best
     interest of the Company. Notwithstanding the foregoing, Officer shall not
     be deemed to have been terminated for cause unless and until there shall
     have been delivered to Officer a copy of a notice of termination from the
     Chief Executive Officer of the Company and the Board, after (x) reasonable
     notice to Officer, (y) an opportunity for Officer, together with Officer's
     counsel (the reasonable fees of which the Company shall pay promptly as
     incurred), to be heard before the Board, finding that, in the good faith
     opinion of the Board, Officer was guilty of conduct set forth above in
     clauses (A), (B) or (C) of the first sentence of this Subsection and
     specifying the particulars thereof in detail, and (z) in the case of
     conduct set forth in clauses (B) and (C), a period of not less than 60 days
     to remedy same.

          (c)  "Common Stock" means the common stock, par value $.01 per share,
     of the Company.

          (d)  A "Company Change of Control" shall be deemed to have occurred
     for purposes of this Agreement if:

               (i) individuals who, as of the date hereof, constitute the Board
          of Directors of the Company (the "Company Incumbent Board") cease for
          any reason to constitute at least 40% of such Board of Directors,
          provided that any person becoming a director subsequent to the date
          hereof whose election, or nomination for election by the stockholders
          of the

                                      -2-

<PAGE>

          Company was approved by a vote of at least a majority of the directors
          then comprising the Company Incumbent Board shall be, for purposes of
          this Agreement, considered as though such person were a member of the
          Company Incumbent Board;

               (ii)  the stockholders of the Company approve a reorganization,
          merger or consolidation, in each case, with respect to which persons
          who were the stockholders of the Company immediately prior to such
          reorganization, merger or consolidation do not, immediately
          thereafter, own voting securities representing more than 40% of the
          Voting Securities of the reorganized, merged or consolidated company;

               (iii) the Company sells, leases or exchanges or agrees to sell,
          lease or exchange all or substantially all of its assets to any other
          person or entity;

               (iv)  the Company adopts a plan of dissolution or liquidation; or

               (v)   any "person," as that term is defined in Section 3(a)(9) of
          the Exchange Act (other than Union Oil or any affiliate thereof and
          other than the Company, any of its subsidiaries, any employee benefit
          plan of the Company or any of its subsidiaries, or any entity
          organized, appointed or established by the Company for or pursuant to
          the terms of such a plan), together with all "affiliates" and
          "associates" (as such terms are defined in Rule 12b-2 under the
          Exchange Act) of such person (as well as any "Person" or "group" as
          those terms are used in Sections 13(d) and 14(d) of the Exchange Act),
          shall become the "beneficial owner" or "beneficial owners" (as defined
          in Rules 13d-3 and 13d-5 under the Exchange Act), directly or
          indirectly, of securities of the Company representing in the aggregate
          40% or more of either the then outstanding shares of Common Stock or
          the Voting Securities of the Company.

          (e)  The "Termination Date" shall mean the date of the termination of
     Officer's employment in connection with a Termination Event.

          (f)  A "Termination Event" shall be deemed to have occurred if:

               (i)  at any time:

                    (A)  the Company or any successor thereto (or an affiliate
               of the Company or any successor thereto) shall terminate
               Officer's employment for any reason other than for Cause; or

                    (B)  Officer shall voluntarily terminate his or her
               employment with the Company or any successor thereto (or an
               affiliate of the Company or any successor thereto) for "Good
               Reason." For purposes of this Agreement, "Good Reason" shall mean
               any of the following (without Officer's express written consent):

                         (1) A material change in the nature or scope of
                    Officer's duties or responsibilities from those engaged in
                    by Officer immediately prior to the date of this Agreement,
                    unless such change is approved by Jack Hightower in his
                    capacity, as of the date of such change, as Chairman of the
                    Board and/or chief executive officer of the Company;

                                      -3-

<PAGE>

                         (2) Any removal of Officer from, or any failure to
                    reelect or to reappoint Officer to, the office of Vice
                    President or an office of greater status within the Company;

                         (3) A reduction in Officer's annual base salary from
                    that provided to him or her immediately prior to the date of
                    this Agreement, unless (x) such reduction is part of an
                    annual base salary reduction that applies to all officers of
                    the Company and (y) such reduction is equal or less than, on
                    a percentage basis, to the percentage reduction in annual
                    base salary of each of the other officers of the Company;

                         (4) A material diminution in Officer's eligibility to
                    participate in or in the benefits provided to Officer under
                    any bonus, stock option or other incentive compensation
                    plans or employee welfare and pension benefit plans
                    (including medical, dental, life insurance, retirement and
                    long-term disability plans) from that provided to him or her
                    immediately prior to the date of this Agreement;

                         (5) Any required relocation of Officer outside of Texas
                    (including any required business travel in excess of the
                    greater of 90 days per year or the level of business travel
                    of Officer for the year prior to the date of this
                    Agreement);

                         (6) Officer and the Company, or any successor thereto,
                    shall fail to reach an agreement on or prior to the date of
                    closing of a transaction that constitutes a Company Change
                    of Control or Unocal Change of Control as to the terms of
                    Officer's employment following such Change of Control, which
                    terms are acceptable to Officer in his or her sole
                    discretion; or

                         (7) Union Oil, together with all "affiliates" and
                    "associates" (as such terms are defined in Rule 12b-2 under
                    the Securities Exchange Act of 1934, as amended (the
                    "Exchange Act")) of such person (as well as any "Person" or
                    "group" as those terms are used in Sections 13(d) and 14(d)
                    of the Exchange Act), shall become the "beneficial owner" or
                    "beneficial owners" (as defined in Rules 13d-3 and 13d-5
                    under the Exchange Act), directly or indirectly, of
                    securities of the Company representing in the aggregate 85%
                    or more of either the then outstanding shares of Common
                    Stock of the Company or the Voting Securities of the
                    Company.

          (g)  "Union Oil" means Union Oil Company of California, a California
     corporation.

          (h)  "Unocal" means Unocal Corporation, a Delaware corporation.

          (i)  A "Unocal Change of Control" shall be deemed to have occurred for
     purposes of this Agreement if:

               (i)  individuals who, as of the date hereof, constitute the Board
          of Directors of Unocal (the "Unocal Incumbent Board") cease for any
          reason to constitute at least 50% of such Board of Directors, provided
          that any person becoming a director subsequent to the date hereof
          whose election, or nomination for election by the stockholders of
          Unocal was

                                      -4-

<PAGE>

          approved by a vote of at least a majority of the directors then
          comprising Unocal Incumbent Board shall be, for purposes of this
          Agreement, considered as though such person were a member of Unocal
          Incumbent Board;

               (ii)  the stockholders of Unocal approve a reorganization, merger
          or consolidation, in each case, with respect to which persons who were
          the stockholders of Unocal immediately prior to such reorganization,
          merger or consolidation do not, immediately thereafter, own voting
          securities representing more than 50% of the Voting Securities of the
          reorganized, merged or consolidated company;

               (iii) Unocal sells, leases or exchanges or agrees to sell, lease
          or exchange all or substantially all of its assets to any other person
          or entity;

               (iv)  Unocal adopts a plan of liquidation or dissolution; or

               (v)   any "person," as that term is defined in Section 3(a)(9) of
          the Exchange Act (other than Unocal, any of its subsidiaries, any
          employee benefit plan of Unocal or any of its subsidiaries, or any
          entity organized, appointed or established by Unocal for or pursuant
          to the terms of such a plan), together with all "affiliates" and
          "associates" (as such terms are defined in Rule 12b-2 under the
          Exchange Act) of such person (as well as any "Person" or "group" as
          those terms are used in Sections 13(d) and 14(d) of the Exchange Act),
          shall become the "beneficial owner" or "beneficial owners" (as defined
          in Rules 13d-3 and 13d-5 under the Exchange Act), directly or
          indirectly, of securities of Unocal representing in the aggregate 50%
          or more of either the then outstanding shares of common stock of
          Unocal or the Voting Securities of Unocal.

          (j)  "Voting Securities" means the combined voting power entitled to
     vote generally in the election of directors.


     3.   Gross-Up Payment. Notwithstanding any provision in this Agreement to
the contrary, if it shall be determined that any payment, distribution or
transfer of property or rights thereto by the Company or any successor thereto
(or an affiliate of the Company or any successor thereto) to or for the benefit
of Officer (whether paid, payable, distributed, distributable, transferred or
transferable pursuant to the terms of this Agreement or otherwise, including but
not limited to the acceleration of vesting of stock options), but determined
without regard to any additional payments required pursuant to this Section 3 (a
"Payment") would be subject to the excise tax imposed by Section 4999 of the
Internal Revenue Code of 1986, as amended (the "Code"), or any interest or
penalties are incurred by Officer with respect to such excise tax (such excise
tax, together with any such interest and penalties, hereinafter collectively
referred to as the "Excise Tax"), then the Officer shall be entitled to receive
an additional payment from the Company or its successor (or an affiliate of the
Company or any successor thereto) (a "Gross-Up Payment") in an amount such that
after payment by Officer of all taxes (including any interest or penalties
imposed with respect to such taxes), including, without limitation, any income
taxes (and any interest and penalties imposed with respect thereto) and Excise
Tax imposed upon the Gross-Up Payment, Officer retains an amount of Gross-Up
Payment equal to the Excise Tax imposed upon the Payments. The intent of this
Section 3 is that Officer will retain, on an after-tax basis, the identical
amount Officer would have received had no Excise Tax been assessed.

     4.   Notices. For purposes of this Agreement, notices and all other
communications provided for herein shall be in writing and shall be deemed to
have been duly given when personally delivered or when

                                      -5-

<PAGE>

mailed by United States registered or certified mail, return receipt requested,
postage prepaid, addressed as follows:

     If to the Company to:      Pure Resources, Inc.
                                Attention: Chief Executive Officer
                                500 West Texas, Suite 200
                                Midland, Texas 79701


     If to Officer to:          Jack Harper
                                1703 Country Club Drive
                                Midland, Texas 79701


or to such other address as either party may furnish to the other in writing in
accordance herewith, except that notices of changes of address shall be
effective only upon receipt.

     5.   Applicable Law. This contract is entered into under, and shall be
governed for all purposes by, the laws of the State of Texas.

     6.   Severability. If a court of competent jurisdiction determines that any
provision of this Agreement is invalid or unenforceable, then the invalidity or
unenforceability of that provision shall not affect the validity or
enforceability of any other provision of this Agreement, and all other
provisions shall remain in full force and effect.

     7.   Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original, but all of which
together will constitute one and the same Agreement.

     8.   Withholding. The Company or any affiliate of the Company employing
Officer shall withhold from any amount payable to Officer pursuant to this
Agreement or from other remuneration payable to Officer, and shall remit to the
appropriate governmental authority if required by applicable law, any income,
employment or other tax such entity is required by applicable law to so withhold
from and remit on behalf of Officer and any other amounts authorized in writing
by Officer.

     9.   No Continued Employment and Effect of Agreement. This Agreement shall
not enlarge or otherwise affect the terms of Officer's employment with the
Company or its affiliate, and the Company or an affiliate employing Officer may
terminate his or her employment as freely and with the same effect as if this
Agreement had not been established. This Agreement is the sole and exclusive
program of severance benefits provided to Officer. It is intended that any and
all other representations, agreements or descriptions of similar benefits be
superseded hereby with respect to Officer; provided, however, that nothing
herein is intended to modify or affect in any way the terms of any written
employment agreement signed between the Company and Officer. No oral or written
representation or promise concerning severance or retention bonus pay which is
inconsistent with the provisions of this Agreement shall have any force or
effect.

     10.  Assignment.

          (a) This Agreement is personal in nature and neither of the parties
     hereto shall, without the consent of the other, assign or transfer this
     Agreement or any rights or obligations hereunder, except as provided in the
     remainder of this Section 10. Without limiting the foregoing, Officer's
     right to receive payments hereunder shall not be assignable or
     transferable, whether by pledge,

                                      -6-

<PAGE>

     creation of a security interest or otherwise, other than a transfer by him
     or her will or by the laws of descent or distribution, and in the event of
     any attempted assignment or transfer contrary to this Section 10 the
     Company shall have no liability to pay any amount so attempted to be
     assigned or transferred. This Agreement shall inure to the benefit of and
     be enforceable by Officer's personal or legal representatives, executors,
     administrators, successors, heirs, distributees, devisees and legatees.

          (b) The Company may: (x) as long as it remains obligated with respect
     to this Agreement, cause its obligations hereunder to be performed by a
     subsidiary or subsidiaries for which Officer performs services, in whole or
     in part; (y) assign this Agreement and its rights hereunder in whole, but
     not in part, to any corporation with or into which it may hereafter merge
     or consolidate or to which it may transfer all or substantially all of its
     assets, if said corporation shall by operation of law or expressly in
     writing assume all liabilities of the Company hereunder as fully as if it
     has been originally named the Company herein; but may not otherwise assign
     this Agreement or its rights hereunder. Subject to the foregoing, this
     Agreement shall inure to the benefit of and be enforceable by the Company's
     successors and assigns.

     11.  Modifications. This Agreement shall not be varied, altered, modified,
canceled, changed or in any way amended except by mutual agreement of the
parties in a written instrument executed by the parties hereto or their legal
representatives.

     13.  Confidentiality and Non-Compete Agreement. Concurrently with the
execution of this Agreement, Officer shall execute the Confidentiality and
Non-Compete Agreement attached hereto as Exhibit B. The effectiveness of this
Agreement is expressly contingent on Officer's execution of the Confidentiality
and Non-Compete Agreement. In the event that Officer shall not execute the
Confidentiality and Non-Compete Agreement, this Agreement shall be null and
void.

     IN WITNESS WHEREOF, the parties have caused this Agreement to be executed
and delivered as of the day and year first above written.

                                        PURE RESOURCES, INC.



                                        By: /s/ Jack Hightower
                                            ------------------------------------
                                            Name:  Jack Hightower
                                            Title: Chairman, President, CEO



                                        OFFICER



                                        /s/ Jack Harper
                                        ----------------------------------------
                                        Jack Harper

                                      -7-

<PAGE>

                                                                     EXHIBIT A

                            GENERAL RELEASE AGREEMENT

NOTICE: If you wish to accept the Severance Payment, you must return an executed
copy of this form to the Company by the close of business on the thirtieth day
after the Termination Event, as defined in the Officer Severance Agreement
between you and Pure Resources, Inc.

     1. GENERAL RELEASE OF CLAIMS UNDER AGE DISCRIMINATION IN EMPLOYMENT ACT. In
consideration of the Severance Payment ("Payment") to be made to me under the
Officer Severance Agreement (the "Agreement"), I hereby release, acquit, and
forever discharge (i) Pure Resources, Inc. and any parent, subsidiary,
affiliated entity, successors or assigns (the "Company"), and (ii) the
stockholders, officers, directors, employees, agents, representatives, and
fiduciaries of the Company (collectively the "Released Parties"), from any and
all claims, liabilities, demands, and causes of action of whatever kind or
character, whether vicarious, derivative, or direct, that I now have or claim
against them arising under the Age Discrimination in Employment Act. This
General Release does not waive rights or claims that may arise after the date
this General Release is executed. Further, in consideration of the Payment to be
made to me under the Agreement, I acknowledge and agree that the Released
Parties may recover from me any loss, including attorneys' fees and costs of
defending against any claim brought by me, they may incur arising out of my
breach of this General Release.

     I understand that I may revoke my acceptance of paragraph 1 of this General
Release by so notifying the Company within seven days of the date I execute this
General Release. I further understand that if I do not timely revoke my
acceptance of paragraph 1, paragraph 1 of this General Release is final and
binding, and I agree not to challenge its enforceability. If I do challenge its
enforceability, I agree initially to tender to the Company the Payment made
under the Agreement, and invite the Company to retain such money and agree with
me to cancel this General Release. In the event the Company accepts my offer,
the Company shall retain such money and paragraph 1 of this General Release will
be void. In the event the Company does not accept my offer, the Company shall
place such money in an escrow account pending the resolution of any dispute as
to whether paragraph 1 of this General Release shall be set aside and/or
otherwise rendered unenforceable.

     2. GENERAL RELEASE OF CLAIMS OTHER THAN UNDER AGE DISCRIMINATION IN
EMPLOYMENT ACT. In consideration of the Payment to be made to me under the
Agreement, I hereby release, acquit, and forever discharge (i) the Company, and
(ii) the Released Parties, from any and all claims, liabilities, demands, and
causes of action of whatever kind or character, whether vicarious, derivative,
or direct, that I now have or claim against them connected in any way to the
Agreement or any claim for benefits under the Agreement, or my employment,
continuation of employment, or, if applicable, termination of employment with
any of the Released Parties, or with any other act, conduct, or omission of any
of the Released Parties, including but not limited to claims arising under any
federal, state, or local laws relating to the employment relationship, other
than claims, liabilities, demands, and causes of action under the Age
Discrimination in Employment Act. This General Release does not waive rights or
claims that may arise after the date this General Release is executed. Further
in consideration of the Payment to be made to me under the 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, they may incur arising out of my breach of this General Release.

     3. NO RELEASE OF COMPANY'S OBLIGATION TO MAKE TAX GROSS-UP PAYMENT UNDER
THE AGREEMENT. Any provision of this General Release to the contrary
notwithstanding, my execution of this General Release does not constitute a
release of the Company's obligation under the Agreement to make additional
payments to me if it shall be determined that I am subject to additional excise
tax under Section 4999 of the Internal Revenue Code of 1986, as amended, as a
result of any payments made or benefits provided to me pursuant to the Agreement
or otherwise in connection with a Company Change of Control or a Unocal Change
of Control (as defined in the Agreement).

     I understand that I may not revoke my acceptance of paragraph 2 of this
General Release and that it is binding upon me whether or not I revoke my
acceptance of paragraph 1 of this General Release.

     I have read and fully understand all of the provisions of this General
Release. I acknowledge that none of the Released Parties has made any promise or
representation to me in consideration for my agreement to execute this General
Release that is not set out in this General Release, and that in executing this
General Release I am not relying on any such

<PAGE>

promise or representation but instead am relying solely on my own judgment. I
further acknowledge that my execution of this General Release is knowing and
voluntary, that I have had a reasonable time to consider its terms, and that I
have been advised to consult with an attorney about this General Release.

Date signed:________________________                 ___________________________
                                                     Signature of Employee


Date signed:_________________________                ___________________________
                                                     Witness

                                      -2-

<PAGE>

                                                                      EXHIBIT B

                    CONFIDENTIALITY AND NON-COMPETE AGREEMENT

     This CONFIDENTIALITY AND NON-COMPETE AGREEMENT (the "Agreement") is made by
and between Pure Resources, Inc., (along with its shareholders, subsidiaries,
successors, and assigns, the "Related Parties"),and Jack Harper ("Employee").

     WHEREAS, Pure Resources, Inc. ("Employer") currently employs and desires to
continue to employ Employee, and Employee desires to continue his employment
with Employer;

     WHEREAS, Employee acknowledges that he is privy to various business
opportunities, economic and trade secrets, and confidential and proprietary
business information of the Related Parties, his knowledge of and access to
which are essential to the performance of his job duties; and

     WHEREAS, subject to Officer's execution of this Agreement, Pure is entering
into an Officer Severance Agreement providing Officer with certain compensation
and benefit arrangements upon certain events.

     NOW, THEREFORE, in consideration of Employee's access to various business
opportunities, economic and trade secrets, and confidential and proprietary
business information of the Related Parties, and the Officer Severance Agreement
between Employee and Pure of even date herewith, the Related Parties and
Employee, intending to be legally bound, agree as follows:

     1. Contingency of Agreement; Effective Date of Agreement. This Agreement
will become effective on May 16th, 2002 (the "Effective Date"). The
effectiveness of this Agreement is expressly contingent on Pure's execution of
the Officer Severance Agreement between Employee and Pure of even date herewith.

     2. Business Opportunities and Intellectual Property.

     (a) Employee shall promptly disclose to Employer, its successors, assigns,
or designees, all "Business Opportunities" and "Intellectual Property" (as
defined below).

     (b) Employee hereby assigns and agrees to assign to Employer, its
successors, assigns, or designees, all of Employee's right, title, and interest
in and to all Business Opportunities and Intellectual Property, and further
acknowledges and agrees that all Business Opportunities and Intellectual
Property constitute the exclusive property of the Related Parties.

     (c) For purposes hereof "Business Opportunities" shall mean all business
ideas, prospects, proposals or other opportunities pertaining to the lease,
acquisition, exploration, production, gathering or marketing of hydrocarbons and
related products and the exploration potential of geographical areas on which
hydrocarbon exploration prospects are located, which are developed by Employee
during any period that Employee is or was employed by Employer or one of the
other Related Parties (the "Employment Term") or originated by any third party
and brought to the attention of Employee, together with information relating
thereto (including, without

                                      -1-

<PAGE>

limitation, geological and seismic data and interpretations thereof, whether in
the form of maps, charts, logs, seismographs, calculations, summaries,
memoranda, opinions or other written or charted means).

     (d) For purposes hereof "Intellectual Property" shall mean all ideas,
inventions, discoveries, processes, designs, methods, substances, articles,
computer programs, and improvements (including, without limitation, enhancements
to, or further interpretation or processing of, information that was in the
possession of Employee prior to the date of this Agreement), whether or not
patentable or copyrightable, which do not fall within the definition of Business
Opportunities, which Employee discovers, conceives, invents, creates, or
develops, alone or with others, during any Employment Term, if such discovery,
conception, invention, creation, or development (i) occurs or occurred in the
course of Employee's employment with Employer or one of the other Related
Parties, (ii) occurs or occurred with the use of any of the Related Parties'
time, materials, or facilities, or (iii) in the opinion of the Board of
Directors of Employer, relates or pertains in any way to Employer's or one of
the other Related Parties' purposes, activities, or affairs.

     3. Non-Compete Obligations During Employment Term. Employee agrees that
during any Employment Term, Employee will not, other than through Employer or
one of the other Related Parties, engage or participate in any manner, whether
directly or indirectly through any family member or as an employee, employer,
consultant, agent, principal, partner, more than one percent shareholder,
officer, director, licensor, lender, lessor or in any other individual or
representative capacity, in any business or activity which is engaged in
leasing, acquiring, exploring, producing, gathering or marketing hydrocarbons
and related products; provided that this Section 3 shall not apply to personal
oil and gas investments owned by Employee, his family members, or his controlled
affiliates as of the date this Agreement is executed and of which Employer is
aware.

     4. Confidentiality Obligations.

     (a) Employee hereby acknowledges that all trade secrets and confidential
and proprietary business information of the Related Parties (collectively
referred to herein as "Confidential Information") constitutes valuable, special
and unique assets of the Related Parties' business, and that access to and
knowledge of such Confidential Information is essential to the performance of
Employee's job duties. Employee agrees that during any Employment Term and
during the two-year period following the date of termination of Employee's
employment with Employer or one of the other Related Parties (the "Termination
Date"), Employee will hold the Confidential Information in strict confidence and
will not publish, disseminate or otherwise disclose, directly or indirectly, to
any person other than the Related Parties and their respective officers,
directors and employees or otherwise in proper performance of Employee's job
duties, any Confidential Information or use any Confidential Information for
Employee's own personal benefit or for the benefit of anyone other than the
Related Parties.

     (b) For purposes of this Section 4, it is agreed that Confidential
Information includes, without limitation, any information heretofore or
hereafter acquired, developed or used by any of the Related Parties relating to
Business Opportunities or Intellectual Property or other geological,
geophysical, economic, financial or management aspects of the business,
operations, properties or prospects of the Related Parties, whether oral or in
written form in a "Related Parties' Business

                                      -2-

<PAGE>

Records" (as defined in Section 6 below), but shall exclude any information
which has become part of the common knowledge or understanding in the oil and
gas industry or otherwise in the public domain (other than from disclosure by
Employee in violation of this Agreement) and provided further that this Section
4 shall not be applicable to the extent Employee is required to testify in a
judicial or regulatory proceeding pursuant to the order of a judge or
administrative law judge after Employee requests that such Confidential
Information be preserved and after prior notice to the Related Parties.

     5. Post Employment Non-Compete And Non-Solicitation Obligations.

     (a) Employee agrees that during the two-year period following the
Termination Date, he will not compete, either directly or indirectly with any of
the Released Parties for any acquisition, prospect, or project that any of the
Related Parties was pursuing prior to the Termination Date.

     (b) Employee agrees that during the two-year period following the
Termination Date, he will not solicit, entice, persuade or induce, directly or
indirectly, any employee (or person who within the preceding ninety (90) days
was an employee) of any of the Related Parties or any other person who is under
contract with or rendering services to any of the Related Parties, to (i)
terminate his or her employment by, or contractual relationship with, such
person, (ii) refrain from extending or renewing the same (upon the same or new
terms), (iii) refrain from rendering services to or for such person, (iv) become
employed by or to enter into contractual relations with any persons other than
such person, or (v) enter into a relationship with a competitor of any of the
Related Parties.

     6. Business Records.

     (a) Employee agrees to promptly deliver to Employer or its designee, upon
termination of his employment by Employer or any of the Related Parties, or at
any other time when any of the Related Parties so requests, all documents
relating to the business of the Related Parties, including, without limitation:
all geological and geophysical reports and related data such as maps, charts,
logs, seismographs, seismic records and other reports and related data,
calculations, summaries, memoranda and opinions relating to the foregoing,
production records, electric logs, core data, pressure data, lease files, well
files and records, land files, abstracts, title opinions, title or curative
matters, contract files, notes, records, drawings, manuals, correspondence,
financial and accounting information, customer lists, statistical data and
compilations, patents, copyrights, trademarks, trade names, inventions,
formulae, methods, processes, agreements, contracts, manuals or any other
documents relating to the business of the Related Parties (collectively, the
"Related Parties' Business Records"), and all copies thereof and therefrom.

     (b) Employee confirms that all of the Related Parties' Business Records
(and all copies thereof and therefrom) which are required to be delivered to
Employer or its designee pursuant to this Section constitute the exclusive
property of Employer and the other Related Parties.

     (c) The obligation of confidentiality set forth in Section 4 shall continue
notwithstanding Employee's delivery of any such documents to Employer and its
designee.

                                      -3-

<PAGE>

     (d) Notwithstanding the foregoing provisions of this Section 6 or any other
provision of this Agreement, Employee shall be entitled to retain any written
materials received by Employee in the capacity as a shareholder of Pure.

     7. Miscellaneous.

     (a) The invalidity or non-enforceability of any provision of this Agreement
in any respect shall not affect the validity or enforceability of this Agreement
in any other respect or of any other provision of this Agreement. In the event
that any provision of this Agreement shall be held invalid or unenforceable by a
court of competent jurisdiction by reason of the geographic or business scope or
the duration thereof, such invalidity or unenforceability shall attach only to
the scope or duration of such provision and shall not affect or render invalid
or unenforceable any other provision of this Agreement, and, to the fullest
extent permitted by law, this Agreement shall be construed as if the geographic
or business scope or the duration of such provision had been more narrowly
drafted so as not to be invalid or unenforceable.

     (b) Employee acknowledges that the Related Parties' remedy at law for any
breach of the provisions of this Agreement is and will be insufficient and
inadequate and that the Related Parties shall be entitled to equitable relief,
including by way of temporary and permanent injunction, in addition to any
remedies the Related Parties may have at law.

     (c) The existence of any claim or cause of action of Employee against any
of the Related Parties or any officer, director, or shareholder of any of the
other Related Parties, whether predicated on Employee's employment or otherwise,
shall not constitute a defense to the enforcement by any of the Related Parties
of the covenants of Employee contained in this Agreement. In addition, the
provisions of this Agreement shall continue to be binding upon Employee in
accordance with their terms, notwithstanding the termination of Employee's
employment with Employer or any of the other Related Parties for any reason.

     (d) The parties to this Agreement agree that the limitations contained in
Section 5 with respect to time, geographical area, and scope of activity are
reasonable. However, if any court shall determine that the time, geographical
area, or scope of activity of any restriction contained in Section 5 is
unenforceable, it is the intention of the parties that such restrictive covenant
set forth herein shall not thereby be terminated but shall be deemed amended to
the extent required to render it valid and enforceable.

     (e) This Agreement may be assigned or transferred by any of the Related
Parties, and shall inure to the benefit of the successors and assigns of any of
the Related Parties.

     (f) This Agreement is not intended to be and does not constitute a contract
or promise of employment or continued employment for any specified term or other
than at will.

     (g) This Agreement may not be altered or amended except by a writing, duly
executed by the party against whom such alteration or amendment is sought to be
enforced.

                                      -4-

<PAGE>

     (h) This Agreement may be executed in counterparts, each of which shall be
an original and all of which together shall constitute one and the same
instrument.

     IN WITNESS WHEREOF, each of the parties hereto has executed this Agreement
in multiple counterparts on the 18th day of July, 2002.

                                    PURE RESOURCES, INC.



                                    By: /s/ Jack Hightower
                                       -----------------------------------------
                                       Name: Jack Hightower
                                       Title: Chairman, President, CEO

                                    EMPLOYEE



                                    /s/ Jack Harper
                                    --------------------------------------------
                                    Jack Harper

                                      -5-