Document:

<PAGE>

                             Pure Resources, Inc.

                                 Exhibit 10.10
                                 -------------

Letter Agreement, dated June 22, 2000, among Titan Exploration, Inc., Chase Bank
of Texas, N.A., and Financial Institutions now and thereafter parties thereto.

<PAGE>

                                                                  EXHIBIT 10.10

                                 June 22, 2000

To the Banks and Financial Institutions
Listed on Schedule 1 Hereto

     Re:  Credit Agreement dated as of June 24, 1999 (as amended to date, the
          "Credit Agreement") among Titan Exploration, Inc., as Borrower
          ("Borrower"), Chase Bank of Texas, National Association, as Agent, and
          the Lenders Signatory Thereto

Ladies and Gentlemen:

     Reference is made to the Credit Agreement for the meanings of terms defined
therein which, unless otherwise defined in this letter, shall have the same
meanings when used herein.

     Last December, Agent and Lenders agreed with Borrower to extend the
Maturity Date under the Credit Agreement to April 1, 2001.  Borrower now
requests Lenders' and Agent's agreement that the term "Maturity Date" in the
Credit Agreement will hereafter refer to July 1, 2001 rather than April 1, 2001.

     Please execute a copy of this letter in the space provided below to
evidence this  requested agreement.  Thank you very much for your cooperation.

                         Yours truly,

                         TITAN EXPLORATION, INC.

                         By:/s/ John L. Benfatti
                            --------------------
                            Name: John L. Benfatti
                            Title: Vice President - Accounting & Controller
<PAGE>

AGREED TO as of the date first written above:

CHASE BANK OF TEXAS, NATIONAL
 ASSOCIATION
Individually, as Issuing Bank, and as
Administrative Agent

By: /s/ Robert C. Mertensotto
   --------------------------
   Name: Robert C. Mertensotto
   Title: Managing Director

FIRST UNION NATIONAL BANK, Individually
and as Documentation Agent

By: /s/ David Humphreys
   --------------------
   Name: David Humphreys
   Title: Vice President

MORGAN GUARANTY TRUST COMPANY OF NEW YORK,
Individually and as Syndication Agent

By: /s/ Colleen Galle
   ------------------
   Name: Colleen Galle
   Title: Vice President

CREDIT LYONNAIS NEW YORK BRANCH

By: /s/ Philippe Soustra
   ---------------------
   Name: Philippe Soustra
   Title: Senior Vice President

BANK ONE, TEXAS, N.A.

By: /s/ Wm. Mark Cranmer
   ---------------------
   Name: Wm. Mark Cranmer
   Title: Vice President
<PAGE>

PARIBAS

By: /s/ Brian Malone
   -----------------
   Name: Brian Malone
   Title: Director

UNION BANK OF CALIFORNIA, N.A.

By: /s/ Gary Shekerjian
   --------------------
   Name: Gary Shekerjian
   Title: Vice President
<PAGE>

                                 SCHEDULE 1

Chase Bank of Texas, N.A.
One Chase Manhattan Plaza, 8th Floor
New York, NY 10081
Attention: Muniram Appanna Agency Services

First Union National Bank
c/o First Union Corporation
1001 Fannin Street, Suite 2255
Houston, Texas 77002-6709
Attention: Ms. Vicki Crispens

Morgan Guaranty Trust
 Company of New York
60 Wall Street
New York, New York 10260
Attention: Phillip McNeal

Credit Lyonnais New York Branch
c/o Credit Lyonnais
Houston Representative Office
1000 Louisiana, Suite 5360
Houston, Texas 77002
Attention: John M. Falbo

Bank One, Texas, N.A.
1717 Main Street
Dallas, Texas 75201
Attention: Mark Cranmer

Paribas
1200 Smith Street, Suite 3100
Houston, Texas 77002
Attention:  Brian Malone
<PAGE>

Union Bank of California, N.A.
4200 Lincoln Plaza
500 North Akard
Dallas, Texas 75201
Attention: Gary Shekerjian

cc:  Chase Securities, Inc.
     707 Travis Street, 5N86
     Houston, Texas 77002
     Attention: Robert C. Mertensotto<PAGE>

                                                                   EXHIBIT 10.16

                             EMPLOYMENT AGREEMENT

     EMPLOYMENT AGREEMENT (this "Agreement"), dated as of May 26, 2000 (the
"Effective Date"), between The Wiser Oil Company, a Delaware corporation (the
"Company"), and George K. Hickox, Jr. (the "Employee").

     WHEREAS, the Company desires to employ the Employee, and the Employee
desires to be employed by the Company, on the terms and conditions hereinafter
set forth;

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
and agreements herein contained, and intending to be legally bound hereby, the
Company and the Employee hereby agree as follows:

      1.  Employment.  The Company agrees to employ the Employee, and the
          ----------
Employee agrees to undertake employment with the Company, for the period set
forth in Paragraph 2, in the positions and with the duties and responsibilities
set forth in Paragraph 3, and upon the other terms and conditions herein
provided.

      2.  Term.  The employment of the Employee by the Company as provided in
          ----
Paragraph 1 shall be for a period commencing on the Effective Date and ending
upon the second anniversary thereof unless further extended or sooner terminated
as herein provided (the "Employment Term").  The Employment Term may be extended
for such additional period as may from time to time be mutually agreed upon in
writing between the parties hereto.

      3.  Position and Duties.
          -------------------

     (a)  During the Employment Term, the Employee shall serve as Chief
Executive Officer and (to the extent elected or appointed as a director of the
Company) Chairman of the Board of the Company, accountable only to the Board of
Directors of the Company (the "Board"). In such capacities, the Employee shall
perform the duties of Chief Executive Officer and Chairman of the Board, as set
forth in the Company's Bylaws, as they may be amended from time to time, and
shall have such other duties, functions, responsibilities, and authority
commensurate with such offices as are from time to time delegated to the
Employee by the Board, provided that such duties, functions, responsibilities,
and authority are reasonable and customary for a person serving as Chief
Executive Officer and Chairman of the Board of an enterprise comparable to the
Company.

     (b)  During the Employment Term, the Employee shall devote a substantial
majority of his time, skill, and attention and his best efforts during normal
business hours to the business and affairs of the Company necessary to discharge
faithfully and efficiently the duties and responsibilities delegated and
assigned to the Employee herein or pursuant hereto, except for usual, ordinary,
and customary periods of vacation and absence due to illness or other
disability.  The Company acknowledges that the Employee has outside business
interests and agrees that the Employee may devote a portion of his time and
attention to such business interests provided such business interests do not
materially interfere with the Employee's performance of his duties
<PAGE>

hereunder; provided, however, in no event shall such other activities by the
Employee be deemed to materially interfere with the Employee's duties hereunder
until the Employee has been notified in writing thereof by the Board and been
given a reasonable period in which to cure such interference.

     (c)  During the Employment Term, the Employee shall serve, if elected or
appointed, as a director of the Company, as a director and officer of any
subsidiary of the Company, and as a member of any committee of the Board or of
the board of directors of any subsidiary of the Company.

     (d)  All services that the Employee may render to the Company or any of its
subsidiaries in any capacity during the Employment Term shall be deemed to be
services required by this Agreement and consideration for the compensation
provided for herein.

      4.  Compensation and Related Matters.
          --------------------------------

      (a) Base Salary. During the Employment Term, the Company shall pay to the
          -----------
Employee for his services hereunder a base salary at the rate of one dollar
($1.00) per year, subject to adjustment as set forth herein, payable prior to
the end of each year during the Employment Term. If during the Employment Term
the Employee's base salary exceeds one dollar per year, such salary shall be
paid in equal installments in accordance with the Company's standard payroll
practices. In addition to base salary, the Employee may be paid bonuses in such
amounts as may be determined by the Board, in its discretion.

     (b)  Base Salary Adjustments.  The base salary payable to the Employee
          -----------------------
hereunder may be adjusted from time to time by the Board, in its discretion.

      (c) Employee Benefits.  During the Employment Term, the Employee shall be
          -----------------
entitled to participate in any and all employee benefit plans, programs, and
arrangements provided by the Company to its executive officers generally,
subject to and on a basis consistent with the terms, conditions, and overall
administration (including eligibility and vesting requirements) of such plans,
programs, and arrangements; provided, however, that, unless otherwise determined
by the Board, the Employee shall not be entitled to receive any stock options,
restricted stock or other similar stock-based awards under the Company's stock
incentive plans.

      (d) Expenses.
          --------

          (i)   During the Employment Term, the Employee shall be entitled to
     receive prompt reimbursement for all reasonable expenses incurred by the
     Employee in performing his duties and responsibilities hereunder, in
     accordance with the policies, practices, and procedures of the Company from
     time to time in effect for its executive officers.

          (ii)  During the Employment Term, the Company shall, at its sole
     expense, provide the Employee with a leased automobile, of a make, model,
     color and year reasonably

                                      -2-
<PAGE>

     acceptable to him, for the Employee's business and private use while in
     Dallas, Texas on Company business. In addition, during the Employment Term,
     the Company shall, upon receipt of itemized vouchers for expenses,
     submitted to the Company on a monthly basis, reimburse the Employee for his
     reasonable and necessary expenses, including maintenance, repairs, gasoline
     and insurance, incurred in the operation of such leased automobile.

          (iii) During the Employment Term, the Company shall reimburse the
     Employee for all actual and reasonable expenses associated with the
     Employee's travel to and from Philadelphia, Pennsylvania for purposes of
     Company business.

          (iv)  During the Employment Term, the Company shall, at its sole
     expense, provide the Employee with suitable alternative housing in Dallas,
     Texas, and shall pay or reimburse the Employee for all utility and hook-up
     costs associated with such alternative housing.

      5.  Termination of Employment by Company.
          ------------------------------------

      (a) Death. The Employee's employment hereunder shall terminate
          -----
automatically upon his death.

      (b) Disability. If the Disability (as defined below) of the Employee
          ----------
occurs during the Employment Term, the Company may notify the Employee of the
Company's intention to terminate the Employee's employment hereunder for
Disability. In such event, the Employee's employment hereunder shall terminate
effective on the 30th day following the date such notice of termination is
received by the Employee, provided that the Employee shall not have returned to
the full-time performance of his duties hereunder and performed the same free of
any Disability through such 30-day period. For purposes of this Agreement, the
"Disability" of the Employee shall be deemed to have occurred if the Employee
shall have been unable to perform substantially his duties hereunder for 90
consecutive days (excluding any leaves of absence approved by the Company) as a
result of his physical or mental incapacity. If so terminated, the Employee
shall be entitled to receive the amount of any insurance benefits and proceeds
payable to the Employee under disability insurance programs and policies, if
any, then maintained by the Company for the Employee's benefit.

      (c) Cause. The Board may terminate the Employee's employment hereunder
          -----
for Cause (as defined below).  For purposes of this Agreement, "Cause" shall
mean any of the following:

          (i)   conduct by the Employee that constitutes willful misconduct,
     fraud, dishonesty, or a criminal act with respect to the Company or its
     subsidiaries;

          (ii)  conviction of the Employee of a felony involving fraud,
     dishonesty, or moral turpitude;

                                      -3-
<PAGE>

          (iii) the willful and continued failure by the Employee to
     substantially perform his duties hereunder; or

          (iv)  the willful and material breach by the Employee of any of the
     provisions of this Agreement.

Notwithstanding the foregoing, the Employee shall not be deemed to have been
terminated for Cause without (i) first, notice to the Employee setting forth the
reasons for the Board's intention to terminate his employment for Cause, (ii)
next, an opportunity for the Employee, together with his counsel, to be heard
before the Board, and (iii) thereafter, delivery to the Employee of a Notice of
Termination (as defined below) from the Company, which notice shall be
accompanied by a resolution duly adopted by the Board finding that, in the good
faith opinion of the Board, Cause has occurred as defined hereunder.

      (d) Notice of Termination.  Any termination of the Employee's employment
          ---------------------
hereunder by the Company shall be communicated by a Notice of Termination to the
Employee.  For purposes of this Agreement, a "Notice of Termination" shall mean
a written notice that (i) indicates the specific termination provision in this
Agreement relied upon, (ii) sets forth in reasonable detail the facts and
circumstances claimed to provide a basis for termination of the Employee's
employment under the provision so indicated, and (iii) specifies the effective
date of termination.

     (e)  Obligations.  If the Employee's employment hereunder is terminated by
          -----------
reason of his death or Disability or for Cause, the Company shall thereafter
have no further obligations to the Employee under this Agreement, except as
provided in Paragraphs 12 and 13.

     6.   Termination of Employment by Employee.  The Employee shall have the
          -------------------------------------
right to terminate his employment hereunder at any time by providing at least 30
days prior written notice of termination to the Company.  Following such notice,
the Employee shall continue to receive his base salary at the then current
annual rate fixed herein or pursuant hereto for the period through the date of
termination, provided his employment is not terminated earlier pursuant to
Paragraph 5 hereof, but the Company shall not be obligated to pay any base
salary or compensation (including severance pay) for any period of time after
such termination.  The foregoing shall not prevent the Company or the Board from
terminating the Employee's employment pursuant to Paragraph 5 hereof earlier
than the date of termination fixed pursuant to this Paragraph 6.

      7.  Compliance With Other Agreements.
          --------------------------------

     (a)  The Company represents and warrants to the Employee that the
execution, delivery, and performance by the Company of this Agreement have been
duly authorized by all necessary corporate action of the Company and do not and
will not conflict with or result in a violation of any provision of, or
constitute a default under, any contract, agreement, instrument, or obligation
to which the Company is a party or by which it is bound.

                                      -4-
<PAGE>

     (b)  The Employee represents and warrants to the Company that the
execution, delivery, and performance by the Employee of this Agreement do not
and will not conflict with or result in a violation of any provision of, or
constitute a default under, any contract, agreement, instrument, or obligation
to which the Employee is a party or by which he is bound.

     8.   Certain Additional Payments by the Company.  Notwithstanding
          ------------------------------------------
anything to the contrary in this Agreement, in the event that any payment or
distribution by the Company to or for the benefit of the Employee, whether paid
or payable or distributed or distributable pursuant to the terms of this
Agreement or otherwise (a "Payment"), would be subject to the excise tax imposed
by Section 4999 of the Internal Revenue Code or any interest or penalties with
respect to such excise tax (such excise tax, together with any such interest or
penalties, are hereinafter collectively referred to as the "Excise Tax"), the
Company shall pay to the Employee an additional payment (a "Gross-up Payment")
in an amount such that after payment by the Employee of all taxes (including any
interest or penalties imposed with respect to such taxes), including any Excise
Tax imposed on any Gross-up Payment, the Employee retains an amount of the
Gross-up Payment equal to the Excise Tax imposed upon the Payments.  The Company
and the Employee shall make an initial determination as to whether a Gross-up
Payment is required and the amount of any such Gross-up Payment.  The Employee
shall notify the Company immediately in writing of any claim by the Internal
Revenue Service which, if successful, would require the Company to make a Gross-
up Payment (or a Gross-up Payment in excess of that, if any, initially
determined by the Company and the Employee) within five days of the receipt of
such claim.  The Company shall notify the Employee in writing at least five days
prior to the due date of any response required with respect to such claim if it
plans to contest the claim.  If the Company decides to contest such claim, the
Employee shall cooperate fully with the Company in such action; provided,
however, the Company shall bear and pay directly or indirectly all costs and
expenses (including additional interest and penalties) incurred in connection
with such action and shall indemnify and hold the Employee 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 the Company's action.
If, as a result of the Company's action with respect to a claim, the Employee
receives a refund of any amount paid by the Company with respect to such claim,
the Employee shall promptly pay such refund to the Company.  If the Company
fails to timely notify the Employee whether it will contest such claim or the
Company determines not to contest such claim, then the Company shall immediately
pay to the Employee the portion of such claim, if any, which it has not
previously paid to the Employee.

     9.   Confidentiality.  During the Employment Term and thereafter without
          ---------------
limitation of time, the Employee shall hold in strict confidence and shall not,
directly or indirectly, disclose or reveal to any person, or use for his own
personal benefit or for the benefit of anyone else, any trade secrets,
confidential dealings, or other confidential or proprietary information of any
kind, nature, or description (whether or not acquired, learned, obtained, or
developed by the Employee alone or in conjunction with others) belonging to or
concerning the Company or any of its subsidiaries (collectively, the
"Information"), except (a) with the prior written consent of the Company duly
authorized by the Board, (b) in the course of the proper performance of the
Employee's duties hereunder, or (c) as required by applicable law or legal
process.  The provisions of this Paragraph 9 shall be inoperative as to such
portions of the Information that (a) are or become generally available

                                      -5-
<PAGE>

to the public other than as a result of a disclosure by the Employee in
violation of this Agreement or (b) become available to the Employee on a non-
confidential basis from a source that is not bound by an obligation of
confidentiality to the Company. The provisions of this Paragraph 9 shall
continue in effect notwithstanding termination of the Employee's employment
hereunder for any reason.

     10.  Arbitration. Any controversy or claim arising out of or relating to
          -----------
this Agreement or the breach thereof, excepting any controversy or claim arising
out of or relating to Paragraph 9 of this Agreement or any breach thereof, shall
be settled by arbitration before an arbitrator in accordance with the Commercial
Arbitration Rules of the American Arbitration Association, and judgment on the
award rendered by the arbitrator may be entered in any court having jurisdiction
thereof. The arbitration shall be conducted in Houston, Texas. In any such
arbitration, the arbitrator shall not have the power to reform or modify this
Agreement in any way and to that extent his powers are so limited. Neither party
shall resort to litigation except to enforce or appeal from such arbitration or
to enforce Paragraph 9 of this Agreement.

     If arbitration is necessary to enforce or interpret any of the Employee's
rights or obligations under this Agreement, and the Employee is the prevailing
party in such arbitration, the Employee shall be entitled to reimbursement by
the Company for any reasonable attorneys' fees, costs, and necessary
disbursements in addition to any other relief to which the Employee may be
entitled.

      11. Withholding Taxes.  The Company shall withhold from any payments to
          -----------------
be made to the Employee hereunder such amounts (including social security
contributions and federal income taxes) as shall be required by federal, state,
and local withholding tax laws.

      12. No Effect on Other Contractual Rights.  The provisions of this
          -------------------------------------
Agreement, and any payment provided for hereunder, shall not reduce any amounts
otherwise payable to the Employee, or in any way diminish the Employee's rights
as an employee of the Company, whether existing now or hereafter, under any
employee benefit plan, program, or arrangement or other contract or agreement of
the Company providing benefits to the Employee.

      13. Survival.  Neither the expiration or the termination of the term of
          --------
the Employee's employment hereunder shall impair the rights or obligations of
either party hereto which shall have accrued hereunder prior to such expiration
or termination.

      14. Notices.  All notices and other communications required or permitted
          -------
to be given hereunder by either party hereto shall be in writing and shall be
given by hand delivery or by first class registered or certified United States
mail, postage prepaid, return receipt requested, to the party for which intended
at the following addresses (or at such other addresses as shall be specified by
the parties by like notice):

                                      -6-
<PAGE>

          If to the Company, at:

               The Wiser Oil Company
               8115 Preston Road, Suite 400
               Dallas, Texas 75225-6311
               Attention:  President

          If to the Employee, at:

               George K. Hickox, Jr.
               1629 Locust Street
               Philadelphia, Pennsylvania 19103

All such notices and other communications shall be effective only upon receipt
by the addressee.

      15. Entire Agreement. This Agreement constitutes the entire agreement
          ----------------
between the parties hereto concerning the subject matter hereof and supersedes
all prior agreements and understandings, both written and oral, between the
parties with respect to such subject matter.

      16. Binding Effect; Assignment. This Agreement shall be binding upon and
          --------------------------
inure to the benefit of the parties hereto and their respective heirs, legal
representatives, successors, and permitted assigns; provided, however, that the
neither the Company nor the Employee shall assign or otherwise transfer this
Agreement or any of the respective rights or obligations hereunder without the
prior written consent of the other party hereto (except that any rights that the
Employee may have hereunder at the time of his death may be transferred by will
or pursuant to the laws of descent and distribution and the Company may assign
this Agreement to any successor to all or substantially all its business and
assets without the consent of the Employee).

      17. Amendment. This Agreement may not be modified or amended in any
          ---------
respect except by an instrument in writing signed by the party against whom such
modification or amendment is sought to be enforced.

      18. Waiver. Any term or condition of this Agreement may be waived at any
          ------
time by the party hereto which is entitled to have the benefit thereof, but such
waiver shall only be effective if evidenced by a writing signed by such party,
and a waiver on one occasion shall not be deemed to be a waiver of the same or
any other type of breach on a future occasion.  No failure or delay by a party
hereto in exercising any right or power hereunder shall operate as a waiver
thereof nor shall any single or partial exercise thereof preclude any other or
further exercise thereof or the exercise of any other right or power.

      19. Authority. No person, other than pursuant to a resolution of the
          ---------
Board, shall have authority on behalf of the Company to agree to modify, amend,
or waive any provision of this Agreement or anything in reference thereto.

                                      -7-
<PAGE>

     20.  Severability. If any provision of this Agreement is held to be
          ------------
unenforceable, (a) this Agreement shall be considered divisible, (b) such
provision shall be deemed inoperative to the extent it is deemed unenforceable,
and (c) in all other respects this Agreement shall remain in full force and
effect; provided, however, that if any such provision may be made enforceable by
limitation thereof, then such provision shall be deemed to be so limited and
shall be enforceable to the maximum extent permitted by applicable law.

     21.  Governing Law. This Agreement shall be governed by and construed and
          -------------
enforced in accordance with the laws of the State of Delaware, without regard to
the principles of conflicts of laws thereof.

     22.  Injunctive Relief. In recognition of the fact that a breach by the
          -----------------
Employee of any of the provisions of Paragraph 9 will cause irreparable damage
to the Company for which monetary damages alone will not constitute an adequate
remedy, the Company shall be entitled as a matter of right to obtain a
restraining order, an injunction, an order of specific performance, or other
equitable or extraordinary relief from any court of competent jurisdiction
restraining any further violation of such provisions by the Employee or
requiring him to perform his obligations hereunder.  Such right to equitable or
extraordinary relief shall not be exclusive but shall be in addition to all
other rights and remedies to which the Company may be entitled at law or in
equity, including without limitation the right to recover monetary damages for
the breach by the Employee of any of the provisions of this Agreement.

     23.  Counterparts. This Agreement may be executed by the parties hereto in
          ------------
any number of counterparts, each of which shall be deemed an original, but all
of which shall constitute one and the same agreement.

                                      -8-
<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Agreement to be executed on
its behalf by its duly authorized officer, and the Employee has executed this
Agreement, as of the date first set forth above.

                                  "COMPANY"

                                  THE WISER OIL COMPANY

                                  By: /s/ Andrew J. Shoup, Jr.
                                     -----------------------------------
                                     Name: Andrew J. Shoup, Jr.
                                          ------------------------------
                                     Title: President
                                           -----------------------------

                                  "EMPLOYEE"

                                  /s/ George K. Hickox, Jr.
                                  --------------------------------------
                                  George K. Hickox, Jr.

                                      -9-

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