<PAGE>
 
                                                                   EXHIBIT 10.11



                     STOCK REPURCHASE AND PROMISSORY NOTE
                    REPAYMENT AGREEMENT AND GENERAL RELEASE


     This STOCK REPURCHASE AND PROMISSORY NOTE REPAYMENT AGREEMENT AND GENERAL
RELEASE (this "Agreement"), dated as of January 31, 1997, among Drilex
International Inc., a Delaware corporation (formerly Drilex Holdings Corp.) (the
"Company"), Cobb Directional Drilling Company, L.L.C., a Delaware limited
liability company ("Cobb LLC"), Drilex Systems, Inc., a Texas corporation ("DSI"
and, together with the Company and Cobb LLC, the "Drilex Parties"), Posi-Trak
Mud Motors, Inc., a Louisiana corporation ("Posi-Trak"), Cobb Directional
Drilling Company, Inc., a Louisiana corporation ("Cobb Inc."), and Archie A.
Cobb, III ("Cobb" and, together with Posi-Trak and Cobb Inc., the "Cobb
Parties"),

                              W I T N E S S E T H:

     WHEREAS, pursuant to an Asset Purchase Agreement dated as of 
September 30, 1994 (the "Asset Purchase Agreement") among the Company, Cobb LLC,
Cobb Inc., Posi-Trak and Cobb, Posi-Trak acquired 133,333 shares of Common
Stock, par value $.01 per share, of the Company (the "Initial Shares");

     WHEREAS, pursuant to the Asset Purchase Agreement, the Company issued a
promissory note payable to Posi-Trak in the aggregate principal amount of
$1,333,340.00 (the "Original Note");

     WHEREAS, pursuant to the Asset Purchase Agreement, Cobb LLC and Cobb
entered into an Employment Agreement dated as of September 30, 1994 (the
"Employment Agreement");

     WHEREAS, pursuant to the Asset Purchase Agreement, the Company and Posi-
Trak entered into a Stockholders' Agreement dated as of September 30, 1994 (the
"Stockholders' Agreement");

     WHEREAS, pursuant to a Stock Repurchase Agreement dated as of 
March 23, 1995 (the "Stock Repurchase Agreement"), among the Company, Posi-Trak
and Cobb, the Company repurchased 80,000 of the Initial Shares;

     WHEREAS, pursuant to a Stock Purchase Agreement dated as of March 23, 1995
(the "Stock Purchase Agreement"), by and among the Company, DSI, Cobb Inc. and
Cobb, the Company issued a promissory note payable to Cobb Inc. in the original
aggregate principal amount of $1,000,000 (the "Amortizing Note");

     WHEREAS, as a result of the stock split effected May 16, 1996, the 53,333
Initial Shares not repurchased from Posi-Trak pursuant to the Stock Repurchase
Agreement now constitute 96,523 shares of Common Stock; and

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<PAGE>
 
     WHEREAS, the parties to this Agreement mutually desire that, among other
things, (i) the Company prepay the outstanding principal amount of each of the
Original Note and the Amortizing Note, together with interest accrued and unpaid
thereon through the Closing (as hereinafter defined), respectively, (ii) the
Company purchase the 96,523 shares of Common Stock held by Posi-Trak (the
"Shares"), (iii) the employment of Cobb with Cobb LLC, the Company or any other
affiliate of the Company, be terminated and (iv) the Non-Competition Period (as
defined in the Employment Agreement) be reduced to two years;

     NOW, THEREFORE, in consideration of the premises and of the respective
representations, warranties, covenants, agreements and conditions contained
herein, the parties hereto hereby agree as follows:


                                   ARTICLE I

                        PURCHASE AND SALE OF THE SHARES

     1.1  The Sale.  Upon the terms and subject to the conditions of this
Agreement, at the Closing, Posi-Trak will sell, assign, transfer and deliver the
Shares to the Company, and the Company will purchase and acquire the Shares from
Posi-Trak.

     1.2  Purchase Price.  The aggregate purchase price for the Shares (the
"Purchase Price") is $1,303,061.00 to be paid to Posi-Trak against delivery of
the Shares, which payment shall be offset by the amount of $313,665.00, in
consideration of the amendment of the Employment Agreement provide for in
Section 3.2 hereof; all in accordance with Article VI hereof.

                                  ARTICLE II

                            PREPAYMENT OF THE NOTES

     2.1  Prepayment of the Original Note.  Upon the terms and subject to the
conditions of this Agreement, at the Closing, the Company will pay $1,341,267.00
to Posi-Trak in accordance with Article VI hereof, in full satisfaction of the
outstanding principal of the Original Note and interest accrued but unpaid
thereon, against delivery of the Original Note, and Cobb will accept such
prepayment.

     2.2  Prepayment of the Amortizing Note.  Upon the terms and subject to the
conditions of this Agreement, at the Closing, the Company will pay $419,337.00
to Cobb Inc. in accordance with Article VI hereof, in full satisfaction of the
outstanding principal of the Amortizing Note and interest accrued but unpaid
thereon, against delivery of the Amortizing Note, and Cobb will accept such
prepayment.

     2.3  Termination of Security Agreements.  Upon the terms and subject to the
conditions of this Agreement, at the Closing, the Security Agreement dated as of
September 30, 1994, made by the Company to Posi-Trak (the "First Security
Agreement") will terminate.  Upon

                                      -2-
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the terms and subject to the conditions of this Agreement, at the Closing, Posi-
Trak will release and deliver the certificates representing the Pledged Shares
and any other Pledged Collateral (each as defined in the First Security
Agreement).  Upon the terms and subject to the conditions of this Agreement, at
the Closing, the Security Agreement dated as of March 23, 1995, made by the
Company to Cobb Inc. (the "Second Security Agreement") will terminate.  Upon the
terms and subject to the conditions of this Agreement, at the Closing, Posi-Trak
will release and deliver the certificates representing the Pledged Shares and
any other Pledged Collateral (each as defined in the Second Security Agreement).


                                  ARTICLE III

                              EMPLOYMENT MATTERS

     3.1  Termination of Employment.  Upon the terms and subject to the
conditions of this Agreement, effective January 31, 1997, Cobb's employment with
Cobb LLC, the Company or any other affiliate of the Company, is deemed to be
terminated pursuant to Section 4(d) (Termination by Employee) of the Employment
Agreement.

     3.2  Amendment of Employment Agreement.  Upon the terms and subject to the
conditions of this Agreement, the Non-Competition Period as referenced in
Section 7 of the Employment Agreement shall be reduced from five years to two
years, with the date of termination of Cobb's employment for such purpose to be
deemed to be January 31, 1997.

     3.3  Waiver and Release.  In consideration of Company's payment pursuant
hereto the receipt and sufficiency of which are hereby acknowledged, Cobb hereby
releases and forever discharges the Drilex Parties and the officers, directors,
agents, servants, and employees of the foregoing, their successors, assigns, and
insurers, and their parents, subsidiaries, and affiliates, and any and all other
persons, firms, organizations, and corporations from any and all damage, losses,
causes of action, expenses, demands, liabilities, and claims on behalf of
himself, his heirs, executors, administrators, and assigns with respect to his
employment relationship (including the Employment Agreement) other than benefits
or matters to which Cobb is entitled under this Agreement.  Further, Cobb and
the Drilex Parties agree to terminate his employment relationship on the basis
and terms described herein, and Cobb hereby accepts payment pursuant hereto in
full settlement of all such damages, losses, causes of action, expenses,
demands, liabilities, and claims he now has or may have with respect to such
employment relationship.

     Such release includes, but is not limited to, claims arising under the Age
Discrimination in Employment Act, the Older Workers' Benefit Protection Act,
Title VII of the Civil Rights Act of 1964, the Americans with Disabilities Act,
the Family and Medical Leave Act, the Texas Labor Code, any claims for breach of
contract, tort or personal injury of any sort, and any claim under any other
state or federal statute or regulation.  Further, by accepting the payment
pursuant hereto, Cobb agrees not to sue the Drilex Parties or the related
persons and entities described above with respect to the matters released above
other than to enforce rights or benefits

                                      -3-
<PAGE>
 
provided herein.  Cobb affirms and agrees that his employment relationship will
end as set forth above and waives all rights in connection with such
relationship.

     Provided, however, that the parties to this Agreement agree that Cobb has
the right to revoke or cancel this Agreement, by delivery of written notice to
the Company within seven days after its execution by him (the "Recession
Period").  In the event that this Agreement is cancelled or revoked, this
Agreement shall be terminated and the Company shall have no obligation to
furnish the payments described herein.  Cobb acknowledges and represents that he
has been advised in writing to consult with an attorney prior to signing this
Agreement and has had an adequate opportunity to seek advice of his own
choosing.  Cobb acknowledges and represents that he understands that this
Agreement will have the effect of knowingly and voluntarily waiving any action
he might pursue, including breach of contract, personal injury, retaliation,
discrimination on the basis of race, age, sex, national origin, or disability
and any other claims arising prior to the date of this Agreement.

                                  ARTICLE IV

                           SALE OF ANCILLARY ASSETS

     4.1  The Sale.  Upon the terms and subject to the conditions of this
Agreement, the Company, Cobb LLC or DSI, as the case may be, will sell,
transfer, convey, assign and deliver to Cobb and Cobb will acquire and purchase,
the assets  listed on Schedule 4.1 hereto (the "Ancillary Assets"), effective
upon the respective dates set forth in such schedule or on such earlier date
(but in no event prior to the Closing Date) as Cobb shall specify in writing, in
a notice that is received by the Company at least three business days in advance
of such proposed date (the "Asset Transfer Date").

     4.2  Purchase Price.  Upon the terms and subject to the conditions of this
Agreement, at the Closing, Cobb shall pay $23,695.00, in the aggregate, for the
Ancillary Assets, in accordance with Article VI hereof.  On the Asset Transfer
Date, the Company, Cobb LLC or DSI, as the case may be, shall deliver
certificates of title to Cobb in respect of the Ancillary Assets which are motor
vehicles.

     4.3  Taxes Upon Conveyance and Transfer. The Company shall pay all sales,
use, transfer or similar taxes payable in connection with the sale, transfer and
assignment of the Ancillary Assets to Cobb.

                                   ARTICLE V

                                    CLOSING

     The closing of the transactions contemplated hereby (the "Closing") will be
held at the offices of Baker & Botts, L.L.P., Houston, Texas, on or before
February 10, 1997 (but in no event prior to the expiration of the Recession
Period as defined in Section 3.3 hereof), at 11:00 a.m., Houston time.  The date
of the Closing is referred to herein as the "Closing Date."  Delivery to the

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offices of Baker & Botts, L.L.P. of documents and other materials in connection
with the Closing may be made in person or otherwise, in any event prior to 11:00
a.m. on the Closing Date.  No party to this Agreement need be present at the
Closing.

                                  ARTICLE VI

                                    PAYMENT

     At the Closing, and upon the terms and subject to the conditions of this
Agreement, the Company shall pay to Cobb Inc. and Posi-Trak a total of
$2,726,305.00, equal to the sum of: the net of the amounts referenced in Section
1.2, plus the amount referenced in Section 2.1, plus the amount referenced in
Section 2.2, less the amount referenced in Section 4.2, by wire transfer of
immediately available funds to an account designated by Cobb.  Cobb shall make
no payment pursuant to either of Sections 1.2 or 4.2, respectively, except by
offset to the amounts payable by the Company as provided in Section 1.2 and the
foregoing sentence, respectively.

                                  ARTICLE VII

                REPRESENTATIONS AND WARRANTIES OF COBB PARTIES

     The Cobb Parties, jointly and severally, represent and warrant to the
Company:

     7.1  Corporate Status and Good Standing.  Each of Cobb Inc. and Posi-Trak
is a corporation duly organized, validly existing and in good standing under the
laws of Louisiana, with full corporate power and authority under its certificate
or articles of incorporation and by-laws to own and lease its properties and to
conduct business as the same exists, respectively.  Each of Cobb Inc. and Posi-
Trak is duly qualified to do business as a foreign corporation in all states in
which the nature of its business requires such qualification and the failure to
do so would have an adverse effect on either of Cobb Inc. and Posi-Trak,
respectively.

     7.2  Authorization.  Each of Cobb Inc. and Posi-Trak has full corporate
power and authority under its certificate or articles of incorporation and by-
laws, and its board of directors and stockholders have taken all necessary
action to authorize each such corporation, to execute and deliver this
Agreement, to consummate the transactions contemplated herein and to take all
actions required to be taken by it pursuant to the provisions hereof, and this
Agreement constitutes the valid and binding obligation of each of Cobb Inc. and
Posi-Trak, respectively, enforceable in accordance with its terms.

     7.3  Non-Contravention.  Neither the execution and delivery of this
Agreement or any documents executed in connection herewith, nor the consummation
of the transactions contemplated herein or therein, does or will violate,
conflict with, result in breach of or require notice or consent under any law,
the charter or bylaws of either of Cobb Inc. or Posi-Trak or any provision of
any agreement or instrument to which any Cobb Party is a party.  Cobb owns 100%
of the outstanding securities of each of Cobb Inc. and Posi-Trak.

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<PAGE>
 
     7.4  Validity.  There are no pending or threatened judicial or
administration actions, proceedings or investigations which question the
validity of this Agreement or any action taken or contemplated by any Cobb Party
in connection with this Agreement.

     7.5  Broker Involvement.  No Cobb Party has hired, retained or dealt with
any broker or finder in connection with the transactions contemplated by this
Agreement.

     7.6  Title to Shares.  Posi-Trak owns beneficially and of record the
Shares, free and clear of all liens, charges, encumbrances, rights of others,
mortgages, pledges or security interests, and the Shares are not subject to any
agreements or understandings with respect to the voting or transfer thereof
other than as set forth in the Stockholders' Agreement.  Except as set forth in
the Stockholders' Agreement, there are no outstanding subscriptions, options,
convertible securities, warrants or calls of any kind issued or granted by, or
binding upon, Posi-Trak to purchase or otherwise acquire or to sell or otherwise
dispose of any security of or equity interest in the Company.  Posi-Trak has
full legal right to sell, assign and transfer the Shares to the Company and
will, upon delivery of a certificate or certificates representing such Shares to
the Company pursuant to the terms hereof, transfer to the Company title to such
Shares, free and clear of any liens, charges, encumbrances, rights of others,
mortgages, pledges or security interests.

     7.7  Title to Original Note.  Posi-Trak owns beneficially and of record the
Original Note, free and clear of all liens, charges, encumbrances, rights of
others, mortgages, pledges or security interests.  Posi-Trak has full legal
right to sell, assign and transfer the Original Note to the Company and will,
upon delivery of the Original Note to the Company pursuant to the terms hereof,
transfer to the Company title to the Original Note, free and clear of any liens,
charges, encumbrances, rights of others, mortgages, pledges or security
interests.

     7.8  Title to Amortizing Note.  Cobb Inc. owns beneficially and of record
the Amortizing Note, free and clear of all liens, charges, encumbrances, rights
of others, mortgages, pledges or security interests.  There are no outstanding
subscriptions, options, convertible securities, warrants or calls of any kind
issued or granted by, or binding upon, Cobb Inc. to purchase or otherwise
acquire or to sell or otherwise dispose of any security of or equity interest in
the Company. Cobb Inc. has full legal right to sell, assign and transfer the
Amortizing Note to the Company and will, upon delivery of the Amortizing Note to
the Company pursuant to the terms hereof, transfer to the Company title to the
Amortizing Note, free and clear of any liens, charges, encumbrances, rights of
others, mortgages, pledges or security interests.

                                 ARTICLE VIII

                 REPRESENTATIONS AND WARRANTIES OF THE COMPANY

     The Company represents and warrants to each Cobb Party the following:

     8.1  Corporate Status and Good Standing.  The Company is a corporation duly
organized, validly existing and in good standing under the laws of Delaware,
with full corporate

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power and authority under its certificate or articles of incorporation and by-
laws to conduct its business as the same exists.

     8.2  Authorization.  The Company has full corporate power and authority
under its certificate or articles of incorporation and by-laws, and its board of
directors has taken all necessary corporate action to authorize it, to execute
and deliver this Agreement, to consummate the transactions contemplated herein
and to take all actions required to be taken by it pursuant to the provisions
hereof or thereof, and this Agreement constitutes the valid and binding
obligation of the Buyer enforceable in accordance with its terms.

     8.3  Non-Contravention.  Neither the execution and delivery of this
Agreement, nor the consummation of the transactions contemplated herein, does or
will violate, conflict with, result in breach of or require notice or consent
under any law, the charter or bylaws of the Company or any provision of any
agreement or instrument to which the Company is a party.

     8.4  Validity.  There are no pending or threatened judicial or
administrative actions, proceedings or investigations which question the
validity of this Agreement or any action taken or contemplated by Company in
connection with this Agreement.

     8.5  Broker Involvement.  The Company has not hired, retained or dealt with
any broker or finder in connection with the transactions contemplated by this
Agreement.

     8.6  Title to Ancillary Assets.  The Company, DSI or Cobb LLC, as the case
may be, is the true and lawful owner of the Ancillary Assets, free and clear of
any and all liens, encumbrances, mortgages, options, security interests,
restrictions, liabilities, pledges and assignments of any kind other than
Permitted Encumbrances (as defined herein), and the same has the full right to
sell and transfer to Cobb good and marketable title to the Ancillary Assets,
free and clear of any and all liens and encumbrances of any nature or
description other than Permitted Encumbrances.  The delivery to Cobb of the
instruments of transfer of ownership contemplated by this Agreement will vest
good and marketable title to Ancillary Assets in Cobb, free and clear of all
liens and encumbrances of any nature or description other than Permitted
Encumbrances.  For purposes hereof, "Permitted Encumbrances" means liens for
taxes not yet due and payable, materialmen's, mechanics', workmen's, repairmen's
or other like liens arising against any of the Drilex Parties or the Ancillary
Assets in the ordinary course of business, in each case with respect to
obligations or claims which are either not delinquent or are being contested in
good faith and by appropriate proceedings conducted with due diligence.

                                  ARTICLE IX

                      ADDITIONAL AGREEMENTS AND COVENANTS

     9.1  Prior Agreements Unaffected.  The parties agree that, except as
specifically provided herein, the Asset Purchase Agreement, the Stock Purchase
Agreement, the Repurchase Agreement, and the Employment Agreement, and all
documents executed in connection with each of the foregoing or that otherwise
relate thereto shall not be affected, modified or changed by this

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<PAGE>
 
Agreement or the transactions contemplated hereby, and that, except as set forth
herein, the rights of the parties thereunder shall be unaffected hereby.

     9.2  Further Assurances.  Each Cobb Party shall execute, acknowledge and
deliver or cause to be executed, acknowledged and delivered to the Company or
its affiliates such assignments or other instruments of transfer, assignment,
release of liens and security interests, and conveyance, in form and substance
satisfactory to counsel of the Company, as shall be necessary to vest in the
Company all of the right, title and interest in and to each of the Shares, the
Original Note and the Amortizing Note free and clear of all liens, charges,
encumbrances, rights of others, mortgages, pledges or security interests.

     9.3  Agreements with Respect to Stockholders' Agreement.  The Company and
Posi-Trak agree that (i) the sale of the Shares is in compliance with Section
7(i) and 2(vi) of the Stockholders' Agreement and (ii) the Stockholders'
Agreement shall not be affected, modified or changed by this Agreement or the
transactions contemplated hereby, and that the rights of the parties thereunder
shall be unaffected hereby.

     9.4  COBRA Matters.  The Drilex Parties shall make available to Cobb, at
Cobb's expense, health insurance continuation coverage to the extent required
under Part 6 Title I of the Employee Retirement Income Security Act of 1974, as
amended (COBRA).

     9.5  Records.  The Drilex Parties shall make available to Cobb, during
normal business hours and at Cobb's expense, the records of Posi-Trak and Cobb
Inc. acquired by the Drilex Parties in connection with the Asset Purchase
Agreement, for a period of three (3) years following the Closing Date.

     9.6  Insurance on Ancillary Assets.  Between the date of this Agreement and
the Asset Transfer Date with respect to each Ancillary Asset which is a motor
vehicle, the Company shall use reasonable best efforts to maintain the
automobile insurance in place on the date of this Agreement with respect to each
such vehicle.

                                   ARTICLE X

                             CONDITIONS TO CLOSING

     10.1  Conditions Precedent to Obligations of the Drilex Parties.  The
obligation of the Drilex Parties to consummate the transactions contemplated by
this Agreement is subject to the fulfillment, prior to or at the Closing, of
each of the following conditions (any or all of which may be waived by the
Drilex Parties):

     (a) all representations and warranties of the Cobb Parties contained in
this Agreement shall be true and correct in all respects at and as of the time
of the Closing with the same effect as though made again at, and as of, that
time;

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     (b) the Cobb Parties shall have performed and complied in all material
respects with all obligations and covenants required by this Agreement to be
performed or complied with by the Cobb Parties prior to or at the Closing;

     (c) no provision of any applicable law or regulation shall prohibit, and
there shall not be in effect any injunction or restraining order issued by a
court of competent jurisdiction in any action or proceeding against, the
consummation of this Agreement; and

     (d)  The Company shall have received any and all necessary consents,
including pursuant to its Restated and Amended Credit Agreement.

     10.2  Conditions Precedent to Obligations of the Cobb Parties.  The
obligation of the Cobb Parties to consummate the sale under this Agreement is
subject to the fulfillment, prior to or at the Closing, of each of the following
conditions (any or all of which may be waived by the Cobb Parties):

     (a) all representations and warranties of the Company contained in this
Agreement shall be true and correct in all respects at and as of the time of the
Closing with the same effect as though made again at, and as of, that time;

     (b) the Company shall have performed and complied in all material respects
with all obligations and covenants required by this Agreement to be performed or
complied with by the Company prior to or at the Closing;

     (c)  no provision of any applicable law or regulation shall prohibit, and
there shall not be in effect any injunction or restraining order issued by a
court of competent jurisdiction in any action or proceeding against, the
consummation of this Agreement.

                                  ARTICLE XI

                            NOTICES; MISCELLANEOUS

     11.1  Expenses.  The Drilex Parties and the Cobb Parties shall pay their
own respective expenses, including the fees and disbursements of their
respective counsel in connection with the negotiation, preparation and execution
of this Agreement and the consummation of the transactions contemplated herein.

     11.2  Entire Agreement.  This Agreement, including all exhibits hereto,
constitutes the entire agreement of the parties with respect to the subject
matter hereof, and may not be modified, amended or terminated except by a
written instrument specifically referring to this Agreement signed by all the
parties hereto.

     11.3  Waivers and Consents.  All waivers and consents given hereunder shall
be in writing.  No waiver by any party hereto of any breach or anticipated
breach of any provision hereof

                                      -9-
<PAGE>
 
by any other party shall be deemed a waiver of any other contemporaneous,
preceding or succeeding breach or anticipated breach, whether or not similar.

     11.4  Notices.  All notices and other communications hereunder shall be in
writing and shall be deemed to have been received only if and when (i)
personally delivered or (ii) on the third day after mailing, by United States
mail, first class, postage prepaid, by certified mail return receipt requested,
addressed in each case as follows (or to such other address as may be specified
by like notice):

          (a)  If to any Drilex Party, to:

               Drilex International Inc.
               15151 Sommermeyer
               Houston, Texas  77041
               Attention:  John Forrest

          (b)  If to any Cobb Party, to:

               Archie Cobb III        
               P. O. Box 59           
               Milton, Louisiana 70558 
    

     11.5  Successors and Assigns.  This Agreement shall be binding upon and
shall inure to the benefit of the parties hereto and their respective
successors, legal representatives and assigns.  No third party shall have any
rights hereunder.  No assignment shall release the assigning party.

     11.6  Performance.  Cobb agrees to cause each of Cobb Inc. and Posi-Trak to
perform all their obligations and agreements under this Agreement, respectively,
and hereby guarantees the payment and performance by each of Cobb Inc. and Posi-
Trak, respectively of all such obligations and agreements.

     11.7  Choice of Law; Section Headings.  This Agreement shall be governed by
the internal laws of the State of Texas (without regard to the choice of law
provisions thereof).  The section headings contained in this Agreement are for
reference purposes only and shall not affect the meaning or interpretation of
this Agreement.

     11.8  Counterparts.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original and all of which
together shall be deemed to be one and the same instrument.

                                      -10-
<PAGE>
 
     IN WITNESS WHEREOF, the parties hereto have executed this Agreement on the
date first above written.

                                       DRILEX INTERNATIONAL INC.

                                            /s/ G. BRUCE BROUSSARD
                                           __________________________________ 
                                       By: G. Bruce Broussard
                                           Vice President--Finance 
                                           and Administration


                                       COBB DIRECTIONAL DRILLING COMPANY, L.L.C.

                                       By: DRILEX INTERNATIONAL INC.


                                                 /s/ G. BRUCE BROUSSARD
                                            By: _____________________________
                                                G. Bruce Broussard
                                                Vice President--Finance 
                                                and Administration


                                       DRILEX SYSTEMS, INC.


                                             /s/ G. BRUCE BROUSSARD
                                       By: __________________________________
                                           Name: 
                                           Title:


                                       POSI-TRAK MUD MOTORS, INC.


                                            /s/ ARCHIE A. COBB, III
                                       By: __________________________________
                                           Archie A. Cobb, III

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<PAGE>
 
                                       COBB DIRECTIONAL DRILLING COMPANY, INC.


                                            /s/ ARCHIE A. COBB, III
                                       By: __________________________________
                                           Archie A. Cobb, III

                                            /s/ ARCHIE A. COBB, III
                                           __________________________________
                                           Archie A. Cobb, III

                                      -12-
<PAGE>
 
                                  Schedule 4.1
 
 
Asset                                             Asset Transfer Date
-----                                             ------------------- 
1985 Toyota Landcruiser                           March 1, 1997
 
1988 Jeep Wrangler                                March 1, 1997
 
Oakbourne Country Club Stock                      Closing Date
 
1994 GMC Surburban                                March 1, 1997

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