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                                                                   EXHIBIT 10.45


                    FOURTH AMENDMENT TO AMENDED AND RESTATED
                          CREDIT AND SECURITY AGREEMENT

         This Amendment, dated as of January 30, 2004, is made by and between
Strata Directional Technology, Inc., a Texas corporation (the "Borrower"), and
Wells Fargo Credit, Inc., a Minnesota corporation (the "Lender").

                                    Recitals
                                    --------

         The Borrower and the Lender are parties to an Amended and Restated
Credit and Security Agreement dated as of February 1, 2002, as previously
amended (the "Credit Agreement"). Capitalized terms used in these recitals have
the meanings given to them in the Credit Agreement unless otherwise specified.

         The Borrower has requested that certain amendments be made to the
Credit Agreement, which the Lender is willing to make pursuant to the terms and
conditions set forth herein.

         NOW, THEREFORE, in consideration of the premises and of the mutual
covenants and agreements herein contained, it is agreed as follows:

         1. Defined Terms. Capitalized terms used in this Amendment which are
defined in the Credit Agreement shall have the same meanings as defined therein,
unless otherwise defined herein. In addition, Section 1.1 of the Credit
Agreement is amended by adding or amending, as the case may be, the following
definitions:

         "Maximum Line" means, from the date hereof through February 28, 2004,
$2,750,000; and, thereafter, $2,500,000.

         2. No Other Changes. Except as explicitly amended by this Amendment,
all of the terms and conditions of the Credit Agreement shall remain in full
force and effect and shall apply to any advance or letter of credit thereunder.

         3. Conditions Precedent. This Amendment shall be effective when the
Lender shall have received an executed original hereof, together with each of
the following, each in substance and form acceptable to the Lender in its sole
discretion:

                  (a) The Acknowledgment and Agreement of Guarantors set forth
         at the end of this Amendment, duly executed by each Guarantor.

                  (b) A Certificate of the Secretary of the Borrower certifying
         as to the resolutions of the board of directors of the Borrower
         approving the execution and delivery of this Amendment.


                                       21
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                  (c) The replacement note substantially in the form of Exhibit
         A hereto, duly executed on behalf of the Borrower (the "Replacement
         Note").

                  (d) Such other matters as the Lender may require.

         4. Representations and Warranties. The Borrower hereby represents and
warrants to the Lender as follows:

                  (a) The Borrower has all requisite power and authority to
         execute this Amendment and the Replacement Note and to perform all of
         its obligations hereunder, and this Amendment and Replacement Note have
         been duly executed and delivered by the Borrower and constitutes the
         legal, valid and binding obligation of the Borrower, enforceable in
         accordance with its terms.

                  (b) The execution, delivery and performance by the Borrower of
         this Amendment and the Replacement Note have been duly authorized by
         all necessary corporate action and do not (i) require any
         authorization, consent or approval by any governmental department,
         commission, board, bureau, agency or instrumentality, domestic or
         foreign, (ii) violate any provision of any law, rule or regulation or
         of any order, writ, injunction or decree presently in effect, having
         applicability to the Borrower, or the articles of incorporation or
         by-laws of the Borrower, or (iii) result in a breach of or constitute a
         default under any indenture or loan or credit agreement or any other
         agreement, lease or instrument to which the Borrower is a party or by
         which it or its properties may be bound or affected.

                  (c) All of the representations and warranties contained in
         Article V of the Credit Agreement are correct on and as of the date
         hereof as though made on and as of such date, except to the extent that
         such representations and warranties relate solely to an earlier date.

         5. No Other Waiver. The execution of this Amendment and acceptance of
the Replacement Note and any documents related hereto shall not be deemed to be
a waiver of any Default or Event of Default under the Credit Agreement or
breach, default or event of default under any Security Document or other
document held by the Lender, whether or not known to the Lender and whether or
not existing on the date of this Amendment.

         6. Release. The Borrower, and each Guarantor by signing the
Acknowledgment and Agreement of Guarantors set forth below, each hereby
absolutely and unconditionally releases and forever discharges the Lender, and
any and all participants, parent corporations, subsidiary corporations,
affiliated corporations, insurers, indemnitors, successors and assigns thereof,
together with all of the present and former directors, officers, agents and
employees of any of the foregoing, from any and all claims, demands or causes of
action of any kind, nature or description, whether arising in law or equity or
upon contract or tort or under any state or federal law or otherwise, which the
Borrower or such Guarantor has had, now has or has made claim to have against
any such person for or by reason of any act, omission, matter, cause or thing
whatsoever arising from the beginning of time to and including the date of this
Amendment, whether such claims, demands and causes of action are matured or
unmatured or known or unknown.

                                      -2-
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         7. Costs and Expenses. The Borrower hereby reaffirms its agreement
under the Credit Agreement to pay or reimburse the Lender on demand for all
costs and expenses incurred by the Lender in connection with the Loan Documents,
including without limitation all reasonable fees and disbursements of legal
counsel. Without limiting the generality of the foregoing, the Borrower
specifically agrees to pay all fees and disbursements of counsel to the Lender
for the services performed by such counsel in connection with the preparation of
this Amendment and the documents and instruments incidental hereto. The Borrower
hereby agrees that the Lender may, at any time or from time to time in its sole
discretion and without further authorization by the Borrower, make a loan to the
Borrower under the Credit Agreement, or apply the proceeds of any loan, for the
purpose of paying any such fees, disbursements, costs and expenses.

         8. Miscellaneous. This Amendment and the Acknowledgment and Agreement
of Guarantors may be executed in any number of counterparts, each of which when
so executed and delivered shall be deemed an original and all of which
counterparts, taken together, shall constitute one and the same instrument.

                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be duly executed as of the date first written above.


WELLS FARGO CREDIT, INC.                     STRATA DIRECTIONAL TECHNOLOGY, INC.



By /S/ MICHELLE SALISBURY                    By /S/ MUNAWAR H. HIDAYATALLAH
   ----------------------                       --------------------------------
   Michelle Salisbury, Vice President           Munawar Hidayatallah
                                                Chairman of the Board and
                                                Chief Executive Officer

                                      -3-
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                   ACKNOWLEDGMENT AND AGREEMENT OF GUARANTORS

                  The undersigned, each a guarantor of the indebtedness of
Strata Directional Technology, Inc. (the "Borrower") to Wells Fargo Credit, Inc.
(the "Lender") pursuant to a separate Guaranty each dated as of February 1, 2002
(each, a "Guaranty"), hereby (i) acknowledges receipt of the foregoing
Amendment; (ii) consents to the terms (including without limitation the release
set forth in paragraph 6 of the Amendment) and execution thereof; (iii)
reaffirms his or its obligations to the Lender pursuant to the terms of his or
its Guaranty; and (iv) acknowledges that the Lender may amend, restate, extend,
renew or otherwise modify the Credit Agreement and any indebtedness or agreement
of the Borrower, or enter into any agreement or extend additional or other
credit accommodations, without notifying or obtaining the consent of the
undersigned and without impairing the liability of the undersigned under his or
its Guaranty for all of the Borrower's present and future indebtedness to the
Lender.



                                               /S/ MUNAWAR H. HIDAYATALLAH
                                               ---------------------------
                                               Munawar Hidayatallah



                                               JENS' OIL FIELD SERVICE, INC.

                                               By /S/ MUNAWAR H. HIDAYATALLAH
                                                  ------------------------------
                                                     Munawar Hidayatallah
                                                     Chairman of the Board and
                                                     Chief Executive Officer


                                               ALLIS-CHALMERS CORPORATION


                                               By /S/ MUNAWAR H. HIDAYATALLAH
                                                  ------------------------------
                                                     Munawar Hidayatallah
                                                     Chairman of the Board and
                                                     Chief Executive Officer

<PAGE>

                                                   Exhibit A to Fourth Amendment

                   SECOND AMENDED AND RESTATED REVOLVING NOTE

$2,750,000                                                Minneapolis, Minnesota
                                                                January 30, 2004

                  For value received, the undersigned, STRATA DIRECTIONAL
TECHNOLOGY, INC., a Texas corporation (the "Borrower"), hereby promises to pay
on the Maturity Date under the Credit Agreement (defined below), to the order of
WELLS FARGO CREDIT, INC., a Minnesota corporation (the "Lender"), at its main
office in Minneapolis, Minnesota, or at any other place designated at any time
by the holder hereof, in lawful money of the United States of America and in
immediately available funds, the principal sum of Two Million Seven Hundred
Fifty Thousand Dollars ($2,750,000) or, if less, the aggregate unpaid principal
amount of all Revolving Advances made by the Lender to the Borrower under the
Credit Agreement (defined below) together with interest on the principal amount
hereunder remaining unpaid from time to time, computed on the basis of the
actual number of days elapsed and a 360-day year, from the date hereof until
this Note is fully paid at the rate from time to time in effect under the
Amended and Restated Credit and Security Agreement dated as of February 1, 2002,
as amended (as the same may hereafter be amended, supplemented or restated from
time to time, the "Credit Agreement") by and between the Lender and the
Borrower. The principal hereof and interest accruing thereon shall be due and
payable as provided in the Credit Agreement. This Note may be prepaid only in
accordance with the Credit Agreement.

                  This Note is issued pursuant, and is subject, to the Credit
Agreement, which provides, among other things, for acceleration hereof. This
Note is the Amended and Restated Revolving Note referred to in the Credit
Agreement. This Note is issued in replacement of and in substitution for, but
not in repayment of, the Amended and Restated Revolving Note of Strata
Directional Technology, Inc., dated as of February 1, 2002, and payable to the
order of the Lender in the original principal amount of $2,500,000. This Note is
secured, among other things, pursuant to the Credit Agreement and the Security
Documents as therein defined, and may now or hereafter be secured by one or more
other security agreements, mortgages, deeds of trust, assignments or other
instruments or agreements.

                  The Borrower hereby agrees to pay all costs of collection,
including attorneys' fees and legal expenses in the event this Note is not paid
when due, whether or not legal proceedings are commenced.

                  Presentment or other demand for payment, notice of dishonor
and protest are expressly waived.



                                            STRATA DIRECTIONAL TECHNOLOGY, INC.

                                            By:  /S/ MUNAWAR H. HIDAYATALLAH
                                                 ---------------------------
                                                 Munawar Hidayatallah
                                                 Chairman of the Board and
                                                 Chief Executive Officer


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