Document:

<PAGE>

                                                                   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
<PAGE>

                  (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-
<PAGE>

         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-
<PAGE>

                   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

<PAGE><PAGE>

                                                                   EXHIBIT 10.46

                      SECOND AMENDMENT TO CREDIT AGREEMENT

         THIS SECOND AMENDMENT TO CREDIT AGREEMENT (as same may be renewed,
extended, modified, restated amended and/or rearranged, the "Second Amendment")
dated as of April 2, 2004, is between AIRCOMP L.L.C., a Delaware limited
liability company (hereinafter referred to as "Borrower") and WELLS FARGO BANK,
NATIONAL ASSOCIATION, successor-by-merger to Wells Fargo Bank Texas, National
Association, a national banking association ("Bank").

                                    RECITALS:

         A. Bank and Borrower entered into that certain Credit Agreement dated
as of June 27, 2003 (the "Original Agreement"); as amended by that certain First
Amendment to Credit Agreement dated as of December 31, 2003 (the "First
Amendment", together with the Original Agreement, referred to herein as the
"Agreement").

         B. Borrower has requested that Bank amend certain covenants set forth
in the Agreement. Bank has agreed to do so, subject to the terms and conditions
contained herein.

         C. Mountain Compressed Air, Inc., a Texas corporation ("MCA"), M-I
L.L.C., a Delaware limited liability company ("M-I"), and Munawar and Jayne
Hidayatallah (the "Hidayatallahs") each guaranteed to the Bank the payment and
performance of certain indebtedness and obligations of Borrower to Bank.

         D. Borrower and Bank now desire to enter into this Second Amendment on
the terms set forth herein.

         NOW, THEREFORE, in consideration of the premises herein contained and
other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the parties hereto agree as follows:

                                    ARTICLE 1

                                  GENERAL TERMS

         Section 1.1 TERMS DEFINED IN AGREEMENT. As used in this Second
Amendment, except as may otherwise be provided herein, all capitalized terms
which are defined in the Agreement, as amended, have the same meaning herein as
therein, all of such terms and their definitions being incorporated herein by
reference.

         Section 1.2 CONFIRMATION AND EXTENT OF CHANGES. All terms which are
defined or referred to in the Agreement shall remain unchanged except as
otherwise specifically provided in this Second Amendment. It is hereby confirmed
that the term "Agreement" includes the Agreement as amended by this Second
Amendment.

<PAGE>

                                    ARTICLE 2

                                   AMENDMENTS

         Section 2.1 AMENDMENT TO SECTION 5.9. Effective as of the date hereof,
Section 5.9 of the Agreement is hereby amended to read in its entirety as
follows:

                  "SECTION 5.9 LIMITATIONS ON LEASES. Create, incur, assume or
         permit to exist any obligation for the payment of rent or hire or
         property of any kind whatsoever under leases or lease agreements
         including, without limitation, operating leases which will cause the
         aggregate amount of all payments made by Borrower pursuant to all such
         leases or lease agreements to exceed $200,000.00 in any fiscal year."

                                    ARTICLE 3

                         REPRESENTATIONS AND WARRANTIES

         In order to induce the Bank to enter into this Second Amendment and to
continue to make the loans provided for in the Agreement, the Borrower
represents and warrants (which representations and warranties will survive the
execution and delivery hereof and will be deemed for all purposes to be
additional representations and warranties of the Agreement) that:

         Section 3.1 REPRESENTATIONS AND WARRANTIES OF THE AGREEMENT AND THE
LOAN DOCUMENTS. The representations and warranties of the Borrower contained in
the Agreement and the Loan Documents and otherwise made in writing by or on
behalf of the Borrower pursuant to the Agreement and the Loan Documents were
true and correct when made, and are true and correct in all material respects at
and as of the time of delivery of this Second Amendment, except for such changes
in the facts represented and warranted as are not in violation of the Agreement
and the Loan Documents.

         Section 3.2 COMPLIANCE WITH OBLIGATIONS. The Borrower has performed and
complied with all agreements and conditions contained in the Agreement and the
Loan Documents required to be performed or complied with by the Borrower prior
to or at the time of delivery of this Second Amendment.

         Section 3.3 DEFAULTS. There exists, and after giving effect to this
Second Amendment, will exist, no default or Event of Default, or any condition,
or act which constitutes, or with notice or lapse of time (or both) would
constitute an event of default under any loan agreement, note agreement, or
trust indenture to which the Borrower is a party.

         Section 3.4 NO AMENDMENTS. Nothing in Article 3 of this Second
Amendment is intended to amend any of the representations or warranties of the
Agreement.

                                      -2-
<PAGE>

                                    ARTICLE 4

                                   CONDITIONS

         The Bank has relied upon the representations and warranties contained
in this Second Amendment in agreeing to the amendments and supplements to the
Agreement set forth herein and the amendments and supplements to the Agreement
set forth herein are conditioned upon and subject to the accuracy of each and
every representation and warranty of the Borrower made or referred to herein, to
the performance by the Borrower of its obligations to be performed under the
Agreement and the Loan Documents on or before the date of this Second Amendment
and to the following further conditions:

         Section 4.1 CERTIFICATE AND AGREEMENT OF MANAGERS - BORROWER. The Bank
shall have received a certificate and agreement of managers of the Borrower
setting forth (i) resolutions of its managers in form and substance satisfactory
to the Bank authorizing the Borrower (and such other parties as may be required
by Bank) to execute the Loan Documents to which it is a party, and (ii) specimen
signatures of the managers so authorized.

         Section 4.2 ADDITIONAL DOCUMENTATION. The Borrower shall deliver to the
Bank such additional approvals, opinions or documents as Bank may reasonably
require.

                                    ARTICLE 5

                                  MISCELLANEOUS

         Section 5.1 LOAN DOCUMENTS. All Loan Documents shall secure the
indebtedness and obligations previously secured by such Loan Documents, as such
indebtedness and obligations are affected by this Second Amendment (including,
without limitation, the $1,000,000.00 Renewed Line of Credit Note, the
$8,000,000.00 Term Note, and the $1,000,000.00 Delayed Draw Term Note, each
dated as of June 27, 2003 from the Borrower to the Bank), whether or not such
Loan Documents shall be expressly amended or supplemented in connection with
this Second Amendment.

         Section 5.2 EXTENT OF AMENDMENTS. Except as otherwise expressly
provided herein, the Agreement, the Loan Documents, the other instruments and
agreements referred to therein are not amended, modified or affected by this
Second Amendment.

         Section 5.3 EFFECTIVE DATE. Except as otherwise expressly provided
herein, the effective date of all provisions of this Second Amendment shall be
the date indicated below.

         Section 5.4 TITLES OF ARTICLES, SECTIONS AND SUBSECTIONS. All titles or
headings to articles, sections, subsections or other divisions of this Second
Amendment are only for the convenience of the parties and shall not be construed
to have any effect or meaning with respect to the other content of such
articles, sections, subsections, or other divisions, such other content being
controlling as to the Agreement among the parties hereto.

         Section 5.5 COUNTERPARTS. This Second Amendment may be executed in two
or more counterparts. It will not be necessary that the signatures of all
parties hereto be contained on any one counterpart hereof; each counterpart
shall be deemed an original, but all of which together shall constitute one and
the same instrument.

                                      -3-
<PAGE>

         Section 5.6 FEES AND EXPENSES. Borrower will pay all fees and expenses
incurred by Bank in connection with this Second Amendment and the transactions
contemplated herein including, without limitation filing fees, search fees, and
reasonable attorneys' fees.

         Section 5.7 ENTIRE AGREEMENT. THIS SECOND AMENDMENT AND ALL OTHER
INSTRUMENTS, DOCUMENTS, AND AGREEMENTS EXECUTED AND DELIVERED IN CONNECTION WITH
THIS SECOND AMENDMENT EMBODY THE FINAL, ENTIRE AGREEMENT AMONG THE PARTIES
HERETO WITH RESPECT TO THE SUBJECT MATTER HEREOF AND THEREOF AND SUPERSEDE ANY
AND ALL PRIOR COMMITMENTS, AGREEMENTS, REPRESENTATIONS AND UNDERSTANDINGS,
WHETHER WRITTEN OR ORAL, RELATING TO THIS SECOND AMENDMENT AND THE OTHER
INSTRUMENTS, DOCUMENTS AND AGREEMENTS EXECUTED AND DELIVERED IN CONNECTION WITH
THIS SECOND AMENDMENT, AND MAY NOT BE CONTRADICTED OR VARIED BY EVIDENCE OF
PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OR DISCUSSIONS OF THE
PARTIES HERETO. THERE ARE NO ORAL AGREEMENTS AMONG THE PARTIES HERETO.

         IN WITNESS WHEREOF, the parties hereto have caused this instrument to
be effective as of the 2nd day of April, 2004.

                                                     BORROWER:

                                                     AIRCOMP L.L.C.

                                                     By:   /S/ TERRY KEANE
                                                           ---------------------
                                                           Terry Keane
                                                           President

                                      -4-
<PAGE>

                                                     BANK:

                                                     WELLS FARGO BANK,
                                                     NATIONAL ASSOCIATION,
                                                     SUCCESSOR-BY-MERGER TO
                                                     WELLS FARGO BANK TEXAS,
                                                     NATIONAL ASSOCIATION

                                                     By:   /S/ ALAN SMITH
                                                           ---------------------
                                                           Alan Smith
                                                           Vice President

                                      -5-
<PAGE>

MCA hereby consents and agrees to this Second Amendment and agrees that its (i)
guaranty executed on June 27, 2003 ("MCA Guaranty") and (ii) Third Party Pledge
executed on June 27, 2003 ("MCA Pledge") shall each remain in full force and
effect, shall continue to be legal, valid, and binding obligations of MCA, and
shall continue to guarantee and secure the indebtedness and obligations
described in the MCA Guaranty and the MCA Pledge as such guaranteed and secured
obligations are amended by this Second Amendment including, without limitation,
the MCA Guaranty shall cover the $1,000,000.00 Line of Credit Note, the
$8,000,000.00 Term Note, and the $1,000,000.00 Delayed Draw Term Note, together
with any and all renewals, rearrangements, amendments, increases, extensions
and/or modifications of any of the aforesaid, and the MCA Guaranty and the MCA
Pledge shall each be enforceable against MCA in accordance with their terms.

                                          GUARANTOR:

                                          Mountain Compressed Air, Inc.,
                                          a Texas corporation

                                          By:      /S/ TED POUND
                                                   -----------------------------
                                                   Theodore F. Pound, III
                                                   Vice President and Secretary

                                      -6-
<PAGE>

Munawar and Jayne Hidayatallah hereby jointly and severally consent and agree to
this Second Amendment and agree that the Hidayatallah Guaranty executed June 27,
2003 shall remain in full force and effect, shall continue to be legal, valid,
and binding obligations of Munawar and Jayne Hidayatallah, and shall continue to
guaranty the indebtedness and obligations described in the Hidayatallah Guaranty
as such guaranteed obligations are amended by this Second Amendment including,
without limitation, such Hidayatallah Guaranty shall cover the $1,000,000.00
Line of Credit Note, the $8,000,000.00 Term Note, and the $1,000,000.00 Delayed
Draw Term Note, together with any and all renewals, rearrangements, amendments,
increases, extensions and/or modifications of any of the aforesaid, and such
Hidayatallah Guaranty shall be enforceable against Munawar and Jayne
Hidayatallah in accordance with its terms.

                                                     GUARANTOR:

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

                                                     JAYNE HIDAYATALLAH
                                                     ---------------------------
                                                     Jayne Hidayatallah

                                      -7-
<PAGE>

M-I consents and agrees to this Second Amendment and agrees that its (i)
guaranty executed on June 27, 2003 ("M-I Guaranty") and (ii) Third Party Pledge
executed on June 27, 2003 ("M-I Pledge") shall each remain in full force and
effect, shall continue to be legal, valid, and binding obligations of M-I, and
shall continue to guarantee and secure the indebtedness and obligations
described in the M-I Guaranty and the M-I Pledge as such guaranteed and secured
obligations are amended by this Second Amendment including, without limitation,
the M-I Guaranty shall cover the $1,000,000.00 Line of Credit Note, the
$8,000,000.00 Term Note, and the $1,000,000.00 Delayed Draw Term Note, together
with any and all renewals, rearrangements, amendments, and/or modifications of
any of the aforesaid, and such M-I Guaranty and the M-I Pledge shall each be
enforceable against M-I in accordance with their terms.

                                     GUARANTOR:

                                     M-I L.L.C.,
                                     a Delaware limited liability company

                                     By:    /S/ CHRIS RIVERS
                                            ------------------------------------
                                            Chris Rivers
                                            Senior Vice President, Chief
                                             Financial Officer and Treasurer

                                      -8-

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