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                                                                  EXHIBIT 10.1.5

                 FIFTH AMENDMENT TO LOAN AND SECURITY AGREEMENT


         THIS FIFTH AMENDMENT TO LOAN AND SECURITY AGREEMENT (this "Amendment")
is made and entered into as of this 29th day of June, 2001, by and among THE CIT
GROUP/BUSINESS CREDIT, INC., a New York corporation (hereinafter "CITBC"), in
its individual capacity and as Agent for the Lenders hereinafter named
(hereinafter the "AGENT"), Foothill Capital Corporation, a California
corporation ("FCC"), Fleet Capital Corporation, a Rhode Island corporation
("FLEET"), The CIT Group/Equipment Financing, Inc., a Delaware corporation
("CITEF"), and any other party hereafter becoming a Lender pursuant to Section
13, Paragraph 9 of the Agreement (as hereinafter defined), each individually
sometimes referred to as a "LENDER" and, collectively, the "LENDERS"), UTI
Drilling, L.P., a Texas limited partnership ("UTI"), Norton Drilling, L.P., a
Delaware limited partnership, as successor in interest (by conversion) to Norton
Drilling Company, a Delaware corporation ("NDLP"), Universal Well Services,
Inc., a Delaware corporation ("UWSI"), UTI Management Services, L.P., a Texas
limited partnership ("UTIMS"), and Suits Drilling Company, an Oklahoma
corporation ("SDC"), (UTI, NDLP, UWSI, UTIMS and SDC, being referred to herein
individually as a "UTI COMPANY" and, collectively, as the "UTI COMPANIES"), and
Patterson-UTI Drilling Company LP, LLLP, a Delaware limited liability limited
partnership ("PUDC"), Patterson-UTI Drilling Company South LP, LLLP, a Delaware
limited liability limited partnership ("PUDCS"), Patterson-UTI Drilling Company
West LP, LLLP, a Delaware limited liability limited partnership ("PUDCW"), Lone
Star Mud LP, LLLP, a Delaware limited liability limited partnership ("LSM"),
Ambar Drilling Fluids LP, LLLP, a Delaware limited liability limited partnership
("ADF") (PUDC, PUDCS, PUDCW, LSM and ADF, being referred to herein individually
as a "PATTERSON COMPANY" and, collectively, as the "PATTERSON COMPANIES", and
the UTI Companies and the Patterson Companies, together with any additional
entities which may become a Company under the Agreement from time to time, being
referred to herein individually as a "COMPANY" and, collectively, as the
"COMPANIES"), Patterson-UTI Energy, Inc., a Delaware corporation ("PARENT"),
Patterson Petroleum LP, LLLP, a Delaware limited liability limited partnership
("PPLP"), Patterson Petroleum Trading Company LP, LLLP, a Delaware limited
liability limited partnership ("PPTC") and Patterson (LP) LLC, a Delaware
limited liability company ("PATTERSON LP"). Patterson (GP) LLC, a Delaware
limited liability company ("PATTERSON GP") and Patterson (GP2) LLC, a Delaware
limited liability company ("PATTERSON GP2") (Parent, PPLP, PPTC, Patterson LP,
Patterson GP and Patterson GP2, being referred to herein individually as a
"PATTERSON GUARANTOR" and, collectively, as the "PATTERSON GUARANTORS").

                                    RECITALS

         A. WHEREAS, pursuant to the terms and subject to the conditions of that
certain Loan and Security Agreement dated as of November 22, 1999 between the
UTI Companies and the Lenders (such Loan and Security Agreement, as the same has
been amended, is hereby amended and may hereafter be amended from time to time,
being hereinafter referred to as the "Agreement"), the UTI Companies were
granted a revolving line of credit which included a letter of credit facility;


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 1
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         B. WHEREAS, the indebtedness of the UTI Companies to the Lenders is
currently evidenced by that certain Revolving Loan Promissory Note dated May 8,
2001 (the "Existing Revolving Note"), executed by the UTI Companies and payable
to CITBC as Agent for the benefit of the Lenders in the stated principal amount
of $70,000,000;

         C. WHEREAS, payment of the Obligations of the Companies is currently
supported by the guaranties of UTICO, Inc., a Delaware corporation ("HOLDING"),
UTICO Hard Rock Boring, Inc., a Delaware corporation ("UHRB"), International
Petroleum Services Company, a Pennsylvania corporation ("IPSCO"), Norton
Drilling Services, Inc., a Delaware corporation ("NDS"), Norton Drilling Company
Mexico, Inc., a Delaware corporation ("NDM") and UTI Drilling Canada, Inc., a
Delaware corporation ("UTI CANADA") (Holding, UHRB, IPSCO, NDS, NDM and UTI
Canada are referred to herein, individually, as a "UTI GUARANTOR" and,
collectively, as the "UTI GUARANTORS");

         D. WHEREAS, to secure, in part, the indebtedness under the Agreement
and the Existing Revolving Note (and all renewals, extensions, modifications
and/or rearrangements thereof and in connection therewith) and all other
indebtedness, liabilities and obligations of the UTI Companies to the Agent for
the benefit of the Lenders, then existing or thereafter arising, (i) the UTI
Companies and UTI Guarantors have heretofore executed in favor of the Agent
certain Loan Documents (as defined in the Agreement), including, without
limitation, the Guaranty, (as defined in the Agreement), which Loan Documents
shall continue as amended in connection herewith in full force and effect upon
the execution of this Amendment, all of the Loan Documents to continue to secure
the payment by the UTI Companies of the Obligations (as defined in the
Agreement) all as more fully set forth therein and herein;

         E. WHEREAS, the Companies have requested and, pursuant to the terms and
subject to the conditions hereof and in connection herewith, the Agent and the
Lenders have agreed, to add the Patterson Companies as Companies and Obligors
under the Loan Agreement and to add the Patterson Guarantors as Guarantors and
Obligors under the Loan Agreement;

         F. WHEREAS, the Companies have requested and, pursuant to the terms and
subject to the conditions hereof and in connection herewith, the Agent and the
Lenders have agreed to increase the amount of the Line of Credit (as defined in
the Agreement) to $100,000,000, and accept the Revolving Note (as herein
defined) in replacement and substitution (but not extinguishment) of the
Existing Revolving Note;

         G. WHEREAS, in furtherance of the foregoing and to evidence the
agreements of the parties hereto in relation thereto the parties hereto desire
to amend the Agreement as hereinafter provided;

         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 Companies, the Agent and the Lenders, intending to be
legally bound, agree as follows:

                                    AGREEMENT

                                    ARTICLE I
                                   DEFINITIONS

         1.01 Capitalized terms used in this Amendment are defined in the
Agreement, as amended hereby, unless otherwise stated herein.

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 2
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                                   ARTICLE II
                             AMENDMENTS TO AGREEMENT

         Effective as of the respective dates herein indicated, the Agreement is
hereby amended as follows:

         2.01 AMENDMENT OF DEFINITION OF "COMPANY" AND "COMPANIES". Effective as
of the date of execution of this Amendment, the references to "Company" and
"Companies" in the preamble to the Agreement and throughout the Agreement shall
be amended so as to refer to and to include the UTI Companies and the Patterson
Companies.

         2.02 AMENDMENT OF DEFINITION OF "GUARANTOR" AND "GUARANTORS". Effective
as of the date of execution of this Amendment, the references to "Guarantor" and
"Guarantors" in the preamble to the Agreement and throughout the Agreement shall
be amended to include the UTI Guarantors and the Patterson Guarantors.

         2.03 AMENDMENT AND RESTATEMENT OF DEFINITION OF "ACQUISITION FACILITY
COMMITMENT". Effective as of the date of execution of this Amendment, the
definition of "Acquisition Facility Commitment" set forth in Section 1 of the
Agreement is amended and restated to read in its entirety as follows:

         " `ACQUISITION FACILITY COMMITMENT' shall mean, with respect to any
         Lender, a portion of the Revolving Loans which may be advanced as
         Acquisition Facility Loans, evidencing the amount of its commitment to
         make Acquisition Facility Loans (all such loans being Revolving Loans),
         as modified from time to time pursuant to the terms hereof, not to
         exceed $80,000,000 in the aggregate."

         2.04 AMENDMENT AND RESTATEMENT OF DEFINITION OF "ANNIVERSARY DATE".
Effective as of the date of this Amendment, the definition of "Anniversary Date"
set forth in Section 1 of the Agreement is amended and restated to read in its
entirety as follows:

         " `ANNIVERSARY DATE' shall mean June 29, 2005 and the same date in
every year thereafter."

         2.05 AMENDMENT OF DEFINITION OF "CUSTOMARILY PERMITTED LIENS".
Effective as of the date of execution of this Amendment, the definition of
"Customarily Permitted Liens" set forth in Section 1 of the Agreement is amended
by adding a new subparagraph (j) thereto to read in its entirety as follows:

                  "(j) with respect of the assets of PPLP and PPTC, (i) liens
                  reserved in customary oil, gas and/or mineral leases for bonus
                  or rental payments and for compliance with the terms of such
                  leases and liens reserved in customary operating agreements,
                  farm out and farm in agreements, exploration agreements,
                  development agreements and other similar agreements for
                  compliance with the terms of such agreements, (ii) liens or
                  charges reserved for royalties, overriding royalties, revenue
                  interests, net revenue interests and advance payment
                  obligations, (iii) any lien or charge securing indebtedness
                  neither assumed nor guaranteed by PPLP or PPTC nor on which


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                  either customarily pays interest, existing upon real estate or
                  rights in or relating to real estate acquired by PPLP or PPTC
                  for substation, metering station, pump station, storage
                  gathering line, transmission line, transportation line,
                  distribution line or for right of way purposes, and (iv) liens
                  and charges arising out of all presently existing and future
                  division and transfer orders, advance payment agreements,
                  processing contracts, gas processing plant agreements,
                  operating agreements, gas balancing or deferred production
                  agreements, pooling, unitization or communitization
                  agreements, pipeline, gathering or transportation agreements,
                  platform agreements, drilling contracts, injection or
                  repressuring agreements, cycling agreements, construction
                  agreements, salt water or other disposal agreements, leases or
                  rental agreements, farm out and farm in agreements,
                  exploration and development agreements, and any and all other
                  contracts or agreements covering, arising out of, used or
                  useful in connection with or pertaining to the exploration,
                  development, operation, production, sale, use, purchase,
                  exchange, storage, separation, dehydration, treatment,
                  compression, gathering, transportation, processing,
                  improvement, marketing, disposal or handling of any property
                  of by PPLP or PPTC, provided that such agreements are entered
                  into in the ordinary course of business on terms customary in
                  the industry."



         2.06 AMENDMENT AND RESTATEMENT OF DEFINITION OF "EARLY TERMINATION
FEE". Effective as of the date of this Amendment, the definition of "Early
Termination Fee" set forth in Section 1 of the Agreement is amended and restated
to read in its entirety as follows:

         " `EARLY TERMINATION FEE' shall: (a) mean the fee the Agent on behalf
         of the Lenders is entitled to charge the Companies if the Companies
         terminate the Line of Credit or this Agreement on a date prior to the
         fourth anniversary of the Fifth Amendment Date; and (b) be determined
         by multiplying the Line of Credit by (i) seven-tenths of one percent
         (0.70%) if the Early Termination Date occurs on or prior to one (1)
         year after the Fifth Amendment Date, (ii) one-half of one percent
         (0.50%) if the Early Termination Date occurs after one (1) year after
         the Fifth Amendment Date but on or prior to two (2) years after the
         Fifth Amendment Date (iii) three-tenths of one percent (0.30%) if the
         Early Termination Date occurs after two (2) years after the Fifth
         Amendment Date but on or prior to three (3) years after the Fifth
         Amendment Date; and (iv) two-tenths of one percent (0.20%) if the Early
         Termination Date occurs after three (3) years but prior to four (4)
         years after the Fifth Amendment Date."

         2.07 AMENDMENT AND RESTATEMENT OF DEFINITION OF "EXCLUDED L/CS".
Effective as of the date of execution of this Amendment, the definition of
"Excluded L/Cs" set forth in Section 1 of the Agreement is amended and restated
to read in its entirety as follows:

         " `EXCLUDED L/CS' shall mean the aggregate undrawn face amount of
standby Letters of Credit, not to exceed $3,000,000 in the aggregate, which
Letters of Credit were issued on account of the Companies to insurance companies
to assure payment of premiums and workers' claims in connection with workers'
compensation claims."



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         2.08 AMENDMENT AND RESTATEMENT OF DEFINITION OF "LETTER OF CREDIT
SUB-LINE". Effective as of the date hereof, the definition of "Letter of Credit
Sub-Line" set forth in Section 1 of the Agreement is amended and restated to
read in its entirety as follows:

         " `LETTER OF CREDIT SUB-LINE' shall mean $20,000,000 in the aggregate."

         2.09 AMENDMENT AND RESTATEMENT OF DEFINITION OF "LINE OF CREDIT".
Effective as of the date of execution of this Amendment, the definition of "Line
of Credit" set forth in Section 1 of the Agreement is amended and restated to
read in its entirety as follows:

         " `LINE OF CREDIT' shall mean the commitment of the Lenders in the
         aggregate amount of $100,000,000 to (a) make Revolving Loans pursuant
         to Sections 3 and 4 of this Agreement, and (b) assist the Companies in
         opening Letters of Credit pursuant to Section 5 of this Agreement (up
         to the Letter of Credit Sub-Line)."

         2.10 AMENDMENT AND RESTATEMENT OF DEFINITION OF "PARENT". Effective as
of the date of execution of this Amendment, the definition of "Parent" set forth
in Section 1 of the Agreement is amended and restated to read in its entirety as
follows:

         " "PARENT' shall mean Patterson-UTI Energy, Inc., a Delaware
         corporation formerly known as Patterson Energy, Inc., successor in
         interest by merger to UTI Energy Corp., a Delaware corporation."

         2.11 AMENDMENT AND RESTATEMENT OF DEFINITION OF "PERMITTED BUSINESS
INVESTMENT". Effective as of the date of execution of this Amendment,
subparagraphs (a), (b) and (c) of the definition of "Permitted Business
Investment" set forth in Section 1 of the Agreement are amended and restated and
a new subparagraph (h) is added to such Section, each to read in its entirety as
follows:

                  "(a) investments by any Company in any Person engaged
         primarily in a Qualified Business which, immediately after the making
         of such investment, is or becomes a Substantially-Owned Subsidiary of
         any Company and an Obligor pursuant to Section 4, provided that the
         Parent has furnished to the Agent the information described in Section
         4 of this Agreement, except that such investments shall not be
         Permitted Business Investments to the extent that the Agent reasonably
         determines that the liabilities and other obligations (contingent or
         otherwise) of any Obligor resulting therefrom or associated therewith
         could reasonably be expected to have a Material Adverse Effect;"

                  "(b) loans and other extensions of credit to officers,
         directors and employees of any Obligor and its Subsidiaries for travel,
         entertainment and moving and other relocation expenses made in direct
         furtherance and in the ordinary course of the business of any such
         Obligor or its Subsidiaries, provided that the aggregate principal
         amount of loans and other extensions of credit made pursuant to this
         clause (b) does not exceed $4,000,000 at any one time outstanding;"


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 5
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                  "(c) loans by any Obligor to NDM for NDM's working capital
         needs in an amount not to exceed $6,000,000 outstanding at any one time
         in the aggregate with respect to all loans by Obligors."

                  "(h) investments made in the ordinary course of, and of a
         nature that is or shall have become customary in, the oil and gas
         business as a means of actively exploiting, exploring for, acquiring,
         developing, processing, gathering, marketing or transporting oil and
         gas through agreements, transactions, interests, or arrangements which
         permit one to share risks or costs, comply with regulatory requirements
         regarding local ownership or satisfy other objectives customarily
         achieved through the conduct of oil and gas business jointly with third
         parties, including, without limitation, the entry into operating
         agreements, working interests, royalty interests, mineral leases,
         processing agreements, farm out and farm in agreements, division
         orders, contracts for the sale, transportation or exchange of oil or
         natural gas, unitization and pooling declarations and agreements and
         area of mutual interest agreements, production sharing agreements or
         other similar or customary agreements, transactions, properties,
         interests, and investments and expenditures in connection therewith;
         provided that an investment pursuant to this clause (h) in capital
         stock, partnership interests, joint venture interests, limited
         liability company interests or other similar equity interests in a
         Person shall not constitute a Permitted Business Investment."

         2.12 AMENDMENT AND RESTATEMENT OF SUBPARAGRAPH (a) OF DEFINITION OF
"PERMITTED FINANCIAL INVESTMENTS". Effective as of the date of execution of this
Amendment, the introductory phrase and subparagraph (a) of the definition of
"Permitted Financial Investments" set forth in Section 1. Definitions of the
Agreement is amended and restated to read in its entirety as follows:

         'PERMITTED FINANCIAL INVESTMENTS' means the following kinds of
instruments to the extent that the aggregate amount thereof outstanding do not
exceed $35,000,000 at any time (except that such $35,000,000 limitation shall
not apply for instruments described in subparagraphs (c) or (g) or (h)
immediately below or in the event that no Revolving Loan is outstanding) during
which there are any Revolving Loans outstanding:

         (a) investments in (1) certificates of deposit in United States dollars
         or Canadian dollars maturing within one year from the date of issuance
         thereof, and overnight investments, issued by a bank or trust (i)
         organized under the laws of the United States or any state thereof,
         having capital, surplus and undivided profits aggregating at least
         $500,000,000, or (ii) organized under the laws of any jurisdiction
         other than the United States or any state thereof, provided that such
         foreign bank shall be one of the three most reputable, creditworthy
         banks in such country; or (iii) organized under the laws of Canada or
         any province thereof, having capital, surplus and undivided profits
         aggregating at least $500,000,000 or the Canadian dollar equivalent
         thereto, and (2) commercial paper rated A-1 or the equivalent thereof
         by Standard & Poor's Ratings Group, a Division of McGraw-Hill, Inc., a
         New York corporation or P-1, or the equivalent thereof by Moody's
         Investors Service, Inc. and in each case maturing within six months
         after the date of acquisition;"

         2.13 AMENDMENT AND RESTATEMENT OF CLAUSE (vii) OF DEFINITION OF
"PERMITTED INDEBTEDNESS". Effective as of the date of execution of this
Amendment, clauses (vii) and (xv) of the definition "Permitted Indebtedness" set
forth in Section 1. Definitions of the Agreement is amended and restated to read
in its entirety as follows:

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         "(vii) Indebtedness assumed as part of the acquisition of any entity or
         asset by any Obligor or any Subsidiary thereof, whether by merger,
         consolidation, purchase of assets or otherwise; provided that (A) such
         Indebtedness is not created, incurred or assumed in contemplation of
         such acquisition of such entity or asset and (B) the aggregate amount
         of all such Indebtedness constituting Indebtedness For Borrowed Money
         does not exceed $10,000,000 outstanding at any time, and (C) any
         Indebtedness discharged at the closing of such acquisition shall not be
         deemed or constitute assumed Indebtedness;"

         "(xv) Indebtedness of any Obligor or any Subsidiary thereof, not
         otherwise described above, not to exceed in the aggregate with respect
         to all Obligors and Subsidiaries taken as a whole $10,000,000
         outstanding at any one time."

         2.14 AMENDMENT AND RESTATEMENT OF DEFINITION OF "PERMITTED INTERCOMPANY
BALANCES". Effective as of the date of the execution of this Amendment, the
definition of "Permitted Intercompany Balances" set forth in Section 1 of the
Agreement is amended and restated to read in its entirety as follows:

         "'PERMITTED INTERCOMPANY BALANCES' means loans, advances, inter-company
         accounts, transfers and investments (including, but not limited to,
         loans made pursuant to the concentrated cash management system for
         collections of accounts receivable or disbursements to trade creditors)
         by any Obligor in, with or to any other Obligor; provided that (i) each
         such lender and borrower (or transferor and transferee, as the case may
         be) Obligor is Solvent after giving effect thereto, (ii) each such
         Obligor has received reasonably equivalent value in exchange for the
         transfers made and obligations incurred by it in connection therewith,
         (iii) loans, transfers or advances to or investments in Restricted
         Subsidiaries which were effected after the date of acquisition thereof
         by an Obligor that do not exceed in the aggregate the amount obtained
         by subtracting from the applicable Restricted Subsidiary Borrowing Base
         an amount equal to Revolving Loans from the Lenders to such Restricted
         Subsidiary, and (iv) loans, transfers or advances to or investments in
         PPLP and PPTC may not be made during any time a Triggering Event has
         occurred and is continuing."

         2.15 AMENDMENT OF DEFINITION OF "PERMITTED LIENS". Effective as of the
date of execution of this Amendment, the definition of "Permitted Liens" set
forth in Section 1 of the Agreement is hereby amended to add a new clause (j)
thereto to read in its entirety as follows:

         "(j) liens granted to Snyder National Bank in a $750,000 certificate of
         deposit which secures an outstanding letter of credit issued by Snyder
         National Bank."

         2.16 AMENDMENT AND RESTATEMENT OF DEFINITION OF "PURCHASE MONEY LIENS".
Effective as of the date of execution of this Amendment, the definition
"Purchase Money Liens" set forth in Section 1. Definitions of the Agreement is
amended and restated to read in its entirety as follows:

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 7

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         "`PURCHASE MONEY LIENS' shall mean liens on any item of equipment
         acquired after the date of this Agreement; provided that (i) each such
         lien shall attach only to the property to be acquired, and (ii) the
         debt incurred in connection with such acquisitions shall not exceed in
         the aggregate $10,000,000 incurred in any Fiscal Year."

         2.17 AMENDMENT AND RESTATEMENT OF DEFINITION OF "REQUIRED LENDERS".
Effective as of the date of execution of this Amendment, the definition of
"Required Lender" set forth in Section 1. Definitions of the Agreement is
amended and restated to read in its entirety as follows:

         "`REQUIRED LENDERS' shall mean Lenders holding more than fifty-one
percent (51%) of the outstanding loans, advances, extensions of credit and
commitments to each Company hereunder."

         2.18 AMENDMENT AND RESTATEMENT OF DEFINITION OF "QUALIFIED BUSINESS".
Effective as of the date of execution of this Amendment, the definition of
"Qualified Business" set forth in Section 1. Definitions of the Agreement is
amended and restated to read in its entirety as follows:

         " `QUALIFIED BUSINESS' means, with respect to all Obligors, the
         business of oil and gas well drilling, oil and gas well construction,
         oil and gas well completion and oil and gas well workover or well
         service, oil and gas well stimulation, drilling mud manufacturing,
         drilling and completion fluids services and any business or services
         reasonably related to any foregoing, and with respect to PPLP and PPTC,
         the business of oil and gas exploration and production and any business
         or services reasonably related to any of the foregoing."

         2.19 NEW DEFINITION. Effective as of the date of this Amendment,
Section 1 of the Agreement is amended by adding the following new definition
thereto, to be inserted in appropriate alphabetical order:

         "FIFTH AMENDMENT DATE" shall mean June 29, 2001."

         2.20 DELETION OF DEFINITIONS. Effective as of the date of execution of
this Amendment, Section 1 of the Agreement is amended by deleting the
definitions "Merger Date", "Patterson Loan Agreement", Patterson Negative Pledge
Assets" and "Patterson Subsidiaries".

         2.21 AMENDMENT AND RESTATEMENT OF SECTION 3, PARAGRAPH 1 OF THE
AGREEMENT. Effective as of the date of execution of this Amendment, the last
sentence of Section 3, Paragraph 1 of the Agreement is amended and restated to
read in its entirety as follows:

         "Should the Agent for any reason honor requests for advances in excess
         of the limitations set forth herein, such advances shall be considered
         "Overadvances" and shall be made at the Agent's sole discretion,
         subject to any additional terms the Agent deems necessary and the other
         terms and provisions of this Agreement; provided, however, Agent may
         not make Overadvances which exceed the Line of Credit.

         2.22 AMENDMENT AND RESTATEMENT OF SECTION 4, PARAGRAPH 1 OF THE
AGREEMENT. Effective as of the date of execution of this Amendment, Section 4,
Subparagraph 1(a)(i) of the Agreement and the introduction thereto is amended
and restated to read in its entirety as follows:

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         "1. Dollar Amount of Acquisition Facility Loans. Each of the Companies
         shall be permitted to borrow Revolving Loans for the purpose of the
         Parent, or a wholly-owned Subsidiary of the Parent that is one of the
         Companies or Obligors, consummating Permitted Acquisitions
         ("Acquisition Facility Loans") subject to the following conditions:

                  (a) (i) Following the making of such Revolving Loan and
                  consummation of the Permitted Acquisition, there is at least
                  $15 million of Availability (determined without regard to the
                  Excluded L/Cs) and no more than an aggregate of $80 million of
                  Revolving Loans outstanding, and (ii) until the Obligors have
                  invested in the aggregate $25 million in cash (whether cash on
                  hand or cash provided from Revolving Loans to consummate
                  Permitted Acquisitions pursuant to this Section 4) in
                  Permitted Acquisitions that are Domestic Acquisitions, the
                  aggregate amount of Revolving Loans outstanding for the
                  purpose of consummating Canadian Acquisitions cannot exceed
                  the sum of (A) $20 million plus (B) the amount of cash
                  invested in Domestic Acquisitions (whether cash on hand or
                  cash provided from Revolving Loans); or"

         2.23 AMENDMENT AND RESTATEMENT OF SECTION 4, SUBPARAGRAPH 1(b) OF THE
AGREEMENT. Effective as of the date of execution of the Amendment, Section 4,
Subparagraph 1(b) of the Agreement is amended and restated to read in its
entirety as follows:

                  " (b) UTI and the Parent received the Required Lenders' prior
                  written approval, which approval shall be given or not given
                  in the sole and absolute discretion of the Lenders."

         2.24 AMENDMENT AND RESTATEMENT OF SECTION 5, PARAGRAPH 1. Effective as
of the date of execution of the Amendment, the second sentence of Section 5,
Paragraph 1 of the Agreement is amended and restated to read in its entirety as
follows:

                  "The Agent's and Lenders' assistance for amounts in excess of
                  the limitations set forth herein shall at all times and in all
                  respects be in the sole discretion of the Agent prior to the
                  occurrence and continuance of an Event of Default and
                  thereafter shall require the consent of the Required Lenders."

         2.25 AMENDMENT AND RESTATEMENT OF SECTION 6, PARAGRAPH 4. Effective as
of the date of execution of this Amendment, clauses (a) and (b) of Section 6,
Paragraph 4 of the Agreement are hereby amended and restated in their entirety
to read as follows:

                  "(a) the Obligors, taken as a whole, own at least two hundred
                  (200) Domestic Rigs upon which the Agent, for the benefit of
                  the Lenders, has a first priority lien and fully perfected
                  security interest, and (b) the Orderly Liquidation Value of
                  the Domestic Rigs upon which the Agent, for the benefit of the
                  Lenders, has such first priority lien and fully perfected
                  security interest exceeds $200,000,000 in aggregate,"

         2.26 AMENDMENT TO SECTION 7, SUBPARAGRAPH 8(b). Effective as of the
date of execution of this Amendment, Section 7, Paragraph 8(b) is amended to
permit, consent to and authorize the monthly Financial Statements for the month
ending May 31, 2001 to be delivered by Parent on or before July 31, 2001.



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         2.27 AMENDMENT OF INTRODUCTION TO SECTION 7, PARAGRAPH 10. Effective as
of the date of execution of this Amendment, the introduction to Section 7,
Paragraph 10 is amended and restated to read in its entirety as follows:

                  "Until termination of this Agreement and payment and
                  satisfaction of all Obligations due hereunder, each Obligor
                  agrees that, without the prior written consent of Agent (or
                  the Required Lenders for any matter prohibited by
                  Subparagraphs 10A, 10B, 10C and 10D in this Section 7 or for
                  all matters prohibited by this Paragraph at any time during
                  which Availability is less than $20,000,000), except as
                  otherwise herein provided, it will not and it will not permit
                  any other Obligor to:"

         2.28 AMENDMENT OF INTRODUCTION TO SECTION 7, PARAGRAPH 10(J). Effective
as of the date of execution of this Amendment, the introduction to Section 7,
Paragraph 10(J) is amended and restated to read in its entirety as follows:

                  "Without the prior written consent of the Required Lenders,"

         2.29 AMENDMENT OF SECTION 7, PARAGRAPH 10D. Effective as of the date of
execution of this Amendment, Section 7, Paragraph 10D of the Agreement is
amended by deleting the clauses (ix) and (x), by amending and restating clauses
(ii), (iii), (iv) and (viii) and by adding a new clause (ix), each to read in
its entirety as follows:

         "(ii)    (a) the sale, lease, assignment, transfer or other disposition
                  of Inventory in the ordinary course of business, and (b) the
                  lease of Rigs or other Equipment in the ordinary course of
                  business of the Companies, provided that each such lease shall
                  be subordinate (in form and substance reasonably satisfactory
                  to the Agent) to the terms of the liens and security interests
                  created in connection herewith in favor of the Agent, the
                  aggregate fair market value of such Rigs and other Equipment
                  so leased to third parties not affiliated with any Obligor
                  does not exceed $10,000,000 in the aggregate during the term
                  of this Agreement and all such Rigs and other Equipment so
                  leased are disclosed to the Agent in writing as such and are
                  excluded from Eligible Equipment;

         (iii)    the sale, transfer or disposition approved by the Board of
                  Directors of the Parent to a Person that is not an Obligor of
                  (a) the capital stock or substantially all of the assets of
                  UWSI, IPSCO, ADF, LSM, PPLP and PPTC (so long as such entities
                  do not own any Rigs or Rig Accessories), (b) UHRB's hard rock
                  boring business or assets or (c) all of the capital stock or
                  substantially all of the assets of any other Obligor (other
                  than UTI) that has Tangible Net Worth on a consolidated basis
                  for such Obligor and its Subsidiaries of less than
                  $15,000,000;

         (iv)     the sale, lease, assignment, transfer or other disposition of
                  any or all of the assets of any Obligor to any other Obligor
                  to the extent that the same qualifies as a Permitted
                  Intercompany Balance, except that no more than an aggregate of
                  ten (10) Rigs may be leased at any one time to NDM and no Rigs
                  may be sold, transferred or leased to any Guarantor;

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 10
<PAGE>   11

         (viii)   the sale, transfer or other disposition of oil and gas mineral
                  interests (and related operating agreements covering the
                  operation of such interests) and including, without limiting
                  the generality of the foregoing, dispositions of oil and gas
                  properties pursuant to farm-ins and farm-outs and transfers of
                  royalty interests, overriding royalty interests, net revenue
                  interests and other similar transfers, all pursuant to
                  exploration and development activity in the ordinary course of
                  business;

         (ix)     the sale, transfer, lease or assignment by any of the
                  Companies or the Obligors of up to 15 Rigs in aggregate to a
                  Canadian Operating Company;"

         2.30 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 10, SUBPARAGRAPH
E OF THE AGREEMENT. Effective as of the date of this Amendment, Section 7,
Paragraph 10, Subparagraph E, clause (i) of the Agreement is amended and
restated to read in its entirety as follows:

                  "(i) the merger or consolidation of any Subsidiary of Parent
         into any one or more of the Companies in a transaction in which a
         Company is the surviving Person and no Person other than a Company
         receives any consideration or if such consideration is paid to others
         that are not Subsidiaries, if such payment would be permitted to be
         made if it was made as a Restricted Payment (and in such case such
         payment shall constitute a Restricted Payment for all purposes of this
         Agreement);"

         2.31 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 10, SUBPARAGRAPH
G OF THE AGREEMENT. Effective as of the date of this Amendment, Section 7,
Paragraph 10, Subparagraph G of the Agreement is amended to add a new clause (x)
thereto to read in its entirety as follows:

         "(x)     the payment of dividends on the Parent's Preferred Stock if
                  and when issued pursuant to the Parent's Rights Agreement,
                  dated as of January 2, 1997, between the Parent and
                  continental Stock Transfer & Trust Company or its successor,
                  provided that the aggregate amount of all such dividends paid
                  thereon shall not exceed $100,000 per calendar quarter."

         2.32 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 10, SUBPARAGRAPH
H OF THE AGREEMENT. Effective as of the date of this Amendment, clause (xii) of
Section 7, Paragraph 10, Subparagraph H of the Agreement is amended and restated
and a new clause (xiii) is added to such subparagraph each to read in their
entirety as follows:

         "(xii)   the purchase by any Obligor of an airplane to be used for the
                  Obligors in their businesses with a purchase price not to
                  exceed $6,000,000; and

         (xiii)   any other loans, advances or investments in an amount not to
                  exceed $5,000,000 in the aggregate for all Obligors at any one
                  time outstanding ."

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 11
<PAGE>   12

         2.33 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 10, SUBPARAGRAPH
I OF THE AGREEMENT. Effective as of the date of this Amendment, Section 7,
Paragraph 10, Subparagraph I, clauses (ii), (iii) and (v) of the Agreement is
amended and restated, and new clauses (vii), (viii) and (ix) are hereby added to
such Subparagraph to read in their entirety as follows:

                           "(ii) loans and advances to officers, directors and
                  employees of the Obligors or its Subsidiaries for travel,
                  entertainment and moving and other relocation expenses made in
                  direct furtherance and in the ordinary course of business of
                  the Obligor and its Subsidiaries; provided, however, the
                  aggregate principal amount of loans and advances made pursuant
                  to this clause (ii) shall not exceed $3,000,000 at any time
                  outstanding;"

                           "(iii) any other transaction with any employee,
                  officer or director of the Obligor or any of its Subsidiaries
                  pursuant to employee benefit or compensation arrangements
                  entered into in the ordinary course of business and approved
                  by the Board of Directors of the Obligor or the Board of
                  Directors of such Subsidiary; provided, however, the aggregate
                  principal amount of loans and advances made pursuant to this
                  clause (iii) shall not exceed $3,000,000 at any time
                  outstanding;"

                           "(v) licenses and other transfers of patents,
                  trademarks, trade names, copyrights, trade secrets, know-how
                  and other intellectual property between and among any two or
                  more of the Obligors and Subsidiaries of the Parent;"

                           "(vii) any other transaction entered into in the
                  ordinary course of business with any employee, officer or
                  director of Parent or any of its Subsidiaries pursuant to
                  drilling arrangements, exploration and production
                  arrangements, benefit plans, compensation or other similar
                  arrangements entered into in the ordinary course of business
                  and the leasing of aircraft by any senior officer of Parent to
                  any Obligor, all as more fully described in the Parent's
                  annual report on Form 10-K for the year ended December 31,
                  2000.

                           (viii) the charter from time to time by an employee
                  of the Parent, or any Subsidiary thereof, of any aircraft
                  owned or leased by the Parent or such subsidiary, without
                  regard to the terms of such charter;

                           (ix) the performance of drilling services on a
                  contract basis by Parent or any Subsidiary of the Parent for,
                  or the sales of drilling mud, drilling fluids or other related
                  goods or services to (A) Parent or any other Subsidiary of
                  Parent, or (B) any joint venture or other oil and gas
                  development activity incident to the oil and gas exploration
                  and development activity of any such Subsidiary, without
                  regard to any beneficial interest that an officer or employee
                  of Parent or any such Subsidiary may have in the exploration
                  or development venture for which the drilling services are
                  being performed and as long as such services also comply with
                  Section 7, Subparagraph 10(I) of this Agreement;"

         2.34 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 11 OF THE
AGREEMENT. Effective as of the date of execution of this Amendment, the
Availability threshold in Section 7, Paragraph 11 of the Agreement is amended
from $15,000,000 to $20,000,000."

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 12
<PAGE>   13

         2.35 AMENDMENT OF SECTION 7 OF THE AGREEMENT. Effective as of the date
of this Amendment, Section 7 of the Agreement is hereby amended by deleting
Paragraphs 19, 20 and 21 thereof.

         2.36 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 18, SUBPARAGRAPH
(h) OF THE AGREEMENT. Effective as of the date of this Amendment, Section 7,
Paragraph 18, Subparagraph (h), clause (i) of the Agreement is amended and
restated to read in its entirety as follows:

                           "(i) under any material provisions of any instrument
                  evidencing any Indebtedness For Borrowed Money or other
                  Indebtedness with an outstanding balance in excess of
                  $2,000,000 or of any agreement relating thereto in such manner
                  as to cause a Material Adverse Effect or"

         2.37 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 18, SUBPARAGRAPH
(l) OF THE AGREEMENT. Effective as of the date of execution of this Amendment,
the second sentence of Section 7, Paragraph 18, Subparagraph (l) of the
Agreement is hereby amended and restated to read in its entirety as follows:

                           "(l) The proceeds of the Acquisition Facility Loans
                  will be used by the Companies for the purpose of funding
                  Permitted Acquisitions. None of the proceeds of any Advance
                  will be used directly or indirectly for the purpose of
                  purchasing or carrying any "margin stock" within the meaning
                  of Regulation U (herein called "MARGIN STOCK") or for the
                  purpose of reducing or retiring any indebtedness which was
                  originally incurred to purchase or carry margin stock, or for
                  any other purpose which might constitute this transaction as a
                  "purpose credit" within the meaning of Regulation U."

         2.38 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 18, SUBPARAGRAPH
(n)(ii) OF THE AGREEMENT. Effective as of the date of execution of this
Amendment, Section 7, Paragraph 18, Subparagraphs (n)(ii)(A), (n)(ii)(D) and
(n)(ii)(E) are amended and restated to read in their entirety as follows:

                  "(A) Commercial General Liability insurance written on an
                  occurrence basis, including coverage for premises, operations,
                  products and completed operations, explosion, collapse and
                  underground, broad form commercial general liability
                  equivalent coverages with a minimum combined single limit for
                  bodily injury and property damage of $2,000,000 per occurrence
                  and $2,000,000 in the aggregate, with a self-insured retention
                  not greater than $1,000,000;"

                  "(D) umbrella (or excess form should umbrella coverage be
                  unavailable) liability coverage written on an occurrence basis
                  with a limit of liability of $40,000,000, and also to include
                  a "drop down" provision which will pick up any exhaustion of
                  limits under the primary coverages subject to a retention of
                  $100,000. Such insurance coverage shall provide substantially
                  identical coverages as are set forth in the form of the
                  insurance required in clauses (i), (ii)(A)/(B)/(C) and (iii);"

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 13
<PAGE>   14

                  "(E) All-Risk Physical Loss or Damage Property Insurance
                  (including water damage, Domestic transit coverage, collapse
                  coverage, coverage of fire, flood and earthquakes and rapid
                  means of transportation coverages on an agreed value basis)
                  with respect to all Rigs (on a "no-coinsurance" basis) in an
                  aggregate amount equal to or greater than $200,000,000 with a
                  deductible not greater than $100,000 per occurrence;"

         2.39 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 18, SUBPARAGRAPH
(n)(iii) OF THE AGREEMENT. Effective as of the date of the execution of this
Amendment, the first sentence of Section 7, Paragraph 18, Subparagraph (n)(iii)
is amended and restated to read in its entirety as follows:

                           "(iii) All policies except Workers' Compensation
                  shall insure the interests of the Agent and the Lenders (and
                  their respective employees, agents, attorneys, representatives
                  and officers) as additional insureds (each, an "ADDITIONAL
                  INSURED") and the policies required by subclause (ii)(E) of
                  this Paragraph 18(n) (in the nature of property damage
                  insurance) shall provide for the direct payment of all
                  proceeds to the Agent and the applicable Company or Companies,
                  as their interests may appear, which proceeds shall then be
                  deposited to the Agent or, if so directed in writing by the
                  Agent, to the Depository Account."

         2.40 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 18, SUBPARAGRAPH
(n)(vi) OF THE AGREEMENT. Effective as of the date of the execution of this
Amendment, Section 7, Paragraph 18, Subparagraph (n)(vi) is amended and restated
to read in its entirety as follows:

                           "(vi) Physical Damage Insurance proceeds paid to the
                  Agent and the applicable Company or Companies (with the
                  proceeds to be deposited in the Depository Account) shall be
                  applied to the repair or replacement of Collateral at such
                  times and in such amounts as the Companies may require, except
                  that after the occurrence of any Event of Default that is
                  continuing, such proceeds shall, in their entirety, be held as
                  cash Collateral and/or applied by the Agent in satisfaction of
                  the Revolving Loans as it determines in its sole discretion."

         2.41 AMENDMENT OF SECTION 8, PARAGRAPH 7 OF THE AGREEMENT. Effective as
of the date of execution of this Amendment, Section 8, Paragraph 7 of the
Agreement is amended to add a new Subparagraph 7(d) as follows:

          "(d) Upon the execution of an amendment to this Agreement increasing
          the Line of Credit to $100,000,000, the Companies shall pay to the
          Agent an additional one time Loan Facility Fee in the amount of Three
          Hundred Twenty-Five Thousand U.S. Dollars ($325,000.00) to be
          allocated among the Lenders based on Agent's sole discretion."


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 14
<PAGE>   15

         2.42 AMENDMENT AND RESTATEMENT OF SECTION 10, PARAGRAPH 1, SUBPARAGRAPH
(h) OF THE AGREEMENT. Effective as of the date of this Amendment, Section 10,
Paragraph 1, Subparagraph (h) of the Agreement is amended and restated to read
in its entirety as follows:

          "(h) the occurrence of any default or event of default (after giving
          effect to any applicable grace or cure periods) under any instrument
          or agreement evidencing (x) Subordinated Debt or (y) any other
          Indebtedness For Borrowed Money of any Company having a principal
          amount in excess of $2,000,000;"

         2.43 AMENDMENT AND RESTATEMENT OF SECTION 13, PARAGRAPH 9 OF THE
AGREEMENT. Effective as of the date of this Amendment, the first sentence of
Section 13, Paragraph 9 of the Agreement is amended and restated to read in its
entirety as follows:

         "CITBC shall have the right at any time to assign to one or more
         Eligible Assignees, all or a portion (but in an amount that is not less
         than $5,000,000) of its rights and obligations under this Agreement;
         provided that no such assignment shall be made to any Person that does
         not, prior to the execution of such Assignment Agreement, execute and
         deliver to the Agent and the Parent IRS Form W-8BEN, Form W-8ECI or
         successors forms, and is other exempt from IRS interest withholding
         obligations. Upon execution of an Assignment and Transfer Agreement,
         (i) the assignee thereunder shall be a party hereto and, to the extent
         that rights and obligations hereunder have been assigned to it pursuant
         to such assignment, have the rights and obligations of CITBC as the
         case may be hereunder and (ii) CITBC shall, to the extent that rights
         and obligations hereunder have been assigned by it pursuant to such
         assignment, relinquish its rights and be released from its obligations
         under this Agreement."

         2.44 AMENDMENT AND RESTATEMENT OF SECTION 14, PARAGRAPH 10. Effective
as of the date of execution of this Amendment, Section 14, Paragraph 10 of the
Agreement is hereby amended and restated to read in its entirety as follows:

         "Notwithstanding anything contained in this Agreement to the contrary,
         the Agent will not, without the prior written consent of all Lenders:
         (a) amend this Agreement to (i) increase the Line of Credit; (ii)
         reduce the interest rates; (iii) reduce or waive (A) any fees in which
         the Lenders share hereunder; or (B) the repayment of any Obligations
         due the Lenders; (iv) extend the maturity of the Obligations; or (v)
         alter or amend (1) this Paragraph 10 or (2) the definitions of Accounts
         Receivable Advance Percentage, Equipment Advance Percentage, or
         Required Lenders, or the Agent's criteria for determining compliance
         with such definitions of eligibility; or (b) release Collateral in bulk
         without a corresponding reduction in the Obligations to the Lenders,
         except that dispositions of Collateral by any of the Companies which
         are expressly permitted under this Agreement shall not require consent
         of the Agent or the other Lenders or any reduction in Lenders'
         Obligations. The Agent will not increase any Lender's commitment to
         provide financing hereunder without such Lender's prior written
         consent. Agent may, in its sole discretion (a) provided no Event of
         Default has occurred and is continuing, intentionally make Overadvances
         as long as any such Overadvance is not outstanding for more than ninety
         (90) consecutive days and after giving effect thereto the total
         outstanding Revolving Loans for each Company would not exceed one
         hundred and ten percent (110%) of the maximum amount available under
         Sections 3 and 4 of this Agreement, and (b) after and during the
         continuance of an Event of Default, intentionally make Overadvances for
         purposes of



FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 15

<PAGE>   16

         preserving or protecting the Collateral. Any Overadvance by Agent which
         is contrary to the limitations set forth in the immediately preceding
         sentence shall require the written consent of the Required Lenders. In
         all other respects the Agent is authorized to take such actions or fail
         to take such actions if the Agent, in its reasonable discretion, deems
         such to be advisable and in the best interest of the Lenders,
         including, but not limited to, the making of an overadvance or the
         termination of this Agreement upon the occurrence and during the
         continuance of an Event of Default unless it is specifically instructed
         to the contrary by the Required Lenders."

         2.45 AMENDMENT OF SCHEDULE 7(1). Effective as of the date of execution
of this Amendment, Schedule 7(1) of the Agreement is amended to add the Chief
Executive Office for the Patterson Companies and the Patterson Guarantors as
4510 Lamesa Highway, Snyder, Texas 79549.

         2.46 REVOLVING LOAN COMMITMENT. Effective as of the date of execution
of this Amendment, the Revolving Loan Commitment for each Lender will be the
amount set forth under each Lender's name on the signature page hereof.

         2.47 AMENDMENT AND RESTATEMENT OF EXHIBIT A TO THE AGREEMENT. Effective
as of the date of execution of this Amendment, Exhibit A to the Agreement is
amended and restated in its entirety as set forth on Exhibit A attached hereto.

                                   ARTICLE III
                  ASSUMPTION OF OBLIGATIONS AND GRANT OF LIENS

         3.01 ASSUMPTION OF OBLIGATIONS. Effective as of the date of this
Amendment, the Patterson Companies each hereby assumes and is jointly and
severally liable with the UTI Companies for all Obligations as of the date
hereof and all Obligations incurred thereafter (including, without limitation,
the indebtedness and obligations under the Existing Revolving Note, the
Agreement and the other Loan Documents). The UTI Companies shall continue to be
jointly and severally liable for all Obligations.

         3.02 GRANT OF LIEN. The Patterson Companies each hereby grants to Agent
for the benefit of the Lenders a security interest in all Collateral now or
hereafter owned by the Patterson Companies pursuant to the terms and provisions
of Section 6 of the Agreement.

         3.03 REPRESENTATIONS AND DUTIES UNDER THE AGREEMENT. The Patterson
Companies hereby (a) make all of the representations and warranties made by the
UTI Companies under the Agreement, and (b) agree to be bound by the terms and
provisions of the Agreement as a Company and Obligor thereunder to the same
extent and with the same force and effect as if the Patterson Companies had been
originally named as parties in such document.

         3.04 GRANT OF LIEN BY PATTERSON GUARANTORS. Effective as of the date of
this Amendment, the Patterson Guarantors (other than PPLP and PPTC) each agrees
to be bound by the terms and provisions of the Agreement as a Guarantor and
Obligor thereunder to the same extent and with the same force and effect as if
the Patterson Guarantors (other than PPLP and PPTC) had been originally named as
parties to such document. The Patterson Guarantors (other than PPLP and PPTC)
also each hereby grants to Agent for the benefit of the Lenders a security
interest in all Collateral now or hereafter owned by the Patterson Guarantors
pursuant to the terms of Section 6 of the Agreement.


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 16
<PAGE>   17

         3.05 NEGATIVE PLEDGE AGREEMENT. PPLP and PPTC agree that until
termination of the Agreement and satisfaction of all Obligations due under the
Agreement, PPLP and PPTC shall not mortgage, pledge, encumber or assign any of
their respective assets except for Permitted Liens.

         3.06 AUTHORIZED FILING. The Companies and the Guarantors (other than
PPLP and PPTC) authorize CITBC as Agent to file financing statements covering
the Collateral in an authenticated record without the Debtor's signature.

         3.07 STATES IN WHICH BUSINESS IS CONDUCTED. The Patterson Companies and
the Patterson Guarantors (other than PPLP and PPTC) hereby represent and warrant
that they are currently conducting their businesses in the States of Delaware,
Texas, Pennsylvania, California, Alabama, Colorado, Louisiana, Mississippi, New
Mexico, Oklahoma, Utah and Kansas.

                                   ARTICLE IV
                              CONDITIONS PRECEDENT

         4.01 CONDITIONS TO EFFECTIVENESS. The effectiveness of this Amendment
is subject to the satisfaction of the following conditions precedent in a manner
satisfactory to CITBC, unless specifically waived in writing by CITBC:

                  (a) CITBC shall have received each of the following, each in
form and substance satisfactory to Agent, in its sole discretion, and, where
applicable, each duly executed by each party thereto, other than Agent:

                           (i) This Amendment, duly executed by the Companies
         and the Consent, Ratification and Release executed by the UTI
         Guarantors;

                           (ii) A Revolving Loan Promissory Note in the stated
         principal amount of $100,000,000 in amendment, substitution and
         replacement of the Existing Revolving Note duly signed by the Companies
         (the "Revolving Note"); and

                           (iii) A Guaranty duly executed by the Patterson
         Guarantors; and

                           (iv) certified copies of the resolutions of the Board
         of Directors of each of the Companies and the Guarantors authorizing
         the execution, delivery and performance of the Revolving Loan
         Promissory Note, this Amendment and any and all other Loan Documents
         executed by any of the Companies or the Guarantors in connection
         therewith, along with a certificate of incumbency certified by the
         secretary of each of the Companies and the Guarantors with specimen
         signatures of the officers of the Companies and the Guarantors who are
         authorized to sign such documents, all in form and substance
         satisfactory to the Agent; and

                           (v) A Pledge Agreement duly signed by Parent,
         Patterson GP, Patterson LP, PUDC and Patterson GP2 pledging all of
         their respective ownership interests in Holding, the Patterson
         Companies and the Patterson Guarantors (other than Parent); and

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 17
<PAGE>   18

                           (vi) A copy of the signed payoff letter from
         Transamerica Business Credit with respect to the current financing
         facilities covering some or all of the Patterson Companies and
         Patterson Guarantors; and

                           (vii) Wire transfer advice confirming the full and
         complete payment of all indebtedness owing to Transamerica Business
         Credit in accordance with the payoff letter referenced in clause (vi)
         above;

                           (viii) Opinion from Fulbright & Jaworski L.L.P.
         opining in form and substance satisfactory to CITBC which shall cover
         such matters incident to the transactions contemplated by this
         Amendment and the other Loan Document as CITBC may reasonably require
         and the Companies and Guarantors hereby authorize and direct such
         counsel to deliver such opinions to CITBC; and

                           (ix) All other documents CITBC may reasonably request
         with respect to any matter relevant to this Amendment or the
         transactions contemplated hereby.

                  (b) The representations and warranties contained herein and in
the Agreement and the other documents executed in connection with the Agreement
(herein referred to as "Loan Documents"), as each is amended hereby, shall be
true and correct as of the date hereof, as if made on the date hereof.

                  (c) No Default or Event of Default shall have occurred and be
continuing, unless such Default or Event of Default has been otherwise
specifically waived in writing by CITBC.

                  (d) All corporate, partnership and limited liability company
proceedings taken in connection with the transactions contemplated by this
Amendment and all documents, instruments and other legal matters incident
thereto shall be satisfactory to CITBC.

                  (e) CITBC's receipt of the fee described in Section 2.41 of
this Amendment.

         4.02 CONDITIONS TO ELIGIBILITY. The Patterson Companies Accounts and
Equipment shall not be considered by Agent as Eligible Accounts Receivable or
Eligible Equipment under the Agreement until satisfaction of the following
conditions precedent in a manner satisfactory to CITBC, unless specifically
waived in writing by CITBC:

         (a) Any financing statements required to be filed in order to create,
in favor of CITBC, a first perfected security interest in the Collateral,
subject only to the Permitted Encumbrances, shall have been properly filed in
each office within ten (10) days after the date of this Amendment in each
jurisdiction required in order to create in favor of CITBC a perfected lien on
the Collateral. CITBC shall have received acknowledgment copies of all such
filings (or, in lieu thereof, CITBC shall have received other evidence
satisfactory to CITBC that all such filings have been made) and CITBC shall have
received evidence that all necessary filing fees and all taxes or other expenses
related to such filings have been paid in full.

         (b) Within ten (10) days from the date of this Amendment, CITBC shall
have received an Opinion from Fulbright & Jaworski L.L.P. opining in form and
substance satisfactory to CITBC which


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 18
<PAGE>   19

shall cover such matters incident to the transactions contemplated by this
Amendment and the other Loan Documents as CITBC may require in its sole
discretion and the Companies and Guarantors hereby authorize and direct such
counsel to deliver such opinion to CITBC.

         (c) Within ten (10) days from the date of this Amendment, CITBC shall
have received original signed UCC termination statements from Transamerica
Business Credit covering all financing statements filed by Transamerica, as
secured party, on the Patterson Companies and the Patterson Guarantors.

         (d) Within ten (10) days from the date of this Amendment, CITBC shall
have received updated Collateral Locations for the Companies and the Guarantors,
in the form previously provided in Schedule 7(1) of the Agreement.

         (e) Within 30 days from the date of this Amendment, CITBC shall have
received from Parent evidence satisfactory to the Agent that casualty insurance
policies of all Companies and Guarantors listing Agent as loss payee or
mortgagee, as the case may be, are in full force and effect, all as set forth in
Section 7, Paragraph 5 of the Agreement, in form and substance satisfactory to
CITBC.

         (f) Within 30 days from the date of this Amendment, CITBC shall have
received security agreement(s), in form and substance satisfactory to CITBC,
granting to the Lenders a first priority lien in the Trademarks and Patents of
the Patterson Companies and the Patterson Guarantors (other than PPLP and PPTC).

         (g) Within 90 days from the date of this Amendment, CITBC shall have
received desktop appraisals on each Patterson Company's Rigs, which appraisals
shall be by an appraiser acceptable to CITBC and shall indicate an aggregate
Orderly Liquidation Value of not less than $200,000,000 with respect to such
Rigs.

         (h) Within 90 days from the date of this Amendment, CITBC shall have
completed to the satisfaction of CITBC an examination and verification of the
Accounts, Inventory, Equipment, books and records of each Patterson Company and
Patterson Guarantor.

         (i) Within 120 days from the date of this Amendment, the Patterson
Companies and the Patterson Guarantors shall enter into tri-party blocked
account agreements with CITBC and the depository institutions of the Depository
Accounts, in form and substance acceptable to CITBC and as required by Section
3, Paragraph 4 of the Agreement.

                                    ARTICLE V
                  RATIFICATIONS, REPRESENTATIONS AND WARRANTIES

         5.01 RATIFICATIONS. The terms and provisions set forth in this
Amendment shall modify and supersede all inconsistent terms and provisions set
forth in the Agreement and the other Loan Documents, and, except as expressly
modified and superseded by this Amendment, the terms and provisions of the
Agreement and the other Loan Documents are ratified and confirmed and shall
continue in full force and effect. The Companies and CITBC agree that the
Agreement and the other Loan Documents, as amended hereby, shall continue to be
legal, valid, binding and enforceable in accordance with their respective terms.

FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 19
<PAGE>   20

         5.02 REPRESENTATIONS AND WARRANTIES. The Companies hereby represent and
warrant to CITBC that (a) the execution, delivery and performance of this
Amendment and any and all other Loan Documents executed and/or delivered in
connection herewith have been authorized by all requisite corporate, limited
partnership or limited liability company action (as applicable) on the part of
the Companies and will not violate the Articles (or Certificates) of
Incorporation or Bylaws of the Companies that are corporations or the limited
partnership agreements or certificates of limited partnership of the Companies
that are limited partnerships or regulations of limited liability company
agreements of the Companies that are limited liability companies; (b) each of
the Company's Board of Directors (or the general partner of the applicable
limited partnership) or the members or the Board of Managers of the applicable
limited liability company has authorized the execution, delivery and performance
of this Amendment and any and all other Loan Documents executed and/or delivered
in connection herewith; (c) the representations and warranties contained in the
Agreement, as amended hereby, and any other Loan Document are true and correct
on and as of the date hereof and on and as of the date of execution hereof as
though made on and as of each such date; (d) no Default or Event of Default
under the Agreement, as amended hereby, has occurred and is continuing, unless
such Default or Event of Default has been specifically waived in writing by
CITBC; (e) the Companies are in full compliance with all covenants and
agreements contained in the Agreement and the other Loan Documents, as amended
hereby; and (f) the Companies have not amended their Articles (or Certificates)
of Incorporation or their Bylaws or similar organizational documents since the
date of the Agreement, except as otherwise disclosed to Agent.

                                   ARTICLE VI
                            MISCELLANEOUS PROVISIONS

         6.01 SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations
and warranties made in the Agreement or any other Loan Document, including,
without limitation, any document furnished in connection with this Amendment,
shall survive the execution and delivery of this Amendment and the other Loan
Documents, and no investigation by CITBC or any closing shall affect the
representations and warranties or the right of CITBC to rely upon them.

         6.02 REFERENCE TO AGREEMENT. Each of the Agreement and the other Loan
Documents, and any and all other Loan Documents, documents or instruments now or
hereafter executed and delivered pursuant to the terms hereof or pursuant to the
terms of the Agreement, as amended hereby, are hereby amended so that any
reference in the Agreement and such other Loan Documents to the Agreement shall
mean a reference to the Agreement, as amended hereby.

         6.03 EXPENSES OF CITBC. As provided in the Agreement, the Companies
agree to pay on demand all reasonable costs and expenses incurred by CITBC in
connection with the preparation, negotiation, and execution of this Amendment
and the other Loan Documents executed pursuant hereto and any and all
amendments, modifications, and supplements thereto, including, without
limitation, the reasonable costs and fees of CITBC's legal counsel, and all
reasonable costs and expenses incurred by CITBC in connection with the
enforcement or preservation of any rights under the Agreement, as amended
hereby, or any other Loan Documents, including, without limitation, the
reasonable costs and fees of CITBC's legal counsel.



FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 20
<PAGE>   21

         6.04 SEVERABILITY. Any provision of this Amendment held by a court of
competent jurisdiction to be invalid or unenforceable shall not impair or
invalidate the remainder of this Amendment and the effect thereof shall be
confined to the provision so held to be invalid or unenforceable.

         6.05 SUCCESSORS AND ASSIGNS. The Agreement, as amended hereby, is
binding upon and shall inure to the benefit of CITBC, the other Lenders and the
Companies and their respective successors and assigns, except that the Companies
may not assign or transfer any of their rights or obligations hereunder without
the prior written consent of CITBC.

         6.06 COUNTERPARTS. This Amendment may be executed in one or more
counterparts, each of which when so executed shall be deemed to be an original,
but all of which when taken together shall constitute one and the same
instrument.

         6.07 EFFECT OF WAIVER. No consent or waiver, express or implied, by
CITBC to or for any breach of or deviation from any covenant or condition by the
Companies shall be deemed a consent to or waiver of any other breach of the same
or any other covenant, condition or duty.

         6.08 HEADINGS. The headings, captions, and arrangements used in this
Amendment are for convenience only and shall not affect the interpretation of
this Amendment.

         6.09 APPLICABLE LAW. THIS AMENDMENT AND ALL OTHER LOAN DOCUMENTS
EXECUTED PURSUANT HERETO SHALL BE DEEMED TO HAVE BEEN MADE AND TO BE PERFORMABLE
IN AND SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE
STATE OF NEW YORK.

         6.10 FINAL AGREEMENT. THE AGREEMENT AND THE OTHER LOAN DOCUMENTS, EACH
AS AMENDED HEREBY, REPRESENT THE ENTIRE EXPRESSION OF THE PARTIES WITH RESPECT
TO THE SUBJECT MATTER HEREOF ON THE DATE THIS AMENDMENT IS EXECUTED. THE
AGREEMENT AND THE OTHER LOAN DOCUMENTS, AS AMENDED HEREBY, MAY NOT BE
CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS
OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES. NO
MODIFICATION, RESCISSION, WAIVER, RELEASE OR AMENDMENT OF ANY PROVISION OF THIS
AMENDMENT SHALL BE MADE, EXCEPT BY A WRITTEN AGREEMENT SIGNED BY THE COMPANIES
AND CITBC.

         6.11 RELEASE. THE COMPANIES HEREBY ACKNOWLEDGE THAT THEY HAVE NO
DEFENSE, COUNTERCLAIM, OFFSET, CROSS-COMPLAINT, CLAIM OR DEMAND OF ANY KIND OR
NATURE WHATSOEVER THAT CAN BE ASSERTED TO REDUCE OR ELIMINATE ALL OR ANY PART OF
ITS LIABILITY TO REPAY THE "OBLIGATIONS" OR TO SEEK AFFIRMATIVE RELIEF OR
DAMAGES OF ANY KIND OR NATURE FROM CITBC. THE COMPANIES HEREBY VOLUNTARILY AND
KNOWINGLY RELEASE AND FOREVER DISCHARGE CITBC, THE OTHER LENDERS, AND THEIR
RESPECTIVE PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS, FROM ALL
POSSIBLE CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES,
AND LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN, ANTICIPATED OR


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- Page 21
<PAGE>   22

UNANTICIPATED, SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR CONDITIONAL, AT
LAW OR IN EQUITY, ORIGINATING IN WHOLE OR IN PART ON OR BEFORE THE DATE THIS
AMENDMENT IS EXECUTED, WHICH THE COMPANIES MAY NOW OR HEREAFTER HAVE AGAINST
CITBC, THE OTHER LENDERS, AND THEIR RESPECTIVE PREDECESSORS, AGENTS, EMPLOYEES,
SUCCESSORS AND ASSIGNS, IF ANY, AND IRRESPECTIVE OF WHETHER ANY SUCH CLAIMS
ARISE OUT OF CONTRACT, TORT, VIOLATION OF LAW OR REGULATIONS, OR OTHERWISE, AND
ARISING FROM ANY "LOANS", INCLUDING, WITHOUT LIMITATION, ANY CONTRACTING FOR,
CHARGING, TAKING, RESERVING, COLLECTING OR RECEIVING INTEREST IN EXCESS OF THE
HIGHEST LAWFUL RATE APPLICABLE, THE EXERCISE OF ANY RIGHTS AND REMEDIES UNDER
THE AGREEMENT OR OTHER LOAN DOCUMENTS, AND NEGOTIATION FOR AND EXECUTION OF THIS
AMENDMENT.


              [The Remainder of this Page Intentionally Left Blank]



FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT- 22
<PAGE>   23





                  IN WITNESS WHEREOF, this Amendment has been executed and is
effective as of the date first above-written.


<Table>
<S>                                                                    <C>
COMPANIES:

UTI DRILLING, L.P.                                                     PATTERSON-UTI DRILLING COMPANY WEST LP, LLLP
UTI MANAGEMENT SERVICES, L.P.
                                                                       By:  Patterson (GP2) LLC, its general partner
By: Utico Hard Rock Boring, Inc., the sole general partner
of UTI Drilling, L.P. and UTI Management Services, L.P.                         By:
                                                                                   -----------------------------------
                                                                                Name:
                                                                                     ---------------------------------
         By:                                                                    Title:
              ----------------------------------------------                          --------------------------------
         Name:  Jonathan D. Nelson
         Title:  Vice President                                        LONE STAR MUD LP, LLLP

NORTON DRILLING, L.P.                                                  By:  Patterson (GP) LLC, its general partner

By:  Norton GP, L.L.C., its sole general partner                                By:
      By:  Norton Drilling Services, Inc., as Sole Member                          -----------------------------------
      of Norton GP, L.L.C.                                                      Name:
                                                                                     ---------------------------------
         By:                                                                    Title:
              ----------------------------------------------                          --------------------------------
         Name:
                 -------------------------------------------           AMBAR DRILLING FLUIDS LP, LLLP
         Title:
                 -------------------------------------------           By:  Patterson (GP) LLC, its general partner

UNIVERSAL WELL SERVICES, INC.                                                   By:
SUITS DRILLING COMPANY                                                             -----------------------------------
                                                                                Name:
                                                                                     ---------------------------------
         By:                                                                    Title:
              ----------------------------------------------                          --------------------------------
         Name:  Jonathan D. Nelson
         Title: Vice President of each of the foregoing
                 Companies

PATTERSON-UTI DRILLING COMPANY LP, LLLP

By:  Patterson (GP) LLC, its general partner

         By:
              ----------------------------------------------
         Name:
              ----------------------------------------------
         Title:
                 -------------------------------------------

PATTERSON-UTI DRILLING COMPANY SOUTH LP, LLLP
By:  Patterson (GP2) LLC., its general partner

         By:
              ----------------------------------------------
         Name:
              ----------------------------------------------
         Title:
                 -------------------------------------------
</Table>


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   24

<Table>
<S>                                              <C>

PATTERSON GUARANTORS:                            LENDERS:


PATTERSON-UTI ENERGY, INC.                       THE CIT GROUP/BUSINESS CREDIT,INC.
                                                 as Agent and Lender
By:
   ------------------------------------------
Name:                                            By:
     ----------------------------------------       --------------------------------
Title:                                           Name:
      ---------------------------------------         ------------------------------
                                                 Title:
                                                       -----------------------------

PATTERSON (LP) LLC                               Revolving Loan Commitment:  $30,000,000.00

By:
   ------------------------------------------
Name:                                            FOOTHILL CAPITAL CORPORATION
     ----------------------------------------
Title:                                           as Documentation Agent and Lender
      ---------------------------------------

                                                 By:
                                                    --------------------------------
PATTERSON (GP) LLC                               Name:
                                                      ------------------------------
                                                 Title:
By:                                                    -----------------------------
   ------------------------------------------
Name:                                            Revolving Loan Commitment:  $35,000,000.00
     ----------------------------------------
Title:
      ---------------------------------------
                                                 THE CIT GROUP/EQUIPMENT FINANCING, INC.
PATTERSON (GP2) LLC
                                                 By:
                                                    --------------------------------
 By:                                             Name:
    -----------------------------------------         ------------------------------
 Name:                                           Title:
      ---------------------------------------          -----------------------------
 Title:
       --------------------------------------
                                                 Revolving Loan Commitment:  $10,000,000.00

 PATTERSON PETROLEUM LP, LLLP
                                                 FLEET CAPITAL CORPORATION
 By:  Patterson (GP) LLC, its general partner

          By:                                    By:
             --------------------------------       --------------------------------
          Name:                                  Name:
               ------------------------------         ------------------------------
          Title:                                 Title:
                -----------------------------          -----------------------------

 PATTERSON PETROLEUM TRADING COMPANY LP, LLLP    Revolving Loan Commitment:  $25,000,000.00

 By: Patterson (GP) LLC, its general partner

          By:
             --------------------------------
          Name:
               ------------------------------
          Title:
                -----------------------------
</Table>






FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT



<PAGE>   25




                        CONSENT, RATIFICATION AND RELEASE

         The undersigned each hereby consents to the terms of the within and
foregoing Amendment, confirms and ratifies the terms of that certain Guaranty
Agreement dated November 22, 1999 executed (or assumed) by the undersigned for
the benefit of Agent and the other Lenders (the "Guaranty Agreement"), and
acknowledges that the Guaranty Agreement is in full force and effect and
ratifies the same, that the undersigned each has no defense, counterclaim,
set-off or any other claim to diminish the undersigned's liability under such
document, that the undersigned's consent is not required to the effectiveness of
the within and foregoing Amendment, and that no consent by the undersigned is
required for the effectiveness of any future amendment, modification,
forbearance or other action with respect to the Obligations, the Collateral, or
any of the other Loan Agreements. THE UNDERSIGNED EACH HEREBY VOLUNTARILY AND
KNOWINGLY RELEASES AND FOREVER DISCHARGES AGENT AND EACH LENDER, ITS
PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS, FROM ALL POSSIBLE
CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES, AND
LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN, ANTICIPATED OR UNANTICIPATED,
SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR CONDITIONAL, AT LAW OR IN
EQUITY, ORIGINATING IN WHOLE OR IN PART ON OR BEFORE THE DATE THIS AMENDMENT IS
EXECUTED, WHICH THE UNDERSIGNED MAY NOW OR HEREAFTER HAVE AGAINST AGENT AND EACH
LENDER, ITS PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS, IF ANY, AND
IRRESPECTIVE OF WHETHER ANY SUCH CLAIMS ARISE OUT OF CONTRACT, TORT, VIOLATION
OF LAW OR REGULATIONS, OR OTHERWISE, AND ARISING FROM ANY "LOANS", INCLUDING,
WITHOUT LIMITATION, ANY CONTRACTING FOR, CHARGING, TAKING, RESERVING, COLLECTING
OR RECEIVING INTEREST IN EXCESS OF THE HIGHEST LAWFUL RATE APPLICABLE, THE
EXERCISE OF ANY RIGHTS AND REMEDIES UNDER THE LOAN AGREEMENT OR OTHER
AGREEMENTS, AND NEGOTIATION FOR AND EXECUTION OF THIS AMENDMENT.

GUARANTORS:

UTI DRILLING CANADA, INC.
UTICO HARD ROCK BORING, INC.
NORTON DRILLING SERVICES, INC.
NORTON DRILLING COMPANY
         MEXICO, INC.
INTERNATIONAL PETROLEUM
          SERVICES COMPANY
UTICO, INC.


By:
   -------------------------------------
Jonathan D. Nelson, Vice President
signing as such on behalf of each of the
foregoing Obligors


FIFTH AMENDMENT TO LOAN & SECURITY AGREEMENT