<PAGE>

                                                                    EXHIBIT 99.3

                      SECOND AMENDMENT TO CREDIT AGREEMENT

     THIS SECOND AMENDMENT TO CREDIT AGREEMENT (this "AMENDMENT") is entered
into as of June 1, 2001 (the "EFFECTIVE DATE") among NABORS INDUSTRIES, INC., a
Delaware corporation (the "COMPANY"), NABORS ALASKA DRILLING, INC. ("ALASKA
DRILLING"), an Alaska corporation and a Wholly-Owned Subsidiary of the Company,
NABORS DRILLING USA, LP ("DRILLING USA LP"), a Delaware limited partnership
(successor to Nabors Drilling USA, Inc. ("DRILLING USA INC"), a Delaware
corporation, by reason of conversion) and a Wholly-Owned Subsidiary of the
Company, NABORS OFFSHORE CORPORATION ("NOC"), a Delaware corporation, and a
Wholly-Owned Subsidiary of the Company (successor by merger to Sundowner
Offshore Services, Inc. and Nabors Offshore Drilling, Inc.), and NABORS
INTERNATIONAL, INC. ("INTERNATIONAL," and together with Alaska Drilling,
Drilling USA LP, and NOC, the "SUBSIDIARY BORROWERS"), the Subsidiary Guarantors
named on the signature pages hereof, BANK OF AMERICA, N.A., formerly known as
BANK OF AMERICA NATIONAL TRUST AND SAVINGS ASSOCIATION, as Administrative Agent
(the "ADMINISTRATIVE AGENT") for the Banks under the Credit Agreement (defined
below) and the Banks (as defined in the Credit Agreement) a party hereto.

     Reference is made to that certain Credit Agreement dated as of September 5,
1997 (as amended, the "CREDIT AGREEMENT") among the Company, each Subsidiary
Borrower, the Administrative Agent, Wells Fargo Bank (Texas), National
Association, as Documentation Agent, and the Banks party thereto.

                                    RECITALS

     A. The Company is proposing to restructure its Wholly-Owned Subsidiary,
Drilling USA Inc., from a Delaware corporation into a Delaware limited
partnership.

     B. The restructuring is proposed to be conducted pursuant to Section 266 of
the Delaware General Corporation Law and Section 17-217 of the Delaware Revised
Uniform Limited Partnership Act.

     C. To facilitate the Drilling USA Inc. restructuring, the Company has
incorporated two new Wholly-Owned Subsidiaries: (i) one in Delaware named NDUSA
Holdings Corp. ("GP Co") as the sole general partner of the proposed limited
partnership, and (ii) another in Nevada named Yellow Deer Investments Corp. ("LP
Co") as the sole limited partner of the proposed limited partnership. The
Company then: (i) contributed 1% of the common stock of Drilling USA Inc. to GP
Co in exchange for 100 shares of GP Co common stock, which constitutes all of
the issued and outstanding common stock of GP Co; and (ii) contributed 99% of
the common stock of Drilling USA Inc. to LP Co in exchange for 100 shares of LP
Co common stock, which constitutes all of the issued and outstanding common
stock of LP Co. GP Co and LP Co collectively own 100% of Drilling USA Inc.

     D. Drilling USA Inc. will then convert from corporate form to limited
partnership form, and continue as Drilling USA LP.

     E. The Company has requested the Banks consent to the foregoing
restructure, to which the undersigned Banks are willing to consent subject to
the terms and conditions of this Amendment.

     Accordingly, for adequate and sufficient consideration, the parties hereto
agree as follows:

     PARAGRAPH 1 TERMS AND REFERENCES.  Unless otherwise stated in this
amendment (a) terms defined in the Credit Agreement have the same meanings when
used in this amendment, and (b) references to "SECTIONS," "SCHEDULES," and
"EXHIBITS" are to the Credit Agreement's sections, schedules, and exhibits.

     PARAGRAPH 2 CONSENT.  Subject to the terms and conditions contained herein,
the undersigned Banks hereby consent to the restructuring of Nabors Drilling
USA, Inc., a Delaware

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corporation, to Nabors Drilling USA, LP, a Delaware limited partnership,
pursuant to, and in accordance with, Section 266 of the Delaware General
Corporation Law and Section 17-217 of the Delaware Revised Uniform Limited
Partnership Act. Accordingly: (i) each reference within the Loan Documents to
Nabors Drilling USA, Inc. shall mean and refer to Nabors Drilling USA LP, as
successor to Nabors Drilling USA, Inc., by reason of conversion; and (ii) the
term "Borrowers," "Subsidiary Borrowers," and "Subsidiary Guarantors" shall be
deemed to cover and include Nabors Drilling USA, LP in such capacity.

     PARAGRAPH 3 AMENDMENT.  The Credit Agreement is amended as follows:

          A. Section 1.01 is amended by amending the terms "Organization
     Documents" and "Wholly-Owned Subsidiary" to read as follows:

             "Organization Documents" means, with respect to any Person, its
        articles or certificate of incorporation, bylaws, partnership
        agreements, organizational documents, limited liability company
        agreements, trust agreement, resolutions or agreements among the
        applicable governing board or body, and any other document as may govern
        such Person's formation, organization, and management.

             "Wholly-Owned Subsidiary" means any Subsidiary with respect to
        which 100% of the issued and outstanding shares of voting stock (other
        than directors' qualifying shares required by law) or partnership,
        membership or other equity interests (in the case of Persons other than
        corporations) of such Person, in each case, at the time as of which any
        determination is being made, is owned, beneficially of record, by the
        Company, or by one or more of the other Wholly-Owned Subsidiaries, or
        both.

          B. The title to Section 6.01 is amended to delete the word "Corporate"
     from the title. Additionally, Sections 6.01(a) and (b) are amended in their
     entirely to read as follows:

             (a) the Company, each Subsidiary Borrower and each Subsidiary
        Guarantor is duly organized or formed and validly existing under the
        Requirements of Laws of the jurisdiction of its organization or
        formation;

             (b) the Company, each Subsidiary Borrower and each Subsidiary
        Guarantor is in good standing under the Requirements of Laws of the
        jurisdiction of its organization or formation;

          C. Section 6.01(e) is amended in its entirety to read as follows:

             (e) the Company and each of its Subsidiaries is duly qualified and
        (where required) licensed to transact business, and is in good standing,
        under the Requirements of Laws of each jurisdiction where its ownership,
        lease or operation of property or the conduct of its business requires
        such qualification, license or good standing; and

          D. The title to Section 6.02 is amended to delete the word "Corporate"
     from the title. Additionally, the first paragraph to Section 6.02 is
     amended by adding the phrase "or other organizational" after the word
     "corporate."

          E. The title to Section 7.04 is amended by replacing the word
     "Corporate" with the word "Organizational." Additionally, Section 7.04(a)
     is amended in its entirety to read as follows:

             (a) The Company shall: (i) preserve and maintain in full force and
        effect its corporate existence under the laws of the State of Delaware;
        (ii) cause each Subsidiary Borrower and each Subsidiary Guarantor to,
        preserve and maintain in full force and effect its corporate or
        partnership existence under the laws of its state or jurisdiction of
        organization.

          F. Section 7.04(b) is amended by adding the phrase "which is a
     corporation" after the term "Subsidiary Guarantor."

          G. Section 7.13 is amended by replacing the word "incorporated" with
     "organized or formed."

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          H. Section 8.01(a)(IX) is amended by replacing the word "corporations"
     each time it appears with the term "Persons."

          I. Section 8.03(a) is amended in its entirety to read as follows:

             (a) any Subsidiary may merge, combine, consolidate, or amalgamate
        with the Company, provided that the Company shall be the continuing or
        surviving corporation, or with any one or more Subsidiaries, provided
        that if any transaction shall be between a Subsidiary and a Wholly-
        Owned Subsidiary, the Wholly-Owned Subsidiary shall be the continuing or
        surviving entity and, if any transaction shall be between a Borrower and
        a non-Borrower, the Borrower shall be the continuing or surviving
        corporation;

          J. Section 8.03 is supplemented by adding a new subparagraph (d) which
     shall read in its entirety as follows:

             (d) Any Subsidiary may adopt a plan of conversion and convert to a
        corporation of a foreign jurisdiction or to a limited liability company,
        limited partnership, limited liability partnership or other entity of
        the same or a foreign jurisdiction; provided that the jurisdiction of
        the surviving entity shall be a State of the United States; and provided
        further that, if such Subsidiary is a Subsidiary Guarantor, the Company
        shall cause the Administrative Agent to be provided with an opinion of
        counsel in the form of Exhibit D-2 coincident with such adoption;

          K. The first sentence of Section 8.08 is amended in its entirety to
     read as follows:

             The Company shall not, and shall not permit any Subsidiary to, make
        any changes in its capital structure (including, without limitation, in
        the terms of its outstanding capital stock or partnership, membership or
        other equity interests) or amend its Organization Documents in a manner
        that will adversely affect performance of the obligations under the Loan
        Documents.

          L. References within the Credit Agreement to: (i) "corporate affairs"
     or "corporate purposes" shall be deemed to refer to the organizational
     affairs or purposes consistent with the form of organization of the Person
     to whom they refer; and (ii) "corporate records" shall be deemed to refer
     to the Organization Documents of the Person to whom they refer.

     PARAGRAPH 4 EFFECTIVE DATE.  This Amendment shall be effective as of the
Effective Date, provided that: (a) the representations and warranties in this
document are true and correct; and (b) the Administrative Agent shall have
received: (i) counterparts of this Amendment, executed by the Company, the
Subsidiary Borrowers, the Subsidiary Guarantors, and the Majority Banks, (ii)
Subsidiary Guaranties executed in favor of Administrative Agent from each of
Drilling USA LP, GP Co. and LP Co.

     PARAGRAPH 5 ACKNOWLEDGMENT AND RATIFICATION.  As a material inducement to
the Administrative Agent and the Banks to execute and deliver this Amendment:
(a) Drilling USA LP ratifies and confirms that all Obligations of Drilling USA
Inc. under the Loan Documents -- whether as a Subsidiary Borrower, Subsidiary
Guarantor or otherwise -- have been assumed by, and continue in full force and
effect as the Obligations of Drilling USA LP as if it had executed the Loan
Documents to which Drilling USA Inc. was originally a party, and Drilling USA LP
agrees to perform such acts and duly authorize, execute, acknowledge, and
deliver such additional agreements, documents, instruments, and certificates as
Administrative Agent may reasonably deem necessary or appropriate in order to
preserve and protect those Obligations, and (b) the Company, the Subsidiary
Borrowers, and the Subsidiary Guarantors each (i) consent to the agreements in
this Amendment and (ii) agree and acknowledge that the execution, delivery, and
performance of this Amendment shall in no way release, diminish, impair, reduce,
or otherwise affect the respective obligations of the Company, the Subsidiary
Borrowers, or the Subsidiary Guarantors under the Loan Documents to which it is
a party, which Loan Documents shall remain in full force and effect, and all
guaranties and rights thereunder are hereby ratified and confirmed.

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     PARAGRAPH 6 REPRESENTATIONS.  As a material inducement to the Banks to
execute and deliver this Amendment, the Company, the Subsidiary Borrowers, and
the Subsidiary Guarantors each represent and warrant to the Banks (with the
knowledge and intent that the Banks are relying upon the same in entering into
this Amendment) that as of the Effective Date of this Amendment and as of the
date of execution of this Amendment, (a) all representations and warranties in
the Loan Documents are true and correct in all material respects as though made
on the date hereof, except to the extent that any of them speak to a different
specific date, (b) each Material Subsidiary is listed on the Exhibit A attached
hereto, and (c) no Event of Default or Default exists.

     PARAGRAPH 7 COVENANTS.  Within ten days (10) following the Effective Date,
the Company shall furnish to the Administrative Agent the following: (i)
Subsidiary Guaranties executed in favor of Administrative Agent from each of the
Material Subsidiaries which have not previously delivered a Subsidiary
Guarantee; (ii) such certificates of resolutions or other action, incumbency
certificates and/or other certificates of Responsible Officers of each of the
Company, the Subsidiary Borrowers, the Subsidiary Guarantors as the
Administrative Agent may require to establish the identities of and verify the
authority and capacity of each Responsible Officer thereof authorized to act as
a Responsible Officer in connection with this Amendment and the other Loan
Documents; (iii) opinions of legal counsel to each of the Company, Subsidiary
Borrowers and Subsidiary Guarantors regarding: (1) execution, delivery,
authorization and enforceability of this Amendment, (2) formation and existence
of Drilling USA LP as a Delaware limited partnership, and (3) as may otherwise
be required under Section 7.13 of the Credit Agreement; and (iv) such other
documents, instruments or agreements reasonably required by Administrative
Agent. Additionally, the Company shall -- in a timely manner, in the ordinary
course of business -- pay all costs, fees, and expenses paid or incurred by the
Administrative Agent incident to this Amendment, including, without limitation,
the fees and expenses of the Administrative Agent's counsel in connection with
the negotiation, preparation, delivery, and execution of this Amendment and any
related documents.

     PARAGRAPH 8 MISCELLANEOUS.  This Amendment is a "LOAN DOCUMENT" referred to
in the Credit Agreement. All references in the Loan Documents to the "CREDIT
AGREEMENT" refer to the Credit Agreement as amended by this Amendment. The
provisions relating to Loan Documents in Article XI of the Credit Agreement are
incorporated in this Amendment by reference. Unless stated otherwise (a) the
singular number includes the plural and vice versa and words of any gender
include each other gender, in each case, as appropriate, (b) headings and
captions may not be construed in interpreting provisions, (c) this Amendment
must be construed, and its performance enforced, under New York law, (d) if any
part of this Amendment is for any reason found to be unenforceable, all other
portions of it nevertheless remain enforceable, and (e) this Amendment may be
executed in any number of counterparts with the same effect as if all
signatories had signed the same document, and all of those counterparts must be
construed together to constitute the same document.

     PARAGRAPH 9 ENTIRE AGREEMENT.  THIS AMENDMENT REPRESENTS THE FINAL
AGREEMENT BETWEEN THE PARTIES ABOUT THE SUBJECT MATTER OF THIS AMENDMENT AND 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.

     PARAGRAPH 10 PARTIES.  This Amendment binds and inures to the benefit of
the Company, the Subsidiary Borrowers, the Subsidiary Guarantors, the
Administrative Agent, the Banks, and their respective successors and assigns.

     PARAGRAPH 11 LIMITATIONS.  The consent set forth herein is limited
precisely as written and shall not be deemed to (a) be a consent to, or waiver
or modification of, any other term or condition of the Credit Agreement or any
other Loan Document, or (b) prejudice any right or rights which the
Administrative Agent and the Banks may now have or may have in the future or in
connection with the

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Credit Agreement, the Loan Documents, or any other documents referred to
therein. Except as expressly modified hereby or by express written amendments
thereof, the terms and provisions of the Credit Agreement, the Notes, and the
other Loan Documents and all other documents and instruments executed in
connection with any of the foregoing are and shall remain in full force and
effect.

     The parties hereto have executed this Amendment in multiple counterparts to
be effective as of the Effective Date.

                     REMAINDER OF PAGE INTENTIONALLY BLANK.
                          SIGNATURE PAGE(s) TO FOLLOW.

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COMPANY:

NABORS INDUSTRIES, INC.

By /s/ BRUCE P. KOCH
   -----------------------------------
   Bruce P. Koch,
   Vice President-Finance

NABORS DRILLING USA, LP, as a
Subsidiary Borrower and as a
Subsidiary Guarantor (successor to
Nabors Drilling USA, Inc. by reason of
conversion)

By: NDUSA Holdings Corp., its sole
General Partner

By /s/ BRUCE P. KOCH
   -----------------------------------
   Bruce P. Koch,
   Attorney-in-Fact

POOL COMPANY OF TEXAS, LTD., as a
Subsidiary Guarantor

By: Pool Well Services Co. its General
Partner

By /s/ BRUCE P. KOCH
   -----------------------------------
   Bruce P. Koch,
   Attorney-in-Fact

NABORS HOLDING COMPANY, as a
Subsidiary Guarantor

NABORS ALASKA DRILLING, INC. as a
Subsidiary Borrower and as a
Subsidiary Guarantor

                                        6
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PCNV, INC., as a Subsidiary Guarantor

POOL WELL SERVICES CO., as a
Subsidiary Guarantor

NABORS INTERNATIONAL, INC., as a
Subsidiary Borrower and as a
Subsidiary Guarantor

POOL COMPANY, as a Subsidiary
Guarantor NABORS OFFSHORE CORPORATION,
as a Subsidiary Borrower and as a
Subsidiary Guarantor

By /s/ BRUCE P. KOCH
   -----------------------------------
   Bruce P. Koch,
   Attorney-in-Fact

BANK OF AMERICA, N.A. formerly known
as BANK OF AMERICA NATIONAL TRUST AND
SAVINGS ASSOCIATION, as Administrative
Agent and as a Bank

By /s/ CLAIRE M. LIU
    ----------------------------------
   Name: Claire M. Liu
   Title:  Managing Director

THE BANK OF TOKYO-MITSUBISHI, LTD.,
HOUSTON AGENCY, as a Bank

By /s/ K. GLASSCOCK
   -----------------------------------
   Name: K. Glasscock
   Title:  VP & Manager

THE DAI-ICHI KANGYO BANK, LIMITED, as
a Bank

By /s/ PERZEMEK T. BLAZIAK
   -----------------------------------
   Name: Perzemek T. Blaziak
   Title:  Account Officer
                                        7
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THE FUJI BANK AND TRUST COMPANY, as a
Bank

By /s/
   -----------------------------------
   Name:
   Title:

WELLS FARGO BANK TEXAS, N.A. formerly
known as WELLS FARGO BANK (TEXAS),
NATIONAL ASSOCIATION, as Documentation
Agent and as a Bank

By /s/ BRET C. WEST
   -----------------------------------
   Name: Bret C. West
   Title:  Vice President

THE BANK OF NOVA SCOTIA

By /s/ F.C.H. ASHBY
   -----------------------------------
   Name: F.C.H. Ashby
   Title:  Senior Manager Loan
   Operations

BANK ONE, NA (main office Chicago)
formerly known as BANK ONE TEXAS, as a
Bank

By /s/ DIANNE L. RUSSELL
   -----------------------------------
   Name: Dianne L. Russell
   Title:  Vice President

                                        8
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EXPORT DEVELOPMENT CORPORATION, as a
Bank

By /s/
   -----------------------------------
   Name:
   Title:

ROYAL BANK OF CANADA, as a Bank

By /s/
   -----------------------------------
   Name:
   Title:

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                                                                       EXHIBIT A

                             MATERIAL SUBSIDIARIES

Nabors Alaska Drilling, Inc.

Nabors Corporate Services, Inc.

Nabors Drilling USA, LP (successor to Nabors Drilling USA, Inc. by reason of
conversion)

Nabors International, Inc.

Nabors Offshore Corporation (successor by merger to Sundowner Offshore Services,
Inc. and Nabors Offshore Drilling, Inc.)

Nabors Holding Company

NDUSA Holdings Corp.

PCNV, Inc.

Pool Well Services Co.

Pool Company

Pool Company of Texas, Ltd.

Serendipity Investments, Ltd.

Yellow Deer Investments Corp.

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