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                                                                     EXHIBIT 4.1

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                             NABORS HOLDING COMPANY
                (successor by merger of POOL ENERGY SERVICES CO.)

                                       and

                           THE GUARANTORS NAMED HEREIN

                                       and

                             NABORS INDUSTRIES, INC.


                                  $150,000,000


                    8 5/8% Senior Subordinated Notes due 2008


                          THIRD SUPPLEMENTAL INDENTURE

                          Dated as of February 14, 2000


                                 HSBC BANK USA,

                                   AS TRUSTEE



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         This THIRD SUPPLEMENTAL INDENTURE, dated as of February 14, 2000, is
among Nabors Holding Company, a Delaware corporation (successor by merger of
Pool Energy Services Co., a Texas corporation) ("NHC" or the "Company"), Nabors
Industries, Inc. ("Nabors" or the "Parent Guarantor"), a Delaware corporation
and parent corporation of the Company, Associated Petroleum Services, Inc.,
International Air Drilling Company, Kuukpik-Pool Arctic Alaska, Pool Alaska,
Inc., Pool Americas, Inc., Pool-Australia, Inc., Pool Company, Pool Company
Texas, Ltd., Pool International, Inc., Pool Well Services Co., PCNV, Inc., PTX,
Inc., Sea Mar, Inc. and Sea Mar Management, Inc. (collectively referred to
herein as the "Subsidiary Guarantors") and HSBC Bank USA (formerly known as
Marine Midland Bank), as trustee (the "Trustee").

                                    RECITALS

         WHEREAS, Pool Energy Services Co., a Texas corporation ("PESC"), the
subsidiary guarantors referred to therein and the Trustee entered into an
Indenture, dated as of March 31, 1998, as amended by the First Supplemental
Indenture, dated as of March 31, 1998 (as amended, the "First Indenture"),
pursuant to which PESC issued $150,000,000 in aggregate principal amount of 8
5/8% Senior Subordinated Notes due 2008 (the "Notes"), the payment of which was
guaranteed by such subsidiary guarantors;

         WHEREAS, on November 24, 1999 (i) Starry Acquisition Corp. merged with
and into PESC, and as a result PESC became an indirectly wholly-owned subsidiary
of Nabors and (ii) PESC changed its state of incorporation and name through a
merger with and into NHC (such transactions are collectively referred to as the
"Acquisition"), in each case in accordance with Section 5.01 of the First
Indenture;

         WHEREAS, in connection with the Acquisition, certain subsidiary
guarantors named in the First Indenture merged, dissolved and/or engaged in
transactions with an affiliate (together with the Acquisition, the
"Transactions"), in each case in accordance with the terms of the First
Indenture;

         WHEREAS, the Company, the Subsidiary Guarantors and the Trustee entered
into a Second Supplemental Indenture, dated as of December 1, 1999 (together
with the First Indenture, the "Indenture") to, among other things, (i) reflect
the Acquisition and the change of the name of the issuer of the Notes to "Nabors
Holding Company" and the change of its jurisdiction of incorporation to
Delaware, (ii) provide for the assumption or reaffirmation of the obligations of
PESC to the Holders by the Company, and (iii) reflect the Transactions and
provide for the assumption and/or ratification of the obligations of the
applicable subsidiary guarantors by the applicable surviving entities, in each
case in accordance with the terms of the Indenture;

         WHEREAS, Section 9.02 of the Indenture provides that, with the written
consent of the Holders of at least a majority of the principal amount of the
Notes then outstanding, the Company, the Subsidiary Guarantors and the Trustee
may enter into one or more indentures supplemental to the Indenture for the
purpose of adding any provisions to or changing or eliminating any of the
provisions of the Indenture or modifying the rights of the Holders of the Notes,
subject to certain exceptions specified in Section 9.02 of the Indenture;

         WHEREAS, the Company desires to and has requested that the Trustee
enter into this Third Supplemental Indenture to, among other things, (i) provide
for the guarantee of the obligations of the Company by the Parent Guarantor;
(ii) provide for the release of the guarantees of the Subsidiary Guarantors; and
(iii) amend and/or eliminate certain provisions of the Indenture and the Note;

         WHEREAS, the Holders of in excess of a majority of the principal amount
at the stated maturity of the outstanding Notes have duly consented to the
execution and delivery of this Third Supplemental Indenture, pursuant to the
Change of Control Offer and Consent Solicitation Statement of the Company, dated
December 24, 1999;

         WHEREAS, the execution and delivery of this Third Supplemental
Indenture has been duly authorized by the appropriate resolutions of the Board
of Directors of the Company, the Parent Guarantor and each of the Subsidiary
Guarantors; and



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         WHEREAS, all conditions and requirements necessary to make this Third
Supplemental Indenture a valid, binding and legal instrument enforceable in
accordance with its terms have been performed and fulfilled by the parties
hereto and the execution and delivery thereof have been in all respects duly
authorized by the parties hereto.

         NOW, THEREFORE, in consideration of the above premises, each party
hereto agrees, for the benefit of the other and for the equal and ratable
benefit of the Holders of the Notes, as follows:


                                   ARTICLE I
                       ADDITION AND RELEASE OF GUARANTEES

         Section 1.1. Addition of Guarantor. The Parent Guarantor
unconditionally guarantees the obligations of the Company under the Indenture
and the Notes and agrees to be subject to the obligations of a Guarantor under
the Indenture and the Notes, each as modified hereby, in accordance with the
provisions thereof.

         Section 1.2. Release of Subsidiary Guarantors. The Subsidiary
Guarantors are hereby fully and finally released and relieved of any and all
obligations under the Indenture, the Notes and any Note Guarantees.

                                   ARTICLE II
                           AMENDMENTS TO THE INDENTURE

         Section 2.1. Amendment to the Introductory Paragraph and Change of
Name. The introductory paragraph of the Indenture is amended by being replaced
in its entirety with the following:

                  "INDENTURE, dated as of March 31, 1998, by and among Nabors
         Holdings Company (as further defined below, the 'Company'), Nabors
         Industries, Inc. (as further defined below, the 'Parent Guarantor') and
         HSBC Bank USA, a New York banking corporation and trust company, as
         trustee (the 'Trustee')."


         Section 2.2. Amendments to Article 1 of the Indenture. For all purposes
of the Indenture, the following amendments shall be made to Article 1 thereof
and elsewhere within the Indenture and the Notes as the context requires:

                  (1) The terms "Subsidiary Guarantor" and "Subsidiary
Guarantors" are amended to read "Parent Guarantor" and all verbs or verb tenses
following such terms and articles preceding such terms as well as signature
blocks shall be deemed to be amended as appropriate to reflect such changes.

                  (2) The terms "Guarantees" and "Guarantors" shall be deemed to
mean "Guarantee" and "Guarantor", respectively, as the context requires and all
verbs or verb tenses following such terms and articles preceding such terms
shall be deemed to be amended to reflect such changes.

                  (3) The term "Company" or "Company's" is hereby deleted in its
entirety from the following definitions contained in Section 1.01 of the
Indenture and replaced with "Parent Guarantor" or "Parent Guarantor's", as
applicable:

                           (a)      Acquired Indebtedness;
                           (b)      Attributable Indebtedness;
                           (c)      Board Resolution;
                           (d)      Cash Equivalents;
                           (e)      Corporate Trust Office;
                           (f)      Designated Senior Indebtedness;
                           (g)      Foreign Subsidiary;
                           (h)      Indebtedness;
                           (i)      Independent Director;
                           (j)      Officer;
                           (k)      Opinion of Counsel;
                           (l)      Permitted Junior Securities;



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                           (m)      Permitted Liens;
                           (n)      Refinancing Indebtedness; (o) Restricted
                                    Investment;
                           (p)      Restricted Subsidiary;
                           (q)      Senior Indebtedness;
                           (r)      Senior Subordinated Indebtedness;
                           (s)      Significant Subsidiary;
                           (t)      Subordinated Indebtedness;
                           (u)      Subsidiary;
                           (v)      Unrestricted Subsidiary; and
                           (w)      Wholly-Owned Restricted Subsidiary.

                  (4) The following terms and the definitions thereof, as listed
in Sections 1.01 and 1.02 of the Indenture, are deleted in their entireties
together will all references thereto and any related syntax, as case may be, in
the Indenture:

                           (a)      Affiliate Transaction;
                           (b)      Asset Sale;
                           (c)      Asset Sale Offer;
                           (d)      Asset Sale Offer Amount;
                           (e)      Asset Sale Trigger Date;
                           (f)      Consolidated Amortization Expense;
                           (g)      Consolidated Depreciation Expense;
                           (h)      Consolidated Income Tax Expense;
                           (i)      Consolidated Interest Coverage Ratio;
                           (j)      Consolidated Interest Expense;
                           (k)      Consolidated Net Income;
                           (l)      Coverage Ratio Incurrence Condition;
                           (m)      EBITDA; (n) Excess Proceeds;
                           (o)      Existing Indebtedness;
                           (p)      Independent Financial Advisor;
                           (q)      Net Available Proceeds;
                           (r)      Net Proceeds Deficiency;
                           (s)      Net Proceeds Offer Period;
                           (t)      Net Proceeds Purchase Date;
                           (u)      Offered Price;
                           (v)      Payment Amount;
                           (w)      Payment Restriction;
                           (x)      Related Business;
                           (y)      Related Business Investment;
                           (z)      Related Party Agreement;
                           (aa)     Replacement Facility
                           (bb)     Restricted Debt Payment; and
                           (cc)     Restricted Payment.

                  (5) The definition of "Change of Control" is amended by (a)
inserting the following phrase at the end of paragraph (i): "(other than such a
change resulting from a reorganization transaction which does not result in such
a change in the ultimate beneficial ownership of the Parent Guarantor)" and (b)
deleting all references to the term "Company" located therein and replacing them
with "Parent Guarantor".

                  (6) The definition of "Credit Agreement" is deleted in its
entirety and replaced with the following:

                           "Credit Agreement" means the Credit Agreement, dated
         as of September 7, 1997, by and among the Parent Guarantor, the
         subsidiary borrowers named therein, Bank of America National Trust and
         Savings Association, as administrative agent, Wells Fargo Bank (Texas),
         National Association, as



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         documentation agent, and BancAmerica Securities, Inc., as arranger,
         together with any additional guarantees thereof and security
         agreements, as any of the foregoing may be subsequently amended,
         restated, refinanced, or replaced from time to time, and shall include
         agreements in respect of Hedging Obligations designed to protect
         against fluctuations in interest rates and entered into with respect to
         loans thereunder."

                  (7) In addition to the amendments provided in paragraph (3) of
this Section, the definition of "Designated Senior Indebtedness" is amended by
deleting clause (i) in its entirety through and including the symbol "(ii)" and
replacing it with the following:

                  "Designated Senior Indebtedness" means (i) Indebtedness
         incurred or permitted to be incurred under the Credit Agreement; (ii)
         Indebtedness incurred pursuant to the Indenture, dated as of March 1,
         1999 (as supplemented by Supplemental No. 1 thereto dated as of March
         1, 1999), between the Parent Guarantor and Norwest Bank Minnesota,
         National Association, as trustee; and (iii)"

                  (8) The definition of "Equity Offering" is amended by: (a)
inserting the clause "Parent Guarantor or the" in front of the first occurrence
of the term "Company" therein; and (b) replacing the second occurrence of the
term "Company" therein with "Parent Guarantor."

                  (9) The definition of "Guarantor" is deleted in its entirety
and replaced with:

                  "'Guarantor' means the Parent Guarantor."

                  (10) The term and definition of "Non-Recourse Purchase Money
Indebtedness" is deleted in its entirety and replaced with the definition set
forth below. In addition, all references to "Non-Recourse Purchase Money
Indebtedness" in the Indenture are replaced with "Non-Recourse Indebtedness."

                  "'Non-Recourse Indebtedness' means Indebtedness of the Parent
         Guarantor or any of its Subsidiaries to the extent that such
         Indebtedness is non-recourse to the Parent Guarantor or any of its
         Subsidiaries or any of their respective assets other than the assets
         specifically secured thereby."

                  (11) The definition of "Offer" and "Offer Period" are amended
by deleting the references to "or a Net Proceeds Offer, as the context requires"
located therein.

                  (12) The following definition of "Parent Guarantor" is
inserted in the appropriate alphabetical order:

                  "'Parent Guarantor' means Nabors Industries, Inc., a Delaware
         corporation and parent corporation of the Company."

                  (13) The definition of "Permitted Indebtedness" is amended by:

                           (a) deleting all references to "Company" in
                  paragraphs (vi) and (vii) thereof replacing them, in each
                  instance, with: "Parent Guarantor";

                           (b) deleting paragraph (i) thereof in its entirety
                  and replacing it with the following:

                  "(i) Indebtedness of the Parent Guarantor and any Subsidiary
         thereof under the Credit Agreement;";

                           (c) deleting paragraph (iii) thereof in its entirety
                  and replacing it with the following:

                  "(iii) Indebtedness of the Parent Guarantor and/or its
         Subsidiaries existing on the date of the Third Supplemental Indenture
         hereto;";

                           (d) deleting the reference to "or Indebtedness
                  permitted by Section 4.07" from paragraph



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                  (iv) thereof;

                           (e) deleting paragraph (v) thereof in its entirety
                  and replacing it with the following:

                  "(v) Indebtedness of the Company to the Parent Guarantor and
         Indebtedness of the Parent Guarantor to the Company;";

                           (f) amending paragraph (ix) by deleting the terms
                  "$10.0 million" and "$20.0 million" and replacing them with:
                  "$30.0 million" and "$60.0 million", respectively; and

                           (g) deleting paragraph (x) thereof in its entirety
                  and replacing it with the following:

                  "(x) Acquired Indebtedness."

                  (14) In addition to the amendments provided in paragraph (3)
of this Section, the definition of "Permitted Liens" is amended by (a) inserting
at the end of paragraph (i) thereof: "or as of the date of the Third
Supplemental Indenture hereto", (b) inserting ", (ix)" between the terms "(i)"
and "and" in paragraph (iv), (c) deleting paragraph (xii) in its entirety and
replacing it with the following: "(xii) Liens securing Non-Recourse
Indebtedness;", and (d) deleting the entirety of paragraph (xiii) after the
first instance of the term "Acquired Indebtedness."

                  (15) In addition to the amendments provided in paragraph (3)
of this Section, the definition of "Refinancing Indebtedness" is amended by
inserting the term "150% of" after the clauses: (a) "in a principal amount not
in excess of"; and (b) "with a maximum commitment not to exceed".

                  (16) In addition to the amendments provided in paragraph (3)
of this Section, the definition of "Senior Indebtedness" is amended by: (a)
inserting after the words "Issue Date" located therein: ", as of the date of the
Third Supplemental Indenture hereto"; (b) deleting the reference to "not
prohibited by Section 4.07" located in clause (iii) thereof; (c) deleting the
word "and" which immediately precedes the figures "(v)" located therein; and (d)
inserting the following as clause (vi) after the provisions of clause (v):

                  ";and (vi) the principal of and interest on and all other
         Indebtedness and Obligations related to Designated Senior
         Indebtedness."

                  (17) The definition of "Significant Subsidiary" is amended by
deleting the reference to: ", except all references to '10 percent' in such
definition shall be changed to '2 percent'".

                  (18) The definition of "Unrestricted Subsidiary" is amended by
deleting from the third sentence thereof, the following phrases: (i) the phrase
that begins with: "and any such designation" and ends with "the dates of such
designation,"; and (ii) the phrase that begins with: "and the incurrence" and
ends with "Coverage Ratio Incurrence Condition and (y)".

         Section 2.3. Amendments to Article 2 of the Indenture. Section 2.13 is
amended by deleting the reference to "Sections 4.15 or 4.16" and replacing it
with "Section 4.15."

         Section 2.4. Amendments to Article 3 of the Indenture. For all purposes
of the Indenture, the following amendments shall be made to Article 3:


                  (1) Section 3.01 is amended by deleting the references to
"Section 4.15 or 4.16" and "Section 4.15 or 4.16, as the case may be" and
replacing them with "Section 4.15."

                  (2) Section 3.08(a) is amended by: (a) deleting the clause "or
Asset Sale Trigger Date" from the first sentence thereof; (b) deleting, in all
instances, the clause "or 4.16, as the case may be"; and (c) deleting the clause
"or Asset Sale, as the case may be" from clause (1) of paragraph (a).



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                  (3) Section 3.08(b) is amended by deleting the text of clause
(i)(y) thereof and inserting in its place the following: "[Intentionally
Omitted]".

                  (4) Section 3.08(d) is amended by deleting from clause (i)
thereof the phrase "or Offered Price, as the case may be".

                  (5) Section 3.08(f) is amended by deleting the clause "Section
3.08, Section 4.15 or Section 4.16" and replacing it with "Section 3.08 or
Section 4.15".

         Section 2.5. Amendments to Article 4 of the Indenture. For all purposes
of the Indenture, the following amendments shall be made to Article 4: (1)
Sections 4.05, 4.07, 4.08, 4.09, 4.10, 4.13, 4.16 and 4.17 of the Indenture are
hereby deleted in their entireties, together with any references thereto in the
Indenture. "[Intentionally Omitted]" shall be inserted in place of the text of
such Sections; and (2) Section 4.02 is amended by: (a) deleting both references
to "the Company and the Subsidiary Guarantors" located in the first sentence
thereof, and (b) inserting, after the reference to "Exchange Act" located in the
first sentence thereof, the following: "(including therein any summary or other
information with respect to the Company as may be required thereby taking into
account the guarantee by the Parent Guarantor) if the Parent Guarantor was".

         Section 2.6. Amendment to Article 5 of the Indenture. Each and every
occurrence of the term "Company" in Section 5.01 of the Indenture is hereby
amended to read: "Parent Guarantor" and the text of clauses (x)(2) and (y)
thereof are deleted in their entireties and, in each instance, replaced with
"[Intentionally Omitted]".

         Section 2.7. Amendment to Article 6 of the Indenture. For all purposes
of the Indenture, the following amendments shall be made to Article 6: (1)
Section 6.01 is amended by (a) deleting from paragraph (a)(iii) thereof the
reference to: "or a Net Proceeds Offer" and (b) deleting the reference to
"Sections 4.15 and 4.16, respectively" and replacing it with "Section 4.15"; (2)
Section 6.01 is amended by deleting paragraphs (a)(v) and (vi) thereof in their
entireties and replacing them with the following: "[Intentionally Omitted]"; (3)
Section 6.01 is amended by deleting from paragraph (a)(viii) the word "Company"
and replacing it with "Parent Guarantor"; (4) Section 6.02 is amended by
inserting in paragraph (a) and (b) thereof the following clause after each
occurrence of the word "Company": "or the Parent Guarantor" in all instances
therein. (5) Section 6.10 is amended by inserting immediately after the clause
"to the Company", the following: "or the Parent Guarantor". (6) Section 6.12 of
the Indenture is deleted in its entirety, together with any references thereto.
"[Intentionally Omitted]" shall be inserted in place of the text in such
Section.

         Section 2.8. Amendments to Article 11 of the Indenture. For all
purposes of the Indenture, the following amendments shall be made to Article 11:

                  (1) Sections 11.04 and 11.05 of the Indenture are deleted in
their entireties, together with any references thereto. "[Intentionally
Omitted]" shall be inserted in place of the text of such Sections.

                  (2) Section 11.06 of the Indenture is amended by:



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                  (i) deleting all references to "Subsidiary Guarantor" or
         "Subsidiary Guarantors" located therein, including the reference in the
         heading thereof, and replacing them with "Company";

                  (ii) inserting the word "not" between the words "may" and
         "consolidate" contained in the second line thereof;

                  (iii) making all conforming changes required to articles,
         verbs and verb tenses;

                  (iv) amending paragraph (a) by deleting the phrase, "subject
         to the provisions of Section 11.07 hereof," and references to, "this
         Indenture and such Subsidiary Guarantor's Note Guarantee" located in
         the last line of paragraph (a) thereof and replacing it with "and this
         Indenture.";

                  (v) deleting from paragraph (c) thereof, the phrase beginning
         with the word "immediately" and ending with the word "met"; and

                  (vi) deleting the last paragraph of Section 11.06 in its
         entirety and replacing it with following:

                           "Except as set forth in Articles 4 and 5 hereof,
                  nothing contained in this Indenture shall prevent any
                  consolidation or merger of the Company with or into the Parent
                  Guarantor, or shall prevent any sale or conveyance of the
                  property of the Company as an entirety or substantially as an
                  entirety to the Parent Guarantor."

                  (3) Section 11.07 of the Indenture is deleted in its entirety
together with any references thereto in the Indenture and replaced with
"[Intentionally Omitted]."

         Section 2.9. Conforming Changes. The provisions of the Indenture and
all Exhibits thereto shall be deemed revised to make all conforming changes as
well as changes to articles, verbs, verb tenses, singular and plural word forms,
syntax and other word forms or usage as may be necessary to accomplish the
intent of this Third Supplemental Indenture and as the context of such
provisions require.

                                  ARTICLE III
                                NOTATION OF NOTES

         Notes authenticated and delivered for transfer or exchange of
outstanding Notes after the Effective Time (as defined below), and all Notes
presented or delivered to the Trustee on after such date for the purpose of
being stamped, shall be stamped (unless textually revised as hereinafter
provided) by the Trustee with a notation substantially in the form as follows:

                           "THE INDENTURE DATED AS OF MARCH 31, 1998 REFERRED TO
                           IN THIS NOTE HAS BEEN AMENDED BY A FIRST SUPPLEMENTAL
                           INDENTURE DATED AS OF MARCH 31, 1998, A SECOND
                           SUPPLEMENTAL INDENTURE DATED AS OF DECEMBER 1, 1999,
                           AND A THIRD SUPPLEMENTAL INDENTURE DATED AS OF
                           FEBRUARY 14, 2000, PURSUANT TO WHICH CERTAIN
                           PROVISIONS OF THE INDENTURE HAVE BEEN AMENDED,
                           ELIMINATED OR OTHERWISE MODIFIED AS SET FORTH IN SUCH
                           FIRST, SECOND AND THIRD SUPPLEMENTAL INDENTURES.
                           COPIES OF THE FIRST, SECOND AND THIRD SUPPLEMENTAL
                           INDENTURES ARE ON FILE WITH, AND AVAILABLE ON REQUEST
                           FROM, THE TRUSTEE AND THE COMPANY."



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Any Notes hereafter authenticated or delivered may be textually revised, making
changes in phraseology and form (but not in substance) as may be appropriate so
as to conform, in the opinion of the Trustee and the Company, to modifications
made by this Third Supplemental Indenture.


                                   ARTICLE IV
                                  MISCELLANEOUS

         Section 4.1. Capitalized Terms. Capitalized terms used herein and not
otherwise defined have the meaning set forth in the Indenture.

         Section 4.2. Operation of Third Supplemental Indenture. This Third
Supplemental Indenture will become effective as of the date hereof.

         Section 4.3. Conflict with the Trust Indenture Act. If any provision of
this Third Supplemental Indenture modifies or excludes any provision of the
Trust Indenture Act that is required under such Act to be part of and govern
this Third Supplemental Indenture, the latter provision of the Trust Indenture
Act shall control. If any provision hereof modifies or excludes any provision of
the Trust Indenture Act that may be so modified or excluded, the latter
provision of the Trust Indenture Act shall be deemed to apply to this Third
Supplemental Indenture, as so modified or excluded, as the case may be.

         Section 4.4. Notes Deemed Conformed. As of the Effective Time, the
provisions of each Note then outstanding shall be deemed to be conformed,
without the necessity for any reissuance or exchange of such Note or any other
action on the part of the Holders, the Company, the Parent Guarantor or the
Trustee, so as to reflect this Third Supplemental Indenture.

         Section 4.5. Mutatis Mutandis. Except as specifically modified herein,
the Indenture and the Notes are in all respects ratified and confirmed (mutatis
mutandis) and shall remain in full force and effect in accordance with their
terms with all capitalized terms used herein without definition having the same
definition ascribed to them as in the Indenture. The Indenture shall be deemed
to have such other changes as to grammar, tense, syntax and like concepts as
shall be necessary to effect the changes contemplated herein.

         Section 4.6. No Additional Trustee Obligations. Except as otherwise
expressly provided herein, no duties, responsibilities or liabilities are
assumed, or shall be construed to be assumed, by the Trustee by reason of this
Third Supplemental Indenture. This Third Supplemental Indenture is executed and
accepted by the Trustee subject to all the terms and conditions set forth in the
Indenture with the same force and effect as if those terms and conditions were
repeated at length herein and made applicable to the Trustee with respect
hereto.

         Section 4.7. Successors. All agreements of the Company, the Parent
Guarantor and the Trustee in this Third Supplemental Indenture and in the
Indenture shall bind their respective successors.

         Section 4.8. Benefits of Third Supplemental Indenture. Nothing in this
Third Supplemental Indenture, express or implied, shall give to any person,
other than the parties hereto and their successors hereunder and the Holders,
any benefit or any legal or equitable right, remedy or claim under this Third
Supplemental Indenture or the Indenture.

         Section 4.9. Severability. In case any provision in this Third
Supplemental Indenture, or in the Indenture, shall be invalid, illegal or
unenforceable, the validity, legality and enforceability of the remaining
provisions shall not in any way be affected or impaired thereby, it being
intended that all of the provisions hereof shall be enforceable to the full
extent permitted by law.



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         Section 4.10. Headings. The Section headings of this Third Supplemental
Indenture have been inserted for convenience of reference only, are not to be
considered a part of this Third Supplemental Indenture and shall not modify or
restrict any of the terms or provisions hereof.

         Section 4.11. Multiple Originals. The parties may sign any number of
copies of this Third Supplemental Indenture. Each signed copy shall be an
original, but all of them together represent the same agreement.

         Section 4.12. The Trustee. The Trustee is not responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Third
Supplemental Indenture or for or in respect of the recitals contained herein,
all of which are made solely by the Company.

         Section 4.13. Governing Law. THE LAW OF THE STATE OF NEW YORK SHALL
GOVERN AND BE USED TO CONSTRUE AND ENFORCE THIS THIRD SUPPLEMENTAL INDENTURE.

                            [Signature Pages Follow]

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

                              COMPANY:
                              NABORS HOLDING COMPANY (formerly known as POOL
                              ENERGY SERVICES CO.)


                              By:  /s/ Daniel McLachlin
                                   ---------------------------------------------
                                   Name:  Daniel McLachlin
                                   Title: Secretary

                              GUARANTORS:
                              ASSOCIATED PETROLEUM SERVICES, INC.
                              INTERNATIONAL AIR DRILLING COMPANY
                              KUUKPIK - POOL ARCTIC ALASKA
                                   By:  Pool Alaska, Inc., d/b/a Pool Arctic
                                        Alaska
                              POOL ALASKA, INC.
                              POOL AMERICAS, INC.
                              POOL-AUSTRALIA, INC.
                              POOL COMPANY
                              POOL COMPANY TEXAS, LTD.
                                   By:  Pool Well Services Co., General Partner
                              POOL INTERNATIONAL, INC.
                              POOL WELL SERVICES CO.
                              PTX, INC.
                              SEA MAR, INC.
                              SEA MAR MANAGEMENT, INC.

                              By:  /s/ Daniel McLachlin
                                   ---------------------------------------------
                                   Name:  Daniel McLachlin
                                   Title: Secretary


                              PCNV, INC.

                              By:  /s/ Jay Weidenbach
                                   ---------------------------------------------
                                   Name:  Jay Weidenbach
                                   Title: Secretary



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                              PARENT GUARANTOR:
                              NABORS INDUSTRIES, INC.


                              By:  /s/ Anthony G. Petrello
                                   ---------------------------------------------
                                   Name:  Anthony G. Petrello
                                   Title: President and Chief Operating Officer



                              TRUSTEE:
                              HSBC BANK USA, as Trustee


                              By:  /s/ Frank J. Godino
                                   ---------------------------------------------
                                   Name:  Frank J. Godino
                                   Title: Vice President



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