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                                                                     EXHIBIT 4.1

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                          FOURTH SUPPLEMENTAL INDENTURE


                                     BETWEEN


                           TRANSOCEAN SEDCO FOREX INC.


                                       AND


                            THE CHASE MANHATTAN BANK,

                                   AS TRUSTEE


                                 ---------------


                                  MAY 11, 2001




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                                TABLE OF CONTENTS


ARTICLE One THE 2021 DEBENTURES..............................................2
  SECTION 101    Designation of 2021 Debentures; Establishment of Form.......2
  SECTION 102    Amount......................................................3
  SECTION 103    Interest....................................................3
  SECTION 104    Additional Amounts..........................................3
  SECTION 105    Denominations...............................................3
  SECTION 106    Place of Payment............................................3
  SECTION 107    Redemption..................................................4
  SECTION 108    Conversion..................................................4
  SECTION 109    Maturity....................................................4
  SECTION 110    Repurchase..................................................4
  SECTION 111    Discharge of Liability on 2021 Debentures...................4
  SECTION 112    Other Terms of 2021 Debentures..............................4

ARTICLE Two AMENDMENTS TO THE INDENTURE......................................5
  SECTION 201    Definitions.................................................5
  SECTION 202    Registration, Registration of Transfer and Exchange.........7
  SECTION 203    Mutilated, Destroyed, Lost and Stolen Securities............8
  SECTION 204    Payment of Interest; Interest Rights Preserved..............8
  SECTION 205    Satisfaction and Discharge of Indenture.....................8
  SECTION 206    Discharge of Liability on Securities of Any Series..........9
  SECTION 207    Unconditional Right of Holders to Receive Principal,
                 Premium and Interest........................................9
  SECTION 208    Consolidation, Merger and Sale..............................9
  SECTION 209    Supplemental Indentures Without Consent of Holders..........9
  SECTION 210    Supplemental Indenture with Consent of Holder..............10
  SECTION 211    Maintenance of Office or Agency............................10
  SECTION 212    Redemption.................................................10
  SECTION 213    Conversion, Repurchase.....................................16
  SECTION 214    Amendment to Events of Default.............................37

ARTICLE Three MISCELLANEOUS PROVISIONS......................................37
  SECTION 301    Integral Part..............................................37
  SECTION 302    General Definitions........................................37
  SECTION 303    Adoption, Ratification and Confirmation....................38
  SECTION 304    Counterparts...............................................38
  SECTION 305    Governing Law..............................................38

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                           TRANSOCEAN SEDCO FOREX INC.

                          FOURTH SUPPLEMENTAL INDENTURE

      THIS FOURTH SUPPLEMENTAL INDENTURE, dated as of May 11, 2001 (the "Fourth
Supplemental Indenture"), between Transocean Sedco Forex Inc. (formerly
Transocean Offshore Inc.), a Cayman Islands exempted company limited by shares
(the "Company"), and The Chase Manhattan Bank (formerly Texas Commerce Bank
National Association) (the "Trustee").

                             W I T N E S S E T H

      WHEREAS, the Company has heretofore executed and delivered to the Trustee
an Indenture, dated as of April 15, 1997 (as supplemented by the First
Supplemental Indenture thereto dated as of April 15, 1997, the Second
Supplemental Indenture thereto dated as of May 14, 1999, the Third Supplemental
Indenture thereto dated as of May 24, 2000 and this Fourth Supplemental
Indenture, the "Indenture"), providing for the issuance from time to time of one
or more series of the Company's Securities;

      WHEREAS, Section 901(5) of the Indenture provides that the Company and the
Trustee may from time to time enter into one or more indentures supplemental
thereto to establish the form or terms of Securities of a new series;

      WHEREAS, Section 901(8) of the Indenture provides that the Company and the
Trustee may from time to time enter into one or more indentures supplemental
thereto to make provision with respect to matters or questions arising under the
Indenture which do not adversely affect the interests of the Holders of
Securities of any series in any material respect;

      WHEREAS, Sections 901(2) and 901(3) of the Indenture permit the execution
of supplemental indentures without the consent of any Holders to add to the
covenants of the Company for the benefit of, and to add any additional Events of
Default with respect to, all or any series of Securities;

      WHEREAS, Section 901(4) of the Indenture permits the execution of
supplemental indentures without the consent of any Holders to change or
eliminate any of the provisions of the Indenture; provided that such change or
elimination does not adversely affect any outstanding Security of any series
created prior to the execution of such supplemental indenture;

      WHEREAS, Section 301 of the Indenture provides that the Company may enter
into supplemental indentures to establish the terms and provisions of a series
of Securities issued pursuant to the Indenture;

      WHEREAS, the Company desires to issue 1.5% Convertible Debentures due May
15, 2021 (the "2021 Debentures"), a new series of Security the issuance of which
was authorized by or pursuant to resolution of the Board of Directors of the
Company;
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      WHEREAS, the Company, pursuant to the foregoing authority, proposes in and
by this Fourth Supplemental Indenture to supplement and amend the Indenture
insofar as it will apply only to the 2021 Debentures in certain respects; and

      WHEREAS, all things necessary have been done to make the 2021 Debentures,
when executed by the Company and authenticated and delivered hereunder and duly
issued by the Company, the valid obligations of the Company, and to make this
Fourth Supplemental Indenture a valid agreement of the Company, in accordance
with their and its terms.

      NOW THEREFORE:

      In consideration of the premises provided for herein, the Company and the
Trustee mutually covenant and agree for the equal and proportionate benefit of
all Holders of the 2021 Debentures as follows:

                                  ARTICLE ONE

                               THE 2021 DEBENTURES

SECTION 101 Designation of 2021 Debentures; Establishment of Form.

      There shall be a series of Securities designated "1.5% Convertible
Debentures Due May 15, 2021" of the Company (the "2021 Debentures"), and the
form thereof shall be substantially as set forth in Annex A hereto, which is
incorporated into and shall be deemed a part of this Fourth Supplemental
Indenture, in each case with such appropriate insertions, omissions,
substitutions and other variations as are required or permitted by the
Indenture, and may have such letters, numbers or other marks of identification
and such legends or endorsements placed thereon as may be required to comply
with the rules of any securities exchange or as may, consistently herewith, be
determined by the officers of the Company executing such 2021 Debentures, as
evidenced by their execution of the 2021 Debentures.

      The 2021 Debentures will initially be issued in permanent global form,
substantially in the form set forth in Annex A hereto (the "Global Securities"),
as a Book-Entry Security. Each Global Security shall represent such of the
Outstanding 2021 Debentures as shall be specified therein and shall provide that
it shall represent the aggregate amount of Outstanding 2021 Debentures from time
to time endorsed thereon and that the aggregate amount of Outstanding 2021
Debentures represented thereby may from time to time be reduced to reflect
exchanges and redemptions. Any endorsement of a Global Security to reflect the
amount, or any increase or decrease in the amount, of Outstanding 2021
Debentures represented thereby shall be made by the Trustee in accordance with
written instructions or such other written form of instructions as is customary
for the Depositary, from the Depositary or its nominee on behalf of any Person
having the beneficial interest in the Global Security.

      The Company initially appoints The Depository Trust Company to act as
Depositary with respect to the Global Securities.

      The Company initially appoints the Trustee to act as Paying Agent and
Conversion Agent with respect to the 2021 Debentures.

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SECTION 102 Amount.

      (a) The Trustee shall authenticate and deliver 2021 Debentures for
original issue in an aggregate Principal Amount of up to $400,000,000 upon
Company Order for the authentication and delivery of 2021 Debentures, without
any further action by the Company. The aggregate Principal Amount of 2021
Debentures that may be authenticated and delivered under the Indenture may not
exceed the amount set forth in the foregoing sentence, except for 2021
Debentures authenticated and delivered upon registration of transfer of, or in
exchange for, or in lieu of, other 2021 Debentures pursuant to Section 204, 304,
305, 306, 906 or 1107 of the Indenture.

      (b) The Company may not issue new 2021 Debentures to replace 2021
Debentures that it has paid or delivered to the Trustee for cancellation or that
any Holder has converted pursuant to Article Fourteen.

SECTION 103 Interest.

      The 2021 Debentures shall bear interest at the rate set forth under the
caption "Interest" in the 2021 Debentures, commencing on the Issue Date of the
2021 Debentures. Interest on the 2021 Debentures shall be payable to the persons
in whose name the 2021 Debentures are registered at the close of business on the
Regular Record Date for such interest payment. The date from which interest
shall accrue for each 2021 Debenture shall be May 11, 2001. The Interest Payment
Dates on which interest on the 2021 Debentures shall be payable are May 15 and
November 15, commencing on November 15, 2001. The Regular Record Dates for the
interest payable on the 2021 Debentures on any Interest Payment Date shall be
May 1 or November 1, as the case may be, immediately preceding such Interest
Payment Date.

SECTION 104 Additional Amounts.

      Additional Amounts with respect to the 2021 Debentures shall be payable in
accordance with the provisions and in the amounts set forth under the caption
"Tax Additional Amounts" in the 2021 Debentures and in accordance with the
provisions of the Indenture.

SECTION 105 Denominations.

      The 2021 Debentures shall be in fully registered form without coupons in
denominations of $1,000 of Principal Amount or any integral multiple thereof.

SECTION 106 Place of Payment.

      The Place of Payment for the 2021 Debentures and the place or places where
the principal of and interest on the 2021 Debentures shall be payable, the 2021
Debentures may be surrendered for registration of transfer, the 2021 Debentures
may be surrendered for exchange, repurchase, redemption or conversion and where
notices may be given to the Company in respect of the 2021 Debentures is at the
office or agency of the Trustee in New York, New York or in Dallas, Texas;
provided that payment of interest may be made at the option of the Company by
check mailed to the address of the person entitled thereto as such address shall
appear in the

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Security Register (as defined in the Indenture) or by wire transfer of
immediately available funds to the accounts specified by the Holder of such 2021
Debentures.

SECTION 107 Redemption.

      (a) There shall be no sinking fund for the retirement of the 2021
Debentures.

      (b) The Company, at its option, may redeem the 2021 Debentures in
accordance with the provisions of and at the Redemption Prices set forth under
the captions "Optional Redemption" and "Notice of Redemption" in the 2021
Debentures and in accordance with the provisions of the Indenture, including,
without limitation, Article Eleven.

      (c) The Company, at the option of the Holders thereof, shall redeem the
2021 Debentures in accordance with the provisions of and at the Change in
Control Purchase Prices set forth under the caption "Purchase of Securities at
Option of Holder Upon a Change in Control" in the 2021 Debentures and in
accordance with the provisions of the Indenture, including, without limitation,
Article Eleven.

SECTION 108 Conversion.

      The 2021 Debentures shall be convertible in accordance with the provisions
and at the Conversion Rate set forth under the caption "Conversion" in the 2021
Debentures and in accordance with the provisions of the Indenture, including,
without limitation, Article Fourteen.

SECTION 109 Maturity.

      The date on which the principal of the 2021 Debentures is payable, unless
accelerated pursuant to the Indenture, shall be May 15, 2021.

SECTION 110 Repurchase.

      The 2021 Debentures shall be repurchased by the Company in accordance with
the provisions and at the Repurchase Prices set forth under the caption
"Repurchase by the Company at the Option of the Holder" in the 2021 Debentures
and in accordance with the provisions of the Indenture, including, without
limitation, Article Fifteen.

SECTION 111 Discharge of Liability on 2021 Debentures.

      Section 403 of the Indenture shall be applicable to the 2021 Debentures.

SECTION 112 Other Terms of 2021 Debentures.

      Without limiting the foregoing provisions of this Article One, the terms
of the 2021 Debentures shall be as set forth in the form of 2021 Debentures set
forth in Annex A hereto and as provided in the Indenture.

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                                  ARTICLE TWO

                           AMENDMENTS TO THE INDENTURE

      The amendments contained herein shall apply to 2021 Debentures only and
not to any other series of Security issued under the Indenture and any covenants
provided herein are expressly being included solely for the benefit of the 2021
Debentures. These amendments shall be effective for so long as there remains any
2021 Debentures Outstanding.

SECTION 201 Definitions.

      Section 101 of the Indenture is amended by inserting or restating, as the
case may be, in their appropriate alphabetical position, the following
definitions:

      "Capital Stock" or "capital stock" of any Person means any and all shares,
interests, partnership interests, participations, rights or other equivalents
(however designated) of such Person's equity interest (however designated)
issued by that Person.

      "Change in Control" has the meaning specified in Section 1110.

      "Change in Control Purchase Date" has the meaning specified in Section
1110.

      "Change in Control Purchase Notice" has the meaning specified in Section
1110.

      "Change in Control Purchase Price" has the meaning specified in Section
1110.

      "Company Notice Date" has the meaning specified in Section 1503.

      "Conversion Agent" shall be the agent specified in Section 101.

      "Conversion Date" has the meaning specified in Section 1402.

      "Conversion Rate" has the meaning specified in Section 1401.

      "Exchange Act" means the Securities Exchange Act of 1934, as amended, or
any successor statute.

      "Global Securities" has the meaning specified in Section 101.

      "Issue Date" of any 2021 Debenture means the date on which the 2021
Debenture was originally issued or deemed issued as set forth on the face of the
2021 Debenture.

      "Issue Price" of any 2021 Debenture means, in connection with the original
issuance of such 2021 Debenture, the initial issue price at which the 2021
Debenture is sold as set forth on the face of the 2021 Debenture.

      "Market Price" has the meaning specified in Section 1504.

      "non-electing share" has the meaning specified in Section 1411.

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      "Ordinary Shares" means any stock of any class of the Company (including,
without limitation, the Company's ordinary shares of a nominal or par value of
$0.01 per share) which has no preference in respect of dividends or of amounts
payable in the event of any voluntary or involuntary liquidation, dissolution or
winding up of the Company and which is not subject to redemption by the Company.

      "Outstanding", when used with respect to Securities, means, as of the date
of determination, all Securities theretofore authenticated and delivered under
this Indenture, except:

            (i) Securities theretofore cancelled by the Trustee or delivered to
the Trustee for cancellation;

            (ii) Securities for whose payment, repurchase or redemption money or
Ordinary Shares in the necessary amount has been theretofore deposited with the
Trustee or any Paying Agent (other than the Company) in trust or set aside and
segregated in trust by the Company (if the Company shall act as its own Paying
Agent) for the Holders of such Securities; provided that, if such Securities are
to be redeemed, notice of such redemption has been duly given pursuant to this
Indenture or provision therefor satisfactory to the Trustee has been made;

            (iii) Securities which have been cancelled pursuant to Section 309
or in exchange for or in lieu of which other Securities have been authenticated
and delivered pursuant to this Indenture, other than any such Securities in
respect of which there shall have been presented to the Trustee proof
satisfactory to it that such Securities are held by a bona fide purchaser in
whose hands such Securities are valid obligations of the Company; and

            (iv) 2021 Debentures converted for Ordinary Shares pursuant to
Article Fourteen;

provided, however, that in determining whether the Holders of the requisite
principal amount of the Outstanding Securities have given any request, demand,
authorization, direction, notice, consent or waiver hereunder, Securities owned
by the Company or any other obligor upon the Securities or any Affiliate of the
Company or of such other obligor shall be disregarded and deemed not to be
Outstanding, except that, in determining whether the Trustee shall be protected
in relying upon any such request, demand, authorization, direction, notice,
consent or waiver, only Securities which the Trustee knows to be so owned shall
be so disregarded. Securities so owned which have been pledged in good faith may
be regarded as Outstanding if the pledgee establishes to the satisfaction of the
Trustee the pledgee's right so to act with respect to such Securities and that
the pledgee is not the Company or any other obligor upon the Securities or any
Affiliate of the Company or of such other obligor.

      "Principal Amount" of a 2021 Debenture means the Principal Amount as set
forth on the face of the 2021 Debenture.

      "Repurchase Date" has the meaning specified in Section 1501.

      "Repurchase Notice" has the meaning specified in Section 1501.

      "Repurchase Price" has the meaning specified in Section 1501.

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      "Sale Price" has the meaning specified in Section 1504.

      "Securities" has the meaning stated in the first recital of this Indenture
and more particularly means any Securities authenticated and delivered under
this Indenture, including 2021 Debentures.

      "Securities Act" means the Securities Act of 1933, as amended, or any
successor statute.

      "Tax Additional Amounts" has the meaning specified in the form of 2021
Debentures attached hereto as Annex A.

      "Trading Day" means a day during which trading in securities generally
occurs on the New York Stock Exchange or, if the Ordinary Shares are not listed
on the New York Stock Exchange, on the principal other national or regional
securities exchange on which the Ordinary Shares are then listed or, if the
Ordinary Shares are not listed on a national or regional securities exchange, on
the National Association of Securities Dealers Automated Quotation System or, if
the Ordinary Shares are not quoted on the National Association of Securities
Dealers Automated Quotation System, on the principal other market on which the
Ordinary Shares are then traded.

      "2021 Debentures" means the 1.5% Convertible Debentures due May 15, 2021
of the Company authorized by or pursuant to resolution of the Board of
Directors.

      "Voting Stock" means any class or classes of Capital Stock pursuant to
which the holders thereof under ordinary circumstances have the power to vote in
the election of the board of directors, managers or trustees of any Person (or
other Persons performing similar functions), irrespective of whether or not, at
the time, Capital Stock of any other class or classes shall have, or might have,
voting power by reason of the happening of any contingency.

SECTION 202 Registration, Registration of Transfer and Exchange.

      The Indenture shall be amended by replacing the eighth paragraph of
Section 305 with the following paragraph:

            The Company shall not be required (i) to issue, register the
      transfer of or exchange the Securities of any series during a period
      beginning at the opening of business 15 days before the day of the mailing
      of a notice of redemption of Securities of that series selected for
      redemption and ending at the close of business on the day of such mailing,
      (ii) to register the transfer of or exchange any 2021 Debenture so
      selected for redemption in whole or in part, except the unredeemed portion
      of any Security being redeemed in part, or (iii) to exchange or register a
      transfer of any 2021 Debenture or portions thereof in respect of which a
      Change in Control Purchase Notice or Repurchase Notice has been delivered
      and not withdrawn by the Holder thereof (except, in the case of the
      purchase of a 2021 Debenture in part, the portion not to be purchased).

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SECTION 203 Mutilated, Destroyed, Lost and Stolen Securities.

      The Indenture shall be amended by replacing the fourth paragraph of
Section 306 with the following paragraph:

            In case any such mutilated, destroyed, lost or stolen Security has
      or is about to become due and payable, or is about to be redeemed or
      purchased by the Company upon a Change in Control pursuant to Article
      Eleven or purchased by the Company on a Repurchase Date pursuant to
      Article Fifteen, the Company in its discretion may, instead of issuing a
      new Security, pay such Security.

SECTION 204 Payment of Interest; Interest Rights Preserved.

      The Indenture shall be amended by inserting the following paragraph before
the final paragraph in Section 307:

            In the case of any 2021 Debenture or portion thereof which is
      surrendered for conversion after the close of business on the Regular
      Record Date immediately preceding any Interest Payment Date and prior to
      the opening of business on such next succeeding Interest Payment Date
      (unless such 2021 Debenture or portion thereof which is being surrendered
      for conversion has been called for redemption on a Redemption Date within
      such period), interest whose Stated Maturity is on such Interest Payment
      Date shall be payable on such Interest Payment Date notwithstanding such
      conversion, and such interest (whether or not punctually paid or duly
      provided for) shall be paid to the Person in whose name that 2021
      Debenture (or one or more Predecessor Securities) is registered at the
      close of business on such Regular Record Date; provided, however, that
      such payment of interest shall be subject to the payment to the Company by
      the Holder of such 2021 Debenture or portion thereof surrendered for
      conversion (such payment to accompany such surrender) of an amount equal
      to the amount of such interest, in accordance with but only to the extent
      required by Section 1402. Except as otherwise provided in the immediately
      preceding sentence, in the case of any 2021 Debenture which is converted,
      interest whose Stated Maturity is after the date of conversion of such
      2021 Debenture shall not be payable.

SECTION 205 Satisfaction and Discharge of Indenture.

      The Indenture shall be amended by replacing the last paragraph of Section
401 with the following paragraph:

            Notwithstanding the satisfaction and discharge of this Indenture
      with respect to the Outstanding Securities of such series pursuant to this
      Section 401, the obligations of the Company to the Trustee under Section
      607, the obligations of the Trustee to any Authenticating Agent under
      Section 614 and, except for a discharge pursuant to subclause (A) of
      clause (1) of this Section 401, the obligations of the Company under
      Sections 305, 306, 404, 610(e), 701, 1001 and 1002 and Articles Eleven,
      Fourteen and Fifteen and the obligations of the Trustee under Section 402
      and the last paragraph of Section 1003 shall survive.

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SECTION 206 Discharge of Liability on Securities of Any Series.

      The Indenture shall be amended by replacing the last paragraph of Section
403 with the following paragraph:

            Upon the satisfaction of the conditions set forth in this Section
      with respect to all the Outstanding Securities of any series, the terms
      and conditions of such series, including the terms and conditions with
      respect thereto set forth in this Indenture, shall no longer be binding
      upon, or applicable to, the Company; provided that the Company shall not
      be discharged from (a) any payment obligations in respect of Securities of
      such series that are deemed not to be Outstanding under clause (iii) of
      the definition thereof if such obligations continue to be valid
      obligations of the Company under applicable law or (b) any obligations
      pursuant to Section 305 or 306 or Articles Eleven, Fourteen and Fifteen.

SECTION 207 Unconditional Right of Holders to Receive Principal, Premium and
            Interest.

      Section 508 of the Indenture shall be amended by replacing that section
with the following:

            Section 508. Unconditional Right of Holders to Receive Principal,
                         Premium, Interest and Tax Additional Amounts.

            Notwithstanding any other provision in this Indenture, the Holder of
      any Security shall have the right, which is absolute and unconditional, to
      receive payment of the principal of (and premium, if any) and (subject to
      Section 307) interest on and Tax Additional Amounts, if any, with respect
      to such Security on the Stated Maturity or Maturities expressed in such
      Security (or in the case of redemption, to receive the Redemption Price on
      the Redemption Date, in the case of a repurchase, to receive the
      Repurchase Price on the Repurchase Date, or in the case of a Change in
      Control, to receive the Change in Control Purchase Price on the Change in
      Control Purchase Date) and to institute suit for the enforcement of any
      such payment on or after such respective dates, and such rights shall not
      be impaired without the consent of such Holder.

SECTION 208 Consolidation, Merger and Sale.

      The Indenture shall be amended by inserting "and shall have provided for
conversion rights in accordance with Section 1411" at the end of Section 801(1).

SECTION 209 Supplemental Indentures Without Consent of Holders.

      Section 901 of the Indenture shall be amended by inserting the following
paragraph:

            (9) to make provision with respect to the conversion rights, if any,
      to Holders of 2021 Debentures pursuant to the requirements of Article
      Fourteen hereof.

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SECTION 210 Supplemental Indenture with Consent of Holder.

      The Indenture shall be amended by inserting ", or adversely affect the
right to convert any 2021 Debenture as provided in Article Fourteen, or
adversely affect the right to require the Company to repurchase the 2021
Debentures as provided in Article Fifteen." at the end of Section 902(1).

SECTION 211 Maintenance of Office or Agency.

      The first paragraph of Section 1002 of the Indenture is amended by
changing the first sentence thereof to read in its entirety as follows:

            If Securities of a series are issuable only as Registered
      Securities, the Company will maintain in each Place of Payment for any
      series of Securities an office or agency where Securities of that series
      may be presented or surrendered for payment, where Securities of that
      series may be surrendered for registration of transfer or exchange, where
      2021 Debentures may be surrendered for conversion and where notices and
      demands to or upon the Company in respect of the Securities of that series
      and this Indenture may be served. The Company will give prompt written
      notice to the Trustee of the location, and any change in the location, of
      such office or agency. If at any time the Company shall fail to maintain
      any such required office or agency or shall fail to furnish the Trustee
      with the address thereof, such presentations, surrenders, notices and
      demands may be made or served at the Corporate Trust Office of the
      Trustee, and the Company hereby appoints the Trustee as its agent to
      receive all such presentations, surrenders, notices and demands.

SECTION 212 Redemption.

      Article Eleven shall be amended by inserting the following sections in
their entirety:

      Section 1109 Conversion Arrangement on Call for Redemption

            In connection with 2021 Debentures, the Company may arrange for the
      purchase and conversion of any 2021 Debentures called for redemption by an
      agreement with one or more investment bankers or other purchasers to
      purchase such 2021 Debentures by paying to a Paying Agent (other than the
      Company or any of its Affiliates) in trust for the Holders, on or before
      11:00 A.M. New York City time on the Redemption Date, an amount that,
      together with any amounts deposited with such Paying Agent by the Company
      for the redemption of such 2021 Debentures, is not less than the
      Redemption Price of such 2021 Debentures. Notwithstanding anything to the
      contrary contained in this Article Eleven, the obligation of the Company
      to pay the Redemption Price of such 2021 Debentures, including interest,
      if any, shall be deemed to be satisfied and discharged to the extent such
      amount is so paid by such purchasers; provided, however, that nothing in
      this Section 1109 shall relieve the Company of its obligation to pay the
      Redemption Price on 2021 Debentures called for redemption. If such an
      agreement is entered into, any 2021 Debentures called for redemption and
      not

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      surrendered for conversion by the Holders thereof prior to the relevant
      Redemption Date may, at the option of the Company upon written notice to
      the Trustee, be deemed, to the fullest extent permitted by law, acquired
      by such purchasers from such Holders and (notwithstanding anything to the
      contrary contained in Article Fourteen) surrendered by such purchasers for
      conversion, all as of 11:00 A.M. New York City time on the Redemption
      Date, subject to payment of the above amount as aforesaid. The Paying
      Agent shall hold and pay to the Holders whose 2021 Debentures are selected
      for redemption any such amount paid to it for purchase in the same manner
      as it would money deposited with it by the Company for the redemption of
      2021 Debentures. Without the Paying Agent's prior written consent, no
      arrangement between the Company and such purchasers for the purchase and
      conversion of any 2021 Debentures shall increase or otherwise affect any
      of the powers, duties, responsibilities or obligations of the Paying Agent
      as set forth in this Indenture, and the Company agrees to indemnify the
      Paying Agent from, and hold it harmless against, any loss, liability or
      expense arising out of or in connection with any such arrangement for the
      purchase and conversion of any 2021 Debentures between the Company and
      such purchasers, including the costs and expenses incurred by the Paying
      Agent in the defense of any claim or liability reasonably incurred without
      negligence or bad faith on their part arising out of or in connection with
      the exercise or performance of any of its powers, duties, responsibilities
      or obligations under this Indenture, in accordance with the indemnity
      provisions applicable to the Trustee set forth herein.

      Section 1110 Purchase of Securities at Option of the Holder Upon Change in
                   Control

            (a) If at any time that 2021 Debentures remain Outstanding there
      shall occur a Change in Control, 2021 Debentures shall be purchased by the
      Company at the option of the Holders thereof as of a date that is within
      35 Business Days after the occurrence of the Change in Control (the
      "Change in Control Purchase Date") at a purchase price equal to the
      Principal Amount plus accrued and unpaid interest up to but excluding the
      Change in Control Purchase Date (the "Change in Control Purchase Price"),
      subject to satisfaction by or on behalf of any Holder of the requirements
      set forth in subsection (c) of this Section 1110.

            A "Change in Control" shall be deemed to have occurred if any of the
      following occurs after the Issue Date:

            (1) any "person" or "group" (as such terms are defined below) is or
      becomes the "beneficial owner" (as defined below), directly or indirectly,
      of shares of Voting Stock of the Company representing 50% or more of the
      total voting power of all outstanding classes of Voting Stock of the
      Company or has the power, directly or indirectly, to elect a majority of
      the members of the Board of Directors of the Company (but specifically
      excluding any right of any Person or Persons to designate directors of the
      Company pursuant to Article 3 of the

                                       11
<PAGE>   14
      Agreement and Plan of Merger dated July 12, 1999 among Schlumberger
      Limited, the Company and certain of their respective subsidiaries); or

            (2) the Company consolidates with, or merges with or into, another
      person or the Company sells, assigns, conveys, transfers, leases or
      otherwise disposes of all or substantially all of the assets of the
      Company, or any person consolidates with, or merges with or into, the
      Company, or the Company completes a scheme of arrangement under Cayman
      Islands law with another Person, in any such event other than pursuant to
      a transaction in which the persons that "beneficially owned" (as defined
      below), directly or indirectly, shares of Voting Stock of the Company
      immediately prior to such transaction "beneficially own" (as defined
      below), directly or indirectly, shares of Voting Stock of the Company
      representing at least a majority of the total voting power of all
      outstanding classes of Voting Stock of the surviving or transferee person;
      or

            (3) there shall occur the liquidation or dissolution of the Company.

            For the purpose of the definition of "Change in Control", (i)
      "person" and "group" have the meanings given such terms under Section
      13(d) and 14(d) of the Exchange Act or any successor provision to either
      of the foregoing, and the term "group" includes any group acting for the
      purpose of acquiring, holding or disposing of securities within the
      meaning of Rule 13d-5(b)(1) under the Exchange Act (or any successor
      provision thereto), (ii) a "beneficial owner" shall be determined in
      accordance with Rule 13d-3 under the Exchange Act, as in effect on May 8,
      2001, except that the number of shares of Voting Stock of the Company
      shall be deemed to include, in addition to all outstanding shares of
      Voting Stock of the Company and Unissued Shares deemed to be held by the
      "person" or "group" (as such terms are defined above) or other person with
      respect to which the Change in Control determination is being made, all
      Unissued Shares deemed to be held by all other persons, and (iii) the
      terms "beneficially owned" and "beneficially own" shall have meanings
      correlative to that of "beneficial owner". The term "Unissued Shares"
      means shares of Voting Stock not outstanding that are subject to options,
      warrants, rights to purchase or conversion privileges exercisable within
      60 days of the date of determination of a Change in Control.

            (b) Within 15 Business Days after the occurrence of a Change in
      Control, the Company shall mail a written notice of the Change in Control
      to the Trustee and to each Holder. The notice shall include the form of a
      Change in Control Purchase Notice to be completed by the Holder and shall
      state:

                  (1) the date of such Change in Control and, briefly, the
            events causing such Change in Control;

                  (2) the date by which the Change in Control Purchase Notice
            pursuant to this Section 1110 must be given;

                                       12
<PAGE>   15
                  (3) the Change in Control Purchase Date;

                  (4) the Change in Control Purchase Price;

                  (5) briefly, the conversion rights of the 2021 Debentures;

                  (6) the name and address of each Paying Agent and Conversion
            Agent;

                  (7) the Conversion Rate and any adjustments thereto;

                  (8) that 2021 Debentures as to which a Change in Control
            Purchase Notice has been given may be converted into Ordinary Shares
            pursuant to Article Fourteen only to the extent that the Change in
            Control Purchase Notice has been withdrawn in accordance with the
            terms of this Indenture;

                  (9) the procedures that the Holder must follow to exercise
            rights under this Section 1110;

                  (10) the procedures for withdrawing a Change in Control
            Purchase Notice, including a form of notice of withdrawal; and

                  (11) that the Holder must satisfy the requirements set forth
            in the 2021 Debentures in order to convert the 2021 Debentures.

            If any of the 2021 Debentures is in the form of a Global Security,
      then the Company shall modify such notice to the extent necessary to
      accord with the procedures of the Depositary applicable to the repurchase
      of Global Securities.

            (c) A Holder may exercise its rights specified in subsection (a) of
      this Section 1110 upon delivery of a written notice (which shall be in
      substantially the form included as an attachment to the Security and which
      may be delivered by letter, overnight courier, hand delivery, facsimile
      transmission or in any other written form and, in the case of Global
      Securities, may be delivered electronically or by other means in
      accordance with the Depositary's customary procedures) of the exercise of
      such rights (a "Change in Control Purchase Notice") to any Paying Agent at
      any time prior to the close of business on the Business Day next preceding
      the Change in Control Purchase Date.

            The delivery of such 2021 Debenture to any Paying Agent (together
      with all necessary endorsements) at the office of such Paying Agent shall
      be a condition to the receipt by the Holder of the Change in Control
      Purchase Price therefor.

            The Company shall purchase from the Holder thereof, pursuant to this
      Section 1110, a portion of a 2021 Debenture if the Principal Amount of
      such portion is $1,000 or an integral multiple of $1,000. Provisions of
      this Indenture

                                       13
<PAGE>   16
      that apply to the purchase of all of a 2021 Debenture pursuant to Sections
      1110 through 1115 also apply to the purchase of such portion of such 2021
      Debenture.

            Notwithstanding anything herein to the contrary, any Holder
      delivering to a Paying Agent the Change in Control Purchase Notice
      contemplated by this subsection (c) shall have the right to withdraw such
      Change in Control Purchase Notice in whole or in a portion thereof that is
      a Principal Amount of $1,000 or in an integral multiple thereof at any
      time prior to the close of business on the Business Day next preceding the
      Change in Control Purchase Date by delivery of a written notice of
      withdrawal to the Paying Agent in accordance with Section 1111.

            A Paying Agent shall promptly notify the Company of the receipt by
      it of any Change in Control Purchase Notice or written withdrawal thereof.

            Anything herein to the contrary notwithstanding, in the case of
      Global Securities, any Change in Control Purchase Notice may be delivered
      or withdrawn and such 2021 Debentures may be surrendered or delivered for
      purchase in accordance with the applicable procedures of the Depositary as
      in effect from time to time.

      Section 1111 Effect of Change in Control Purchase Notice

            Upon receipt by any Paying Agent of the Change in Control Purchase
      Notice specified in Section 1110(c), the Holder of the 2021 Debenture in
      respect of which such Change in Control Purchase Notice was given shall
      (unless such Change in Control Purchase Notice is withdrawn as specified
      below) thereafter be entitled to receive the Change in Control Purchase
      Price with respect to such 2021 Debenture. Such Change in Control Purchase
      Price shall be paid to such Holder promptly following the later of (a) the
      Change in Control Purchase Date with respect to such 2021 Debenture
      (provided the conditions in Section 1110(c) have been satisfied) and (b)
      the time of delivery of such 2021 Debenture to a Paying Agent by the
      Holder thereof in the manner required by Section 1110(c). 2021 Debentures
      in respect of which a Change in Control Purchase Notice has been given by
      the Holder thereof may not be converted into Ordinary Shares on or after
      the date of the delivery of such Change in Control Purchase Notice unless
      such Change in Control Purchase Notice has first been validly withdrawn.

            A Change in Control Purchase Notice may be withdrawn by means of a
      written notice (which may be delivered by letter, overnight courier, hand
      delivery, facsimile transmission or in any other written form and, in the
      case of Global Securities, may be delivered electronically or by other
      means in accordance with the Depositary's customary procedures) of
      withdrawal delivered by the Holder to a Paying Agent at any time prior to
      the close of business on the Business Day immediately preceding the Change
      in Control Purchase Date, specifying the Principal Amount of the Security
      or portion thereof (which must be a Principal

                                       14
<PAGE>   17
      Amount of $1,000 or an integral multiple of $1,000 in excess thereof) with
      respect to which such notice of withdrawal is being submitted.

      Section 1112 Deposit of Change in Control Purchase Price

            On or before 11:00 a.m. New York City time on the Change in Control
      Purchase Date, the Company shall deposit with the Trustee or with a Paying
      Agent (other than the Company or an Affiliate of the Company) an amount of
      money (in immediately available funds if deposited on such Business Day)
      sufficient to pay the aggregate Change in Control Purchase Price of all
      the 2021 Debentures or portions thereof that are to be purchased as of
      such Change in Control Purchase Date. The manner in which the deposit
      required by this Section 1112 is made by the Company shall be at the
      option of the Company, provided that such deposit shall be made in a
      manner such that the Trustee or a Paying Agent shall have immediately
      available funds on the Change in Control Purchase Date.

            If a Paying Agent holds, in accordance with the terms hereof, money
      sufficient to pay the Change in Control Purchase Price of any 2021
      Debenture for which a Change in Control Purchase Notice has been tendered
      and not withdrawn in accordance with this Indenture then, on the Change in
      Control Purchase Date, such 2021 Debenture will cease to be Outstanding
      and the rights of the Holder in respect thereof shall terminate (other
      than the right to receive the Change in Control Purchase Price as
      aforesaid). The Company shall publicly announce the Principal Amount of
      2021 Debentures purchased as a result of such Change in Control on or as
      soon as practicable after the Change in Control Purchase Date.

      Section 1113 Securities Purchased In Part

            Any 2021 Debenture that is to be purchased only in part shall be
      surrendered at the office of a Paying Agent and promptly after the Change
      in Control Purchase Date the Company shall execute and the Trustee shall
      authenticate and deliver to the Holder of such 2021 Debenture, without
      service charge, a new 2021 Debenture or 2021 Debentures, of such
      authorized denomination or denominations as may be requested by such
      Holder, in aggregate Principal Amount equal to, and in exchange for, the
      portion of the Principal Amount of the 2021 Debenture so surrendered that
      is not purchased.

      Section 1114 Compliance With Securities Laws Upon Purchase of Securities

            In connection with any offer to purchase or purchase of 2021
      Debentures under Section 1110, the Company shall (a) comply with Rule
      13e-4 (or any successor to either such Rule), if applicable, under the
      Exchange Act, (b) file the related Schedule TO (or any successor or
      similar schedule, form or report) if required under the Exchange Act, and
      (c) otherwise comply with all federal and state securities laws in
      connection with such offer, all so as to permit the rights of

                                       15
<PAGE>   18
      the Holders and obligations of the Company under Sections 1110 through
      1115 to be exercised in the time and in the manner specified therein.

      Section 1115 Repayment to the Company

            To the extent that the aggregate amount of cash deposited by the
      Company pursuant to Section 1112 exceeds the aggregate Change in Control
      Purchase Price together with interest, if any, thereon of the 2021
      Debentures or portions thereof that the Company is obligated to purchase,
      then promptly after the Change in Control Purchase Date the Trustee or a
      Paying Agent, as the case may be, shall return any such excess to the
      Company.

SECTION 213 Conversion, Repurchase.

      The Indenture is amended by adding the following Articles Fourteen and
Fifteen to the Indenture:

                                ARTICLE FOURTEEN

                                   CONVERSION

      Section 1401 Conversion Privilege

            2021 Debentures shall be convertible in accordance with their terms
      and in accordance with this Article.

            A Holder of a 2021 Debenture may convert the Principal Amount of
      such 2021 Debenture (or any portion thereof equal to a Principal Amount of
      $1,000 or any integral multiple of a Principal Amount of $1,000 in excess
      thereof) into Ordinary Shares at any time during the period set forth
      under the caption "Conversion" in the 2021 Debentures, at the Conversion
      Rate then in effect. In case a 2021 Debenture or portion thereof is called
      for redemption pursuant to Article Eleven, such conversion right shall
      terminate at the close of business on the fourth Trading Day prior to the
      earlier of (a) May 15, 2021 and (b) the date on which such 2021 Debenture
      (or portion thereof) is redeemed (unless the Company shall default in
      making the redemption payment when due, in which case the conversion right
      shall terminate at the close of business on the date such default is cured
      and such 2021 Debenture is redeemed). The number of Ordinary Shares
      issuable upon conversion of a 2021 Debenture per $1,000 of Principal
      Amount thereof (the "Conversion Rate") shall be that set forth under the
      caption "Conversion" in the 2021 Debentures, subject to adjustment as
      herein set forth. Provisions of this Indenture that apply to conversion of
      all of a 2021 Debenture also apply to conversion of a portion of a 2021
      Debenture.

            A 2021 Debenture in respect of which a Holder has delivered a
      Repurchase Notice or Change in Control Purchase Notice exercising the
      option of such Holder to require the Company to purchase such 2021
      Debenture, may be converted only if such notice of exercise is withdrawn
      in accordance with the

                                       16
<PAGE>   19
      terms of this Indenture. A Holder of 2021 Debentures is not entitled to
      any rights of a holder of Ordinary Shares until such Holder has converted
      its 2021 Debentures to Ordinary Shares, and only to the extent such 2021
      Debentures are deemed to have been converted into Ordinary Shares pursuant
      to this Article Fourteen.

      Section 1402 Conversion Procedure

            To convert a 2021 Debenture, a Holder must satisfy the requirements
      set forth under the caption "Conversion" in the 2021 Debenture. The date
      on which the Holder satisfies all of those requirements is the "Conversion
      Date." As soon as practicable after the Conversion Date, the Company shall
      deliver to the Holder through a Conversion Agent a certificate for the
      number of whole Ordinary Shares issuable upon the conversion and cash in
      lieu of any fractional shares pursuant to Section 1403. Anything herein to
      the contrary notwithstanding, in the case of Global Securities, conversion
      notices may be delivered and such 2021 Debentures may be surrendered for
      conversion in accordance with the applicable procedures of the Depositary
      as in effect from time to time. The Person in whose name the Ordinary
      Shares certificate is registered shall be deemed to be a shareholder of
      record on the Conversion Date; provided, however, that no surrender of a
      2021 Debenture on any date when the stock transfer books of the Company
      shall be closed shall be effective to constitute the Person or Persons
      entitled to receive the Ordinary Shares upon such conversion as the record
      holder or holders of such Ordinary Shares on such date, but such surrender
      shall be effective to constitute the Person or Persons entitled to receive
      such Ordinary Shares as the record holder or holders thereof for all
      purposes at the close of business on the next succeeding day on which such
      stock transfer books are open; provided, further, that such conversion
      shall be at the Conversion Rate in effect on the date that such 2021
      Debenture shall have been surrendered for conversion, as if the stock
      transfer books of the Company had not been closed. Upon conversion of a
      2021 Debenture, such Person shall no longer be a Holder of such 2021
      Debenture.

            No payment or adjustment will be made for dividends on, or other
      distributions with respect to, any Ordinary Shares except as provided in
      this Article Fourteen. On conversion of a 2021 Debenture, the fair market
      value of such Ordinary Shares (together with any such cash payment in lieu
      of fractional shares) shall be treated as issued in exchange for the 2021
      Debenture being converted pursuant to the provisions hereof.

            If a Holder converts more than one 2021 Debenture at the same time,
      the number of Ordinary Shares issuable upon the conversion shall be based
      on the aggregate Principal Amount of 2021 Debentures converted.

            Upon surrender of a 2021 Debenture that is converted in part, the
      Company shall execute, and the Trustee shall authenticate and deliver to
      the

                                       17
<PAGE>   20
      Holder, a new 2021 Debenture equal in Principal Amount to the Principal
      Amount of the unconverted portion of the 2021 Debenture surrendered.

            2021 Debentures or portions thereof surrendered for conversion after
      the close of business on any Regular Record Date immediately preceding any
      Interest Payment Date and prior to the opening of business on such
      Interest Payment Date shall (unless such 2021 Debentures or portions
      thereof have been called for redemption on a Redemption Date within such
      period) be accompanied by payment to the Company or its order, in New York
      Clearing House funds or other funds acceptable to the Company, of an
      amount equal to the interest payable on such Interest Payment Date on the
      principal amount of 2021 Debentures or portions thereof being surrendered
      for conversion, and such interest payable on such Interest Payment Date
      shall be payable to the registered Holder notwithstanding the conversion
      of such 2001 Debenture.

      Section 1403 Fractional Shares

            The Company will not issue fractional Ordinary Shares upon
      conversion of 2021 Debentures. In lieu thereof, the Company will pay an
      amount in cash based upon the closing price of the Ordinary Shares on the
      Trading Day immediately prior to the Conversion Date.

      Section 1404 Taxes on Conversion

            If a Holder converts a 2021 Debenture, the Company shall pay any
      documentary, stamp or similar issue or transfer tax due on the issue of
      Ordinary Shares upon such conversion. However, the Holder shall pay any
      such tax which is due because the Holder requests the shares to be issued
      in a name other than the Holder's name. The Conversion Agent may refuse to
      deliver the certificate representing the Ordinary Shares being issued in a
      name other than the Holder's name until the Conversion Agent receives a
      sum sufficient to pay any tax which will be due because the shares are to
      be issued in a name other than the Holder's name. Nothing herein shall
      preclude any tax withholding required by law or regulation.

      Section 1405 Company to Provide Ordinary Shares

            The Company shall, prior to issuance of any 2021 Debentures under
      this Article Fourteen, and from time to time as may be necessary, reserve,
      out of its authorized but unissued Ordinary Shares, a sufficient number of
      Ordinary Shares to permit the conversion of all 2021 Debentures
      Outstanding into Ordinary Shares. All Ordinary Shares delivered upon
      conversion of the 2021 Debentures shall be newly issued shares, shall be
      duly authorized, validly issued, fully paid and nonassessable and shall be
      free from preemptive rights and free of any lien or adverse claim.

            The Company will endeavor promptly to comply with all federal and
      state securities laws regulating the registration of the offer and
      delivery of Ordinary

                                       18
<PAGE>   21
      Shares to a converting Holder upon conversion of 2021 Debentures, if any,
      and will list or cause to have quoted such Ordinary Shares on each
      national securities exchange or on the Nasdaq National Market or other
      over-the-counter market or such other market on which the Ordinary Shares
      are then listed or quoted.

      Section 1406 Adjustment of Conversion Rate

            The Conversion Rate shall be adjusted from time to time by the
      Company as follows:

            (a) In case the Company shall (i) pay a dividend on its Ordinary
      Shares in Ordinary Shares, (ii) make a distribution on its Ordinary Shares
      in Ordinary Shares, (iii) subdivide its outstanding Ordinary Shares into a
      greater number of shares, or (iv) combine its outstanding Ordinary Shares
      into a smaller number of shares, the Conversion Rate in effect immediately
      prior thereto shall be adjusted so that the Holder of any 2021 Debenture
      thereafter surrendered for conversion shall be entitled to receive that
      number of Ordinary Shares which it would have owned had such 2021
      Debenture been converted immediately prior to the happening of such event.
      An adjustment made pursuant to this subsection (a) shall become effective
      immediately after the record date in the case of a dividend or
      distribution and shall become effective immediately after the effective
      date in the case of subdivision or combination.

            (b) In case the Company shall issue rights or warrants to all or
      substantially all holders of its Ordinary Shares entitling them (for a
      period commencing no earlier than the record date described below and
      expiring not more than 60 days after such record date) to subscribe for or
      purchase Ordinary Shares at a price per share less than the current market
      price per Ordinary Share (as determined in accordance with subsection (e)
      of this Section 1406) on the record date for the determination of
      shareholders entitled to receive such rights or warrants, the Conversion
      Rate in effect immediately prior thereto shall be adjusted so that the
      same shall equal the rate determined by multiplying the Conversion Rate in
      effect immediately prior to such record date by a fraction of which the
      numerator shall be the number of Ordinary Shares outstanding on such
      record date plus the number of additional Ordinary Shares offered, and of
      which the denominator shall be the number of Ordinary Shares outstanding
      on such record date plus the number of shares which the aggregate offering
      price of the total number of Ordinary Shares so offered would purchase at
      the current market price per share (as determined in accordance with
      subsection (e) of this Section 1406) of Ordinary Shares on such record
      date. Such adjustment shall be made successively whenever any such rights
      or warrants are issued, and shall become effective immediately after such
      record date. If at the end of the period during which such rights or
      warrants are exercisable not all rights or warrants shall have been
      exercised, the adjusted Conversion Rate shall be immediately readjusted to
      what it would have been based upon the number of additional Ordinary
      Shares actually issued.

                                       19
<PAGE>   22
            (c) In case the Company shall distribute to all or substantially all
      holders of its Ordinary Shares any shares of capital stock (other than
      dividends or distributions of Ordinary Shares on Ordinary Shares to which
      Section 1406(a) applies) of the Company, evidences of indebtedness or
      other securities or assets (including securities of any Person other than
      the Company, but excluding all-cash distributions or any rights or
      warrants referred to in Section 1406(b)), then in each such case the
      Conversion Rate shall be adjusted so that the same shall equal the rate
      determined by multiplying the current Conversion Rate by a fraction of
      which the numerator shall be the current market price per share (as
      determined in accordance with subsection (e) of this Section 1406) of the
      Ordinary Shares on the record date mentioned below, and of which the
      denominator shall be the current market price per share (as determined in
      accordance with subsection (e) of this Section 1406) of the Ordinary
      Shares on such record date less the fair market value on such record date
      (as determined by the Board of Directors, whose determination shall be
      conclusive evidence of such fair market value and which shall be evidenced
      by an Officers' Certificate delivered to the Trustee) of the portion of
      the capital stock, evidences of indebtedness, securities or other non-cash
      assets so distributed applicable to one Ordinary Share (determined on the
      basis of the number of Ordinary Shares outstanding on the record date).
      Such adjustment shall be made successively whenever any such distribution
      is made and shall become effective immediately after the record date for
      the determination of shareholders entitled to receive such distribution.

            In the event that the Company implements a shareholder rights plan,
      such rights plan shall provide, subject to customary exceptions and
      limitations, that upon conversion of the 2021 Debentures the Holders will
      receive, in addition to the Ordinary Shares issuable upon such conversion,
      the rights issued under such rights plan (notwithstanding the occurrence
      of an event causing such rights to separate from the Ordinary Shares at or
      prior to the time of conversion). Any distribution of rights or warrants
      pursuant to a shareholder rights plan complying with the requirements set
      forth in the immediately preceding sentence of this paragraph shall not
      constitute a distribution of securities for the purposes of this Section
      1406(c).

            Rights or warrants distributed by the Company to all holders of
      Ordinary Shares entitling the holders thereof to subscribe for or purchase
      shares of the Company's capital stock (either initially or under certain
      circumstances), which rights or warrants, until the occurrence of a
      specified event or events ("Trigger Event"): (i) are deemed to be
      transferred with such Ordinary Shares; (ii) are not exercisable; and (iii)
      are also issued in respect of future issuances of Ordinary Shares, shall
      be deemed not to have been distributed for purposes of this Section
      1406(c) (and no adjustment to the Conversion Rate under this Section
      1406(c) will be required) until the occurrence of the earliest Trigger
      Event. If such right or warrant is subject to subsequent events, upon the
      occurrence of which such right or warrant shall become exercisable to
      purchase different securities, evidences of indebtedness or other assets
      or entitle the holder to purchase a different number or amount of the
      foregoing or to purchase any of the foregoing at a different

                                       20
<PAGE>   23
      purchase price, then the occurrence of each such event shall be deemed to
      be the date of issuance and record date with respect to a new right or
      warrant (and a termination or expiration of the existing right or warrant
      without exercise by the holder thereof). In addition, in the event of any
      distribution (or deemed distribution) of rights or warrants, or any
      Trigger Event or other event (of the type described in the preceding
      sentence) with respect thereto, that resulted in an adjustment to the
      Conversion Rate under this Section 1406(c), (1) in the case of any such
      rights or warrants which shall all have been redeemed or repurchased
      without exercise by any holders thereof, the Conversion Rate shall be
      readjusted upon such final redemption or repurchase to give effect to such
      distribution or Trigger Event, as the case may be, as though it were a
      cash distribution, equal to the per share redemption or repurchase price
      received by a holder of Ordinary Shares with respect to such rights or
      warrants (assuming such holder had retained such rights or warrants), made
      to all holders of Ordinary Shares as of the date of such redemption or
      repurchase, and (2) in the case of such rights or warrants all of which
      shall have expired or been terminated without exercise, the Conversion
      Rate shall be readjusted as if such rights and warrants had never been
      issued.

            (d) (1) In case the Company shall, by dividend or otherwise, at any
      time distribute (a "Triggering Distribution") to all or substantially all
      holders of its Ordinary Shares all-cash distributions in an aggregate
      amount that, together with the aggregate amount of (A) any cash and the
      fair market value (as determined by the Board of Directors, whose
      determination shall be conclusive evidence thereof and which shall be
      evidenced by an Officers' Certificate delivered to the Trustee) of any
      other consideration, payable in respect of any tender offer by the Company
      or a Subsidiary of the Company for Ordinary Shares consummated within the
      12 months preceding the date of payment of the Triggering Distribution and
      in respect of which no Conversion Rate adjustment pursuant to this Section
      1406 has been made and (B) all other cash distributions to all or
      substantially all holders of its Ordinary Shares made within the 12 months
      preceding the date of payment of the Triggering Distribution and in
      respect of which no Conversion Rate adjustment pursuant to this Section
      1406 has been made, exceeds an amount equal to 12.5% of the product of the
      current market price per Ordinary Share (as determined in accordance with
      subsection (e) of this Section 1406) on the Business Day (the
      "Determination Date") immediately preceding the day on which such
      Triggering Distribution is declared by the Company multiplied by the
      number of Ordinary Shares outstanding on the Determination Date (excluding
      shares held in the treasury of the Company), the Conversion Rate shall be
      increased so that the same shall equal the rate determined by multiplying
      such Conversion Rate in effect immediately prior to the Determination Date
      by a fraction of which the numerator shall be such current market price
      per Ordinary Share (as determined in accordance with subsection (e) of
      this Section 1406) on the Determination Date, and the denominator shall be
      the current market price per Ordinary Share (as determined in accordance
      with subsection (e) of this Section 1406) on the Determination Date less
      the sum of the aggregate amount of cash and the aggregate fair market
      value (determined as aforesaid) of any such other consideration, so
      distributed, paid or payable (in the case of amounts paid in any

                                       21
<PAGE>   24
      tender offer, including only that portion of the aggregate amount paid in
      the tender offer that was in excess of the aggregate value of the shares
      purchased in the tender offer (based on the current market price per
      Ordinary Share as determined in accordance with subsection (e) of this
      Section 1406 on the day the tender offer expired)) within such 12 months
      (including, without limitation, the Triggering Distribution) applicable to
      one Ordinary Share (determined on the basis of the number of Ordinary
      Shares outstanding on the Determination Date), such increase to become
      effective immediately prior to the opening of business on the day
      following the date on which the Triggering Distribution is paid.

            (2) In case any tender offer made by the Company or any of its
      Subsidiaries for Ordinary Shares shall expire and such tender offer (as
      amended upon the expiration thereof) shall involve the payment of
      aggregate consideration in an amount (determined as the sum of the
      aggregate amount of cash consideration and the aggregate fair market value
      (as determined by the Board of Directors, whose determination shall be
      conclusive evidence thereof and which shall be evidenced by an Officers'
      Certificate delivered to the Trustee thereof ) of any other consideration)
      that, together with the aggregate amount of (A) any cash and the fair
      market value (as determined by the Board of Directors, whose determination
      shall be conclusive evidence thereof and which shall be evidenced by an
      Officers' Certificate delivered to the Trustee) of any other consideration
      payable in respect of any other tender offers by the Company or any
      Subsidiary of the Company for Ordinary Shares consummated within the 12
      months preceding the date of the Expiration Date (as defined below) and in
      respect of which no Conversion Rate adjustment pursuant to this Section
      1406 has been made and (B) all cash distributions to all or substantially
      all holders of its Ordinary Shares made within the 12 months preceding the
      Expiration Date and in respect of which no Conversion Rate adjustment
      pursuant to this Section 1406 has been made, exceeds an amount equal to
      12.5% of the product of the current market price per Ordinary Share (as
      determined in accordance with subsection (e) of this Section 1406) as of
      the last date (the "Expiration Date") tenders could have been made
      pursuant to such tender offer (as it may be amended) (the last time at
      which such tenders could have been made on the Expiration Date is
      hereinafter sometimes called the "Expiration Time") multiplied by the
      number of Ordinary Shares outstanding (including tendered shares but
      excluding any shares held in the treasury of the Company) at the
      Expiration Time, then, immediately prior to the opening of business on the
      day after the Expiration Date, the Conversion Rate shall be increased so
      that the same shall equal the rate determined by multiplying the
      Conversion Rate in effect immediately prior to close of business on the
      Expiration Date by a fraction of which the numerator shall be the sum of
      (x) the aggregate consideration (determined as aforesaid) payable to
      stockholders based on the acceptance (up to any maximum specified in the
      terms of the tender offer) of all shares validly tendered and not
      withdrawn as of the Expiration Time (the shares deemed so accepted, up to
      any such maximum, being referred to as the "Purchased Shares") and (y) the
      product of the number of Ordinary Shares outstanding (excluding any
      Purchased Shares and any shares held in the treasury of the Company) at
      the Expiration Time and the current market price per Ordinary Share (as
      determined in accordance with subsection (e) of this Section 1406) on the
      Trading Day next succeeding the Expiration Date, and the denominator shall
      be the product of the number of Ordinary Shares outstanding (including
      tendered shares but excluding any shares held in the treasury of the
      Company) at the Expiration Time multiplied by the current market price per
      Ordinary

                                       22
<PAGE>   25
      Share (as determined in accordance with subsection (e) of this Section
      1406) on the Trading Day next succeeding the Expiration Date, such
      increase to become effective immediately prior to the opening of business
      on the day following the Expiration Date. In the event that the Company is
      obligated to purchase shares pursuant to any such tender offer, but the
      Company is permanently prevented by applicable law from effecting any or
      all such purchases or any or all such purchases are rescinded, the
      Conversion Rate shall again be adjusted to be the Conversion Rate which
      would have been in effect based upon the number of shares actually
      purchased. If the application of this Section 1406(d)(2) to any tender
      offer would result in a decrease in the Conversion Rate, no adjustment
      shall be made for such tender offer under this Section 1406(d)(2).

            (3) For purposes of this Section 1406(d), the term "tender offer"
      shall mean and include both tender offers and exchange offers, all
      references to "purchases" of shares in tender offers (and all similar
      references) shall mean and include both the purchase of shares in tender
      offers and the acquisition of shares pursuant to exchange offers, and all
      references to "tendered shares" (and all similar references) shall mean
      and include shares tendered in both tender offers and exchange offers.

            (e) For the purpose of any computation under subsections (b), (c)
      and (d)(l) of this Section 1406, the current market price per Ordinary
      Share on any date shall be deemed to be the average of the daily closing
      prices for a period selected by the Company of either 5 consecutive
      Trading Days or 30 consecutive Trading Days commencing not more than 45
      Trading Days before, and ending not later than, (i) the Determination Date
      with respect to distributions under subsection (d)(l) of this Section 1406
      or (ii) the record date with respect to distributions, issuances or other
      events requiring such computation under subsection (b) or (c) of this
      Section 1406. For the purpose of any computation under subsection (d)(2)
      of this Section 1406, the current market price per Ordinary Share on any
      date shall be deemed to be the average of the daily closing prices for the
      5 consecutive Trading Days commencing on that date. The closing price for
      each day shall be the last reported sales price or, in case no such
      reported sale takes place on such date, the average of the reported
      closing bid and asked prices in either case on the New York Stock Exchange
      (the "NYSE") or, if the Ordinary Shares are not listed or admitted to
      trading on the NYSE, on the principal national securities exchange on
      which the Ordinary Shares are listed or admitted to trading or, if not
      listed or admitted to trading on any national securities exchange, the
      last reported sales price of the Ordinary Shares as quoted on NASDAQ (the
      term "NASDAQ" shall include, without limitation, the Nasdaq National
      Market) or, in case no reported sales takes place, the average of the
      closing bid and asked prices as quoted on NASDAQ or any comparable system

                                       23
<PAGE>   26
      or, if the Ordinary Shares are not quoted on NASDAQ or any comparable
      system, the closing sales price or, in case no reported sale takes place,
      the average of the closing bid and asked prices, as furnished by any two
      members of the National Association of Securities Dealers, Inc. selected
      from time to time by the Company for that purpose. If no such prices are
      available, the current market price per share shall be the fair value of
      an Ordinary Share as determined by the Board of Directors (which shall be
      evidenced by an Officers' Certificate delivered to the Trustee).

            (f) In any case in which this Section 1406 shall require that an
      adjustment be made following a record date or a Determination Date or
      Expiration Date, as the case may be, established for purposes of this
      Section 1406, the Company may elect to defer (but only until five Business
      Days following the filing by the Company with the Trustee of the
      certificate described in Section 1409) issuing to the Holder of any 2021
      Debenture converted after such record date or Determination Date or
      Expiration Date the Ordinary Shares and other capital stock of the Company
      issuable upon such conversion over and above the Ordinary Shares and other
      capital stock of the Company issuable upon such conversion only on the
      basis of the Conversion Rate prior to adjustment; and, in lieu of the
      shares the issuance of which is so deferred, the Company shall issue or
      cause its transfer agents to issue due bills or other appropriate evidence
      prepared by the Company of the right to receive such shares. If any
      distribution in respect of which an adjustment to the Conversion Rate is
      required to be made as of the record date or Determination Date or
      Expiration Date therefor is not thereafter made or paid by the Company for
      any reason, the Conversion Rate shall be readjusted to the Conversion Rate
      which would then be in effect if such record date had not been fixed or
      such effective date or Determination Date or Expiration Date had not
      occurred.

      Section 1407 No Adjustment

            No adjustment in the Conversion Rate shall be required unless the
      adjustment would require an increase or decrease of at least 1% in the
      Conversion Rate as last adjusted; provided, however, that any adjustments
      which by reason of this Section 1407 are not required to be made shall be
      carried forward and taken into account in any subsequent adjustment. All
      calculations under this Article Fourteen shall be made to the nearest cent
      or to the nearest 1/1000th of a share, as the case may be.

            No adjustment need be made for issuances of Ordinary Shares pursuant
      to a Company plan for reinvestment of dividends or interest or for a
      change in the par value or a change to no par value of the Ordinary
      Shares.

            To the extent that the 2021 Debentures become convertible into the
      right to receive cash, no adjustment need be made thereafter as to the
      cash. Interest will not accrue on the cash.

                                       24
<PAGE>   27
      Section 1408 Adjustment for Tax Purposes

            The Company shall be entitled to make such increases in the
      Conversion Rate, in addition to those required by Section 1406, as it in
      its discretion shall determine to be advisable in order that any stock
      dividends, subdivisions of shares, distributions of rights to purchase
      stock or securities or distributions of securities convertible into or
      exchangeable for stock hereafter made by the Company to its shareholders
      shall not be taxable.

      Section 1409 Notice of Adjustment

            Whenever the Conversion Rate is adjusted, the Company shall promptly
      mail to Holders a notice of the adjustment and file with the Trustee an
      Officers' Certificate specifying the adjusted Conversion Rate, and briefly
      stating the facts requiring the adjustment and the manner of computing it.

      Section 1410 Notice of Certain Transactions

            In the event that:

            (1) the Company takes any action which would require an adjustment
      in the Conversion Rate,

            (2) the Company takes any action that requires a supplemental
      indenture pursuant to Section 1411, or

            (3) there is a dissolution or liquidation of the Company,

      the Company shall mail to Holders and file with the Trustee a notice
      stating the proposed record or effective date, as the case may be. The
      Company shall mail the notice at least fifteen days before such date.
      Failure to mail such notice or any defect therein shall not affect the
      validity of any transaction referred to in clause (1), (2) or (3) of this
      Section 1410.

      Section 1411 Effect of Reclassification, Consolidation, Merger or Sale on
                   Conversion Privilege

            If any of the following shall occur, namely: (a) any
      reclassification or change of Ordinary Shares issuable upon conversion of
      the 2021 Debentures (other than a change in par value, or from par value
      to no par value, or from no par value to par value, or as a result of a
      subdivision or combination); (b) any consolidation, merger or scheme of
      arrangement in which the Company is a party consolidating with another
      entity or merging with or into another entity other than a merger in which
      the Company is the continuing corporation and which does not result in any
      reclassification of, or change (other than a change in par value, or from
      par value to no par value, or from no par value to par value, or as a
      result of a subdivision or combination triggering an adjustment under
      Section 1406(a)) in, Outstanding Ordinary Shares; or (c) any sale or
      conveyance of all or substantially

                                       25
<PAGE>   28
      all of the property and assets of the Company to any Person, then the
      Company, or such successor, purchasing or transferee corporation, as the
      case may be, shall (if consideration is receivable by Holders of the
      Ordinary Shares in such consolidation, merger, scheme of arrangement, sale
      or conveyance), as a condition precedent to such reclassification, change,
      consolidation, merger, scheme of arrangement, sale or conveyance, execute
      and deliver to the Trustee a supplemental indenture providing that the
      Holder of each 2021 Debenture then Outstanding shall have the right to
      convert such 2021 Debenture into the kind and amount of shares of stock
      and other securities and property (including cash) receivable upon such
      reclassification, change, consolidation, merger, scheme of arrangement,
      sale or conveyance by a holder of the number of Ordinary Shares
      deliverable upon conversion of such 2021 Debenture immediately prior to
      such reclassification, change, consolidation, merger, scheme of
      arrangement, sale or conveyance assuming such Holder of Ordinary Shares of
      the Company (i) is not a person party to such transaction and (ii) failed
      to exercise his rights of an election, if any, as to the kind or amount of
      stock and other securities and property (including cash) receivable upon
      such reclassification, change, consolidation, merger, scheme of
      arrangement, sale or conveyance (provided, however, that if the kind or
      amount of stock and other securities and property (including cash)
      receivable upon such reclassification, change, consolidation, merger,
      scheme of arrangement, sale or conveyance is not the same for each
      Ordinary Share of the Company held immediately prior to such
      reclassification, change, consolidation, merger, scheme of arrangement,
      sale or conveyance in respect of which such rights of election shall not
      have been exercised ("non-electing share"), then for the purpose of this
      Section 1411 the kind and amount of stock and other securities and
      property (including cash) receivable upon such reclassification, change,
      consolidation, merger, scheme of arrangement, sale or conveyance by each
      non-electing share shall be deemed to be the kind and amount so receivable
      per share by a plurality of the non-electing shares). Such supplemental
      indenture shall provide for adjustments of the Conversion Rate which shall
      be as nearly equivalent as may be practicable to the adjustments of the
      Conversion Rate provided for in this Article Fourteen. If, in the case of
      any such consolidation, merger, scheme of arrangement, sale or conveyance,
      the stock or other securities and property (including cash) receivable
      thereupon by a holder of Ordinary Shares include shares of stock or other
      securities and property of a Person other than the successor, purchasing
      or transferee corporation, as the case may be, in such consolidation,
      merger, scheme of arrangement, sale or conveyance, then such supplemental
      indenture shall also be executed by such other Person and shall contain
      such additional provisions to protect the interests of the Holders of the
      2021 Debentures as the Board of Directors shall reasonably consider
      necessary by reason of the foregoing. The provisions of this Section 1411
      shall similarly apply to successive reclassifications, changes,
      consolidations, mergers, schemes of arrangements, sales or conveyances.

            In the event the Company shall execute a supplemental indenture
      pursuant to this Section 1411, the Company shall promptly file with the
      Trustee (x) an Officers' Certificate briefly stating the reasons therefor,
      the kind or amount of

                                       26
<PAGE>   29
      shares of stock or other securities or property (including cash)
      receivable by Holders of the 2021 Debentures upon the conversion of their
      2021 Debentures after any such reclassification, change, consolidation,
      merger, scheme of arrangement, sale or conveyance, any adjustment to be
      made with respect thereto and that all conditions precedent have been
      complied with and (y) an Opinion of Counsel that all conditions precedent
      have been complied with, and shall promptly mail notice thereof to all
      Holders.

      Section 1412 Trustee's Disclaimer

            The Trustee shall have no duty to determine when an adjustment under
      this Article Fourteen should be made, how it should be made or what such
      adjustment should be, but may accept as conclusive evidence of that fact
      or the correctness of any such adjustment, and shall be protected in
      relying upon, an Officers' Certificate including the Officers' Certificate
      with respect thereto which the Company is obligated to file with the
      Trustee pursuant to Section 1409. The Trustee makes no representation as
      to the validity or value of any securities or assets issued upon
      conversion of 2021 Debentures, and the Trustee shall not be responsible
      for the Company's failure to comply with any provisions of this Article
      Fourteen.

            The Trustee shall not be under any responsibility to determine the
      correctness of any provisions contained in any supplemental indenture
      executed pursuant to Section 1411, but may accept as conclusive evidence
      of the correctness thereof, and shall be fully protected in relying upon,
      the Officers' Certificate with respect thereto which the Company is
      obligated to file with the Trustee pursuant to Section 1411.

      Section 1413 Voluntary Increase

            The Company from time to time may increase the Conversion Rate by
      any amount for any period of time if the period is at least 20 days or
      such longer period as may be required by law and if the increase is
      irrevocable during the period.

                                 ARTICLE FIFTEEN

                REPURCHASE OF SECURITIES AT OPTION OF THE HOLDER

      Section 1501 General

            The Company may be required to repurchase 2021 Debentures in
      accordance with their terms and in accordance with this Article.

            2021 Debentures shall be purchased by the Company under the
      paragraph "Repurchase by the Company at the Option of the Holder" of the
      2021 Debentures on May 15, 2006, May 15, 2011 and May 15, 2016 (each, a

                                       27
<PAGE>   30
      "Repurchase Date"), at the repurchase price specified therein (the
      "Repurchase Price"), at the option of the Holder thereof, upon:

            (1) delivery to the Paying Agent, by the Holder of a written notice
      of purchase (a "Repurchase Notice") at any time from the opening of
      business on the date that is 20 Business Days prior to a Repurchase Date
      until the close of business on such Repurchase Date stating:

                  (A) the certificate number of the 2021 Debenture which the
            Holder will deliver to be repurchased or if any of the 2021
            Debentures is in the form of a Global Security, then a beneficial
            owner of a 2021 Debenture shall comply with the procedures of the
            Depositary applicable to the repurchase of a Global Security,

                  (B) the portion of the Principal Amount of the 2021 Debenture
            which the Holder will deliver to be repurchased, which portion must
            be $1,000 or an integral multiple thereof,

                  (C) that such 2021 Debenture shall be purchased as of the
            Repurchase Date pursuant to the terms and conditions specified under
            the caption "Repurchase by the Company at the Option of the Holder"
            of the 2021 Debentures and in this Indenture,

                  (D) in the event that the Company elects, pursuant to Section
            1502 hereof, to pay the Repurchase Price to be paid as of such
            Repurchase Date, in whole or in part, in Ordinary Shares but such
            portion of the Repurchase Price shall ultimately be payable to such
            Holder entirely in cash because any of the conditions to payment of
            the Repurchase Price in Ordinary Shares is not satisfied prior to
            the close of business on such Repurchase Date, as set forth in
            Section 1503 hereof, whether such Holder elects (i) to withdraw such
            Repurchase Notice as to some or all of the 2021 Debentures to which
            such Repurchase Notice relates (stating the Principal Amount at
            Maturity and certificate numbers of the 2021 Debentures as to which
            such withdrawal shall relate or if certificated 2021 Debentures have
            not been issued, a beneficial owner of a 2021 Debenture shall comply
            with the procedures of the Depositary applicable to the withdrawal
            of a Repurchase Notice), or (ii) to receive cash in respect of the
            entire Repurchase Price for all 2021 Debentures (or portions
            thereof) to which such Repurchase Notice relates, and

            (2) delivery of such 2021 Debenture to the Paying Agent prior to, on
      or after the Repurchase Date (together with all necessary endorsements) at
      the offices of the Paying Agent, such delivery being a condition to
      receipt by the Holder of the Repurchase Price therefor; provided, however,
      that such Repurchase Price shall be so paid pursuant to this Article
      Fifteen only if the 2021 Debenture so delivered to the Paying Agent shall
      conform in all respects to the description thereof in the related
      Repurchase Notice.

                                       28
<PAGE>   31
            If a Holder, in such Holder's Repurchase Notice and in any written
      notice of withdrawal delivered by such Holder pursuant to the terms of
      Section 1509 hereof, fails to indicate such Holder's choice with respect
      to the election set forth in clause (D) of Section 1501(1), such Holder
      shall be deemed to have elected to receive cash in respect of the
      Repurchase Price for all 2021 Debentures subject to the Repurchase Notice
      in the circumstances set forth in such clause (D).

            The Company shall purchase from the Holder thereof, pursuant to this
      Article Fifteen, a portion of a 2021 Debenture if the Principal Amount of
      such portion is $1,000 or an integral multiple of $1,000. Provisions of
      this Indenture that apply to the purchase of all of a 2021 Debenture also
      apply to the purchase of such portion of such 2021 Debenture.

            Any purchase by the Company contemplated pursuant to the provisions
      of this Article Fifteen shall be consummated by the delivery of the
      consideration to be received by the Holder promptly following the later of
      the Repurchase Date and the time of delivery of the 2021 Debenture.

            Notwithstanding anything herein to the contrary, any Holder
      delivering to the Paying Agent the Repurchase Notice contemplated by this
      Section 1501 shall have the right to withdraw such Repurchase Notice at
      any time prior to the close of business on the Repurchase Date by delivery
      of a written notice of withdrawal to the Paying Agent in accordance with
      Section 1509.

            The Paying Agent shall promptly notify the Company of the receipt by
      it of any Repurchase Notice or written notice of withdrawal thereof.

      Section 1502 The Company's Right to Elect Manner of Payment of Repurchase
                   Price

            (a) The Repurchase Price of 2021 Debentures or a specified portion
      thereof in respect of which a Repurchase Notice pursuant to Section 1501
      has been given will be paid by the Company, at the election of the
      Company, with cash or Ordinary Shares or in any combination of cash and
      Ordinary Shares, subject to the conditions set forth in Section 1503 and
      1504 hereof. The Company shall designate, in the Company Notice delivered
      pursuant to Section 1505 hereof, whether the Company will purchase the
      2021 Debentures for cash or Ordinary Shares, or, if a combination thereof,
      the percentages of the Repurchase Price of 2021 Debentures in respect of
      which it will pay in cash and Ordinary Shares; provided that the Company
      will pay cash for fractional interests in Ordinary Shares. For purposes of
      determining the existence of potential fractional interests, all 2021
      Debentures subject to purchase by the Company held by a Holder shall be
      considered together (no matter how many separate certificates are to be
      presented). Each Holder whose 2021 Debentures are purchased pursuant to
      this Article Fifteen shall receive the same percentage of cash or Ordinary
      Shares in payment of the Repurchase Price for such 2021 Debentures, except
      (i) as provided in Section 1504 with regard to the payment of cash in lieu
      of fractional

                                       29
<PAGE>   32
      Ordinary Shares and (ii) in the event that the Company is unable to
      purchase the 2021 Debentures of a Holder or Holders for Ordinary Shares
      because any necessary qualifications or registrations of the Ordinary
      Shares under applicable state securities laws cannot be obtained, the
      Company may purchase the 2021 Debentures of such Holder or Holders for
      cash. The Company may not change its election with respect to the
      consideration (or components or percentages of components thereof) to be
      paid once the Company has given its Company Notice to Holders except
      pursuant to this Section 1502 or pursuant to Section 1504 in the event of
      a failure to satisfy, prior to the close of business on the Repurchase
      Date, any condition to the payment of the Repurchase Price, in whole or in
      part, in Ordinary Shares.

            At least three Business Days before the Company Notice Date, the
      Company shall deliver an Officers' Certificate to the Trustee specifying:

            (i) the manner of payment selected by the Company,

            (ii) the information required by Section 1505,

            (iii) if the Company elects to pay the Repurchase Price, or a
      specified percentage thereof, in Ordinary Shares, that the conditions to
      such manner of payment set forth in Section 1504 have been or will be
      complied with, and

            (iv) whether the Company desires the Trustee to give the Company
      Notice required by Section 1505.

      Section 1503 Purchase with Cash

            On each Repurchase Date, at the option of the Company, the
      Repurchase Price of 2021 Debentures in respect of which a Repurchase
      Notice pursuant to Section 1501 has been given, or a specified percentage
      thereof, may be paid by the Company with cash equal to the aggregate
      Repurchase Price of such 2021 Debentures. If the Company elects to
      purchase 2021 Debentures with cash, the Company Notice, as provided in
      Section 1505, shall be sent to Holders (and to beneficial owners as
      required by applicable law) not less than 20 Business Days prior to such
      Purchase Date (the "Company Notice Date").

      Section 1504 Payment by Issuance of Ordinary Shares

            On each Repurchase Date, at the option of the Company, the
      Repurchase Price of 2021 Debentures in respect of which a Repurchase
      Notice pursuant to Section 1501 has been given, or a specified percentage
      thereof, may be paid by the Company by the issuance of a number of
      Ordinary Shares equal to the quotient obtained by dividing (i) the amount
      of cash to which the Holders would have been entitled had the Company
      elected to pay all or such specified percentage, as the case may be, of
      the Repurchase Price of such 2021 Debentures in cash by (ii) the Market
      Price of an Ordinary Share, subject to the next succeeding paragraph.

                                       30
<PAGE>   33
            The Company will not issue a fractional Ordinary Share in payment of
      the Repurchase Price. Instead the Company will pay cash for the current
      market value of the fractional share. The current market value of a
      fraction of an Ordinary Share shall be determined by multiplying the
      Market Price by such fraction and rounding the product to the nearest
      whole cent with one half cent being rounded upwards. It is understood that
      if a Holder elects to have more than one 2021 Debenture repurchased, the
      number of Ordinary Shares shall be based on the aggregate amount of 2021
      Debentures to be repurchased.

            If the Company elects to purchase the 2021 Debentures by the
      issuance of Ordinary Shares, the Company Notice, as provided in Section
      1505, shall be sent to the Holders (and to beneficial owners as required
      by applicable law) not later than the Company Notice Date.

            The Company's right to exercise its election to purchase the 2021
      Debentures pursuant to this Article Fifteen through the issuance of
      Ordinary Shares shall be conditioned upon:

            (i) the Company's not having given its Company Notice of an election
      to pay entirely in cash and its giving of timely Company Notice of
      election to purchase all or a specified percentage of the 2021 Debentures
      with Ordinary Shares as provided herein;

            (ii) the registration of the Ordinary Shares to be issued in respect
      of the payment of the Repurchase Price under the Securities Act or the
      Exchange Act, in each case, if required for the initial issuance thereof;

            (iii) any necessary qualification or registration under applicable
      state securities laws or the availability of an exemption from such
      qualification and registration; and

            (iv) the receipt by the Trustee of an Officers' Certificate and an
      Opinion of Counsel each stating that (A) the terms of the issuance of the
      Ordinary Shares are in conformity with this Indenture and (B) the Ordinary
      Shares to be issued by the Company in payment of the Repurchase Price in
      respect of 2021 Debentures have been duly authorized and, when issued and
      delivered pursuant to the terms of this Indenture in payment of the
      Repurchase Price in respect of the 2021 Debentures, will be validly
      issued, fully paid and non-assessable and, to the best of such counsel's
      knowledge, free from preemptive rights, and, in the case of such Officer's
      Certificate, stating that conditions (i), (ii) and (iii) above and the
      condition set forth in the third paragraph of this Section 1504 have been
      satisfied and, in the case of such Opinion of Counsel, stating that
      conditions (ii) and (iii) above have been satisfied.

            Such Officers' Certificate shall also set forth the number of
      Ordinary Shares to be issued for each $1,000 Principal Amount of 2021
      Debentures and the Sale Price of an Ordinary Share on each trading day
      during the period

                                       31
<PAGE>   34
      commencing on the first trading day of the period during which the Market
      Price is calculated and ending three Business Days prior to the applicable
      Repurchase Date. The Company may pay the Repurchase Price (or any portion
      thereof) in Ordinary Shares only if the information necessary to calculate
      the Market Price is published in The Wall Street Journal or another daily
      newspaper of national circulation. If the foregoing conditions are not
      satisfied with respect to a Holder or Holders prior to the close of
      business on the Repurchase Date and the Company has elected to repurchase
      the 2021 Debentures pursuant to this Article Fifteen through the issuance
      of Ordinary Shares, the Company shall pay, without further notice, the
      entire Repurchase Price of the 2021 Debentures of such Holder or Holders
      in cash.

            The "Market Price" means the average of the Sale Prices of the
      Ordinary Shares for the five trading day period ending on the third
      Business Day prior to the applicable Repurchase Date (or if the third
      Business Day prior to the applicable Repurchase Date is not a trading day,
      then on the last trading day prior to such third Business Day),
      appropriately adjusted to take into account the occurrence, during the
      period commencing on the first of such trading days during such five
      trading day period and ending on such Repurchase Date, of any event
      described in Section 1406; subject, however, to the conditions set forth
      in Sections 1406(f) and 1407.

            The "Sale Price" of the Ordinary Shares on any date means the
      closing sale price per Ordinary Share (or, if no closing sale price is
      reported, the average of the closing bid and ask prices or, if more than
      one in either case, the average of the average closing bid and average
      closing ask prices) on such date as reported in the composite transactions
      for the principal United States securities exchange on which the Ordinary
      Shares are traded or, if the Ordinary Shares are not listed on a United
      States national or regional securities exchange, as reported by the
      National Association of Securities Dealers Automated Quotation System or
      its successors.

      Section 1505 Notice of Election

            The Company's notice of election to repurchase with cash or Ordinary
      Shares or any combination thereof shall be sent to the Holders in the
      manner provided in Section 106 at the time specified in Section 1503 or
      1504, as applicable (the "Company Notice"). Such Company Notice shall
      state the manner of payment elected and shall contain the following
      information:

            In the event the Company has elected to pay the Repurchase Price (or
      a specified percentage thereof) with Ordinary Shares, the Company Notice
      shall:

            (1) state that each Holder will receive Ordinary Shares with a
      Market Price equal to the Repurchase Price (or such specified percentage
      thereof) of the 2021 Debentures held by such Holder (except any cash
      amount to be paid in lieu of fractional shares);

                                       32
<PAGE>   35
            (2) set forth the method of calculating the Market Price of the
      Ordinary Shares; and

            (3) state that because the Market Price of Ordinary Shares will be
      determined prior to the Repurchase Date, Holders will bear the market risk
      with respect to the value of the Ordinary Shares to be received from the
      date such Market Price is determined to the Repurchase Date.

            In any case, each Company Notice shall include a form of Repurchase
      Notice to be completed by a Holder and shall state:

            (A) the Repurchase Price and the Conversion Rate;

            (B) the name and address of the Paying Agent and the Conversion
      Agent;

            (C) that 2021 Debentures as to which a Repurchase Notice has been
      given may be converted pursuant to Article Fourteen hereof only if the
      applicable Repurchase Notice has been withdrawn in accordance with the
      terms of this Indenture;

            (D) that 2021 Debentures must be surrendered to the Paying Agent to
      collect payment;

            (E) that the Repurchase Price for any 2021 Debenture as to which a
      Repurchase Notice has been given and not withdrawn will be paid promptly
      following the later of the Repurchase Date and the time of surrender of
      such 2021 Debenture as described in (D);

            (F) the procedures the Holder must follow to exercise repurchase
      rights under this Article Fifteen and a brief description of those rights;

            (G) briefly, the conversion rights of the 2021 Debentures; and

            (H) the procedures for withdrawing a Repurchase Notice (including,
      without limitation, for a conditional withdrawal pursuant to the terms of
      Section 1501 or 1509).

            At the Company's request, the Trustee shall give such Company Notice
      in the Company's name and at the Company's expense; provided, however,
      that, in all cases, the text of such Company Notice shall be prepared by
      the Company.

            Upon determination of the actual number of Ordinary Shares to be
      issued for each $1,000 Principal Amount of 2021 Debentures, the Company
      will publish such determination at the Company's Web site on the World
      Wide Web or through such other public medium as the Company may use at
      that time.

                                       33
<PAGE>   36
      Section 1506 Covenants of the Company

            All Ordinary Shares delivered upon purchase of the 2021 Debentures
      shall be newly issued shares, shall be duly authorized, validly issued,
      fully paid and nonassessable and shall be free from preemptive rights and
      free of any lien or adverse claim. The Company shall use its reasonable
      efforts to list or cause to have quoted any Ordinary Shares to be issued
      to purchase 2021 Debentures on the principal national securities exchange
      or over-the-counter or other domestic market on which the Ordinary Shares
      are then listed or quoted.

      Section 1507 Procedure upon Repurchase

            The Company shall deposit cash (in respect of a cash purchase under
      Section 1503 or for fractional Ordinary Shares, as applicable) or Ordinary
      Shares, or a combination thereof, as applicable, at the time and in the
      manner as provided in Section 1510, sufficient to pay the aggregate
      Repurchase Price of all 2021 Debentures to be purchased on the applicable
      Repurchase Date pursuant to this Article Fifteen.

            As soon as practicable after the Repurchase Date, the Company shall
      deliver to each Holder entitled to receive Ordinary Shares through the
      Paying Agent, a certificate for the number of full Ordinary Shares
      issuable in payment of the Repurchase Price and cash in lieu of any
      fractional Ordinary Shares. The Person in whose name the certificate for
      Ordinary Shares is registered shall be treated as a holder of record of
      Ordinary Shares on the Business Day following the Repurchase Date. Subject
      to Section 1504, no payment or adjustment will be made for dividends on
      the Ordinary Shares the record date for which occurred on or prior to the
      Repurchase Date.

      Section 1508 Taxes

            If a Holder of a 2021 Debenture is paid in Ordinary Shares, the
      Company shall pay any documentary, stamp or similar issue or transfer tax
      due on such issue of Ordinary Shares. However, the Holder shall pay any
      such tax which is due because the Holder requests the Ordinary Shares to
      be issued in a name other than the Holder's name. The Paying Agent may
      refuse to deliver the certificates representing the Ordinary Shares being
      issued in a name other than the Holder's name until the Paying Agent
      receives a sum sufficient to pay any tax which will be due because the
      Ordinary Shares are to be issued in a name other than the Holder's name.
      Nothing herein shall preclude any income tax withholding required by law
      or regulations, subject to the payment by the Company of any Tax
      Additional Amounts required by the terms of each 2021 Debenture.

      Section 1509 Effect of Repurchase Notice

            Upon receipt by the Paying Agent of the Repurchase Notice, the
      Holder of the 2021 Debenture in respect of which such Repurchase Notice
      was given shall (unless such Repurchase Notice is withdrawn as specified
      in the following two

                                       34
<PAGE>   37
      paragraphs) thereafter be entitled to receive solely the Repurchase Price
      with respect to such 2021 Debenture. Such Repurchase Price shall be paid
      to such Holder, subject to receipt of funds and/or Ordinary Shares by the
      Paying Agent, promptly following the later of (x) the Repurchase Date with
      respect to such 2021 Debenture (provided the conditions in Section 1501
      have been satisfied) and (y) the time of delivery of such 2021 Debenture
      to the Paying Agent by the Holder thereof in the manner required by
      Section 1501. 2021 Debentures in respect of which a Repurchase Notice has
      been given by the Holder thereof may not be converted pursuant to Article
      Fourteen hereof on or after the date of the delivery of such Repurchase
      Notice unless such Repurchase Notice has first been validly withdrawn as
      specified in the following two paragraphs.

            A Repurchase Notice may be withdrawn by means of a written notice of
      withdrawal delivered to the office of the Paying Agent in accordance with
      the Repurchase Notice at any time prior to the close of business on the
      applicable Repurchase Date specifying:

            (1) the certificate number of the 2021 Debenture in respect of which
      such notice of withdrawal is being submitted or if any of the 2021
      Debentures is in the form of a Global Security, then a beneficial owner of
      a 2021 Debenture shall comply with the procedures of the Depositary
      applicable to the withdrawal of a Repurchase Notice;

            (2) the Principal Amount of the 2021 Debenture with respect to which
      such notice of withdrawal is being submitted; and

            (3) the Principal Amount, if any, of such 2021 Debenture which
      remains subject to the original Repurchase Notice and which has been or
      will be delivered for purchase by the Company.

            A written notice of withdrawal of a Repurchase Notice may be in the
      form set forth in the preceding paragraph or may be in the form of (i) a
      conditional withdrawal contained in a Repurchase Notice pursuant to the
      terms of Section 1501(1)(D) or (ii) a conditional withdrawal containing
      the information set forth in Section 1501(1)(D) and the preceding
      paragraph and contained in a written notice of withdrawal delivered to the
      Paying Agent as set forth in the preceding paragraph.

            There shall be no purchase of any 2021 Debentures pursuant to this
      Article Fifteen (other than through the issuance of Ordinary Shares in
      payment of the Repurchase Price, including cash in lieu of fractional
      shares) if there has occurred (prior to, on or after, as the case may be,
      the giving, by the Holders of such 2021 Debentures, of the required
      Repurchase Notice) and is continuing an Event of Default (other than a
      default in the payment of the Repurchase Price with respect to such 2021
      Debentures). The Paying Agent will promptly return to the respective
      Holders thereof any 2021 Debentures (x) with respect to which a Repurchase
      Notice has been withdrawn in compliance with this Indenture, or (y)

                                       35
<PAGE>   38
      held by it during the continuance of an Event of Default (other than a
      default in the payment of the Repurchase Price with respect to such 2021
      Debentures) in which case, upon such return, the Repurchase Notice with
      respect thereto shall be deemed to have been withdrawn.

      Section 1510 Deposit of Repurchase Price

            Prior to 11:00 a.m. (New York City time) on the Business Day
      following the Repurchase Date, the Company shall deposit with the Trustee
      or with the Paying Agent an amount of money (in immediately available
      funds if deposited on such Business Day) and/or Ordinary Shares, if
      permitted hereunder, sufficient to pay the aggregate Repurchase Price of
      all of the 2021 Debentures or portions thereof which are to be purchased
      as of the Repurchase Date.

      Section 1511 Securities Repurchased in Part

            Any 2021 Debenture which is to be purchased only in part shall be
      surrendered at the office of the Paying Agent (with, if the Company or the
      Trustee so requires, due endorsement by, or a written instrument of
      transfer in form satisfactory to the Company or the Trustee duly executed
      by, the Holder thereof or such Holder's attorney duly authorized in
      writing) and the Company shall execute and the Trustee shall authenticate
      and deliver to the Holder of such 2021 Debenture, without service charge,
      a new 2021 Debenture or 2021 Debentures, of any authorized denomination as
      requested by such Holder in aggregate Principal Amount equal to, and in
      exchange for, the portion of the Principal Amount of the 2021 Debenture so
      surrendered which is not purchased.

      Section 1512 Comply with Securities Laws Upon Purchase of Securities

            In connection with any offer to purchase or purchase of 2021
      Debentures under this Article Fifteen (provided that such offer or
      purchase constitutes an "issuer tender offer" for purposes of Rule 13e-4
      (which term, as used herein, includes any successor provision thereto)
      under the Exchange Act at the time of such offer or purchase), the Company
      shall (i) comply with Rule 13e-4 under the Exchange Act, (ii) file the
      related Schedule TO (or any successor schedule, form or report) under the
      Exchange Act, and (iii) otherwise comply with all Federal and state
      securities laws so as to permit the rights and obligations under Article
      Fifteen to be exercised in the time and in the manner specified in this
      Article Fifteen.

      Section 1513 Repayment to the Company

            The Trustee and the Paying Agent shall return to the Company any
      cash or Ordinary Shares that remain unclaimed for two years, subject to
      applicable unclaimed property law, together with interest or dividends, if
      any, thereon held by them for the payment of the Repurchase Price;
      provided, however, that to the extent that the aggregate amount of cash or
      Ordinary Shares deposited by the Company pursuant to Section 1510 exceeds
      the aggregate Repurchase Price of the

                                       36
<PAGE>   39
      2021 Debentures or portions thereof which the Company is obligated to
      purchase as of the Repurchase Date, then promptly after the Business Day
      following the Repurchase Date the Trustee shall return any such excess to
      the Company together with interest or dividends, if any, thereon. After
      that, Holders entitled to money must look to the Company for payment as
      general creditors, unless an applicable abandoned property law designates
      another Person.

      Section 1514 Conversion Arrangement on Repurchase

            Any 2021 Debentures required to be repurchased under this Article
      Fifteen, unless surrendered for conversion before the close of business on
      the Repurchase Date, may be deemed to be purchased from the Holders of
      such 2021 Debentures for an amount in cash not less than the Repurchase
      Price, by one or more investment bankers or other purchasers who may agree
      with the Company to purchase such 2021 Debentures from the Holders, to
      convert them into Ordinary Shares of the Company and to make payment for
      such 2021 Debentures to the Trustee in trust for such Holders.

SECTION 214 Amendment to Events of Default.

            (a) Clause (1) of Section 501 of the Indenture is amended to read in
its entirety as follows:

            (1) default in the payment of any interest or of any Tax Additional
      Amounts upon any 2021 Debentures when such interest or Tax Additional
      Amounts become due and payable and continuance of such default for a
      period of 30 days;

            (b) Clause (2) of Section 501 of the Indenture is amended to read in
its entirety as follows:

            (2) default in the payment of the Principal Amount, the Redemption
      Price, the Repurchase Price or the Change in Control Purchase Price when
      the same becomes due and payable at its Stated Maturity upon redemption,
      upon declaration of acceleration, when due for repurchase by the Company
      or otherwise;

                                 ARTICLE THREE

                            MISCELLANEOUS PROVISIONS

SECTION 301 Integral Part.

      This Fourth Supplemental Indenture constitutes an integral part of the
Indenture.

SECTION 302 General Definitions.

      For all purposes of this Fourth Supplemental Indenture:

                                       37
<PAGE>   40
            (a) capitalized terms used herein without definition shall have the
meanings specified in the Indenture; and

            (b) the terms "herein", "hereof", "hereunder" and other words of
similar import refer to this Fourth Supplemental Indenture.

SECTION 303 Adoption, Ratification and Confirmation.

      The Indenture, as supplemented and amended by this Fourth Supplemental
Indenture, is in all respects hereby adopted, ratified and confirmed.

SECTION 304 Counterparts.

      This Fourth Supplemental Indenture may be executed in any number of
counterparts, each of which when so executed shall be deemed an original; and
all such counterparts shall together constitute but one and the same instrument.

SECTION 305 Governing Law.

      THIS FOURTH SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, BUT WITHOUT GIVING EFFECT TO
THE APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THE APPLICATION OF
THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

                                       38
<PAGE>   41
      IN WITNESS WHEREOF, the parties hereto have caused this Fourth
Supplemental Indenture to be duly executed and their respective corporate seals
to be hereunto fixed and attested as of the day and year first written above.

                                          TRANSOCEAN SEDCO FOREX INC.
[SEAL]
                                          By:
                                                ------------------------------
                                                Name:
                                                      ------------------------
                                                Title:
                                                      ------------------------


                                          THE CHASE MANHATTAN BANK, AS TRUSTEE
[SEAL]
                                          By:
                                                ------------------------------
                                                Name:
                                                      ------------------------
                                                Title:
                                                      ------------------------

                                       39
<PAGE>   42

STATE OF TEXAS }

COUNTY OF HARRIS }

      The foregoing instrument was acknowledged before me on May ______, 2001,
by ____________________, the __________________ of TRANSOCEAN SEDCO FOREX INC.,
a Cayman Islands exempted company limited by shares, on behalf of said company.



                                                     ---------------------
                                                         Notary Public



STATE OF TEXAS }

COUNTY OF HARRIS }

      The foregoing instrument was acknowledged before me on May _____, 2001, by
Mauri J. Cowen, a Vice President and Trust Officer of The Chase Manhattan Bank,
a New York banking corporation, on behalf of said banking corporation.




                                                     ---------------------
                                                          Notary Public


                                       40
<PAGE>   43
                                                                         ANNEX A

                             [FORM OF GLOBAL SECURITY]

      UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF
THE DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) TO THE ISSUER
OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY
CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY AND
ANY PAYMENT IS MADE TO CEDE & CO., ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR
VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

      UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR THE INDIVIDUAL
SECURITIES REPRESENTED HEREBY, THIS GLOBAL SECURITY MAY NOT BE TRANSFERRED
EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A
NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY
OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE
OF SUCH SUCCESSOR DEPOSITARY.



                     FORM OF 1.5% CONVERTIBLE DEBENTURES

                               DUE MAY 15, 2021

                         TRANSOCEAN SEDCO FOREX INC.

Issue Date: May 11, 2001                                Maturity: May 15, 2021

Principal Amount: $400,000,000                               CUSIP: 893830 AD1

Registered: No. R-

      Transocean Sedco Forex Inc., a Cayman Islands exempted company limited by
shares (herein called the "Company", which term includes any successor
corporation under the indenture hereinafter referred to), for value received,
hereby promises to pay to Cede & Co., or registered assigns, the principal sum
of Four Hundred Million Dollars ($400,000,000) on May 15, 2021 and to pay
interest thereon and Tax Additional Amounts, if any, in immediately available
funds as specified on the other side of this Security. This Security is
convertible as specified on the other side of this Security.

      Payment of the principal of and interest and Tax Additional Amounts, if
any, on this Security will be made at the office or agency of the Company
maintained for that purpose in the City of New York, New York or Dallas, Texas
in such coin or currency of the United States of

                                      A-1
<PAGE>   44
America as at the time of payment is legal tender for payment of public and
private debts; provided, however, that at the option of the Company, payment of
interest and Tax Additional Amounts, if any, may be made by check mailed to the
address of the Person entitled thereto as such address shall appear in the
Security Register or by wire transfer of immediately available funds to the
accounts designated by the Holder of this Security.

      Reference is hereby made to the further provisions of this Security set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

      Unless the certificate of authentication hereon has been executed by the
Trustee referred to on the reverse hereof by manual signature, this Security
shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.

      IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its corporate seal.

Dated:

                                          TRANSOCEAN SEDCO FOREX INC.

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


----------------------------
Assistant Secretary

[SEAL]

                                      A-2
<PAGE>   45


                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

      This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.

                                          THE CHASE MANHATTAN BANK, AS TRUSTEE


                                          ------------------------------------
                                          Authorized Signature


Date of Authentication:
                        ------------------

                                      A-3
<PAGE>   46
                      [FORM OF REVERSE SIDE OF SECURITY]

                         TRANSOCEAN SEDCO FOREX INC.

                 1.5% CONVERTIBLE DEBENTURE DUE MAY 15, 2021

      This Security is one of a duly authorized issue of senior securities of
the Company issued and to be issued in one or more series under an Indenture,
dated as of April 15, 1997, as amended by the First Supplemental Indenture
thereto dated as of April 15, 1997, the Second Supplemental Indenture thereto
dated as of May 14, 1999, the Third Supplemental Indenture thereto dated as of
May 24, 2000 and the Fourth Supplemental Indenture thereto dated as of May 11,
2001 (as so amended, herein called the "Indenture"), between the Company and The
Chase Manhattan Bank, as Trustee (herein called the "Trustee", which term
includes any successor trustee under the Indenture), or their respective
predecessors, as applicable, to which Indenture and all indentures supplemental
thereto reference is hereby made for a statement of the respective rights,
limitations of rights, duties and immunities thereunder of the Company, the
Trustee and the Holders of the Securities and of the terms upon which the
Securities are, and are to be, authenticated and delivered. This Security is one
of the series designated on the face hereof, limited in aggregate principal
amount to $400,000,000. As used herein, the term "Securities" means securities
of the series designated on the face hereof except that, where the context
requires that such term be construed as including another series of securities
(e.g., where phrase such as "Securities of each series" or Securities of any
series" or similar phrase are used), the term "Securities" means securities of
any series issued or to be issued under the Indenture.

INTEREST

      The rate at which this Security shall bear interest shall be 1.5% per
annum. The date from which interest shall accrue for this Security shall be May
11, 2001. The Interest Payment Dates on which interest on this Security shall be
payable are May 15 and November 15 of each year, commencing on November 15,
2001. The Regular Record Date for the interest payable on this Security on any
Interest Payment Date shall be the May 1 or November 1, as the case may be,
immediately preceding such Interest Payment Date. Interest will cease to accrue
on this Security upon its maturity, conversion, purchase by the Company at the
option of a holder or redemption.

METHOD OF PAYMENT

      Payments in respect of principal of and interest, if any, on the
Securities shall be made by the Company in immediately available funds.

OPTIONAL REDEMPTION

      No sinking fund is provided for the Securities of this series. After May
20, 2006, the Securities of this series are redeemable as a whole, or from time
to time in part, at any time at the option of the Company at a redemption price
(the "Redemption Price") equal to the Principal Amount plus accrued and unpaid
interest up to but not including the Redemption Date.

                                      A-4
<PAGE>   47
      If the Company redeems less than all of the outstanding Securities, the
Trustee will select the Securities to be redeemed (i) by lot, (ii) pro rata or
(iii) by another method the Trustee considers fair and appropriate. If the
Trustee selects a portion of a Holder's Securities for partial redemption and
the Holder converts a portion of the same Securities, the converted portion will
be deemed to be from the portion selected for redemption.

NOTICE OF REDEMPTION

      Notice of redemption will be mailed by first-class mail at least 20 days
but not more than 60 days before the Redemption Date to each Holder of
Securities to be redeemed at its registered address. Securities in denominations
larger than $1,000 Principal Amount may be redeemed in part, but only in whole
multiples of $1,000. On and after the Redemption Date, subject to the deposit
with the Paying Agent of funds sufficient to pay the Redemption Price, interest
ceases to accrue on Securities or portions thereof called for redemption.

PURCHASE OF SECURITIES AT OPTION OF HOLDER UPON A CHANGE IN CONTROL

      At the option of the Holder and subject to the terms and conditions of the
Indenture, the Company shall become obligated to purchase all or any part
specified by the Holder (so long as the Principal Amount of such part is $1,000
or an integral multiple of $1,000 in excess thereof) of the Securities held by
such Holder on the date that is 35 Business Days after the occurrence of a
Change in Control, at a Change in Control Purchase Price equal to the Principal
Amount plus accrued and unpaid interest up to but not including the Change in
Control Purchase Date. The Holder shall have the right to withdraw any Change in
Control Purchase Notice (in whole or in a portion thereof that is $1,000
Principal Amount or an integral multiple of $1,000 in excess thereof) at any
time prior to the close of business on the Business Day prior to the Change in
Control Purchase Date by delivering a written notice of withdrawal to the Paying
Agent in accordance with the terms of the Indenture.

CONVERSION

      A Holder of a Security may convert the Security into Ordinary Shares at
any time until the close of business on the Business Day prior to the Stated
Maturity; provided, that one of the conditions in the following paragraph is
satisfied; provided, further, that if the Security is called for redemption, the
conversion right will terminate at the close of business on the fourth Trading
Day prior to the earlier of (a) May 15, 2021 and (b) the date on which such
Security (or portion thereof) is redeemed (unless the Company shall default in
making the redemption payment when due, in which case the conversion right shall
terminate at the close of business on the date such default is cured and such
Security is redeemed). A Security in respect of which a Holder has delivered a
Repurchase Notice exercising the option of such Holder to require the Company to
purchase such Security may be converted only if such notice of exercise is
withdrawn in accordance with the terms of the Indenture. The initial Conversion
Rate is 13.8627 Ordinary Shares per $1,000 Principal Amount, subject to
adjustment in certain events described in the Indenture. The Company will
deliver cash or a check in lieu of any fractional Ordinary Share.

      Holders may surrender Securities for conversion into Ordinary Shares on a
Conversion Date if the Sale Price (as defined in the Indenture) of the Ordinary
Shares is greater than 110% of

                                      A-5
<PAGE>   48
the then current Conversion Price for at least 20 Trading Days in the 30 Trading
Day period ending on the Trading Day immediately prior to the Conversion Date.
The "Conversion Price", as of any date, means an amount per Ordinary Share equal
to the quotient of (i) $1,000 (representing the Principal Amount of a Security
with such Principal Amount) divided by (ii) the number of Ordinary Shares
issuable upon conversion of a Security with a $1,000 Principal Amount on such
Conversion Date. In addition, a Holder may surrender for conversion a Security
or portion of a Security which has been called for redemption pursuant to the
section "Optional Redemption" hereof, even if the foregoing provision has not
been satisfied. In the event that the Company declares (a) a dividend or
distribution described in Section 1406(b) of the Indenture, or (b) a dividend or
distribution described in Section 1406(c) or (d)(1) of the Indenture where the
fair market value of such dividend or distribution per Ordinary Share, as
determined pursuant to Section 1406(c) or (d)(l), as applicable, of the
Indenture, exceeds 15% of the Sale Price of the Ordinary Shares as of the
Business Day prior to the date of declaration, the Securities may be surrendered
for conversion beginning on the date the Company gives notice to the Holders of
such right, which shall be not less than 20 days prior to the ex-dividend date
for such dividend or distribution and Securities may be surrendered for
conversion at any time thereafter until the close of business on the Business
Day immediately prior to the ex-dividend date or until the Company announces
that such distribution will not take place. Finally, in the event that the
Company is a party to a reclassification or change, consolidation, merger or
scheme of arrangement under Cayman Islands law, or a sale or conveyance of all
or substantially all of the Company's assets to another person, pursuant to
which the Ordinary Shares would be converted into shares of stock and other
securities and property (including cash) as set forth in Section 1411 of the
Indenture, the Securities may be surrendered for conversion at any time from and
after the date which is 15 days prior to the date the Company announces as the
anticipated effective time until 15 days after the actual date of such
transaction.

      Securities surrendered for conversion after the close of business on any
Regular Record Date immediately preceding any Interest Payment Date and prior to
the opening of business of such Interest Payment Date (except Securities or
portions of Securities to be redeemed on a Redemption Date occurring during such
period) must be accompanied by payment from the Holder of an amount equal to the
interest thereon that the registered Holder is to receive from the Company on
such Interest Payment Date. Except where Securities surrendered for conversion
must be accompanied by payment as described above, no interest on converted
Securities will be payable by the Company on any Interest Payment Date
subsequent to the date of conversion.

      A Holder may convert a portion of a Security if the Principal Amount of
such portion is $1,000 or an integral multiple of $1,000. No payment or
adjustment will be made for dividends on the Ordinary Shares except as provided
in the Indenture.

      No fractional shares will be issued upon conversion; in lieu thereof, an
amount will be paid in cash based upon the closing price of the Ordinary Shares
on the Trading Day immediately prior to the Conversion Date.

      To convert a Security, a Holder must (a) complete and manually sign the
conversion notice set forth below and deliver such notice to a Conversion Agent,
(b) surrender the Security to the Conversion Agent, (c) furnish appropriate
endorsements and transfer documents (including

                                      A-6
<PAGE>   49
any certification that may be required under applicable law) if required by the
Conversion Agent, and (d) pay any transfer or similar tax, if required.

REPURCHASE BY THE COMPANY AT THE OPTION OF THE HOLDER

      Subject to the terms and conditions of the Indenture, the Company shall
become obligated to purchase, at the option of the Holder, the Securities held
by such Holder on May 15, 2006, May 15, 2011 and May 15, 2016 (each, a
"Repurchase Date"), upon delivery of a Repurchase Notice containing the
information set forth in the Indenture, at any time from the opening of business
on the date that is 20 Business Days prior to such Repurchase Date until the
close of business on such Repurchase Date and upon delivery of the Securities to
the Paying Agent by the Holder as set forth in the Indenture.

      The "Repurchase Price" shall be equal to the Principal Amount plus accrued
and unpaid interest up to but not including the Business Day immediately
following the Repurchase Date. The Repurchase Price may be paid, at the option
of the Company, in cash or by the issuance of Ordinary Shares at the Conversion
Rate, or in any combination thereof. Interest due on an Interest Payment Date
that is also a Repurchase Date will be paid to the holder of record on the
relevant Regular Record Date and will not be included in the Repurchase Price.

      Holders have the right to withdraw any Repurchase Notice by delivering to
the Paying Agent a written notice of withdrawal prior to the close of business
on the Repurchase Date in accordance with the provisions of the Indenture.

      If cash (and/or securities if permitted under the Indenture) sufficient to
pay the Repurchase Price of all Securities or portions thereof to be purchased
as of the Repurchase Date, is deposited with the Paying Agent on the Business
Day following the Repurchase Date, interest ceases to accrue on such Securities
(or portions thereof) immediately after such Repurchase Date, and the Holder
thereof shall have no other rights as such (other than the right to receive the
Repurchase Price upon surrender of such Security).

CONVERSION ARRANGEMENT ON CALL FOR REDEMPTION

      Any Securities called for redemption, unless surrendered for conversion
before the close of business on the Redemption Date, may be deemed to be
purchased from the Holders of such Securities at an amount not less than the
Redemption Price, by one or more investment bankers or other purchasers who may
agree with the Company to purchase such Securities from the Holders, to convert
them into Ordinary Shares of the Company and to make payment for such Securities
to the Paying Agent in trust for such Holders.

TAX ADDITIONAL AMOUNTS

      The Company agrees that any amounts to be paid by the Company hereunder
with respect to any Security shall be paid without deduction or withholding for
any and all present and future withholding taxes, levies, imposts and charges
whatsoever imposed by or for the account of the Cayman Islands or any political
subdivision or taxing authority thereof or therein, or if deduction or
withholding of any such taxes, levies, imposts or charges shall at any time be
required by the Cayman Islands or any such subdivision or authority thereof or
therein, the Company will

                                      A-7
<PAGE>   50
(subject to compliance by the Holder of such Security with any relevant
administrative requirements) pay such additional amounts ("Tax Additional
Amounts") in respect of principal amount, premiums (if any), Redemption Price,
Repurchase Price and interest (if any), in accordance with the terms of the
Securities and the Indenture, as the case may be, in order that the amounts
received by the Holder of the Security, after such deduction or withholding,
shall equal the respective amounts of principal, premium (if any), Redemption
Price, Repurchase Price and interest (if any), in accordance with the terms of
the Securities and the Indenture, as specified in such Securities to which such
Holder is entitled; provided, however, that the foregoing shall not apply to:

            (1) any such tax, levy, impost or charge which would not be payable
or due but for the fact that (A) the Holder of a Security (or a fiduciary,
settlor, beneficiary of, member or shareholder of, such Holder, if such Holder
is an estate, trust, partnership or corporation) is a domiciliary, national or
resident of, or engaging in business or maintaining a permanent establishment or
being physically present in, the Cayman Islands or such political subdivision or
otherwise having some present or former connection with the Cayman Islands other
than the holding or ownership of such Security or the collection of the
respective amounts of principal, premium (if any), Redemption Price, Repurchase
Price and interest (if any), in accordance with the terms of the Security and
the Indenture, or the enforcement of such Security or (B) where presentation is
required, such Security was presented more than 30 days after the date such
payment became due or was provided for, whichever is later;

            (2) any estate, inheritance, gift, sales, transfer, excise, personal
property or similar tax, levy, impost or charge;

            (3) any tax, levy, impost or charge which is payable otherwise than
by withholding from payment of the respective amounts of principal, premium (if
any), Redemption Price, Repurchase Price and interest (if any);

            (4) any tax, levy, impost or charge which would not have been
imposed but for the failure to comply with certification, information,
documentation or other reporting requirements concerning the nationality,
residence, identity or connections with the relevant tax authority of the Holder
or beneficial owner of such Security, if such compliance is required by statute
or by regulation as a precondition to relief or exemption from such tax, levy,
impost or charge; or

            (5) any combination of (1) through (4);

nor shall any Tax Additional Amounts be paid to any Holder who is a fiduciary or
partnership or other than the sole beneficial owner of such Security to the
extent that a beneficiary or settlor with respect to such fiduciary, or a member
of such partnership or a beneficial owner thereof, would not have been entitled
to the payment of such Tax Additional Amounts had such beneficiary, settlor,
member or beneficial owner been the Holder of the Security.

TRANSFER

      As provided in the Indenture and subject to certain limitations therein
set forth, the transfer of this Security is registrable in the Security
Register, upon surrender of this Security for

                                      A-8
<PAGE>   51
registration or transfer at the office or agency in a Place of Payment for
Securities of this series, duly endorsed by, or accompanied by a written
instrument of transfer in form satisfactory to the Company and the Security
Registrar duly executed by, the Holder hereof or his attorney duly authorized in
writing, and thereupon one or more new Securities of this series, of any
authorized denominations and for the same aggregate principal amount, executed
by the Company and authenticated and delivered by the Trustee, will be issued to
the designated transferee or transferees.

      The Securities of this series are issuable only in registered form without
coupons in denominations of $1,000 and any integral multiple thereof. As
provided in the Indenture and subject to certain limitations set forth therein
and on the face of this Security, Securities of this series are exchangeable for
a like aggregate principal amount of Securities of this series of a different
authorized denomination as requested by the Holder surrendering the same.

      No service charge shall be made for any such registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

      Prior to due presentment of this Security for registration of transfer,
the Company, the Trustee or any agent of the Company or the Trustee may treat
the Person in whose name this Security is registered as the owner hereof for all
purposes, whether or not this Security be overdue, and neither the Company, the
Trustee nor any such agent shall be affected by notice to the contrary.

AMENDMENT, SUPPLEMENT AND WAIVER; LIMITATION ON SUITS

      The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities of each series to be
affected under the Indenture at any time by the Company and the Trustee with the
consent of the Holders of a majority in principal amount of the Securities at
the time Outstanding of each series to be affected. The Indenture also contains
provisions permitting the Holders of specified percentages in principal amount
of the Securities of each series at the time Outstanding, on behalf of the
Holders of all Securities of such series, to waive compliance by the Company
with certain past defaults under the Indenture and their consequences. Any such
consent or waiver by the Holder of this Security shall be conclusive and binding
upon such Holder and upon all future Holders of this Security and of any
Security issued upon the registration of transfer hereof or in exchange hereof
or in lieu hereof, whether or not notation of such consent or waiver is made
upon this Security.

      Subject to the right of the Holder of any Securities of this series to
institute proceedings to enforce the Holder's right to receive payment of the
principal thereof (and premium, if any) and interest thereon (or repurchase
price thereof) and any Tax Additional Amounts with respect thereto and to
receive shares on conversion, no Holder of the Securities of this series shall
have any right to institute any proceeding, judicial or otherwise, with respect
to the Indenture, or for the appointment of a receiver or trustee, or for any
other remedy thereunder, unless

                                      A-9
<PAGE>   52
      (1) an Event of Default with respect to the Securities of this series
shall have occurred and be continuing and such Holder has previously given
written notice to the Trustee of such continuing Event of Default;

      (2) the Holders of not less than 25% in principal amount of the
Outstanding Securities of this series shall have made written request to the
Trustee to institute proceedings in respect of such Event of Default in its own
name as Trustee hereunder;

      (3) such Holder or Holders have offered to the Trustee reasonable
indemnity against the costs, expenses and liabilities to be incurred in
compliance with such request;

      (4) the Trustee for 60 days after its receipt of such notice, request and
offer of indemnity has failed to institute any such proceeding; and

      (5) no direction inconsistent with such written request has been given to
the Trustee during such 60-day period by the Holders of a majority in principal
amount of the Outstanding Securities of this series;

it being understood and intended that no one or more of such Holders shall have
the right in any manner whatever by virtue of, or by availing of, any provision
of the Indenture to affect, disturb or prejudice the rights of any other of such
Holders, or to obtain or to seek to obtain priority or preference over any other
of such Holders or to enforce any right under the Indenture, except in the
manner herein provided and for the equal and ratable benefit of all of such
Holders.

SUCCESSOR CORPORATION

      When a successor corporation assumes all the obligations of its
predecessor under the Securities and the Indenture in accordance with the terms
and conditions of the Indenture, the predecessor corporation will (except in
certain circumstances specified in the Indenture) be released from those
obligations.

DEFAULTS AND REMEDIES

      If an Event of Default with respect to Securities of this series shall
occur and be continuing, all unpaid Principal Amount plus accrued and unpaid
interest through the acceleration date of the Securities of this series may be
declared due and payable in the manner and with the effect provided in the
Indenture.

DEFEASANCE

      The Indenture contains provisions for defeasance at any time of the entire
indebtedness of this Security or certain restrictive covenants and Events of
Default with respect to this Security, in each case upon compliance with certain
conditions set forth in the Indenture.

NO RECOURSE AGAINST OTHERS

      No recourse shall be had for the payment of the principal of or the
interest, if any, on this Security, for any claim based hereon, or otherwise in
respect hereof, or based on or in respect of

                                      A-10
<PAGE>   53
the Indenture or any indenture supplemental thereto, against any incorporator,
shareholder, officer or directory, as such, past, present or future, of the
Company or of any successor corporation, whether by virtue of any constitution,
statute or rule of law or by the enforcement of any assessment of penalty or
otherwise, all such liability being, by acceptance hereof and as part of the
consideration for the issue hereof, expressly waived and released.

INDENTURE TO CONTROL; GOVERNING LAW

      In the case of any conflict between the provisions of this Security and
the Indenture, the provisions of the Indenture shall control.

      THE INDENTURE AND THE SECURITIES SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, BUT WITHOUT GIVING EFFECT TO
THE APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THE APPLICATION OF
THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

DEFINITIONS

      All terms defined in the Indenture and used in this Security but not
specifically defined herein are used herein as so defined.

                                      A-11
<PAGE>   54
                                CONVERSION NOTICE

      To convert this Security into Ordinary Shares of the Company, check the
box: [ ]

      To convert only part of this Security, state the Principal Amount to be
converted (must be $1,000 or a multiple of $1,000): $______________.

      If you want the stock certificate made out in another person's name, fill
in the form below:


--------------------------------------------------------------------------------
                (Insert other person's soc. sec. or tax I.D. no.)


--------------------------------------------------------------------------------
            (Print or type other person's name, address and zip code)

Your Signature:                                      Date:
                ----------------------------------        ----------------------
(Sign exactly as your name appears on the other side of this Security)

*Signature guaranteed by:
                         -------------------------------------------------------

By:
   --------------------------------







--------
*  The signature must be guaranteed by an institution which is a member of one
   of the following recognized signature guaranty programs: (i) the Securities
   Transfer Agent Medallion Program (STAMP); (ii) the New York Stock Exchange
   Medallion Program (MSP); (iii) the Stock Exchange Medallion Program (SEMP);
   or (iv) such other guaranty program acceptable to the Trustee.

                                      A-12
<PAGE>   55

           OPTION OF HOLDER TO ELECT PURCHASE ON CHANGE IN CONTROL

      If you want to elect to have this Security purchased, in whole or in part,
by the Company pursuant to Section 1110 of the Indenture, check the following
box: [ ]

      If you want to have only part of this Security purchased by the Company
pursuant to Section 1110 of the Indenture, state the Principal Amount you want
to be purchased (must be $1,000 or a multiple of $1,000): $_______________


Your Signature:                                      Date:
                ----------------------------------        ----------------------
(Sign exactly as your name appears on the other side of this Security)

*Signature guaranteed by:
                          ------------------------------------------------------

By:
    ------------------------------





-----------
*  The signature must be guaranteed by an institution which is a member of one
   of the following recognized signature guaranty programs: (i) the Securities
   Transfer Agent Medallion Program (STAMP); (ii) the New York Stock Exchange
   Medallion Program (MSP); (iii) the Stock Exchange Medallion Program (SEMP);
   or (iv) such other guaranty program acceptable to the Trustee.


                                      A-13