The following is a composite copy of the Noble Corporation 1991 Stock Option and
             Restricted Stock Plan as amended through April 24, 2003
 
                                NOBLE CORPORATION
                   1991 STOCK OPTION AND RESTRICTED STOCK PLAN
 
      SECTION 1. PURPOSE
 
      The purpose of this Plan is to assist the Company in attracting and
retaining, as officers and key employees of the Company and its Affiliates,
persons of training, experience and ability and to furnish additional incentive
to such persons by encouraging them to become owners of Shares of the Company,
by granting to such persons Incentive Options, Nonqualified Options, Restricted
Stock, or any combination of the foregoing.
 
      SECTION 2. DEFINITIONS
 
      Unless the context otherwise requires, the following words as used herein
shall have the following meanings:
 
            (a) "Affiliate" means any corporation (other than the Company) in
      any unbroken chain of corporations (i) beginning with the Company if, at
      the time of the granting of the Option or award of Restricted Stock, each
      of the corporations other than the last corporation in the unbroken chain
      owns stock possessing 50 percent or more of the total combined voting
      power of all classes of stock in one of the other corporations in such
      chain, or (ii) ending with the Company if, at the time of the granting of
      the Option or award of Restricted Stock, each of the corporations, other
      than the Company, owns stock possessing 50 percent or more of the total
      combined voting power of all classes of stock in one of the other
      corporations in such chain.
 
            (b) "Agreement" means the written agreement (i) between the Company
      and the Optionee evidencing the Option and any SARs that relate to such
      Option granted by the Company and the understanding of the parties with
      respect thereto or (ii) between the Company and a recipient of Restricted
      Stock evidencing the restrictions, terms and conditions applicable to such
      award of Restricted Stock and the understanding of the parties with
      respect thereto.
 
            (c) "Board" means the Board of Directors of the Company as the same
      may be constituted from time to time.
 
            (d) "Code" means the Internal Revenue Code of 1986, as amended.
 
            (e) "Committee" means the Committee provided for in Section 3 of the
      Plan as the same may be constituted from time to time.
 
 
 
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            (f) "Company" means Noble Corporation, a Cayman Islands exempted
      company limited by shares.
 
            (g) "Corporate Transaction" shall have the meaning as defined in
      Section 8 of the Plan.
 
            (h) "Disability" means any termination of employment with the
      Company or an Affiliate because of a long-term or total disability, as
      determined by the Committee in its sole discretion.
 
            (i) "Exchange Act" means the Securities Exchange Act of 1934, as
      amended.
 
            (j) "Fair Market Value" means the fair market value per Share as
      determined by the Committee in good faith; provided, however, that if a
      Share is listed or admitted to trading on a securities exchange registered
      under the Exchange Act, the Fair Market Value per Share shall be the
      average of the reported high and low sales price on the date in question
      (or if there was no reported sale on such date, on the last preceding date
      on which any reported sale occurred) on the principal securities exchange
      on which such Share is listed or admitted to trading, or if a Share is not
      listed or admitted to trading on any such exchange but is listed as a
      national market security on the National Association of Securities
      Dealers, Inc. Automated Quotations System ("NASDAQ") or any similar system
      then in use, the Fair Market Value per Share shall be the average of the
      reported high and low sales price on the date in question (or if there was
      no reported sale on such date, on the last preceding date on which any
      reported sale occurred) on such system, or if a Share is not listed or
      admitted to trading on any such exchange and is not listed as a national
      market security on NASDAQ but is quoted on NASDAQ or any similar system
      then in use, the Fair Market Value per Share shall be the average of the
      closing high bid and low asked quotations on such system for such Share on
      the date in question. For purposes of valuing Shares to be made subject to
      Incentive Options, the Fair Market Value per Share shall be determined
      without regard to any restriction other than one which, by its terms, will
      never lapse.
 
            (k) "Incentive Option" means an Option that is intended to satisfy
      the requirements of Section 422(b) of the Code and Section 17 of the Plan.
 
            (l) "Non-Employee Director" means a director of the Company who
      satisfies the definition thereof under Rule 16b-3 promulgated under the
      Exchange Act.
 
            (m) "Nonqualified Option" means an Option that does not qualify as a
      statutory stock option under Section 422 or 423 of the Code.
 
            (n) "Option" means an option to purchase one or more Shares granted
      under and pursuant to the Plan. Such Option may be either an Incentive
      Option or a Nonqualified Option.
 
            (o) "Optionee" means a person who has been granted an Option and who
      has executed an Agreement with the Company.
 
 
 
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            (p) "Outside Director" means a director of the Company who is an
      outside director within the meaning of Section 162(m) of the Code and the
      regulations promulgated thereunder.
 
            (q) "Plan" means this Noble Corporation 1991 Stock Option and
      Restricted Stock Plan, as amended.
 
            (r) "Restricted Stock" means Shares issued or transferred pursuant
      to Section 20 of the Plan.
 
            (s) "Retirement" means a termination of employment with the Company
      or an Affiliate either (i) on a voluntary basis by a person if,
      immediately prior to such termination of employment, the sum of the age of
      such person and the number of such person's years of continuous service
      with the Company or one or more Affiliates is equal to or greater than 60,
      or (ii) otherwise with the written consent of the Committee in its sole
      discretion.
 
            (t) "SARs" means stock appreciation rights granted pursuant to
      Section 7 of the Plan.
 
            (u) "Securities Act" means the Securities Act of 1933, as amended.
 
            (v) "Share" means a share of the Company's present ordinary shares,
      par value US$0.10 per share, and any share or shares of capital securities
      or other securities of the Company hereafter issued or issuable in respect
      of or in substitution or exchange for each such present share. Such Shares
      may be unissued or reacquired Shares, as the Board, in its sole and
      absolute discretion, shall from time to time determine.
 
            (w) "Immediate Family Members" means the spouse, former spouse,
      children (including stepchildren) or grandchildren of an individual."
 
      SECTION 3. ADMINISTRATION
 
      The Plan shall be administered by, and the decisions concerning the Plan
shall be made solely by, a Committee of two or more directors of the Company,
all of whom are (a) Non-Employee Directors and (b) Outside Directors. Each
member of the Committee shall be appointed by and shall serve at the pleasure of
the Board. The Board shall have the sole continuing authority to appoint members
of the Committee. In making grants or awards, the Committee shall take into
consideration the contribution the person has made or may make to the success of
the Company or its Affiliates and such other considerations as the Board may
from time to time specify.
 
      The Committee shall elect one of its members as its chairman and shall
hold its meetings at such times and places as it may determine. A majority of
the members of the Committee shall constitute a quorum. All decisions and
determinations of the Committee shall be made by the majority vote or decision
of the members present at any meeting at which a quorum is present; provided,
however, that any decision or determination reduced to writing and signed by all
 
 
 
<PAGE>
 
members of the Committee shall be as fully effective as if it had been made by a
majority vote or decision at a meeting duly called and held. The Committee may
appoint a secretary (who need not be a member of the Committee) who shall keep
minutes of its meetings. The Committee may make any rules and regulations for
the conduct of its business that are not inconsistent with the express
provisions of the Plan, the articles of association or memorandum of association
of the Company or any resolutions of the Board.
 
      All questions of interpretation or application of the Plan, or of a grant
of an Option and any SARs that relate to such Option or an award of Restricted
Stock, including questions of interpretation or application of an Agreement,
shall be subject to the determination of the Committee, which determination
shall be final and binding upon all parties.
 
      Subject to the express provisions of the Plan, the Committee shall have
the authority, in its sole and absolute discretion, (a) to adopt, amend or
rescind administrative and interpretive rules and regulations relating to the
Plan; (b) to construe the Plan; (c) to make all other determinations necessary
or advisable for administering the Plan; (d) to determine the terms and
provisions of the respective Agreements (which need not be identical), including
provisions defining or otherwise relating to (i) the term and the period or
periods and extent of exercisability of the Options, (ii) the extent to which
the transferability of Shares issued upon exercise of Options or any SARs that
relate to such Options is restricted, (iii) the effect of termination of
employment upon the exercisability of the Options, and (iv) the effect of
approved leaves of absence (consistent with any applicable regulations of the
Internal Revenue Service) upon the exercisability of such Options; (e) subject
to Sections 9 and 11 of the Plan, to accelerate, for any reason, regardless of
whether the Agreement so provides, the time of exercisability of any Option and
any SARs that relate to such Option that have been granted or the time of the
lapsing of restrictions on Restricted Stock; (f) to construe the respective
Agreements; and (g) to exercise the powers conferred on the Committee under the
Plan. The Board may correct any defect or supply any omission or reconcile any
inconsistency in the Plan in the manner and to the extent it shall deem
expedient to carry it into effect, and it shall be the sole and final judge of
such expediency. The determinations of the Committee or Board, as the case may
be, on the matters referred to in this Section 3 shall be final and conclusive.
 
      SECTION 4. SHARES SUBJECT TO THE PLAN
 
            (a) The total number of Shares that may be purchased pursuant to
      Options, issued or transferred pursuant to the exercise of SARs or awarded
      as Restricted Stock shall not exceed 20,700,000 in the aggregate, and the
      total number of shares for which Options and SARs may be granted, and
      which may be awarded as Restricted Stock, to any one person during any
      continuous five-year period shall not exceed 1,500,000 in the aggregate;
      provided that each such maximum number of shares shall be increased or
      decreased as provided in Section 13 of the Plan.
 
            (b) At any time and from time to time after the Plan takes effect,
      the Committee, pursuant to the provisions herein set forth, may grant
      Options and any SARs that relate to such Options and award Restricted
      Stock until the maximum number of Shares shall be
 
 
 
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      exhausted or the Plan shall be sooner terminated; provided, however, that
      no Incentive Option and any SARs that relate to such Option shall be
      granted after January 29, 2007.
 
            (c) Shares subject to an Option that expires or terminates prior to
      exercise and Shares that had been previously awarded as Restricted Stock
      that have since been forfeited shall be available for further grant of
      Options or award as Restricted Stock. No Option shall be granted and no
      Restricted Stock shall be awarded if the number of Shares for which
      Options have been granted and which pursuant to this Section are not again
      available for Option grant, plus the number of Shares that have been
      awarded as Restricted Stock, would, if such Option were granted or such
      Restricted Stock were awarded, exceed 20,700,000.
 
            (d) Any Shares withheld pursuant to Section 19(c) of the Plan shall
      not be available after such withholding for being optioned or awarded
      pursuant to the provisions hereof.
 
      SECTION 5. ELIGIBILITY
 
      The persons who shall be eligible to receive grants of Options and any
SARs that relate to such Options, and to receive awards of Restricted Stock,
shall be regular salaried officers or other employees of the Company or one or
more of its Affiliates.
 
      SECTION 6. GRANT OF OPTIONS
 
            (a) From time to time while the Plan is in effect, the Committee
      may, in its sole and absolute discretion, select from among the persons
      eligible to receive a grant of Options under the Plan (including persons
      who have already received such grants of Options) such one or more of them
      as in the opinion of the Committee should be granted Options. The
      Committee shall thereupon, likewise in its sole and absolute discretion,
      determine the number of Shares to be allotted for option to each person so
      selected.
 
            (b) Each person so selected shall be offered an Option to purchase
      the number of Shares so allotted to him, upon such terms and conditions,
      consistent with the provisions of the Plan, as the Committee may specify.
      Each such person shall have a reasonable period of time, to be fixed by
      the Committee, within which to accept or reject the proffered Option.
      Failure to accept within the period so fixed may be treated as a
      rejection.
 
            (c) Each person who accepts an Option offered to him shall enter
      into an Agreement with the Company, in such form as the Committee may
      prescribe, setting forth the terms and conditions of the Option, whereupon
      such person shall become a participant in the Plan. In the event a person
      is granted both one or more Incentive Options and one or more Nonqualified
      Options, such grants shall be evidenced by separate Agreements, one for
      each Incentive Option grant and one for each Nonqualified Option grant.
      The date on which the Committee completes all action constituting an offer
      of an Option to a person, including the specification of the number of
      Shares to be subject to the Option, shall constitute the date on which the
      Option covered by such Agreement is granted. In no event, however, shall
      an
 
 
 
<PAGE>
 
      Optionee gain any rights in addition to those specified by the Committee
      in its grant, regardless of the time that may pass between the grant of
      the Option and the actual signing of the Agreement by the Company and the
      Optionee.
 
            (d) Each Agreement that includes SARs in addition to an Option shall
      comply with the provisions of Section 7 of the Plan.
 
      SECTION 7. GRANT OF SARS
 
      The Committee may from time to time grant SARs in conjunction with all or
any portion of any Option either (i) at the time of the initial Option grant
(not including any subsequent modification that may be treated as a new grant of
an Incentive Option for purposes of Section 424(h) of the Code) or (ii) with
respect to Nonqualified Options, at any time after the initial Option grant
while the Nonqualified Option is still outstanding. SARs shall not be granted
other than in conjunction with an Option granted hereunder.
 
      SARs granted hereunder shall comply with the following conditions and also
with the terms of the Agreement governing the Option in conjunction with which
they are granted:
 
            (a) The SAR shall expire no later than the expiration of the
      underlying Option.
 
            (b) Upon the exercise of an SAR, the Optionee shall be entitled to
      receive payment equal to the excess of the aggregate Fair Market Value of
      the Shares with respect to which the SAR is then being exercised
      (determined as of the date of such exercise) over the aggregate purchase
      price of such Shares as provided in the related Option. Payment may be
      made in Shares, valued at their Fair Market Value on the date of exercise,
      or in cash, or partly in Shares and partly in cash, as determined by the
      Committee in its sole and absolute discretion.
 
            (c) SARs shall be exercisable (i) only at such time or times and
      only to the extent that the Option to which they relate shall be
      exercisable, (ii) only when the Fair Market Value of the Shares subject to
      the related Option exceeds the purchase price of the Shares as provided in
      the related Option, and (iii) only upon surrender of the related Option or
      any portion thereof with respect to the Shares for which the SARs are then
      being exercised.
 
            (d) Upon exercise of an SAR, a corresponding number of Shares
      subject to option under the related Option shall be canceled. Such
      canceled Shares shall be charged against the Shares reserved for the Plan,
      as provided in Section 4 of the Plan, as if the Option had been exercised
      to such extent and shall not be available for future Option grants or
      Restricted Stock awards hereunder.
 
 
 
<PAGE>
 
      SECTION 8. OPTION PRICE
 
      The option price for each Share covered by an Incentive Option shall not
be less than the greater of (a) the par value of such Share or (b) the Fair
Market Value of such Share at the time such Option is granted. The option price
for each Share covered by a Nonqualified Option shall not be less than the
greater of (a) the par value of such Share or (b) 100 percent of the Fair Market
Value of such Share at the time the Option is granted, except that the minimum
option price may be equal to or greater than 85 percent of the Fair Market Value
of such Share at the time the Option is granted if and to the extent the
discount from Fair Market Value is expressly granted in lieu of a reasonable
amount of salary or cash bonus. Notwithstanding the two immediately preceding
sentences, if the Company or an Affiliate agrees to substitute a new Option
under the Plan for an old Option, or to assume an old Option, by reason of a
corporate merger, amalgamation, consolidation, acquisition of property or
shares, separation, reorganization, or liquidation (any of such events being
referred to herein as a "Corporate Transaction"), the option price of the Shares
covered by each such new Option or assumed Option may be other than the Fair
Market Value of the Shares at the time the Option is granted as determined by
reference to a formula, established at the time of the Corporate Transaction,
which will give effect to such substitution or assumption; provided, however, in
no event shall:
 
            (a) the excess of the aggregate Fair Market Value of the Shares
      subject to the Option immediately after the substitution or assumption
      over the aggregate option price of such Shares be more than the excess of
      the aggregate Fair Market Value of all Shares subject to the Option
      immediately prior to the substitution or assumption over the aggregate
      option price of such Shares;
 
            (b) in the case of an Incentive Option, the new Option or the
      assumption of the old Option give the Optionee additional benefits that he
      would not have under the old Option; or
 
            (c) the ratio of the option price to the Fair Market Value of the
      shares subject to the Option immediately after the substitution or
      assumption be more favorable to the Optionee than the ratio of the option
      price to the Fair Market Value of the shares subject to the old Option
      immediately prior to such substitution or assumption, on a Share by Share
      basis.
 
Notwithstanding the above, the provisions of this Section 8 with respect to the
option price in the event of a Corporate Transaction shall, in the case of an
Incentive Option, be subject to the requirements of Section 424(a) of the Code
and the Treasury regulations and revenue rulings promulgated thereunder. In the
case of an Incentive Option, in the event of a conflict between the terms of
this Section 8 and the above cited statute, regulations and rulings, or in the
event of an omission in this Section 8 of a provision required by said laws, the
latter shall control in all respects and are hereby incorporated herein by
reference as if set out at length.
 
 
 
<PAGE>
 
      SECTION 9. OPTION PERIOD AND TERMS OF EXERCISE
 
            (a) Each Option shall be exercisable during such period of time as
      the Committee may specify, but in no event for longer than 10 years from
      the date when the Option is granted; provided, however, that
 
                  (i) All rights to exercise an Option and any SARs that relate
            to such Option shall, subject to the provisions of subsection (c) of
            this Section 9, terminate six months after the date the Optionee
            ceases to be employed by at least one of the employers in the group
            of employers consisting of the Company and its Affiliates, for any
            reason other than death, Disability or Retirement, except that, in
            the event of the termination of employment of the Optionee on
            account of fraud, dishonesty or other acts detrimental to the
            interests of the Company or one or more of its Affiliates, the
            Option and any SARs that relate to such Option shall thereafter be
            null and void for all purposes. Employment shall not be deemed to
            have ceased by reason of the transfer of employment, without
            interruption of service, between or among the Company and any of its
            Affiliates. In addition, for purposes of this Plan, employment shall
            not be deemed to have ceased by reason of the termination of
            employment with the Company or an Affiliate, followed by a
            reemployment with the Company or an Affiliate within six months of
            such initial termination, provided such reemployment is approved for
            purposes of this Section 9(a)(i) by the Committee in its sole
            discretion, of (x) a person whose employment terminated initially in
            December 1996 in connection with the sale by the Company and its
            Affiliates of their land drilling assets to Nabors Industries, Inc.
            and its affiliates and (y) any person not otherwise provided for in
            clause (x) immediately preceding.
 
                  (ii) If the Optionee ceases to be employed by at least one of
            the employers in the group of employers consisting of the Company
            and its Affiliates, by reason of his death, Disability or
            Retirement, all rights to exercise such Option and any SARs that
            relate to such Option shall, subject to the provisions of subsection
            (c) of this Section 9, terminate five years thereafter.
 
            (b) If an Option is granted with a term shorter than 10 years, the
      Committee may extend the term of the Option and any SARs that relate to
      such Option, but for not more than 10 years from the date when the Option
      was originally granted.
 
            (c) In no event may an Option or any SARs that relate to such Option
      be exercised after the expiration of the term thereof.
 
      SECTION 10. TRANSFERABILITY OF OPTIONS AND SARS
 
      No Option or any SARs that relate to such Option shall be transferable,
other than by will or the laws of descent and distribution, or the rules
thereunder, and may be exercised during the life of the Optionee only by the
Optionee, except as otherwise provided herein below. Notwithstanding the
foregoing, the Committee may, in its discretion, authorize all or a portion of
 
 
 
<PAGE>
 
any Nonqualified Options and any related SARs to be granted to an Optionee to be
on terms which permit transfer by such Optionee (i) by gift to the Immediate
Family Members of such Optionee, partnerships whose only partners are such
Optionee or the Immediate Family Members of such Optionee, limited liability
companies whose only shareholders or members are such Optionee or the Immediate
Family Members of such Optionee, and trusts established solely for the benefit
of such Optionee or the Immediate Family Members of such Optionee, or (ii) to
any other persons or entities in the discretion of the Committee; provided, that
(x) the Agreement pursuant to which such Nonqualified Options are granted must
be approved by the Committee, and must expressly provide for transferability in
a manner consistent with this Section 10, and (y) subsequent transfers of
transferred Options (and any related SARs) shall be prohibited except those in
accordance with this Section 10 (by will or the laws of descent and
distribution). Following transfer, any such Options (and any related SARs) shall
continue to be subject to the same terms and conditions as were applicable
immediately prior to transfer; provided, that for purposes of the Plan, the term
"Optionee" shall be deemed to refer to the transferee. The events of any
termination of association set forth in Section 9 hereof shall continue to be
applied with respect to the original Optionee, following which the transferred
Options (and any related SARs) shall be exercisable by the transferee only to
the extent, and for the periods, specified in Section 9.
 
      SECTION 11. EXERCISE OF OPTIONS AND SARS
 
            (a) During the lifetime of an Optionee, only such Optionee may
      exercise an Option or any SARs that relate to such Option granted to him.
      In the event of his death, any then exercisable portion of his Option and
      any SARs that relate to such Option may, within five years thereafter, or
      earlier date of termination of the Option, be exercised in whole or in
      part by the duly authorized representative of the deceased Optionee's
      estate.
 
            (b) At any time, and from time to time, during the period when any
      Option and any SARs that relate to such Option, or a portion thereof, are
      exercisable, such Option or SARs, or portion thereof, may be exercised in
      whole or in part; provided, however, that the Committee may require any
      Option or SAR that is partially exercised to be so exercised with respect
      to at least a stated minimum number of Shares.
 
            (c) Each exercise of an Option, or a portion thereof, shall be
      evidenced by a notice in writing to the Company accompanied by payment in
      full of the option price of the Shares then being purchased. Payment in
      full shall mean payment of the full amount due, either in cash, by
      certified check or cashier's check, or, with the consent of the Committee,
      with Shares owned by the Optionee, including an actual or deemed multiple
      series of exchanges of such Shares.
 
            Notwithstanding anything contained herein to the contrary, at the
      request of an Optionee and to the extent permitted by applicable law, the
      Committee may, in its sole and absolute discretion, selectively approve
      arrangements with a brokerage firm or firms under which any such brokerage
      firm shall, on behalf of the Optionee, make payment in full to the Company
      of the option price of the Shares then being purchased, and the Company,
      pursuant to an irrevocable notice in writing from the Optionee, shall make
      prompt delivery of one or
 
 
<PAGE>
 
      more certificates for the appropriate number of Shares to such brokerage
      firm. Payment in full for purposes of the immediately preceding sentence
      shall mean payment of the full amount due, either in cash or by certified
      check or cashier's check.
 
            (d) Each exercise of SARs, or a portion thereof, shall be evidenced
      by a notice in writing to the Company.
 
            (e) No Shares shall be issued upon exercise of an Option until full
      payment therefor has been made, and an Optionee shall have none of the
      rights of a member of the Company until Shares are issued to him.
 
            (f) Nothing herein or in any Agreement shall require the Company to
      issue any Shares upon exercise of an Option or SAR if such issuance would,
      in the opinion of counsel for the Company, constitute a violation of the
      Securities Act or any similar or superseding statute or statutes, or any
      other applicable statute or regulation, as then in effect. Upon the
      exercise of an Option or SAR (as a result of which the Optionee receives
      Shares), or portion thereof, the Optionee shall give to the Company
      satisfactory evidence that he is acquiring such Shares for the purposes of
      investment only and not with a view to their distribution; provided,
      however, if or to the extent that the Shares delivered to the Optionee
      shall be included in a registration statement filed by the Company under
      the Securities Act, such investment representation shall be abrogated.
 
      SECTION 12. DELIVERY OF SHARE CERTIFICATES
 
      As promptly as may be practicable after an Option or SAR (as a result of
the exercise of which the Optionee receives Shares), or a portion thereof, has
been exercised as hereinabove provided, the Company shall make delivery of one
or more certificates for the appropriate number of Shares. In the event that an
Optionee exercises both (i) an Incentive Option or SARs that relate to such
Option (as a result of which the Optionee receives Shares), or a portion
thereof, and (ii) a Nonqualified Option or SARs that relate to such Option (as a
result of which the Optionee receives Shares), or a portion thereof, separate
share certificates shall be issued, one for the Shares subject to the Incentive
Option and one for the Shares subject to the Nonqualified Option.
 
      SECTION 13. CHANGES IN COMPANY'S SHARES AND CERTAIN CORPORATE TRANSACTIONS
 
      If at any time while the Plan is in effect there shall be any increase or
decrease in the number of issued and outstanding Shares of the Company effected
without receipt of consideration therefor by the Company, through the
declaration of a dividend in Shares or through any recapitalization,
amalgamation or merger or otherwise in which the Company is the surviving
corporation, resulting in a split-up, combination or exchange of Shares of the
Company, then and in each such event:
 
 
 
<PAGE>
 
            (a) An appropriate adjustment shall be made in the maximum number of
      Shares then subject to being optioned or awarded as Restricted Stock under
      the Plan, to the end that the same proportion of the Company's issued and
      outstanding Shares shall continue to be subject to being so optioned and
      awarded;
 
            (b) Appropriate adjustment shall be made in the number of Shares and
      the option price per Share thereof then subject to purchase pursuant to
      each Option previously granted and then outstanding, to the end that the
      same proportion of the Company's issued and outstanding Shares in each
      such instance shall remain subject to purchase at the same aggregate
      option price; and
 
            (c) In the case of Incentive Options, any such adjustments shall in
      all respects satisfy the requirements of Section 424(a) of the Code and
      the Treasury regulations and revenue rulings promulgated thereunder.
 
      Except as is otherwise expressly provided herein, the issue by the Company
of shares of its capital securities of any class, or securities convertible into
shares of capital securities of any class, either in connection with a direct
sale or upon the exercise of rights or warrants to subscribe therefor, or upon
conversion of shares or obligations of the Company convertible into such shares
or other securities, shall not affect, and no adjustment by reason thereof shall
be made with respect to, the number of or option price of Shares then subject to
outstanding Options granted under the Plan. Furthermore, the presence of
outstanding Options granted under the Plan shall not affect in any manner the
right or power of the Company to make, authorize or consummate (i) any or all
adjustments, recapitalizations, amalgamations, reorganizations or other changes
in the Company's capital structure or its business; (ii) any merger,
amalgamation or consolidation of the Company; (iii) any issue by the Company of
debt securities or preferred shares that would rank above the Shares subject to
outstanding Options granted under the Plan; (iv) the dissolution or liquidation
of the Company; (v) any sale, transfer or assignment of all or any part of the
assets or business of the Company; or (vi) any other corporate act or
proceeding, whether of a similar character or otherwise.
 
      SECTION 14. EFFECTIVE DATE
 
      The Plan was originally adopted by the Board of Directors of Noble
Drilling Corporation, a Delaware corporation ("Noble-Delaware"), on January 31,
1991 and approved by the stockholders of Noble-Delaware on April 25, 1991. The
Plan was amended and restated on January 30, 1997 and approved by the
stockholders of Noble-Delaware on April 24, 1997. The Plan was amended by the
Board of Directors of Noble-Delaware on July 24, 1997. The Plan was amended by
the Board of Directors of Noble-Delaware on February 4, 1999 and approved by the
stockholders of Noble-Delaware on April 22, 1999. The Plan was amended by the
Board of Directors of Noble-Delaware on October 28, 1999. The Plan was amended
by the Board of Directors of Noble-Delaware on January 31, 2002 and approved by
the stockholders of Noble-Delaware on April 25, 2002.
 
 
 
<PAGE>
 
      On April 30, 2002, the Company became the successor to Noble-Delaware as
part of the internal corporate restructuring of Noble-Delaware and its
subsidiaries. This restructuring was approved by the stockholders of
Noble-Delaware on April 25, 2002. The restructuring was accomplished through the
merger of an indirect, wholly owned subsidiary of Noble-Delaware with and into
Noble-Delaware (the "Merger"). Noble-Delaware survived the Merger as an
indirect, wholly owned subsidiary of the Company. In addition, as a result of
the Merger, all of the outstanding shares of Common Stock (and the related
preferred stock purchase rights) of Noble-Delaware were exchanged for Ordinary
Shares (and related preferred share purchase rights) of the Company. As part of
the Merger, the Company assumed the rights and obligations of Noble-Delaware
under the Plan. Consequently, beginning after April 30, 2002, the Plan is
sponsored by the Company and Ordinary Shares are issuable under the Plan, rather
than shares of Common Stock of Noble-Delaware. The Plan was amended as of May 1,
2002 to reflect the assumption of the Plan by the Company.
 
      SECTION 15. AMENDMENT, SUSPENSION OR TERMINATION
 
      The Board may at any time amend, suspend or terminate the Plan; provided,
however, that after the members of the Company have approved and ratified the
Plan in accordance with Section 14 of the Plan, the Board may not, without
approval of the members of the Company, amend the Plan so as to (a) increase the
maximum number of Shares subject thereto, as specified in Sections 4(a) and 13
of the Plan, (b) reduce the option price for Shares covered by Options granted
hereunder below the price specified in Section 8 of the Plan or (c) permit the
"repricing" of Options and any SARs that relate to such new Options in
contravention of Section 18 of the Plan; and provided further, that the Board
may not modify, impair or cancel any outstanding Option or SAR that relates to
such Option, or the restrictions, terms or conditions applicable to Shares of
Restricted Stock, without the consent of the holder thereof.
 
      SECTION 16. REQUIREMENTS OF LAW
 
      Notwithstanding anything contained herein or in any Agreement to the
contrary, the Company shall not be required to sell or issue Shares under any
Option or SAR if the issuance thereof would constitute a violation by the
Optionee or the Company of any provision of any law or regulation of any
governmental authority or any national securities exchange; and as a condition
of any sale or issuance of Shares upon exercise of an Option or SAR, the Company
may require such agreements or undertakings, if any, as the Company may deem
necessary or advisable to assure compliance with any such law or regulation.
 
      SECTION 17. INCENTIVE OPTIONS
 
      The Committee may, in its sole and absolute discretion, designate any
Option granted under the Plan as an Incentive Option intended to qualify under
Section 422(b) of the Code. Any provision of the Plan to the contrary
notwithstanding, (a) no Incentive Option shall be granted to any person who, at
the time such Incentive Option is granted, owns shares possessing more than
 
 
 
<PAGE>
 
10 percent of the total combined voting power of all classes of shares of the
Company or any Affiliate unless the option price under such Incentive Option is
at least 110 percent of the Fair Market Value of the Shares subject to the
Incentive Option at the date of its grant and such Incentive Option is not
exercisable after the expiration of five years from the date of its grant; and
(b) the aggregate Fair Market Value of the Shares subject to an Incentive Option
and the aggregate Fair Market Value of the shares of the Company or any
Affiliate (or a predecessor corporation of the Company or an Affiliate) subject
to any other incentive stock option (within the meaning of Section 422(b) of the
Code) of the Company and its Affiliates (or a predecessor corporation of any
such corporation), that may become first exercisable in any calendar year, shall
not (with respect to any Optionee) exceed $100,000, determined as of the date
the Incentive Option is granted.
 
      SECTION 18. MODIFICATION OF OPTIONS AND SARS
 
      Subject to the terms and conditions of and within the limitations of the
Plan, the Committee may modify, extend or renew outstanding Options and any SARs
that relate to such Options granted under the Plan. The Committee shall not have
authority to accept the surrender or cancellation of any Options and any SARs
that relate to such Options outstanding hereunder (to the extent not theretofore
exercised) and grant new Options and any SARs that relate to such new Options
hereunder in substitution therefor (to the extent not theretofore exercised) at
any Option Price that is less than the Option Price of the Options surrendered
or cancelled. Notwithstanding the foregoing provisions of this Section 18, no
modification of an outstanding Option and any SARs that relate to such Option
granted hereunder shall, without the consent of the Optionee, alter or impair
any rights or obligations under any Option and any SARs that relate to such
Option theretofore granted hereunder to such Optionee, except as may be
necessary, with respect to Incentive Options, to satisfy the requirements of
Section 422(b) of the Code.
 
      SECTION 19. AGREEMENT PROVISIONS
 
            (a) Each Agreement shall contain such provisions (including, without
      limitation, restrictions or the removal of restrictions upon the exercise
      of the Option and any SARs that relate to such Option and the transfer of
      shares thereby acquired) as the Committee shall deem advisable. Each
      Agreement relating to an Option shall identify the Option evidenced
      thereby as an Incentive Option or Nonqualified Option, as the case may be.
      Incentive Options and Nonqualified Options may not both be covered by a
      single Agreement. Each such Agreement relating to Incentive Options shall
      contain such limitations and restrictions upon the exercise of the
      Incentive Option as shall be necessary for the Incentive Option to which
      such Agreement relates to constitute an incentive stock option, as defined
      in Section 422(b) of the Code.
 
            (b) Each Agreement shall recite that it is subject to the Plan and
      that the Plan shall govern where there is any inconsistency between the
      Plan and the Agreement.
 
 
 
<PAGE>
 
      (c) Each Agreement shall contain a covenant by the Optionee, in such form
as the Committee may require in its discretion, that he consents to and will
take whatever affirmative actions are required, in the opinion of the Committee,
to enable the Company or appropriate Affiliate to satisfy its Federal income tax
and FICA and any applicable state and local withholding obligations. An
Agreement may contain such provisions as the Committee deems appropriate to
enable the Company or its Affiliates to satisfy such withholding obligations,
including provisions permitting the Company, upon the exercise of an Option or
SAR (as a result of which the Optionee receives Shares), to withhold Shares
otherwise issuable to the Optionee exercising the Option or SAR, or to accept
delivery of Shares owned by the Optionee, to satisfy the applicable withholding
obligations.
 
      (d) Each Agreement relating to an Incentive Option shall contain a
covenant by the Optionee immediately to notify the Company in writing of any
disqualifying disposition (within the meaning of Section 421(b) of the Code) of
Shares received upon the exercise of an Incentive Option.
 
SECTION 20. RESTRICTED STOCK
 
      (a) Subject to the provisions of Section 14 of the Plan, the Committee may
from time to time, in its sole and absolute discretion, award Shares of
Restricted Stock to such persons as it shall select from among those persons who
are eligible under Section 5 of the Plan to receive awards of Restricted Stock.
Any award of Restricted Stock shall be made from Shares subject hereto as
provided in Section 4 of the Plan.
 
      (b) A Share of Restricted Stock shall be subject to such restrictions,
terms and conditions, including forfeitures, if any, as may be determined by the
Committee, which may include, without limitation, the rendition of services to
the Company or its Affiliates for a specified time or the achievement of
specific goals, and to the further restriction that no such Share may be sold,
assigned, transferred, discounted, exchanged, pledged or otherwise encumbered or
disposed of until the terms and conditions set by the Committee at the time of
the award of the Restricted Stock have been satisfied; provided, however, that
the minimum restriction period shall be three years from the date of award (one
year in the case of Shares of Restricted Stock awarded with performance-based
conditions); and provided further, that up to 50 percent of the Shares of
Restricted Stock awarded under an Agreement that have not previously vested may
be made subject to vesting annually commencing with the first anniversary of the
award. Each recipient of an award of Restricted Stock shall enter into an
Agreement with the Company, in such form as the Committee shall prescribe,
setting forth the restrictions, terms and conditions of such award, whereupon
such recipient shall become a participant in the Plan.
 
      If a person is awarded Shares of Restricted Stock, whether or not escrowed
as provided below, the person shall be the record owner of such Shares and shall
have all the rights of a member of the Company with respect to such Shares
(unless the escrow agreement, if any, specifically provides otherwise),
including the right to vote and the right to receive dividends
 
 
 
<PAGE>
 
or other distributions made or paid with respect to such Shares. Any certificate
or certificates representing Shares of Restricted Stock shall bear a legend
similar to the following:
 
            The shares represented by this certificate have been issued pursuant
      to the terms of the Noble Corporation 1991 Stock Option and Restricted
      Stock Plan and may not be sold, assigned, transferred, discounted,
      exchanged, pledged or otherwise encumbered or disposed of in any manner
      except as set forth in the terms of the agreement embodying the award of
      such shares dated __________, 20__.
 
      In order to enforce the restrictions, terms and conditions that may be
applicable to a person's Shares of Restricted Stock, the Committee may require
the person, upon the receipt of a certificate or certificates representing such
Shares, or at any time thereafter, to deposit such certificate or certificates,
together with stock powers and other instruments of transfer, appropriately
endorsed in blank, with the Company or an escrow agent designated by the Company
under an escrow agreement in such form as by the Committee shall prescribe.
 
      After the satisfaction of the restrictions, terms and conditions set by
the Committee at the time of an award of Restricted Stock to a person, a new
certificate, without the legend set forth above, for the number of Shares that
are no longer subject to such restrictions, terms and conditions shall be
delivered to the person.
 
      If a person to whom Restricted Stock has been awarded dies after
satisfaction of the restrictions, terms and conditions for the payment of all or
a portion of the award but prior to the actual payment of all or such portion
thereof, such payment shall be made to the person's beneficiary or beneficiaries
at the time and in the same manner that such payment would have been made to the
person.
 
      The Committee shall have the authority (and the Agreement evidencing an
award of Restricted Stock may so provide) to cancel all or any portion of any
outstanding restrictions prior to the expiration of such restrictions with
respect to any or all of the Shares of Restricted Stock awarded to a person
hereunder on such terms and conditions as the Committee may deem appropriate.
 
      (c) Without limiting the provisions of the first paragraph of subsection
(b) of this Section 20, if a person to whom Restricted Stock has been awarded
ceases to be employed by at least one of the employers in the group of employers
consisting of the Company and its Affiliates, for any reason, prior to the
satisfaction of any terms and conditions of an award, any Restricted Stock
remaining subject to restrictions shall thereupon be forfeited by the person and
transferred to, and reacquired by, the Company or an Affiliate at no cost to the
Company or the Affiliate; provided, however, if the cessation is due to the
person's death, Retirement or Disability, the Committee may, in its sole and
absolute discretion, deem that the terms and conditions have been met for all or
part of such remaining portion. In the event of such forfeiture, the person, or
in the event of his death, his personal representative, shall forthwith deliver
to the Secretary of the Company the certificates for the Shares of Restricted
Stock remaining subject to such restrictions, accompanied by such instruments of
transfer, if any, as may reasonably be required by the Secretary of the Company.
 
 
 
<PAGE>
 
      (d) In case of any consolidation or merger of another corporation into the
Company in which the Company is the surviving corporation and in which there is
a reclassification or change (including a change to the right to receive cash or
other property) of the Shares (other than a change in par value, or from par
value to no par value, or as a result of a subdivision or combination, but
including any change in such shares into two or more classes or series of
shares), the Committee may provide that payment of Restricted Stock shall take
the form of the kind and amount of shares and other securities (including those
of any new direct or indirect parent of the Company), property, cash or any
combination thereof receivable upon such consolidation or merger.
 
SECTION 21. GENERAL
 
      (a) The proceeds received by the Company from the sale of Shares pursuant
to Options shall be used for general corporate purposes.
 
      (b) Nothing contained in the Plan or in any Agreement shall confer upon
any Optionee or recipient of Restricted Stock the right to continue in the
employ of the Company or any Affiliate, or interfere in any way with the rights
of the Company or any Affiliate to terminate his employment at any time, with or
without cause.
 
      (c) Neither the members of the Board nor any member of the Committee shall
be liable for any act, omission or determination taken or made in good faith
with respect to the Plan or any Option and any SARs that relate to such Option
granted hereunder or any Restricted Stock awarded hereunder; and the members of
the Board and the Committee shall be entitled to indemnification and
reimbursement by the Company in respect of any claim, loss, damage or expenses
(including counsel fees) arising therefrom to the full extent permitted by law
and under any directors' and officers' liability or similar insurance coverage
that may be in effect from time to time.
 
      (d) Any payment of cash or any issuance or transfer of Shares to the
Optionee, or to his legal representative, heir, legatee or distributee, in
accordance with the provisions hereof, shall, to the extent thereof, be in full
satisfaction of all claims of such persons hereunder. The Committee may require
any Optionee, legal representative, heir, legatee or distributee, as a condition
precedent to such payment, to execute a release and receipt therefor in such
form as it shall determine.
 
      (e) Neither the Committee, the Board nor the Company guarantees the Shares
from loss or depreciation.
 
      (f) All expenses incident to the administration, termination or protection
of the Plan, including, but not limited to, legal and accounting fees, shall be
paid by the Company or its Affiliates.
 
 
 
<PAGE>
 
      (g) Records of the Company and its Affiliates regarding a person's period
of employment, termination of employment and the reason therefor, leaves of
absence, re-employment and other matters shall be conclusive for all purposes
hereunder, unless determined by the Committee to be incorrect.
 
      (h) Any action required of the Company shall be by resolution of its Board
or by a person authorized to act by resolution of the Board. Any action required
of the Committee shall be by resolution of the Committee or by a person
authorized to act by resolution of the Committee.
 
      (i) If any provision of the Plan or any Agreement is held to be illegal or
invalid for any reason, the illegality or invalidity shall not affect the
remaining provisions of the Plan or such Agreement, as the case may be, but such
provision shall be fully severable and the Plan or such Agreement, as the case
may be, shall be construed and enforced as if the illegal or invalid provision
had never been included herein or therein.
 
      (j) Whenever any notice is required or permitted hereunder, such notice
must be in writing and personally delivered or sent by mail. Any notice required
or permitted to be delivered hereunder shall be deemed to be delivered on the
date on which it is personally delivered, or, whether actually received or not,
on the third business day after it is deposited in the United States mail,
certified or registered, postage prepaid, addressed to the person who is to
receive it at the address which such person has theretofore specified by written
notice delivered in accordance herewith. The Company, an Optionee or a recipient
of Restricted Stock may change, at any time and from time to time, by written
notice to the other, the address that it or he had theretofore specified for
receiving notices. Until changed in accordance herewith, the Company and each
Optionee and recipient of Restricted Stock shall specify as its and his address
for receiving notices the address set forth in the Agreement pertaining to the
Shares to which such notice relates.
 
      (k) Any person entitled to notice hereunder may waive such notice.
 
      (l) The Plan shall be binding upon the Optionee or recipient of Restricted
Stock, his heirs, legatees, distributees and legal representatives, upon the
Company, its successors and assigns, and upon the Committee, and its successors.
 
      (m) The titles and headings of Sections and paragraphs are included for
convenience of reference only and are not to be considered in the construction
of the provisions hereof.
 
      (n) All questions arising with respect to the provisions of the Plan shall
be determined by application of the laws of the State of Texas except to the
extent Texas law is preempted by Federal law of the United States, or the laws
of the Cayman Islands.
 
      (o) Words used in the masculine shall apply to the feminine where
applicable, and wherever the context of the Plan dictates, the plural shall be
read as the singular and the singular as the plural.
 
 
 
 
                                    AMENDMENT
 
                                     TO THE
 
                                NOBLE CORPORATION
                   1991 STOCK OPTION AND RESTRICTED STOCK PLAN
 
            WHEREAS, Noble Corporation, a Cayman Islands exempted company
limited by shares (the "Corporation"), has previously assumed the Noble
Corporation 1991 Stock Option and Restricted Stock Plan (the "1991 Plan");
 
            WHEREAS, pursuant to Section 15 of the 1991 Plan, the Board of
Directors has the right under the conditions specified therein to amend the 1991
Plan without obtaining the prior approval of the members of the Corporation; and
 
            WHEREAS, the Board of Directors of the Corporation has determined
that certain amendments to the 1991 Plan are appropriate and in the best
interests of the Corporation and its members;
 
            NOW THEREFORE, the Corporation does hereby amend the 1991 Plan,
effective from and after the date hereof, as follows:
 
      1. Section 2 of the 1991 Plan is hereby amended by adding a new paragraph
"(w)" thereto, such paragraph to read in its entirety as follows:
 
      "(w) "Immediate Family Members" means the spouse, former spouse, children
(including stepchildren) or grandchildren of an individual."
 
      2. Section 10 of the 1991 Plan is hereby deleted in its entirety and the
following is substituted therefor:
 
      "SECTION 10. TRANSFERABILITY OF OPTIONS AND SARS
 
            No Option or any SARs that relate to such Option shall be
      transferable, other than by will or the laws of descent and distribution,
      or the rules thereunder, and may be exercised during the life of the
      Optionee only by the Optionee, except as otherwise provided herein below.
      Notwithstanding the foregoing, the Committee may, in its discretion,
      authorize all or a portion of any Nonqualified Options and any related
      SARs to be granted to an Optionee to be on terms which permit transfer by
      such Optionee (i) by gift to the Immediate Family Members of such
      Optionee, partnerships whose only partners are such Optionee or the
      Immediate Family Members of such Optionee, limited liability companies
      whose only shareholders or members are such Optionee or the Immediate
      Family Members of such Optionee, and trusts established solely for the
      benefit of such Optionee or the Immediate Family Members of such Optionee,
      or (ii) to any other persons or entities in the discretion of the
      Committee; provided, that (x) the
 
<PAGE>
 
      Agreement pursuant to which such Nonqualified Options are granted must be
      approved by the Committee, and must expressly provide for transferability
      in a manner consistent with this Section 10, and (y) subsequent transfers
      of transferred Options (and any related SARs) shall be prohibited except
      those in accordance with this Section 10 (by will or the laws of descent
      and distribution). Following transfer, any such Options (and any related
      SARs) shall continue to be subject to the same terms and conditions as
      were applicable immediately prior to transfer; provided, that for purposes
      of the Plan, the term "Optionee" shall be deemed to refer to the
      transferee. The events of any termination of association set forth in
      Section 9 hereof shall continue to be applied with respect to the original
      Optionee, following which the transferred Options (and any related SARs)
      shall be exercisable by the transferee only to the extent, and for the
      periods, specified in Section 9."
 
      3. This Amendment shall amend only those provisions of the 1991 Plan set
forth herein, and those sections, subsections, phrases or words not expressly
amended hereby shall remain in full force and effect.
 
      IN WITNESS WHEREOF, the undersigned has executed this Amendment as of the
24th day of April, 2003.
 
 
                                        NOBLE CORPORATION
 
                                        By: /s/ JAMES C. DAY
                                            ----------------------
                                        Name:   James C. Day
                                        Title:  Chairman and Chief
                                                Executive Officer
 
 
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