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                                                                   EXHIBIT 10.20

                            NABORS INDUSTRIES, INC.
                1999 POOL EMPLOYEE/DIRECTOR OPTION EXCHANGE PLAN

1.  Purpose.

     (a) General.  The purpose of the 1999 Pool Employee/Director Option
Exchange Plan (the "Plan") is to grant to former employees and non-employee
directors of Pool Energy Services Co. ("Pool") or its subsidiaries who hold
options to purchase shares of Pool common stock ("Pool Options") pursuant to
certain stock option plans of Pool, options to acquire common stock, $.10 par
value per share (the "Nabors Common Stock") of Nabors Industries, Inc. ("Nabors"
or the "Company) in exchange for their existing Pool Options, upon the terms and
conditions of the Plan. The grant of Nabors options shall be effective, and the
Pool Options shall terminate and expire, on the date (the "Acquisition Date")
the merger (the "Merger") of Starry Acquisition Corp. with and into Pool
pursuant to the terms and conditions of the Agreement and Plan of Merger dated
as of January 10, 1999, as amended, among Nabors, Starry Acquisition Corp. and
Pool (the "Merger Agreement"), becomes effective.

     (b) Effective Date.  The Plan shall be effective on the Acquisition Date.
The Plan shall remain effective until ten years after Acquisition Date, or such
earlier date as the Company's Board of Directors (the "Board") shall determine.

2.  Administration.

     (a) General.  The Plan shall be administered by an independent committee
(the "Committee") appointed by the Board, as provided below.

     (b) Committee Structure and Authority.  The Committee shall be appointed
from time to time by the Board and shall consist of not fewer than two members.
The Board shall designate one of the members of the Committee as the Committee
Chairman. The initial members of the Committee shall be Jack Wexler, Chairman,
and Myron M. Sheinfeld. All members of the Committee shall be "disinterested
persons" as defined by Rule 16b-3 of the Securities Exchange Act of 1934, as
amended (the "34 Act") or any successor thereto and "outside directors" as
defined in Section 162(m) of the Internal Revenue Code of 1986, as amended
("IRC"), and the regulations issued thereunder. The Committee shall hold its
meetings at such times and places as it may determine. A majority of its members
shall constitute a quorum. All determinations of the Committee shall be made by
a majority of its members. Any decision or determination reduced to writing and
signed by all members shall be effective as if made by a majority vote at a
meeting duly called and held. The Committee may appoint a secretary (who need
not be a member of the Committee). Service on the Committee shall constitute
service as a director of Nabors for all purposes.

     (c) Committee Discretion.  For purposes of administration, the Committee,
subject to the terms of the Plan, shall have final authority to establish such
rules and regulations, and take such other administrative actions as it deems
necessary or advisable. All determinations and interpretations made by the
Committee shall be final, conclusive and binding on all persons, including
persons awarded options ("Optionees") hereunder, and their legal representatives
and beneficiaries.

     (d) Committee Liability.  No member of the Committee shall be liable for
any act or omission with respect to his or her services on the Committee, if he
or she acts in good faith and in a manner he or she reasonably believes to be in
or not opposed to the best interests of the Company.

3.  Eligibility.

     The persons who shall be eligible to participate in the Plan shall be those
persons (i) who were employed by, or served as non-employee directors of, Pool
or any subsidiary; (ii) who, on the Acquisition Date immediately prior to the
Merger, held validly granted, unexpired Pool Options, whether vested or
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unvested; and (iii) who have elected the Roll-Over Alternative or the Retirement
Roll-Over Alternative pursuant to Section 2.5(a) of the Merger Agreement
("Covered Persons").

4.  Stock Subject to the Plan.

     (a) Stock Authorized.  There shall be available for the grant of options
under the Plan equal to the aggregate number of such shares issuable to all
Covered Persons under the Roll-Over Alternative, not to exceed 1,466,010 shares
of Nabors Common Stock.

     (b) Adjustment of Shares.  The amount of shares that are subject to option
grants are subject to the following adjustments.

          (i) If any change is made in the Nabors Common Stock whether through
     merger, consolidation, reorganization, recapitalization, stock dividend,
     stock split, combination of shares, rights offerings, change in corporate
     structure of the Company, or otherwise, appropriate adjustments will be
     made (A) to the number or type of securities subject to and reserved for
     issuance under the Plan; and (B) in order to prevent dilution or
     enlargement of the rights of Optionees, to the number or type of option
     grants and the exercise price subject to outstanding options.

          (ii) The provisions of this paragraph 4(b) shall apply to any
     unexercised options.

     (c) Registration, Listing and Qualification of Shares of Nabors Common
Stock.  Each option grant shall be subject to the requirements that, if at any
time the Nabors Common Stock covered thereby is not registered, listed or
qualified with or by any securities exchange or under any federal or state law,
and (i) if the Committee shall determine that such registration, listing,
qualification, consent or approval, of any governmental regulatory body is
necessary or desirable as a condition of, or in connection with, the option
grant or the purchase of shares of Nabors Common Stock thereunder, no such
option may be exercised, unless and, until such registration, listing,
qualification, consent or approval shall have been obtained or (ii) if the Board
shall determine that such registration, listing, qualification, consent or
approval of any governmental regulatory body is not necessary and/or not
desirable as a condition of, or in connection with, the option grant or the
purchase of shares of Nabors Common Stock thereunder, the Board may impose any
conditions upon the exercise of such options as it shall deem necessary or
desirable in view of such determination and no such option may be exercised,
unless and until such conditions have been satisfied. Without limiting the
foregoing, the Company may require that any person exercising an option grant
shall make such representations and agreements and furnish such information as
it deems appropriate to assure compliance with the foregoing or any other
applicable legal requirement.

     (d) Release of Shares.  If any options to acquire shares of Nabors Common
Stock that have been granted cease to be subject to a grant, if any options to
acquire shares of Nabors Common Stock that are subject to any grant are
forfeited, if any grant otherwise terminates without issuance of shares of
Nabors Common Stock being made to the Optionee, or if any shares of Nabors
Common Stock that were previously issued under the Plan are received in
connection with the exercise of an option, such shares no longer shall be
available for distribution in connection with option grants under the Plan,
shall cease to be reserved for issuance under the Plan, and shall resume the
status of authorized but unissued shares of the Company.

     (e) Stockholders Rights.  Neither an Optionee nor his or her legal
representatives, legatees or distributees, shall have any of the rights or
privileges of a stockholder of the Company by virtue of a grant of an option,
except with respect to any shares of Nabors Common Stock actually issued or
transferred of record and delivered to one of the aforementioned persons.

5.  Option Grants.

     (a) General.  The Committee shall have the authority to grant options under
the Plan in accordance with the provisions hereof.

     (b) Terms and Conditions of Options.  Grants of options under the Plan
shall be evidenced by an agreement, which shall embody the terms and conditions
of such grants and which shall be subject to the

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terms and conditions set forth in the Plan. The terms and conditions of the
grants pursuant to this Plan shall be as follows:

          (i) Number of Shares.  Each option grant shall state the number of
     shares of Nabors Common Stock to which it pertains. Each Pool Option
     outstanding on the Acquisition Date shall terminate and expire, and the
     Committee shall grant to each Covered Person options to acquire whole
     shares of Nabors Common Stock equal to the number of shares of Pool common
     stock for which the corresponding Pool Options were exercisable, multiplied
     by 1.025, rounded up to the nearest whole number of shares of Nabors Common
     Stock.

          (ii) Option Exercise Price.  The option exercise price shall equal the
     exercise price per share of the corresponding Pool Option, divided by 1.025
     (rounding the resulting exercise price up to the nearest whole cent). The
     option price is to be paid, upon exercise, in cash or, in the discretion of
     the Committee, in options or shares of the Company to be valued at Fair
     Market Value (as defined below) at the time of exercise.

          (iii) Fair Market Value.  For purposes of the Plan, the Fair Market
     Value per share of Nabors Common Stock (and an option to purchase one share
     of Nabors Common Stock) shall be the last sale on the date of reference,
     or, in the case no sale takes place on such date, the average of the
     closing high bid and low asked prices, in either case on the principal
     national securities exchange on which the Nabors Common Stock is listed or
     admitted to trading or, if the Nabors Common Stock is not listed or
     admitted to trading on any national securities exchange, the last sale
     price reported on the National Market System of the National Association of
     Securities Dealers Automated Quotation System ("NASDAQ") on such date, or
     the average of the closing high bid and low asked prices of the Nabors
     Common Stock in the over-the-counter market reported on NASDAQ on such
     date, whichever is applicable or, if there are not such prices reported on
     NASDAQ on such date, then as furnished to the Committee by any New York
     Stock Exchange member selected from time to time by the Committee for such
     purpose. If there is no bid or asked price reported on any such date, the
     market value shall be determined by any other appropriate method selected
     by the Committee.

          (iv) Option Period.  The period for exercise of an option (the "Option
     Period") shall be the same as the period for exercise of the corresponding
     Pool Option. Options may be exercisable in installments during the Option
     Period. Any shares of Nabors Common Stock not purchased on any applicable
     installment date may be purchased thereafter at any time before the
     expiration date of the Option Period.

          (v) Exercise of Options.  In order to exercise an option, the Optionee
     shall deliver to Nabors written notice specifying the number of shares of
     Nabors Common Stock to be purchased, together with a certified or bank
     cashier's check payable to the order of Nabors in the full amount of the
     purchase price therefor; provided, however, that the Committee may, in its
     discretion, allow such payments to be made in whole or in part in Nabors
     Common Stock delivered, or options surrendered, by the Optionee valued at
     the Fair Market Value of such Nabors Common Stock.

     If the Optionee so requests, shares of Nabors Common Stock purchased upon
     exercise of an option may be issued in the name of the Optionee or another
     person. An Optionee shall not have any of the rights of a stockholder until
     the shares of Nabors Common Stock are issued to him or her. An option may
     not be exercised for less than the lesser of (A) ten shares of Nabors
     Common Stock, or (B) the number of shares of Nabors Common Stock remaining
     subject to such option.

          (vi) Vesting.  All options granted pursuant to this Plan shall be
     fully vested on the date of grant.

          (vii) Effect of Termination of Employment or Service.  If an Optionee
     has ceased to be in the employ of the Company or its subsidiaries
     (including but not limited to Pool or its subsidiaries) or to serve as a
     non-employee director of Pool, (A) by reason of death or permanent
     disability (as defined in Section 22(e)(3) of the IRC, as amended) or by a
     bona fide voluntary resignation by the Optionee (as determined in the sole
     discretion of the Committee) which provides at least two weeks' notice of
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     resignation (or longer period if required by other written arrangement) any
     outstanding vested options on the date of termination may be exercised by
     the Optionee (or the Optionee's heirs, devisees or legatees) until the
     applicable expiration date of each option granted to the Optionee; or (B)
     for any other reason (including termination by the Company, Pool or the
     employing subsidiary with or without cause), any outstanding options,
     whether or not vested, may not be exercised after the Optionee's date of
     termination and shall be forfeited; provided, however, in its sole
     discretion the Committee may extend the time to exercise any option to a
     period ending on its applicable expiration date.

          (viii) Nontransferability of Options.  Except as otherwise determined
     by the Committee in its discretion, (A) options shall be exercisable only
     by the Optionee and (B) no option shall be transferable other than by will
     or the laws of descent and distribution or pursuant to a qualified domestic
     relations order as defined by the IRC or Title I of the Employee Retirement
     Income Security Act, or the rules thereunder. The designation of a
     beneficiary by an Optionee shall not constitute a transfer.

          (ix) Wrongful Conduct.  If the Board or any committee of the Board,
     prior to or following the date an Optionee ceases for any reason whatsoever
     to be an employee of the Company or its subsidiaries (including but not
     limited to Pool or its subsidiaries) or to serve as a non-employee director
     of Pool, and after full consideration of the facts, find by majority vote
     that the Optionee has engaged in fraud, embezzlement, theft, commission of
     a felony, dishonesty or any other conduct inimical to the Company or its
     subsidiaries, the Optionee shall forfeit all unexercised options, whether
     or not vested. The decision of the Board or of such committee shall be
     final.

          (x) Other Terms and Conditions.  The Committee may impose such other
     terms and conditions, not inconsistent with the terms hereof, on the grant
     or exercise of options, as it deems advisable; provided, such terms and
     conditions are not inconsistent with the terms of the Merger Agreement.

6.  Change in Control/Extraordinary Transaction.  The Committee, in its
discretion, shall have the authority to make provisions in its grant agreements
to address vesting and other issues arising in connection with a change in
control.

7.  Amendments and Termination.  Either the Board or the Committee may amend or
terminate the Plan at any time, but no amendment or termination shall be made
which would impair the rights of the Optionee without his or her consent. Any
amendment made by the Committee shall be subject to approval or rejection of the
Board. The Committee may amend the terms of any grant, prospectively or
retroactively, except that no such amendment shall impair the rights of the
Optionee. The Committee may also substitute new stock options for previously
granted stock options, including previously granted stock options having higher
option prices, but no such substitution shall be made which would impair the
rights of the Optionee under such stock option theretofore granted without the
Optionee's consent. Subject to the above provisions, the Board shall have
authority to amend the Plan to make changes that are consistent with the purpose
of the Plan or to take into account changes in law and tax and accounting rules,
as well as other developments and to make grants which qualify for beneficial
treatment under such rules without stockholder approval.

8.  Miscellaneous.

     (a) Other Actions.  Nothing contained in the Plan shall be construed to
limit the authority of the Company to exercise its corporate rights and powers,
including but not limited to, the right of the Company to award stock or grant
options for proper corporate purposes other than under the Plan to any employee
or other person, firm, corporation or association.

     (b) Governing Laws.  The Plan and all rights and obligations thereunder
shall be construed in accordance with and governed by the laws of the State of
Delaware.

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     (c) Withholding of Taxes.  No option may be exercised unless the Optionee
has paid, or has made provision, satisfactory to the Committee for payment of
federal, state and local income taxes, or any other taxes (other than stock
transfer taxes), which the Company may be obligated to withhold. The Committee
may authorize that shares of Nabors Common Stock or options be applied toward
the payment of withholding taxes.

     (d) No Right to Continuance of Employment or Service.  Nothing in the Plan
or in any grant pursuant to the Plan shall confer on any Covered Person any
right to continue in the employ of or service to the Company or any of its
subsidiaries or interfere in any way with the right of the Company or a
subsidiary to terminate his or her employment or service at any time.

     (e) Loans or Installment Payments.  The Committee may, in its discretion,
assist any Optionee in the exercise of options including satisfaction of any
federal, state and local income and employment tax obligations arising
therefrom, by authorizing the extension of a loan from the Company to such
Optionee. The terms of any loan and the method of payment (including the
interest rate and terms of repayment) shall be upon such terms as the Committee
deems appropriate under the circumstances. Loans may be authorized with or
without security or collateral.

     (f) Headings.  The headings contained in this Plan are for reference
purposes only and shall not affect the meaning or interpretation of this Plan.

     (g) Severability.  If any provision of this Plan shall for any reason be
held to be invalid or unenforceable, such invalidity or unenforceability shall
not affect any other provision hereby, and this Plan shall be construed as if
such invalid or unenforceable provision were omitted.

     (h) Successors and Assigns.  This Plan shall inure to the benefit of and be
binding upon each successor and assign of the Company. All obligations imposed
upon an Optionee, and all rights granted to the Company hereunder, shall be
binding upon the Optionee's heirs, legal representatives and successors.

     (i) Entire Agreement.  This Plan and any Agreement entered into with an
Optionee shall constitute the entire agreement with respect to the subject
matter thereof, provided that in the event of any inconsistency between the Plan
and the Agreement, the terms and conditions of the Agreement shall control.

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                                                                   EXHIBIT 10.21

                PLAN WITH RESPECT TO OPTIONS ORIGINALLY GRANTED
                     BY BAYARD DRILLING TECHNOLOGIES, INC.
                     AND ASSUMED BY NABORS INDUSTRIES, INC.

[Note: The following excerpt from the Agreement and Plan of Merger dated October
19, 1998, as amended, by and among Nabors Industries, Inc., Nabors Acquisition
Corp. VII and Bayard Drilling Technologies, Inc., together with the Nabors
Industries, Inc. 1998 Employee Stock Option Plan comprise the Plan, with Respect
to Options Originally Granted By Bayard Drilling Technologies, Inc. and Assumed
By Nabors Industries, Inc.]

     At the Effective Time each outstanding Company Stock Option . . . to
purchase shares of Company Common Stock, by virtue of the Merger and without
further action on the part of the Company or the holder of any Company Stock
Option, shall be converted into an option to purchase Parent Common Stock
("Parent Stock Option") exercisable for that number of whole shares of Parent
Common Stock equal to the product of the number of shares of Company Common
Stock covered by Company Stock Option immediately prior to the Effective Time
multiplied by the Exchange Ratio rounded up to the nearest whole number of
shares of Parent Common Stock, and the per share exercise price for the shares
of Parent Common Stock issuable upon the exercise of such Parent Stock Options
shall be equal to the quotient determined by dividing (i) the amount obtained by
subtracting (a) the Cash Consideration from (b) the exercise price per share of
Company Common Stock specified for such Company Stock Option under the
applicable Company Stock Option plan or agreement immediately prior to the
Effective Time, by (ii) the Exchange Ratio (rounding the resulting exercise
price up to the nearest whole cent). The date of grant of the Parent Stock
Option shall be the date on which Company Stock Option was originally granted.
Parent shall reserve for issuance the number of shares of Parent Common Stock
that will become issuable upon the exercise of Parent Stock Options pursuant to
this Section . . . . The Parent Stock Options granted pursuant hereto shall have
the same schedule of vesting and same period for exercise as applies to Company
Stock Options granted prior to the date of this Agreement; provided, however,
that, with respect to the employee holders of Company Stock Options . . . who
are still employed by the Company immediately prior to the Effective Time,
should such an employee holder be terminated by the Surviving Corporation
without cause during the one-year period immediately following the Effective
Time, then the number of Parent Stock Options received by such employee holder
in exchange for such employee holder's Company Stock Options in accordance with
this Section . . . shall immediately and fully vest upon such termination.
Except as otherwise expressly provided herein, the Parent Stock Options shall be
subject to the terms and conditions of Parent's 1998 Employee Stock Option
Plan . . . and consistent with this Section, the form of stock option agreement
shall be Parent's standard form as in effect on [October 18, 1998].

     The capitalized terms used in the preceding paragraph have the following
meanings:

          Cash Consideration:  $0.30 in cash.

          Company:  Bayard Drilling Technologies, Inc., a Delaware corporation.

          Company Common Stock:  The common stock, par value $.01 per share, of
     the Company.

          Company Stock Option:  Options or similar rights to receive or acquire
     1,296,600 shares of Company Common Stock granted on or prior to August 21,
     1998, pursuant to employee incentive or benefit plans, programs and
     arrangements and nonemployee director plans.

          Effective Time:  The effective time of filing of the certificate of
     Merger with the Secretary of State of the State of Delaware in accordance
     with Delaware law, being 9:00 a.m. on April 7, 1999.

          Exchange Ratio:  0.3375 shares of Parent Common Stock per share of
     Company Common Stock.
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          Merger:  The merger in accordance with the General Corporation Law of
     the State of Delaware of Nabors Acquisition Corp. VII with and into Bayard
     Drilling Technologies, Inc., pursuant to which Bayard became a wholly owned
     subsidiary of Nabors Industries, Inc.

          Parent:  Nabors Industries, Inc., a Delaware corporation.

          Parent Common Stock:  The common stock, par value $.10 per share, of
     Parent.

          Surviving Corporation:  Bayard Drilling Technologies, Inc., as the
     surviving corporation in the Merger.

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