Document:

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                                                                    EXHIBIT 10.3

                                   FORM OF

                              SUPPORT AGREEMENT

         THIS SUPPORT AGREEMENT is entered into as of o, 2000, between Oil
States International, Inc., a Delaware corporation ("OSI"), and o, an Alberta
corporation ("PTI Holdco").

                                    RECITALS

A. Pursuant to a Combination Agreement dated as of July 31, 2000, by and among
OSI, HWC Energy Services, Inc., Merger Sub-HWC, Inc., Sooner Inc., Merger
Sub-Sooner Inc. and PTI Group Inc. ("PTI") (such agreement, as it may be amended
or restated, is hereinafter referred to as the "Combination Agreement"), the
parties agreed that on the Effective Date (as defined in the Combination
Agreement), OSI and PTI Holdco would execute and deliver a Support Agreement
containing the terms and conditions set forth in Exhibit C to the Combination
Agreement together with such other terms and conditions as may be agreed to by
the parties to the Combination Agreement acting reasonably;

B. Pursuant to an arrangement (the "Arrangement") effected by Articles of
Arrangement dated o, 2000 filed pursuant to the Business Corporations Act
(Alberta) (or any successor or other corporate statute by which PTI may in the
future be governed) (the "Act") each issued and outstanding common share of PTI
(a "PTI Common Share"), other than those cancelled pursuant to the Arrangement
or held by OSI, by a Subsidiary of OSI or by a U.S. shareholder of PTI, was
ultimately exchanged for Exchangeable Shares of PTI Holdco (the "Exchangeable
Shares");

C. The Articles of Incorporation of PTI Holdco set forth the rights, privileges,
restrictions and conditions (collectively, the "Exchangeable Share Provisions")
attaching to the Exchangeable Shares;

D. The parties hereto desire to make appropriate provision and to establish a
procedure whereby OSI will take certain actions and make certain payments and
deliveries necessary to ensure that PTI Holdco will be able to make certain
payments and to deliver or cause to be delivered shares of OSI Common Stock in
satisfaction of the obligations of PTI Holdco under the Exchangeable Share
Provisions with respect to the payment and satisfaction of dividends,
Liquidation Amounts, Retraction Prices and Redemption Prices, all in accordance
with the Exchangeable Share Provisions and to ensure that the shares of OSI
Common Stock are freely tradable in accordance with the provisions set out
herein;

         NOW, THEREFORE, in consideration of the respective covenants and
agreements provided in this agreement and for other good and valuable
consideration (the receipt and sufficiency of which are hereby acknowledged),
the parties agree as follows:

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                                   ARTICLE 1
                         DEFINITIONS AND INTERPRETATION

1.1      DEFINED TERMS

         Each term used but not otherwise defined herein shall have the meaning
attributed thereto in the Exchangeable Share Provisions, unless the context
requires otherwise.

1.2      INTERPRETATION NOT AFFECTED BY HEADINGS, ETC.

         The division of this agreement into articles, sections and paragraphs
and the insertion of headings are for convenience of reference only and shall
not affect the construction or interpretation of this agreement.

1.3      NUMBER, GENDER, ETC.

         Words importing the singular number only shall include the plural and
vice versa. Words importing the use of any gender shall include all genders.

1.4      DATE FOR ANY ACTION

         If any date on which any action is required to be taken under this
agreement is not a Business Day, such action shall be required to be taken on
the next succeeding Business Day.

                                   ARTICLE 2
                         COVENANTS OF OSI AND PTI HOLDCO

2.1      COVENANTS OF OSI REGARDING EXCHANGEABLE SHARES

         So long as any Exchangeable Shares are outstanding, OSI will:

         (a)   not declare or pay any dividend on the OSI Common Stock unless
               (i) PTI Holdco shall (w) simultaneously declare or pay, as the
               case may be, an equivalent dividend (as provided for in the
               Exchangeable Share Provisions) on the Exchangeable Shares (an
               "Equivalent Dividend"), and (x) have sufficient money or other
               assets or authorized but unissued securities available to enable
               the due declaration and the due and punctual payment, in
               accordance with applicable law, of any Equivalent Dividend, or
               (ii) PTI Holdco shall (y) subdivide the Exchangeable Shares in
               lieu of stock dividend thereon (as provided for in the
               Exchangeable Share Provisions) (an "Equivalent Stock
               Subdivision"), and (z) have sufficient authorized but unissued
               securities available to enable the Equivalent Stock Subdivision;

         (b)   advise PTI Holdco sufficiently in advance of the declaration by
               OSI of any dividend on OSI Common Stock and take all such other
               actions as are reasonably necessary in co-operation with PTI
               Holdco, to ensure that (i) the respective declaration date,
               record date and payment date for an Equivalent Dividend shall be
               the same as the declaration date, record date and payment date
               for the

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               corresponding dividend on the OSI Common Stock or, (ii) the
               record date and effective date for an Equivalent Stock
               Subdivision shall be the same as the record date and payment date
               for the corresponding stock dividend on the OSI Common Stock;

         (c)   ensure that the record date for any dividend declared on OSI
               Common Stock is not less than ten Business Days after the
               declaration date for such dividend;

         (d)   take all such actions and do all such things as are necessary or
               desirable to enable and permit PTI Holdco, in accordance with
               applicable law, to pay and otherwise perform its obligations with
               respect to the satisfaction of the Liquidation Amount in respect
               of each issued and outstanding Exchangeable Share upon the
               liquidation, dissolution or winding-up of PTI Holdco or any other
               distribution of the assets of PTI Holdco for the purpose of
               winding-up its affairs, including without limitation all such
               actions and all such things as are necessary or desirable to
               enable and permit PTI Holdco to cause to be delivered shares of
               OSI Common Stock to the holders of Exchangeable Shares in
               accordance with the provisions of Article 5 of the Exchangeable
               Share Provisions;

         (e)   take all such actions and do all such things as are necessary or
               desirable to enable and permit PTI Holdco, in accordance with
               applicable law, to pay and otherwise perform its obligations with
               respect to the satisfaction of the Retraction Price and the
               Redemption Price, including without limitation all such actions
               and all such things as are necessary or desirable to enable and
               permit PTI Holdco to cause to be delivered shares of OSI Common
               Stock to the holders of Exchangeable Shares, upon the retraction
               or redemption of the Exchangeable Shares in accordance with the
               provisions of Article 6 or Article 7 of the Exchangeable Share
               Provisions, as the case may be; and

         (f)   not exercise its vote as a direct or indirect shareholder to
               initiate the voluntary liquidation, dissolution or winding-up of
               PTI Holdco nor take any action that, or omit to take any action
               the omission of which, is designed to or would result in the
               liquidation, dissolution or winding-up of PTI Holdco.

2.2      SEGREGATION OF FUNDS

         OSI will cause PTI Holdco to deposit a sufficient amount of funds in a
separate account and segregate a sufficient amount of such assets and other
property as is necessary to enable PTI Holdco to pay or otherwise satisfy the
applicable dividends, Liquidation Amount, Retraction Price or Redemption Price,
in each case for the benefit of holders from time to time of the Exchangeable
Shares, and PTI Holdco will use such funds, assets and other property so
segregated exclusively for the payment of dividends and the payment or other
satisfaction of the Liquidation Amount, the Retraction Price or the Redemption
Price, as applicable, net of any corresponding withholding tax obligations and
for the remittance of such withholding tax obligations.

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2.3      RESERVATION OF SHARES OF OSI COMMON STOCK

         OSI hereby represents, warrants and covenants that it has irrevocably
reserved for issuance and will at all times keep available, free from
pre-emptive and other rights, out of its authorized and unissued capital stock
such number of shares of OSI Common Stock (or other shares or securities into
which OSI Common Stock may be reclassified or changed as contemplated by section
2.7 hereof) (i) as is equal to the sum of (A) the number of Exchangeable Shares
issued and outstanding from time to time and (B) the number of Exchangeable
Shares issuable upon the exercise of all rights to acquire Exchangeable Shares
outstanding from time to time and (ii) as are now and may hereafter be required
to enable and permit PTI Holdco to meet its obligations hereunder, under the
Voting and Exchange Trust Agreement, under the Exchangeable Share Provisions and
under any other security or commitment pursuant to the Arrangement with respect
to which OSI may now or hereafter be required to issue shares of OSI Common
Stock.

2.4      NOTIFICATION OF CERTAIN EVENTS

         In order to assist OSI to comply with its obligations hereunder, PTI
Holdco will give OSI notice of each of the following events at the time set
forth below:

         (a)   immediately, in the event of any determination by the Board of
               Directors of PTI Holdco to take any action which would require a
               vote of the holders of Exchangeable Shares for approval;

         (b)   immediately, upon the earlier of (i) receipt by PTI Holdco of
               notice of, and (ii) PTI Holdco otherwise becoming aware of, any
               threatened or instituted claim, suit, petition or other
               proceedings with respect to the involuntary liquidation,
               dissolution or winding-up of PTI Holdco or to effect any other
               distribution of the assets of PTI Holdco among its shareholders
               for the purpose of winding-up its affairs;

         (c)   immediately, upon receipt by PTI Holdco of a Retraction Request
               (as defined in the Exchangeable Share Provisions);

         (d)   at least 45 days prior to any Automatic Redemption Date
               determined by the Board of Directors of PTI Holdco in accordance
               with clause (b) of the definition of Automatic Redemption Date in
               the Exchangeable Share Provisions; and

         (e)   in the event of any determination by the Board of Directors of
               PTI Holdco to institute voluntary liquidation, dissolution or
               winding-up proceedings with respect to PTI Holdco or to effect
               any other distribution of the assets of PTI Holdco among its
               shareholders for the purpose of winding-up its affairs, at least
               30 days prior to the proposed effective date of such liquidation,
               dissolution, winding-up or other distribution.

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2.5      DELIVERY OF SHARES OF OSI COMMON STOCK

         In furtherance of its obligations hereunder, upon notice of any event
which requires PTI Holdco to cause to be delivered shares of OSI Common Stock to
any holder of Exchangeable Shares, OSI shall forthwith issue and deliver the
requisite shares of OSI Common Stock to or to the order of the former holder of
the surrendered Exchangeable Shares, as PTI Holdco shall direct. All such shares
of OSI Common Stock shall be duly issued as fully paid and non-assessable and
shall be free and clear of any lien, claim, encumbrance, security interest or
adverse claim or interest.

2.6      QUALIFICATION OF SHARES OF OSI COMMON STOCK

         OSI covenants that if any shares of OSI Common Stock (or other shares
or securities into which OSI Common Stock may be reclassified or changed as
contemplated by Section 2.7 hereof) to be issued and delivered hereunder
(including for greater certainty, pursuant to the Exchangeable Share Provisions,
or pursuant to the Exchange Right or the Automatic Exchange Rights (all as
defined in the Voting and Exchange Trust Agreement)) require registration or
qualification with or approval of or the filing of any document including any
prospectus or similar document, the taking of any proceeding with or the
obtaining of any order, ruling or consent from any governmental or regulatory
authority under any Canadian or United States federal, provincial or state law
or regulation or pursuant to the rules and regulations of any regulatory
authority, or the fulfillment of any other legal requirement (collectively, the
"Applicable Laws") before such shares (or other shares or securities into which
OSI Common Stock may be reclassified or changed as contemplated by Section 2.7
hereof) may be issued and delivered by OSI to the initial holder thereof (other
than PTI Holdco) or in order that such shares may be freely tradeable thereafter
(other than any restrictions on transfer by reason of a holder being a "control
person" of OSI for purposes of Canadian federal or provincial securities law or
an "affiliate" of OSI for purposes of United States federal or state securities
law and provided such trade is conducted through facilities of a stock exchange
outside Canada), OSI will in good faith expeditiously take all such actions and
do all such things as are necessary and permitted by Applicable Laws to cause
such shares of OSI Common Stock (or other shares or securities into which OSI
Common Stock may be reclassified or changed as contemplated by Section 2.7
hereof) to be and remain duly registered, qualified or approved at all times in
order that such shares may be issued and delivered by OSI to the initial holder
thereof (other than PTI Holdco) and in order that such shares or securities may
be freely tradeable thereafter (other than any restrictions on transfer by
reason of a holder being a "control person" of OSI for purposes of Canadian
provincial securities law or an "affiliate" of OSI for purposes of United States
federal or state securities law provided such trade is conducted through
facilities of a stock exchange outside Canada) including, without limitation,
the filing and maintenance of a registration statement under the Securities Act
of 1933; provided, however, that notwithstanding the foregoing, OSI will not be
required to take any action, including, without limitation, the filing of a
registration statement, under any United States federal or state securities law
in respect of the OSI Common Stock (or other shares or securities into which OSI
common stock may be reclassified or changed as contemplated by Section 2.7
hereof) to be issued and delivered hereunder (including, for greater certainty,
pursuant to the Exchangeable Share Provisions, or pursuant to the Exchange Right
and the Automatic Exchange Rights) until the first anniversary of the Effective
Date unless such shares or securities are being, or are to be, delivered
pursuant to Articles 5 or 7 of the Exchangeable Share Provisions, pursuant to
the Exchange Rights or the Automatic Exchange Rights, or pursuant to the
Liquidation Call Right or the Redemption Call Right. From and after the first
anniversary of the Effective Date (or such earlier date as such shares or
securities may be issued and delivered pursuant to

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Articles 5 or 7 of the Exchangeable Share Provisions, pursuant to the Exchange
Rights or the Automatic Exchange Rights or pursuant to the Liquidation Call
Right or the Redemption Call Right), OSI will in good faith expeditiously take
all such actions and do all such things as are necessary to cause all shares of
OSI Common Stock (or other shares or securities into which OSI Common Stock may
be reclassified or changed as contemplated by Section 2.7 hereof) to be
delivered hereunder (including, for greater certainty, pursuant to Exchangeable
Share Provisions, or pursuant to the Exchange Right or the Automatic Exchange
Rights) to be listed, quoted or posted for trading on all stock exchanges and
quotation systems on which such shares are listed, quoted or posted for trading
at such time immediately upon their issuance.

2.7      EQUIVALENCE

         (a)   OSI will not:

               (i)   issue or distribute shares of OSI Common Stock (or
                     securities exchangeable for or convertible into or carrying
                     rights to acquire shares of OSI Common Stock) to the
                     holders of all or substantially all of the then outstanding
                     shares of OSI Common Stock by way of stock dividend or
                     other distribution; or

               (ii)  issue or distribute rights, options or warrants to the
                     holders of all or substantially all of the then outstanding
                     shares of OSI Common Stock entitling them to subscribe for
                     or to purchase shares of OSI Common Stock (or securities
                     exchangeable for or convertible into or carrying rights to
                     acquire shares of OSI Common Stock); or

               (iii) issue or distribute to the holders of all or substantially
                     all of the then outstanding shares of OSI Common Stock (A)
                     shares or securities of OSI of any class other than OSI
                     Common Stock (other than shares convertible into or
                     exchangeable for or carrying rights to acquire shares of
                     OSI Common Stock), (B) rights, options or warrants other
                     than those referred to in subsection 2.7 (a) (ii) above,
                     (C) evidences of indebtedness of OSI or (D) assets of OSI;

               unless

               (iv)  one or both of OSI and PTI Holdco is permitted under
                     applicable law to issue or distribute the economic
                     equivalent on a per share basis of such rights, options,
                     warrants, securities, shares, evidences of indebtedness or
                     other assets to the holders of the Exchangeable Shares; and

               (v)   one or both of OSI and PTI Holdco shall issue or distribute
                     the economic equivalent on a per share basis of such
                     rights, options, warrants, securities,

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                     shares, evidences of indebtedness or other assets
                     simultaneously to the holders of the Exchangeable Shares.

          (b)  OSI will not:

               (i)   subdivide, redivide or change the then outstanding shares
                     of OSI Common Stock into a greater number of shares of OSI
                     Common Stock; or

               (ii)  reduce, combine or consolidate or change the then
                     outstanding shares of OSI Common Stock into a lesser number
                     of shares of OSI Common Stock; or

               (iii) reclassify or otherwise change the shares of OSI Common
                     Stock or effect an amalgamation, merger, reorganization or
                     other transaction involving or affecting the shares of OSI
                     Common Stock;

               unless

               (iv)  PTI Holdco is permitted under applicable law to
                     simultaneously make the same or an economically equivalent
                     change to, or in the rights of the holders of, the
                     Exchangeable Shares; and

               (v)   the same or an economically equivalent change is
                     simultaneously made to, or in the rights of the holders of,
                     the Exchangeable Shares.

          (c)  OSI will ensure that the record date for any event referred to in
               section 2.7(a) or 2.7(b) above, or (if no record date is
               applicable for such event) the effective date for any such event,
               is not less than 10 Business Days after the date on which such
               event is declared or announced by OSI (with simultaneous notice
               thereof to be given by OSI to PTI Holdco).

          (d)  The Board of Directors of PTI Holdco shall determine, in good
               faith and in its sole discretion, economic equivalence for the
               purposes of any event referred to in Section 2.7(a) or 2.7(b)
               above and each such determination shall be conclusive and binding
               on OSI. In making each such determination, the following factors
               shall, without excluding other factors determined by the Board of
               Directors of PTI Holdco to be relevant, be considered by the
               Board of Directors of PTI Holdco:

               (i)   in the case of any stock dividend or other distribution
                     payable in OSI Common Stock, the number of such shares
                     issued in proportion to the number of shares of OSI Common
                     Stock previously outstanding;

               (ii)  in the case of the issuance or distribution of any rights,
                     options or warrants to subscribe for or purchase OSI Common
                     Stock (or securities exchangeable for or convertible into
                     or carrying rights to acquire OSI Common Stock), the
                     relationship between the exercise price of each such right,
                     option or warrant and the current market value (as
                     determined by the

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                     Board of Directors of PTI Holdco in the manner contemplated
                     below) of a share of OSI Common Stock;

               (iii) in the case of the issuance or distribution of any other
                     form of property (including without limitation any share or
                     securities of OSI of any class other than OSI Common Stock,
                     any rights, options or warrants other than those referred
                     to in Section 2.7(d)(ii) above, any evidences of
                     indebtedness of OSI or any assets of OSI), the relationship
                     between the fair market value (as determined by the Board
                     of Directors of PTI Holdco in the manner above
                     contemplated) of such property to be issued or distributed
                     with respect to each outstanding share of OSI Common Stock
                     and the current market value (as determined by the Board of
                     Directors of PTI Holdco in the manner contemplated below)
                     of a share of OSI Common Stock;

               (iv)  in the case of any subdivision, redivision or change of the
                     then outstanding shares of OSI Common Stock into a greater
                     number of shares of OSI Common Stock or the reduction,
                     combination, consolidation or change of the then
                     outstanding shares of OSI Common Stock into a lesser number
                     of shares of OSI Common Stock or any amalgamation, merger,
                     reorganization or other transaction affecting shares of OSI
                     Common Stock, the effect thereof upon the then outstanding
                     shares of OSI Common Stock; and

               (v)   in all such cases, the general taxation consequences of the
                     relevant event to holders of Exchangeable Shares to the
                     extent that such consequences may differ from the taxation
                     consequences to holders of shares of OSI Common stock as a
                     result of differences between taxation laws of Canada and
                     the United States (except for any differing consequences
                     arising as a result of differing marginal taxation rates
                     and without regard to the individual circumstances of
                     holders of Exchangeable Shares).

               For purposes of the foregoing determinations, the current market
               value of any security listed and traded or quoted on a securities
               exchange shall be the average of the closing price of such
               security during a period of not less than 20 consecutive trading
               days ending not more than five trading days before the date of
               determination on the principal securities exchange on which such
               securities are listed and traded or quoted; provided, however,
               that if in the opinion of the Board of Directors of PTI Holdco
               the public distribution or trading activity of such securities
               during such period does not create a market which reflects the
               fair market value of such securities, then the current market
               value thereof shall be determined by the Board of Directors of
               PTI Holdco, in good faith and in its sole discretion, and
               provided further than any such determination by the Board of
               Directors of PTI Holdco shall be conclusive and binding on OSI.

         (e)   PTI Holdco agrees that, to the extent required, upon due notice
               from OSI, PTI Holdco will use its best efforts to take or cause
               to be taken such steps as may be

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                     necessary for the purposes of ensuring that appropriate
                     dividends are paid or other distributions are made by PTI
                     Holdco, or subdivisions, redivisions or changes are made to
                     the Exchangeable Shares, in order to implement the required
                     economic equivalence with respect to the OSI Common Stock
                     and Exchangeable Shares as provided for in this Section
                     2.7.

2.8      TENDER OFFERS, ETC.

         In the event that a tender offer, share exchange offer, issuer bid,
take-over bid or similar transaction with respect to OSI Common Stock (an
"Offer") is proposed by OSI or is proposed to OSI or its shareholders and is
recommended by the Board of Directors of OSI, or is otherwise effected or to be
effected with the consent or approval of the Board of Directors of OSI, and the
Exchangeable Shares are not redeemed by PTI Holdco or purchased by OSI or OSI
ULC pursuant to the Redemption Call Right, OSI shall, expeditiously and in good
faith, take all such actions and do all such things as are necessary or
desirable to enable and permit holders of Exchangeable Shares to participate in
such Offer to the same extent and on an equivalent basis as the holders of
shares of OSI Common Stock, without discrimination, including, without limiting
the generality of the foregoing, OSI will use its good faith efforts
expeditiously to (and shall, in the case of a transaction proposed by OSI or
where OSI is a participant in the negotiation thereof) ensure that holders of
Exchangeable Shares may participate in all such Offers without being required to
retract Exchangeable Shares as against PTI Holdco (or, if so required, to ensure
that any such retraction shall be effective only upon, and shall be conditional
upon, the closing of the Offer and only to the extent necessary to tender or
deposit to the Offer).

2.9      OWNERSHIP OF OUTSTANDING SHARES

         Without the prior approval of PTI Holdco and the prior approval of the
holders of the Exchangeable Shares given in accordance with Section 9.2 of the
Exchangeable Share Provisions, OSI covenants and agrees in favor of PTI Holdco
that, as long as any outstanding Exchangeable Shares are owned by any person or
entity other than OSI or any of its Subsidiaries, OSI, alone or together with
any direct or indirect wholly-owned subsidiary of OSI, will be and remain the
beneficial owner of all issued and outstanding securities of PTI Holdco.
Notwithstanding the foregoing, OSI shall not be in violation of this Section if
any person or group of persons acting jointly or in concert acquires OSI Common
Stock pursuant to any merger of OSI pursuant to which OSI was not the surviving
corporation.

2.10     OSI NOT TO VOTE EXCHANGEABLE SHARES

         OSI covenants and agrees that it will appoint and cause to be appointed
proxy holders with respect to all Exchangeable Shares held by OSI and its
Subsidiaries for the sole purpose of attending each meeting of holders of
Exchangeable Shares in order to be counted as part of the quorum for each such
meeting. OSI further covenants and agrees that it will not, and will cause its
Subsidiaries not to, exercise any voting rights which may be exercisable by
holders of Exchangeable Shares from time to time pursuant to the Exchangeable
Share Provisions or pursuant to the provisions of the Act with respect to any
Exchangeable Shares held by it or by its Subsidiaries in respect of any matter
considered at any meeting of holders of Exchangeable Shares.

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2.11     DUE PERFORMANCE

         On and after the Effective Date, OSI shall duly and timely perform all
of its obligations provided for in connection with the Plan of Arrangement and
the Articles of Incorporation of PTI Holdco, including any obligations that may
arise upon the exercise of OSI's rights under the Exchangeable Share Provisions.

                                  ARTICLE 3
                                   GENERAL

3.1      TERM

         This agreement shall come into force and be effective as of the date
hereof and shall terminate and be of no further force and effect at such time as
no Exchangeable Shares (or securities or rights convertible into or exchangeable
for or carrying rights to acquire Exchangeable Shares) are held by any party
other than OSI and any of its Subsidiaries.

3.2      CHANGES IN CAPITAL OF OSI AND PTI HOLDCO

         Notwithstanding the provisions of section 3.4 hereof, at all times
after the occurrence of any event effected pursuant to section 2.7 or 2.8
hereof, as a result of which either OSI Common Stock or the Exchangeable Shares
or both are in any way changed, this agreement shall forthwith be amended and
modified as necessary in order that it shall apply with full force and effect,
mutatis mutandis, to all new securities into which OSI Common Stock or the
Exchangeable Shares or both are so changed, and the parties hereto shall as soon
as possible execute and deliver an agreement in writing giving effect to and
evidencing such necessary amendments and modifications.

3.3      SEVERABILITY

         If any provision of this agreement is held to be invalid, illegal or
unenforceable, the validity, legality or enforceability of the remainder of this
agreement shall not in any way be affected or impaired thereby and this
agreement shall be carried out as nearly as possible in accordance with its
original terms and conditions.

3.4      AMENDMENTS, MODIFICATIONS, ETC.

         This agreement may not be amended, modified or waived except by an
agreement in writing executed by PTI Holdco and OSI and approved by the holders
of the Exchangeable Shares in accordance with Section 10.2 of the Exchangeable
Share Provisions.

3.5      MINISTERIAL AMENDMENTS

         Notwithstanding the provisions of section 3.4, the parties to this
agreement may in writing, at any time and from time to time, without the
approval of the holders of the Exchangeable Shares, amend or modify this
agreement for the purposes of:

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         (a)   adding to the covenants of either or both parties for the
               protection of the holders of the Exchangeable Shares;

         (b)   making such amendments or modifications not inconsistent with
               this agreement as may be necessary or desirable with respect to
               matters or questions which, in the opinion of the board of
               directors of each of PTI Holdco and OSI, it may be expedient to
               make, provided that each such board of directors shall be of the
               opinion that such amendments or modifications will not be
               prejudicial to the interests of the holders of the Exchangeable
               Shares; or

         (c)   making such changes or corrections which, on the advice of
               counsel to PTI Holdco and OSI, are required for the purpose of
               curing or correcting any ambiguity or defect or inconsistent
               provision or clerical omission or mistake or manifest error;
               provided that the boards of directors of each of PTI Holdco and
               OSI shall be of the opinion that such changes or corrections will
               not be prejudicial to the interests of the holders of the
               Exchangeable Shares.

3.6      MEETING TO CONSIDER AMENDMENTS

         PTI Holdco, at the request of OSI, shall call a meeting or meetings of
the holders of the Exchangeable Shares for the purpose of considering any
proposed amendment or modification requiring approval of such shareholders. Any
such meeting or meetings shall be called and held in accordance with the by-laws
of PTI Holdco, the Exchangeable Share Provisions and all Applicable Laws.

3.7      AMENDMENTS ONLY IN WRITING

         No amendment to or modification or waiver of any of the provisions of
this agreement otherwise permitted hereunder shall be effective unless made in
writing and signed by both of the parties hereto and approved by holders of
Exchangeable Shares pursuant to Section 9.2 of the Exchangeable Share
Provisions.

3.8      INUREMENT

         This agreement shall be binding upon and inure to the benefit of the
parties hereto and each of their respective heirs, successors and assigns.

3.9      NOTICES TO PARTIES

         All notices and other communications between the parties shall be in
writing and shall be deemed to have been given if delivered personally or by
confirmed telecopy to the parties at the following addresses (or at such other
address for either such party as shall be specified in like notice):

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         (a)   if to OSI:

               Oil States International, Inc.
               Three Allen Center
               333 Clay Street, Suite 333460
               Houston, Texas 77002

               Attention:  Cindy B. Taylor
               Fax:  (713) 652-0499

               with a copy to:

               Donahue, Ernst & Young LLP
               1000 Ernst & Young Tower
               440 - 2nd Avenue S.W.
               P.O. Box 2258, station M
               Calgary, Alberta T2P 5E5

               Attention:  Richard Peters
               Fax:  (403) 206-5525

         (b)   if to PTI Holdco to:

               Three Allen Center
               333 Clay Street, Suite 333460
               Houston, Texas 77002

               Attention:  Cindy B. Taylor
               Fax:  (713) 652-0499

         Any notice or other communication given personally shall be deemed to
have been given and received upon delivery thereof and if given by telecopy
shall be deemed to have been given and received on the date of confirmed receipt
thereof, unless such day is not a Business Day, in which case it shall be deemed
to have been given and received upon the immediately following Business Day.

3.10     COUNTERPARTS

         This agreement may be executed in counterparts, each of which shall be
deemed an original, and all of which taken together shall constitute one and the
same instrument. Executed counterparts of this agreement may be delivered by
facsimile transmission.

3.11     JURISDICTION

         This agreement shall be construed and enforced in accordance with the
laws of the Province of Alberta and the federal laws of Canada applicable
therein.

                                      C-12
<PAGE>   13
3.12     ATTORNMENT

         OSI agrees that any action or proceeding arising out of or relating to
this agreement may be instituted in the courts of the Province of Alberta,
waives any objection which it may have now or hereafter to the venue of any such
action or proceeding, irrevocably submits to the jurisdiction of such courts in
any such action or proceeding, agrees to be bound by any judgment of such courts
and not to seek, and hereby waives, any review of the merits of any such
judgment by the courts of any other jurisdiction and hereby appoints PTI Holdco
at its registered office in the Province of Alberta as OSI's attorney for
service of process.

         IN WITNESS WHEREOF, OSI and PTI Holdco have caused this agreement to be
signed by their respective officers thereunder duly authorized, all as of the
date first written above.

                                           OIL STATES INTERNATIONAL, INC.

                                           Per:
                                               --------------------------------

                                           Per:
                                               --------------------------------

                                      C-13<PAGE>   1
                                                                    EXHIBIT 10.4

                                   FORM OF

                       VOTING AND EXCHANGE TRUST AGREEMENT

         THIS VOTING AND EXCHANGE TRUST AGREEMENT is entered into as of o, 2000,
by and between Oil States International, Inc., a Delaware corporation ("OSI"),
o, an Alberta corporation ("PTI Holdco"), and Montreal Trust Company of Canada,
a Canadian trust company ("Trustee").

RECITALS:

A. Pursuant to a Combination Agreement dated as of July 31, 2000 by and among
OSI, HWC Energy Services, Inc., Sooner Inc. and PTI Group, Inc. ("PTI") and such
other parties referenced therein (such agreement as it may be amended or
restated is hereinafter referred to as the "Combination Agreement"), the parties
agreed that on the Effective Date (as defined in the Combination Agreement), OSI
and PTI Holdco would execute and deliver a Voting and Exchange Trust Agreement
containing the terms and conditions set forth in Exhibit D to the Combination
Agreement together with such other terms and conditions as may be agreed to by
the parties to the Combination Agreement acting reasonably.

B. Pursuant to an arrangement (the "Arrangement") effected by Articles of
Arrangement dated o, 2000 filed pursuant to the Business Corporations Act
(Alberta) (or any successor or other corporate statute by which PTI may in the
future be governed) (the "Act"), each issued and outstanding common share of PTI
(a "PTI Common Share"), other than those cancelled pursuant to the Arrangement
or held by OSI or by a Subsidiary of OSI, was ultimately exchanged for
Exchangeable Shares of PTI Holdco (the "Exchangeable Shares");

C. The Articles of Incorporation of PTI Holdco set forth the rights, privileges,
restrictions and conditions attaching to the Exchangeable Shares (collectively,
the "Exchangeable Share Provisions"), and a copy of such Articles of
Incorporation is attached hereto as Appendix A;

D. OSI is to provide voting rights in OSI to each holder (other than OSI and its
Subsidiaries) from time to time of Exchangeable Shares, such voting rights per
Exchangeable Share to be equivalent to the voting rights per share of OSI Common
Stock;

E. OSI is to grant to and in favor of the holders (other than OSI and its
Subsidiaries) from time to time of Exchangeable Shares the right, in the
circumstances set forth herein, to require OSI or OSI ULC to purchase from each
such holder all or any part of the Exchangeable Shares held by the holder;

F. The parties desire to make appropriate provision and to establish a procedure
whereby voting rights in OSI shall be exercisable by holders (other than OSI and
its Subsidiaries) from time to time of Exchangeable Shares by and through the
Trustee, which will hold legal title to and a share certificate in respect of
one share of OSI Special Voting Stock (the "OSI Special Voting Stock") to which
voting rights attach for the benefit of such holders of Exchangeable Shares and
whereby the rights to require OSI or, at the option of OSI, OSI ULC, to purchase
Exchangeable Shares from the holders thereof (other than OSI and its
Subsidiaries) shall be

                                      D-1
<PAGE>   2

exercisable by such holders from time to time of Exchangeable Shares by and
through the Trustee, which will hold legal title to such rights for the benefit
of such holders;

G. These recitals and any statements of fact in this agreement are made by OSI
and PTI Holdco and not by the Trustee;

         NOW THEREFORE, in consideration of the respective covenants and
agreements provided in this agreement and for other good and valuable
consideration (the receipt and sufficiency of which are hereby acknowledged),
the parties agree as follows:

                                   ARTICLE 1
                         DEFINITIONS AND INTERPRETATION

1.1      DEFINITIONS

         In this agreement, the following terms shall have the following
meanings:

         "Act" has the meaning in the recitals hereto;

         "Aggregate Equivalent Vote Amount" means, with respect to any matter,
proposition or question on which holders of OSI Common Stock are entitled to
vote, consent or otherwise act, the product of (i) the number of shares of
Exchangeable Shares issued and outstanding and held by Holders multiplied by
(ii) the Equivalent Vote Amount.

         "Applicable Laws" has the meaning provided in Section 5.10 hereof.

         "Arrangement" has the meaning provided in the recitals hereto.

         "Automatic Exchange Rights" means the benefit of the obligation of OSI
to effect the automatic exchange of shares of OSI Common Stock for Exchangeable
Shares pursuant to Section 5.12 hereof.

         "Board of Directors" means the Board of Directors of PTI Holdco.

         "Business Day" has the meaning provided in the Exchangeable Share
Provisions.

         "Combination Agreement" has the meaning in the recitals hereto.

         "Equivalent Vote Amount" means, with respect to any matter, proposition
or question on which holders of OSI Common Stock are entitled to vote, consent
or otherwise act, the number of votes to which a holder of one share of OSI
Common Stock is entitled with respect to such matter, proposition or question.

         "Exchange Right" has the meaning provided in Section 5.1(b) hereof.

         "Exchangeable Share Consideration" has the meaning provided in the
Exchangeable Share Provisions.

                                      D-2
<PAGE>   3
         "Exchangeable Share Price" has the meaning provided in the Exchangeable
Share Provisions.

         "Exchangeable Share Provisions" has the meaning provided in the
recitals hereto.

         "Exchangeable Shares" has the meaning provided in the recitals hereto.

         "freely tradeable", with respect to OSI Common Stock, means freely
transferable under Canadian provincial securities laws and U.S. federal and
state securities laws (pursuant to an effective resale shelf registration
statement or otherwise and assuming the reasonable cooperation of the holder or
recipient of OSI Common Stock in connection with any required resale shelf
registration statement), except to the extent restrictions arise by reason of a
person being a "control person" of OSI for the purposes of Canadian provincial
securities laws or an "affiliate" of OSI for the purposes of United States
federal or state securities laws, provided any trades in such securities are
conducted through the facilities of a stock exchange outside Canada.

         "Holder Votes" has the meaning provided in Section 4.2 hereof.

         "Holders" means the registered holders from time to time of
Exchangeable Shares, other than OSI and its Subsidiaries.

         "Insolvency Event" means the institution by PTI Holdco of any
proceeding to be adjudicated a bankrupt or insolvent or to be dissolved or
wound-up, or the consent of PTI Holdco to the institution of bankruptcy,
insolvency, dissolution or winding-up proceedings against it, or the filing of a
petition, answer or consent seeking dissolution or winding-up under any
bankruptcy, insolvency or analogous laws, including without limitation the
Companies' Creditors Arrangement Act (Canada) and the Bankruptcy and Insolvency
Act (Canada), and the failure by PTI Holdco to contest in good faith any such
proceedings commenced in respect of PTI Holdco within 15 days of becoming aware
thereof, or if so contested the adjudication that PTI Holdco is bankrupt or
insolvent or is to be dissolved or wound-up, or the consent by PTI Holdco to the
filing of any such petition or to the appointment of a receiver, or the making
by PTI Holdco of a general assignment for the benefit of creditors, or the
admission in writing by PTI Holdco of its inability to pay its debts generally
as they become due, or PTI Holdco's not being permitted, pursuant to liquidity
or solvency requirements of applicable law, to redeem any Retracted Shares
pursuant to Section 6.6 of the Exchangeable Share Provisions.

         "Liquidation Call Right" has the meaning provided in the Exchangeable
Share Provisions.

         "Liquidation Event" has the meaning provided in subsection 5.12(b)
hereof.

         "Liquidation Event Effective Time" has the meaning provided in
subsection 5.12(c) hereof.

         "List" has the meaning provided in Section 4.6 hereof.

         "Officer's Certificate" means, with respect to OSI or PTI Holdco, as
the case may be, a certificate signed by any one of the Chairman of the Board,
the Vice-Chairman of the Board (if there be one), the President or any
Vice-President of OSI or PTI Holdco, as the case may be.

                                      D-3
<PAGE>   4
         "OSI" has the meaning in the recitals hereto.

         "OSI Common Stock" has the meaning provided in the Exchangeable Share
Provisions.

         "OSI Consent" has the meaning provided in Section 4.2 hereof.

         "OSI Meeting" has the meaning provided in Section 4.2 hereof.

         "OSI Special Voting Stock" has the meaning provided in the recitals
hereto.

         "OSI ULC" means the Subsidiary of OSI incorporated under the Companies
Act (Nova Scotia) for the purpose of delivering OSI Common Stock as provided for
in this Agreement, the Exchangeable Share Provisions or the Support Agreement.

         "PTI" has the meaning in the recitals hereto.

         "PTI Stock Options" means the outstanding options entitling the holders
to acquire upon exercise thereof up to o PTI Common Shares in the aggregate.

         "PTI Holdco" has the meaning in the recitals hereto.

         "Person" includes an individual, body corporate, partnership, company,
unincorporated syndicate or organization, trust, trustee, executor,
administrator and other legal representative.

         "Plan of Arrangement" has the meaning provided in the Exchangeable
Share Provisions.

         "Redemption Call Right" has the meaning provided in the Exchangeable
Share Provisions.

         "Retracted Shares" has the meaning provided in Section 5.7 hereof.

         "Retraction Call Right" has the meaning provided in the Exchangeable
Share Provisions.

         "Subsidiary" has the meaning provided in the Exchangeable Share
Provisions.

         "Successor" has the meaning provided in subsection 11. 1 (a) hereof.

         "Support Agreement" means that certain support agreement made as of
even date hereof by and between OSI and PTI Holdco.

         "Trust" means the trust created by this agreement.

         "Trust Estate" means the Voting Share, any other securities, the
Exchange Right, the Automatic Exchange Rights and any money or other property
which may be held by the Trustee from time to time pursuant to this agreement.

         "Trustee" means Montreal Trust Company of Canada and, subject to the
provisions of Article 10 hereof, includes any successor trustee or permitted
assigns.

         "Voting Rights" means the voting rights attached to the Voting Share.

                                      D-4
<PAGE>   5
         "Voting Share" means the one share of OSI Special Voting Stock, U.S.
$0.0001 par value, issued by OSI to and deposited with the Trustee, which
entitles the holder of record to a number of votes at meetings of holders of OSI
Common Stock equal to the Aggregate Equivalent Vote Amount.

1.2      INTERPRETATION NOT AFFECTED BY HEADINGS, ETC.

         The division of this agreement into articles, sections and paragraphs
and the insertion of headings are for convenience of reference only and shall
not affect the construction or interpretation of this agreement.

1.3      NUMBER, GENDER, ETC.

         Words importing the singular number only shall include the plural and
vice versa. Words importing the use of any gender shall include all genders.

1.4      DATE FOR ANY ACTION

         If any date on which any action is required to be taken under this
agreement is not a Business Day, such action shall be required to be taken on
the next succeeding Business Day.

1.5      PAYMENTS

         All payments to be made hereunder will be made without interest and
less any tax required by Canadian law to be deducted or withheld.

                                   ARTICLE 2
                              PURPOSE OF AGREEMENT

2.1      The purpose of this agreement is to create the Trust for the benefit of
the Holders, as herein provided. The Trustee will hold the Voting Share in order
to enable the Trustee to exercise the Voting Rights and will hold the Exchange
Right and the Automatic Exchange Rights in order to enable the Trustee to
exercise such rights, in each case as trustee for and on behalf of the Holders
as provided in this agreement.

                                   ARTICLE 3
                                  VOTING SHARE

3.1      ISSUANCE AND OWNERSHIP OF THE VOTING SHARE

         OSI hereby issues to and deposits with the Trustee the Voting Share to
be hereafter held of record by the Trustee as trustee for and on behalf of, and
for the use and benefit of, the Holders and in accordance with the provisions of
this agreement. OSI hereby acknowledges receipt from the Trustee as trustee for
and on behalf of the Holders of good and valuable consideration (and the
adequacy thereof) for the issuance of the Voting Share by OSI to the Trustee.
During the term of the Trust and subject to the terms and conditions of this
agreement, the Trustee shall possess and be vested with full legal ownership of
the Voting Share and shall be entitled to exercise all of the rights and powers
of an owner with respect to the Voting Share, provided that the Trustee shall:

                                      D-5
<PAGE>   6
         (a)   hold the Voting Share and the legal title thereto as trustee
               solely for the use and benefit of the Holders in accordance with
               the provisions of this agreement; and

         (b)   except as specifically authorized by this agreement, have no
               power or authority to sell, transfer, vote or otherwise deal in
               or with the Voting Share, and the Voting Share shall not be used
               or disposed of by the Trustee for any purpose other than the
               purposes for which this Trust is created pursuant to this
               agreement.

3.2      LEGENDED SHARE CERTIFICATES

         PTI Holdco will cause each certificate representing Exchangeable Shares
to bear an appropriate legend notifying the Holders of their right to instruct
the Trustee with respect to the exercise of the Voting Rights with respect to
the Exchangeable Shares held by a Holder.

3.3      SAFE KEEPING OF CERTIFICATE

         The certificate representing the Voting Share shall at all times be
held in safe keeping by the Trustee or its agent.

3.4      HOLDERS' BENEFIT

         For greater certainty, the Trustee holds the benefit of the Voting
Rights for the Holders, but all other rights in respect of the Voting Share,
including without limitation any rights to receive dividends on the Voting
Share, are for the benefit of OSI.

                                   ARTICLE 4
                            EXERCISE OF VOTING RIGHTS

4.1      VOTING RIGHTS

         The Trustee, as the holder of record of the Voting Share, shall be
entitled to all of the Voting Rights, including the right to consent to or to
vote in person or by proxy the Voting Share, on any matter, question or
proposition whatsoever that may properly come before the stockholders of OSI at
a OSI Meeting or in connection with a OSI Consent (in each case, as hereinafter
defined). The Voting Rights shall be and remain vested in and exercised by the
Trustee. Subject to Section 7.15 hereof, the Trustee shall exercise the Voting
Rights only on the basis of instructions received pursuant to this Article 4
from Holders entitled to instruct the Trustee as to the voting thereof at the
time at which a OSI Consent is sought or a OSI Meeting is held. To the extent
that no instructions are received from a Holder with respect to the Voting
Rights to which such Holder is entitled, the Trustee shall not exercise or
permit the exercise of such Holder's Voting Rights.

4.2      NUMBER OF VOTES

         With respect to all meetings of stockholders of OSI at which holders of
shares of OSI Common Stock are entitled to vote (a "OSI Meeting") and with
respect to all written consents sought by OSI from its stockholders including
the holders of shares of OSI Common Stock (a "OSI Consent"), each Holder shall
be entitled to instruct the Trustee to cast and exercise, in the manner
instructed, a number of votes equal to the Equivalent Vote Amount for each

                                      D-6
<PAGE>   7

Exchangeable Share owned of record by such Holder on the record date established
by OSI or by applicable law for such OSI Meeting or OSI Consent, as the case may
be, (the "Holder Votes") in respect of each matter, question or proposition to
be voted on at such OSI Meeting or to be consented to in connection with such
OSI Consent.

4.3      MAILINGS TO SHAREHOLDERS

         With respect to each OSI Meeting and OSI Consent, the Trustee will mail
or cause to be mailed (or otherwise communicate in the same manner as OSI
utilizes in communications to holders of OSI Common Stock, subject to the
Trustee's ability to provide this method of communication and upon being advised
in writing of such method) to each of the Holders named in the List on the same
day as the initial mailing or notice (or other communication) with respect
thereto is given by OSI to its stockholders:

         (a)   a copy of such notice, together with any proxy or information
               statement and related materials to be provided to holders of OSI
               Common Stock;

         (b)   a statement of the number of Holder Votes which the Holder is
               entitled to exercise;

         (c)   a statement that such Holder is entitled to instruct the Trustee
               as to the exercise of the Holder Votes with respect to such OSI
               Meeting or OSI Consent, as the case may be, or, pursuant to
               Section 4.7 hereof, to attend such OSI Meeting and to exercise
               personally the Holder Votes thereat;

         (d)   a statement as to the manner in which such instructions may be
               given to the Trustee, including an express indication that
               instructions may be given to the Trustee to give:

               (i)  a proxy to such Holder or such Holder's designee to exercise
                    personally the Holder Votes; or

               (ii) a proxy to a designated agent or other representative of the
                    management of OSI to exercise such Holder Votes;

         (e)   a statement that if no voting instructions are received from the
               Holder, the Holder Votes to which such Holder is entitled will
               not be exercised;

         (f)   a form of direction whereby the Holder may so direct and instruct
               the Trustee as contemplated herein; and

         (g)   a statement of (i) the time and date by which such instructions
               must be received by the Trustee in order to be binding upon it,
               which in the case of a OSI Meeting shall not be earlier than the
               close of business on the Business Day prior to such meeting, and
               (ii) the method for revoking or amending such instructions.

         The materials referred to above are to be provided by OSI to the
Trustee, but shall be subject to review and comment by the Trustee.

                                      D-7
<PAGE>   8
         For the purpose of determining Holder Votes to which a Holder is
entitled in respect of any such OSI Meeting or OSI Consent, the number of
Exchangeable Shares owned of record by the Holder shall be determined at the
close of business on the record date established by OSI or by applicable law for
purposes of determining stockholders entitled to vote at such OSI Meeting or to
give written consent in connection with such OSI Consent. OSI will notify the
Trustee in writing of any decision of the board of directors of OSI with respect
to the calling of any such OSI Meeting or the seeking of any such OSI Consent
and shall provide all necessary information and materials to the Trustee in each
case promptly and in any event in sufficient time to enable the Trustee to
perform its obligations contemplated by this Section 4.3.

4.4      COPIES OF STOCKHOLDER INFORMATION

         OSI will deliver to the Trustee copies of all proxy materials,
(including notices of OSI Meetings, but excluding proxies to vote shares of OSI
Common Stock), information statements, reports (including without limitation all
interim and annual financial statements) and other written communications that
are to be distributed from time to time to holders of OSI Common Stock in
sufficient quantities and in sufficient time so as to enable the Trustee to send
those materials to each Holder, to the extent possible, at the same time as such
materials are first sent to holders of OSI Common Stock. The Trustee will mail
or otherwise send to each Holder, at the expense of OSI, copies of all such
materials (and all materials specifically directed to the Holders or to the
Trustee for the benefit of the Holders by OSI) received by the Trustee from OSI,
to the extent possible, at the same time as such materials are first sent to
holders of OSI Common Stock. The Trustee will make copies of all such materials
available for inspection by any Holder at the Trustee's principal transfer
office in the cities of Calgary and Toronto.

4.5      OTHER MATERIALS

         Immediately after receipt by OSI or any stockholder of OSI of any
material sent or given generally to the holders of OSI Common Stock by or on
behalf of a third party, including without limitation dissident proxy and
information circulars (and related information and material) and tender and
exchange offer circulars (and related information and material), OSI shall use
its reasonable best efforts to obtain and deliver to the Trustee copies thereof
in sufficient quantities so as to enable the Trustee to forward such material
(unless the same has been provided directly to Holders by such third party) to
each Holder as soon as possible thereafter. As soon as practicable after receipt
thereof, the Trustee will mail or otherwise send to each Holder, at the expense
of OSI, copies of all such materials received by the Trustee from OSI. The
Trustee will also make copies of all such materials available for inspection by
any Holder at the Trustee's principal transfer office in the cities of Calgary
and Toronto.

4.6      LIST OF PERSONS ENTITLED TO VOTE

         PTI Holdco shall, (i) prior to each annual, general or special OSI
Meeting or the seeking of any OSI Consent and (ii) forthwith upon each request
made at any time by the Trustee in writing, prepare or cause to be prepared a
list (a "List") of the names and addresses of the Holders arranged in
alphabetical order and showing the number of Exchangeable Shares held of record
by each such Holder, in each case at the close of business on the date specified
by the Trustee in such request or, in the case of a List prepared in connection
with a OSI Meeting or a OSI Consent, at the close of business on the record date
established by OSI or pursuant to

                                      D-8
<PAGE>   9
applicable law for determining the holders of OSI Common Stock entitled to
receive notice of and/or to vote at such OSI Meeting or to give consent in
connection with such OSI Consent. Each such List shall be delivered to the
Trustee promptly after receipt by PTI Holdco of such request or the record date
for such meeting or seeking of consent, as the case may be, and in any event
within sufficient time as to enable the Trustee to perform its obligations under
this agreement. OSI agrees to give PTI Holdco written notice (with a copy to the
Trustee) of the calling of any OSI Meeting or the seeking of any OSI Consent,
together with the record dates therefor, sufficiently prior to the date of the
calling of such meeting or seeking of such consent so as to enable PTI Holdco to
perform its obligations under this Section 4.6.

4.7      ENTITLEMENT TO DIRECT VOTES

         Any Holder named in a List prepared in connection with any OSI Meeting
or any OSI Consent will be entitled (i) to instruct the Trustee in the manner
described in Section 4.3 hereof with respect to the exercise of the Holder Votes
to which such Holder is entitled or (ii) to attend such meeting and personally
to exercise thereat (or to exercise with respect to any written consent), as the
proxy of the Trustee, the Holder Votes to which such Holder is entitled.

4.8      VOTING BY TRUSTEE, AND ATTENDANCE OF TRUSTEE REPRESENTATIVE, AT MEETING

         (a)   In connection with each OSI Meeting and OSI Consent, the Trustee
               shall exercise, either in person or by proxy, in accordance with
               the instructions received from a Holder pursuant to Section 4.3
               hereof, the Holder Votes as to which such Holder is entitled to
               direct the vote (or any lesser number thereof as may be set forth
               in the instructions); provided, however, that such written
               instructions are received by the Trustee from the Holder prior to
               the time and date fixed by it for receipt of such instructions in
               the notice given by the Trustee to the Holder pursuant to Section
               4.3 hereof.

         (b)   The Trustee shall cause such representatives as are empowered by
               it to sign and deliver, on behalf of the Trustee, proxies for
               Voting Rights to attend each OSI Meeting. Upon submission by a
               Holder (or its designee) of identification satisfactory to the
               Trustee's representatives, and at the Holder's request, such
               representatives shall sign and deliver to such Holder (or its
               designee) a proxy to exercise personally the Holder Votes as to
               which such Holder is otherwise entitled hereunder to direct the
               vote, if such Holder either:

               (i)  has not previously given the Trustee instructions pursuant
                    to Section 4.3 hereof in respect of such OSI Meeting, or

               (ii) submits to the Trustee's representatives written revocation
                    of any such previous instructions.

         At such OSI Meeting, the Holder exercising such Holder Votes shall have
the same rights as the Trustee to speak at the meeting in respect of any matter,
question or proposition, to vote by way of ballot at the meeting in respect of
any matter, question or proposition and to vote at such meeting by way of a show
of hands in respect of any matter, question or proposition.

                                      D-9
<PAGE>   10

4.9      DISTRIBUTION OF WRITTEN MATERIALS

         Any written materials to be distributed by the Trustee to the Holders
pursuant to this agreement shall be delivered or sent by mail (or otherwise
communicated in the same manner as OSI utilizes in communications to holders of
OSI Common Stock subject to the Trustee's ability to provide this method of
communication and upon being advised in writing of such method) to each Holder
at its address as shown on the books of PTI Holdco. PTI Holdco shall provide or
cause to be provided to the Trustee for this purpose, on a timely basis and
without charge or other expense:

         (a)   current lists of the Holders; and

         (b)   on the request of the Trustee, mailing labels to enable the
               Trustee to carry out its duties under this agreement.

         The materials referred to above are to be provided by PTI Holdco to the
Trustee, but shall be subject to review and comment by the Trustee.

4.10     TERMINATION OF VOTING RIGHTS

         Except as otherwise provided herein or in the Exchangeable Share
Provisions, all of the rights of a Holder with respect to the Holder Votes
exercisable in respect of the Exchangeable Shares held by such Holder, including
the right to instruct the Trustee as to the voting of or to vote personally such
Holder Votes, shall be deemed to be surrendered by the Holder to OSI, and such
Holder Votes and the Voting Rights represented thereby shall cease immediately,
upon the delivery by such Holder to the Trustee of the certificates representing
such Exchangeable Shares in connection with the exercise by the Holder of the
Exchange Right or the occurrence of the automatic exchange of Exchangeable
Shares for shares of OSI Common Stock, as specified in Article 5 hereof (unless
in any case OSI or OSI ULC shall not have delivered the Exchangeable Share
Consideration deliverable in exchange therefor to the Trustee for delivery to
the Holders), or upon the redemption of Exchangeable Shares pursuant to Article
6 or Article 7 of the Exchangeable Share Provisions, or upon the effective date
of the liquidation, dissolution or winding-up of PTI Holdco or any other
distribution of the assets of PTI Holdco among its shareholders for the purpose
of winding up its affairs pursuant to Article 5 of the Exchangeable Share
Provisions, or upon the purchase of Exchangeable Shares from the holder thereof
by OSI pursuant to the exercise by OSI of the Retraction Call Right, the
Redemption Call Right or the Liquidation Call Right.

                                   ARTICLE 5
                      EXCHANGE RIGHT AND AUTOMATIC EXCHANGE

5.1      GRANT AND OWNERSHIP OF THE EXCHANGE RIGHT AND AUTOMATIC EXCHANGE RIGHTS

         OSI hereby grants to the Trustee as trustee for and on behalf of, and
for the use and benefit of, the Holders:

         (a)   the right (the "Exchange Right"), upon the occurrence and during
               the continuance of an Insolvency Event, to require OSI to
               purchase or cause OSI ULC to purchase

                                      D-10
<PAGE>   11

               from each or any Holder all or any part of the Exchangeable
               Shares held by the Holders; and

         (b)   the Automatic Exchange Rights,

all in accordance with the provisions of this agreement and the Exchangeable
Share Provisions, as the case may be. OSI hereby acknowledges receipt from the
Trustee as trustee for and on behalf of the Holders of good and valuable
consideration (and the adequacy thereof) for the grant of the Exchange Right and
the Automatic Exchange Rights by OSI to the Trustee. During the term of the
Trust and subject to the terms and conditions of this agreement, the Trustee
shall possess and be vested with full legal ownership of the Exchange Right and
the Automatic Exchange Rights and shall be entitled to exercise and enforce for
the benefit of the Holders all of the rights and powers of an owner with respect
to the Exchange Right and the Automatic Exchange Rights, provided that the
Trustee shall:

         (c)   hold the Exchange Right and the Automatic Exchange Rights and the
               legal title thereto as trustee solely for the use and benefit of
               the Holders in accordance with the provisions of this agreement;
               and

         (d)   except as specifically authorized by this agreement, have no
               power or authority to exercise or otherwise deal in or with the
               Exchange Right or the Automatic Exchange Rights, and the Trustee
               shall not exercise any such rights for any purpose other than the
               purposes for which this Trust is created pursuant to this
               agreement.

5.2      LEGENDED SHARE CERTIFICATES

         PTI Holdco will cause each certificate representing Exchangeable Shares
to bear an appropriate legend notifying the Holders of:

         (a)   their right to instruct the Trustee with respect to the exercise
               of the Exchange Right in respect of the Exchangeable Shares held
               by a Holder; and

         (b)   the Automatic Exchange Rights.

5.3      GENERAL EXERCISE OF THE EXCHANGE RIGHT

         The Exchange Right shall be and remain vested in and exercised by the
Trustee. Subject to Section 7.15 hereof, the Trustee shall exercise the Exchange
Right only on the basis of instructions received pursuant to this Article 5 from
Holders entitled to instruct the Trustee as to the exercise thereof. To the
extent that no instructions are received from a Holder with respect to the
Exchange Right, the Trustee shall not exercise or permit the exercise of the
Exchange Right.

5.4      PURCHASE PRICE

         The purchase price payable by OSI or OSI ULC for each Exchangeable
Share to be purchased by OSI or OSI ULC under the Exchange Right shall be an
amount equal to the Exchangeable Share Price on the last Business Day prior to
the day of closing of the purchase and sale of such Exchangeable Share under the
Exchange Right. In connection with each

                                      D-11
<PAGE>   12

exercise of the Exchange Right, OSI will provide to the Trustee an Officer's
Certificate setting forth the calculation of the applicable Exchangeable Share
Price for each Exchangeable Share. The applicable Exchangeable Share Price for
each such Exchangeable Share so purchased may be satisfied only by OSI's issuing
and delivering or causing to be delivered to the Trustee, on behalf of the
relevant Holder, the applicable Exchangeable Share Consideration representing
the total applicable Exchangeable Share Price.

5.5      EXERCISE INSTRUCTIONS FOR EXCHANGE RIGHT

         Subject to the terms and conditions herein set forth, a Holder shall be
entitled, upon the occurrence and during the continuance of an Insolvency Event,
to instruct the Trustee to exercise the Exchange Right with respect to all or
any part of the Exchangeable Shares registered in the name of such Holder on the
books of PTI Holdco. To cause the exercise of the Exchange Right by the Trustee,
the Holder shall deliver to the Trustee, in person or by certified or registered
mail, at its principal transfer offices in Calgary, Alberta or at such other
places in Canada as the Trustee may from time to time designate by written
notice to the Holders, the certificates representing the Exchangeable Shares
which such Holder desires OSI to purchase, duly endorsed in blank, and
accompanied by such other documents and instruments as may be required to effect
a transfer of Exchangeable Shares under applicable law and the by-laws of PTI
Holdco and such additional documents and instruments as the Trustee may
reasonably require, together with:

         (a)   a duly completed form of notice of exercise of the Exchange
               Right, contained on the reverse of or attached to the
               Exchangeable Share certificates, stating:

               (i)   that the Holder thereby instructs the Trustee to exercise
                     the Exchange Right so as to require OSI or OSI ULC to
                     purchase from the Holder the number of Exchangeable Shares
                     specified therein,

               (ii)  that such Holder has good title to and owns all such
                     Exchangeable Shares to be acquired by OSI or OSI ULC free
                     and clear of all liens, claims, encumbrances, security
                     interests and adverse claims or interests,

               (iii) the names in which the certificates representing OSI Common
                     Stock issuable in connection with the exercise of the
                     Exchange Right are to be issued, and

               (iv)  the names and addresses of the persons to whom the
                     Exchangeable Share Consideration should be delivered; and

         (b)   payment (or evidence satisfactory to the Trustee, PTI Holdco and
               OSI or OSI ULC of payment) of the taxes (if any) payable as
               contemplated by Section 5.8 of this agreement.

If only a part of the Exchangeable Shares represented by any certificate or
certificates delivered to the Trustee are to be purchased by OSI or OSI ULC
under the Exchange Right, a new certificate for the balance of such Exchangeable
Shares shall be issued to the Holder at the expense of PTI Holdco.

                                      D-12
<PAGE>   13
5.6      DELIVERY OF EXCHANGEABLE SHARE CONSIDERATION; EFFECT OF EXERCISE

         Promptly after receipt of the certificates representing the
Exchangeable Shares which the Holder desires OSI or OSI ULC to purchase under
the Exchange Right (together with such documents and instruments of transfer and
a duly completed form of notice of exercise of the Exchange Right), duly
endorsed for transfer to OSI, the Trustee shall notify OSI, OSI ULC and PTI
Holdco of its receipt of the same, which notice to OSI, OSI ULC and PTI Holdco
shall constitute exercise of the Exchange Right by the Trustee on behalf of the
Holder of such Exchangeable Shares, and OSI or OSI ULC shall immediately
thereafter deliver or cause to be delivered to the Trustee, for delivery to the
Holder of such Exchangeable Shares (or to such other persons, if any, properly
designated by such Holder), the Exchangeable Share Consideration deliverable in
connection with the exercise of the Exchange Right; provided, however, that no
such delivery shall be made unless and until the Holder requesting the same
shall have paid (or provided evidence satisfactory to the Trustee, PTI Holdco
and OSI or OSI ULC of the payment of) the taxes (if any) payable as contemplated
by Section 5.8 of this agreement. Immediately upon the giving of notice by the
Trustee to OSI, OSI ULC and PTI Holdco of the exercise of the Exchange Right, as
provided in this Section 5.6, (i) the closing of the transaction of purchase and
sale contemplated by the Exchange Right shall be deemed to have occurred, (ii)
OSI or OSI ULC shall be required to take all action necessary to permit it to
occur, including delivery to the Trustee of the relevant Exchangeable Share
Consideration, no later than the close of business on the third Business Day
following the receipt by the Trustee of notice, certificates and other documents
as aforesaid and (iii) the Holder of such Exchangeable Shares shall be deemed to
have transferred to OSI or OSI ULC all of its right, title and interest in and
to such Exchangeable Shares and the related interest in the Trust Estate, shall
cease to be a holder of such Exchangeable Shares and shall not be entitled to
exercise any of the rights of a holder in respect thereof, other than the right
to receive his proportionate part of the total purchase price therefor, unless
such Exchangeable Share Consideration is not delivered by OSI or OSI ULC to the
Trustee by the date specified above, in which case the rights of the Holder
shall remain unaffected until such Exchangeable Share Consideration is delivered
by OSI or OSI ULC and any cheque included therein is paid. Concurrently with
such Holder ceasing to be a holder of Exchangeable Shares, the Holder shall be
considered and deemed for all purposes to be the holder of the shares of OSI
Common Stock delivered to it pursuant to the Exchange Right. Notwithstanding the
foregoing, until the Exchangeable Share Consideration is delivered to the
Holder, the Holder shall be deemed to still be a holder of the sold Exchangeable
Shares for purposes of the Voting Rights with respect thereto.

5.7      EXERCISE OF EXCHANGE RIGHT SUBSEQUENT TO RETRACTION

         In the event that a Holder has exercised its right under Article 6 of
the Exchangeable Share Provisions to require PTI Holdco to redeem any or all of
the Exchangeable Shares held by the Holder (the "Retracted Shares") and is
notified by PTI Holdco pursuant to Section 6.6 of the Exchangeable Share
Provisions that PTI Holdco will not be permitted as a result of liquidity or
solvency provisions of applicable law to redeem all such Retracted Shares,
subject to receipt by the Trustee of written notice to that effect from PTI
Holdco and provided that OSI or OSI ULC shall not have exercised the Retraction
Call Right with respect to the Retracted Shares and that the Holder has not
revoked the retraction request delivered by the Holder to PTI Holdco pursuant to
Section 6.1 of the Exchangeable Share Provisions, the retraction request will
constitute and

                                      D-13
<PAGE>   14

will be deemed to constitute notice from the Holder to the Trustee instructing
the Trustee to exercise the Exchange Right with respect to those Retracted
Shares which PTI Holdco is unable to redeem. In any such event, PTI Holdco
hereby agrees with the Trustee and in favour of the Holder immediately to notify
the Trustee of such prohibition against PTI Holdco's redeeming all of the
Retracted Shares and immediately to forward or cause to be forwarded to the
Trustee all relevant materials delivered by the Holder to PTI Holdco or to the
transfer agent of the Exchangeable Shares (including without limitation a copy
of the retraction request delivered pursuant to Section 6.1 of the Exchangeable
Share Provisions) in connection with such proposed redemption of the Retracted
Shares, and the Trustee will thereupon exercise the Exchange Right with respect
to the Retracted Shares which PTI Holdco is not permitted to redeem and will
require OSI or OSI ULC to purchase such shares in accordance with the provisions
of this Article 5.

5.8      STAMP OR OTHER TRANSFER TAXES

         Upon any sale of Exchangeable Shares to OSI or OSI ULC pursuant to the
Exchange Right or the Automatic Exchange Rights, the share certificate or
certificates representing OSI Common Stock to be delivered in connection with
the payment of the total purchase price therefor shall be issued in the name of
the Holder of the Exchangeable Shares so sold or in such names as such Holder
may otherwise direct in writing without charge to the holder of the Exchangeable
Shares so sold, provided, however, that such Holder:

         (a)   shall pay (and none of OSI, OSI ULC, PTI Holdco or the Trustee
               shall be required to pay) any documentary, stamp, transfer or
               other similar taxes that may be payable in respect of any
               transfer involved in the issuance or delivery of such shares to a
               person other than such Holder; or

         (b)   shall have established to the satisfaction of the Trustee, OSI,
               OSI ULC and PTI Holdco that such taxes, if any, have been paid.

PTI Holdco and the Trustee (as directed in writing by PTI Holdco) shall be
entitled to deduct and withhold from any consideration otherwise payable under
this Agreement to any Holder such amounts as PTI Holdco or the Trustee is
required or permitted to deduct and withhold with respect to such payment under
the Income Tax Act (Canada), the United States Internal Revenue Code of 1986 or
any provision of provincial, state, local or foreign tax law, in each case as
amended or succeeded unless such Holder provides to PTI Holdco certificates or
such other assurances as are provided for under the Income Tax Act (Canada), the
United States Internal Revenue Code of 1986 or such other applicable taxation
provisions. To the extent that amounts are so withheld, such withheld amounts
shall be treated for all purposes as having been paid to the Holder in respect
of which such deduction and withholding was made, provided that such withheld
amounts are actually remitted to the appropriate taxing authority as and when
required. To the extent that the amount so required or permitted to be deducted
or withheld from any payment to a Holder exceeds the cash portion, if any, of
the consideration otherwise payable to the Holder, PTI Holdco and the Trustee
are hereby authorized to sell or otherwise dispose of such portion of the
consideration as is necessary to provide sufficient funds to PTI Holdco or the
Trustee, as the case may be, to enable it to comply with such deduction or
withholding requirement and PTI Holdco or the Trustee shall notify the Holder
and remit to such Holder any unapplied balance of the net proceeds of such sale.

                                      D-14
<PAGE>   15

5.9      NOTICE OF INSOLVENCY EVENT

         Immediately upon the occurrence of an Insolvency Event or any event
which with the giving of notice or the passage of time or both would be an
Insolvency Event, PTI Holdco and OSI shall give written notice thereof to the
Trustee. As soon as practicable after receiving notice from PTI Holdco or OSI of
the occurrence of an Insolvency Event, the Trustee will mail to each Holder, at
the expense of OSI, a notice of such Insolvency Event in the form provided by
OSI, which notice shall contain a brief statement of the right of the Holders
with respect to the Exchange Right.

5.10     QUALIFICATION OF OSI COMMON STOCK

         OSI covenants with the Trustee for the benefit of Holders that if any
shares of OSI Common Stock (or other shares or securities into which OSI Common
Stock may be reclassified or changed as contemplated by Section 2.7 of the
Support Agreement) to be issued and delivered pursuant to the Exchange Right or
the Automatic Exchange Rights require registration or qualification with or
approval of or the filing of any document including any prospectus or similar
document, the taking of any proceeding with or the obtaining of any order,
ruling or consent from any governmental or regulatory authority under any
Canadian or United States federal, provincial or state law or regulation or
pursuant to the rules and regulations of any regulatory authority, or the
fulfillment of any other legal requirement (collectively, the "Applicable Laws")
before such shares (or other shares or securities into which OSI Common Stock
may be reclassified or changed as contemplated by Section 2.7 of the Support
Agreement) may be issued and delivered by OSI to the initial holder thereof
(other than PTI Holdco) or in order that such shares may be freely tradeable
thereafter (other than any restrictions on transfer by reason of a holder being
a "control person" of OSI for purposes of Canadian provincial securities law or
an "affiliate" of OSI for purposes of United States federal or state securities
law and provided such trade is conducted through facilities of a stock exchange
outside Canada), OSI will in good faith expeditiously take all such actions and
do all such things as are necessary and permitted by Applicable Laws to cause
such shares of OSI Common Stock (or other shares or securities into which OSI
Common Stock may be reclassified or changed as contemplated by Section 2.7 of
the Support Agreement) to be and remain duly registered, qualified or approved
at all times in order that such shares may be issued and delivered by OSI to the
initial holder thereof (other than PTI Holdco) and in order that such shares or
securities may be freely tradeable thereafter (other than any restrictions on
transfer by reason of a holder being a "control person" of OSI for purposes of
Canadian provincial securities law or an "affiliate" of OSI for purposes of
United States federal or state securities law and provided such trade is
conducted through facilities of a stock exchange outside Canada) including,
without limitation, the filing and maintenance of a registration statement under
the Securities Act of 1933. OSI will in good faith expeditiously take all such
actions and do all such things as are necessary to cause all shares of OSI
Common Stock (or other shares or securities into which OSI Common Stock may be
reclassified or changed as contemplated by Section 2.7 of the Support Agreement)
to be delivered pursuant to the Exchange Right or the Automatic Exchange Rights
to be listed, quoted or posted for trading on all stock exchanges and quotation
systems on which such shares are listed, quoted or posted for trading at such
time immediately upon their issuance.

                                      D-15
<PAGE>   16
5.11     RESERVATION OF SHARES OF OSI COMMON STOCK

         OSI hereby represents, warrants and covenants with the Trustee for the
benefit of the Holders that it has irrevocably reserved for issuance and will at
all times keep available, free from pre-emptive and other rights, out of its
authorized and unissued capital stock such number of shares of OSI Common Stock:

         (a)   as is equal to the sum of

               (i)   the number of Exchangeable Shares issued and outstanding
                     from time to time, and

               (ii)  the number of PTI Stock Options outstanding on the date
                     hereof; and

         (b)   as are now and may hereafter be required to enable and permit PTI
               Holdco to meet its obligations hereunder, under the Certificate
               of Incorporation of PTI Holdco, under the Support Agreement,
               under the Exchangeable Share Provisions and under any other
               security or commitment pursuant to the Arrangement with respect
               to which OSI may now or hereafter be required to issue shares of
               OSI Common Stock.

5.12     AUTOMATIC EXCHANGE ON LIQUIDATION OF OSI

         (a)   OSI will give the Trustee written notice of each of the following
               events at the time set forth below:

               (i)   in the event of any determination by the board of directors
                     of OSI to institute voluntary liquidation, dissolution or
                     winding-up proceedings with respect to OSI or to effect any
                     other distribution of assets of OSI among its stockholders
                     for the purpose of winding-up its affairs, at least 60 days
                     prior to the proposed effective date of such liquidation,
                     dissolution, winding-up or other distribution; and

               (ii)  immediately, upon the earlier of

                     (A)  receipt by OSI of notice of, and

                     (B)  OSI otherwise becoming aware of

         any threatened or instituted claim, suit, petition or other proceedings
         with respect to the involuntary liquidation, dissolution or winding-up
         of OSI or to effect any other distribution of assets of OSI among its
         stockholders for the purpose of winding up its affairs.

         (b)   Immediately following receipt by the Trustee from OSI of notice
               of any event (a "Liquidation Event") contemplated by Section
               5.12(a) above, the Trustee will give notice thereof to the
               Holders. Such notice will be provided by OSI to the Trustee and
               shall include a brief description of the automatic exchange of

                                      D-16
<PAGE>   17

               Exchangeable Shares for shares of OSI Common Stock provided for
               in Section 5.12(c) below.

         (c)   In order that the Holders will be able to participate on a pro
               rata basis with the holders of OSI Common Stock in the
               distribution of assets of OSI in connection with a Liquidation
               Event, immediately prior to the effective time (the "Liquidation
               Event Effective Time") of a Liquidation Event, all of the then
               outstanding Exchangeable Shares shall be automatically exchanged
               for shares of OSI Common Stock. To effect such automatic
               exchange, OSI shall be deemed to have purchased each Exchangeable
               Share outstanding immediately prior to the Liquidation Event
               Effective Time and held by Holders, and each Holder shall be
               deemed to have sold the Exchangeable Shares held by it at such
               time, for a purchase price per share equal to the Exchangeable
               Share Price applicable at such time. In connection with such
               automatic exchange, OSI will provide to the Trustee an Officer's
               Certificate setting forth the calculation of the Exchangeable
               Share Price for each Exchangeable Share.

         (d)   The closing of the transaction of purchase and sale contemplated
               by Section 5.12(c) above shall be deemed to have occurred
               immediately prior to the Liquidation Event Effective Time, and
               each Holder of Exchangeable Shares shall be deemed to have
               transferred to OSI all of the Holder's right, title and interest
               in and to such Exchangeable Shares and the related interest in
               the Trust Estate and shall cease to be a holder of such
               Exchangeable Shares, and OSI shall deliver to the Holder the
               Exchangeable Share Consideration deliverable upon the automatic
               exchange of Exchangeable Shares. Concurrently with such Holder's
               ceasing to be a holder of Exchangeable Shares, the Holder shall
               be considered and deemed for all purposes to be the holder of the
               shares of OSI Common Stock issued to it pursuant to the automatic
               exchange of Exchangeable Shares for OSI Common Stock, and the
               certificates held by the Holder previously representing the
               Exchangeable Shares exchanged by the Holder with OSI pursuant to
               such automatic exchange shall thereafter be deemed to represent
               the shares of OSI Common Stock issued to the Holder by OSI
               pursuant to such automatic exchange. Upon the request of a Holder
               and the surrender by the Holder of Exchangeable Share
               certificates deemed to represent shares of OSI Common Stock, duly
               endorsed in blank and accompanied by such instruments of transfer
               as OSI may reasonably require, OSI shall deliver or cause to be
               delivered to the Holder certificates representing the shares of
               OSI Common Stock of which the Holder is the holder.
               Notwithstanding the foregoing, until each Holder is actually
               entered on the register of holders of OSI Common Stock, such
               Holder shall be deemed to still be a holder of the transferred
               Exchangeable Shares for purposes of all Voting Rights with
               respect thereto.

                                   ARTICLE 6
              RESTRICTIONS ON ISSUANCE OF OSI SPECIAL VOTING STOCK

         During the term of this agreement, OSI will not issue any shares of OSI
Special Voting Stock in addition to the Voting Share.

                                      D-17
<PAGE>   18

                                   ARTICLE 7
                             CONCERNING THE TRUSTEE

7.1      POWERS AND DUTIES OF THE TRUSTEE

         The rights, powers and authorities of the Trustee under this agreement,
in its capacity as trustee of the Trust, shall include:

         (a)   receipt and deposit of the Voting Share from OSI as trustee for
               and on behalf of the Holders in accordance with the provisions of
               this agreement;

         (b)   granting proxies and distributing materials to Holders as
               provided in this agreement;

         (c)   voting the Holder Votes in accordance with the provisions of this
               agreement;

         (d)   receiving the grant of the Exchange Right and the Automatic
               Exchange Rights from OSI as trustee for and on behalf of the
               Holders in accordance with the provisions of this agreement;

         (e)   exercising the Exchange Right and enforcing the benefit of the
               Automatic Exchange Rights, in each case in accordance with the
               provisions of this agreement, and in connection therewith
               receiving from Holders Exchangeable Shares and other requisite
               documents and distributing to such Holders the shares of OSI
               Common Stock and cheques and property, if any, to which such
               Holders are entitled upon the exercise of the Exchange Right or
               pursuant to the Automatic Exchange Rights, as the case may be;

         (f)   holding title to the Trust Estate;

         (g)   investing any moneys forming, from time to time, a part of the
               Trust Estate as provided in this agreement;

         (h)   taking action at the direction of a Holder or Holders to enforce
               the obligations of OSI under this agreement; and

         (i)   taking such other actions and doing such other things as are
               specifically provided in this agreement.

         In the exercise of such rights, powers and authorities, the Trustee
shall have (and is granted) such incidental and additional rights, powers and
authority not in conflict with any of the provisions of this agreement as the
Trustee, acting in good faith and in the reasonable exercise of its discretion,
may deem necessary, appropriate or desirable to effect the purpose of the Trust.
Any exercise of such discretionary rights, powers and authorities by the Trustee
shall be final, conclusive and binding upon all persons. For greater certainty,
the Trustee shall have only those duties as are set out specifically in this
agreement. The Trustee in exercising its rights, powers, duties and authorities
hereunder shall act honestly and in good faith with a view to the best interests
of the Holders and shall exercise the care, diligence and skill that a
reasonably prudent trustee would exercise in comparable circumstances. The
Trustee shall not be bound to

                                      D-18
<PAGE>   19

give any notice or do or take any act, action or proceeding by virtue of the
powers conferred on it hereby unless and until it shall be specifically required
to do so under the terms hereof nor shall the Trustee be required to take any
notice of, or to do or to take any act, action or proceeding as a result of any
default or breach of any provision hereunder, unless and until notified in
writing of such default or breach, which notices shall distinctly specify the
default or breach desired to be brought to the attention of the Trustee and in
the absence of such notice the Trustee may for all purposes of this agreement
conclusively assume that no default or breach has been made in the observance or
performance of any of the representations, warranties, covenants, agreements or
conditions contained herein.

7.2      NO CONFLICT OF INTEREST

         The Trustee represents to PTI Holdco and OSI that at the date of
execution and delivery of this agreement there exists no material conflict of
interest in the role of the Trustee as a fiduciary hereunder and the role of the
Trustee in any other capacity. The Trustee shall, within 90 days after it
becomes aware that such a material conflict of interest exists, either eliminate
such material conflict of interest or resign in the manner and with the effect
specified in Article 10 hereof. If, notwithstanding the foregoing provisions of
this Section 7.2, the Trustee has such a material conflict of interest, the
validity and enforceability of this agreement shall not be affected in any
manner whatsoever by reason only of the existence of such material conflict of
interest. If the Trustee contravenes the foregoing provisions of this Section
7.2, any interested party may apply to the superior court of the province in
which PTI Holdco has its registered office for an order that the Trustee be
replaced as trustee hereunder.

7.3      DEALINGS WITH TRANSFER AGENTS, REGISTRARS, ETC.

         PTI Holdco and OSI irrevocably authorize the Trustee, from time to
time, to:

         (a)   consult, communicate and otherwise deal with the respective
               registrars and transfer agents, and with any such subsequent
               registrar or transfer agent, of the Exchangeable Shares and OSI
               Common Stock; and

         (b)   requisition, from time to time,

               (i)  from any such registrar or transfer agent any information
                    readily available from the records maintained by it which
                    the Trustee may reasonably require for the discharge of its
                    duties and responsibilities under this agreement, and

               (ii) from the transfer agent of OSI Common Stock, and any
                    subsequent transfer agent of such shares, to complete the
                    exercise from time to time of the Exchange Right and the
                    Automatic Exchange Rights in the manner specified in Article
                    5 hereof, the share certificates issuable upon such
                    exercise.

         PTI Holdco and OSI irrevocably authorize their respective registrars
and transfer agents to comply with all such requests. OSI covenants that it will
supply its transfer agent with duly

                                      D-19
<PAGE>   20

executed share certificates for the purpose of completing the exercise from time
to time of the Exchange Right and the Automatic Exchange Rights, in each case
pursuant to Article 5 hereof.

7.4      BOOKS AND RECORDS

         The Trustee shall keep available for inspection by OSI and PTI Holdco,
at the Trustee's principal transfer office in Calgary, Alberta, correct and
complete books and records of account relating to the Trustee's actions under
this agreement, including without limitation all information relating to
mailings and instructions to and from Holders and all transactions pursuant to
the Voting Rights, the Exchange Right and the Automatic Exchange Rights for the
term of this agreement. On or before March 31, 2001, and on or before March 31
in every year thereafter, so long as the Voting Share is on deposit with the
Trustee, the Trustee shall transmit to OSI and PTI Holdco a brief report, dated
as of the preceding December 31, with respect to:

         (a)   the property and funds comprising the Trust Estate as of that
               date;

         (b)   the number of exercises of the Exchange Right, if any, and the
               aggregate number of Exchangeable Shares received by the Trustee
               on behalf of Holders in consideration of the issue and delivery
               by OSI of shares of OSI Common Stock in connection with the
               Exchange Right, during the calendar year ended on such date; and

         (c)   all other actions taken by the Trustee in the performance of its
               duties under this agreement which it had not previously reported.

7.5      INCOME TAX RETURNS AND REPORTS

         The Trustee shall, to the extent necessary, prepare and file on behalf
of the Trust appropriate United States and Canadian income tax returns and any
other returns or reports as may be required by applicable law or pursuant to the
rules and regulations of any securities exchange or other trading system through
which the Exchangeable Shares are traded and, in connection therewith, may
obtain the advice and assistance of such experts as the Trustee may consider
necessary or advisable. If requested by the Trustee, OSI shall retain such
experts for purposes of providing such advice and assistance.

7.6      INDEMNIFICATION PRIOR TO CERTAIN ACTIONS BY TRUSTEE

         The Trustee shall exercise any or all of the rights, duties, powers or
authorities vested in it by this agreement at the request, order or direction of
any Holder upon such Holder's furnishing to the Trustee reasonable funding,
security and indemnity against the costs, expenses and liabilities which may be
incurred by the Trustee therein or thereby; provided that no Holder shall be
obligated to furnish to the Trustee any such funding, security or indemnity in
connection with the exercise by the Trustee of any of its rights, duties, powers
and authorities with respect to the Voting Share pursuant to Article 4 hereof,
subject to Section 7.15 hereof, and with respect to the Exchange Right pursuant
to Article 5 hereof, subject to Section 7.15 hereof, and with respect to the
Automatic Exchange Rights pursuant to Article 5 hereof. None of the provisions
contained in this agreement shall require the Trustee to expend or risk its own
funds or otherwise incur

                                      D-20
<PAGE>   21

financial liability in the exercise of any of its rights, powers, duties or
authorities unless funded, given funds, security and indemnified as aforesaid.

7.7      ACTIONS BY HOLDERS

         No Holder shall have the right to institute any action, suit or
proceeding or to exercise any other remedy authorized by this agreement for the
purpose of enforcing any of its rights or for the execution of any trust or
power hereunder unless the Holder has requested the Trustee to take or institute
such action, suit or proceeding and furnished the Trustee with the funding,
security and indemnity referred to in Section 7.6 hereof and the Trustee shall
have failed to act within a reasonable time thereafter. In such case, but not
otherwise, the Holder shall be entitled to take proceedings in any court of
competent jurisdiction such as the Trustee might have taken; it being understood
and intended that no one or more Holders shall have any right in any manner
whatsoever to affect, disturb or prejudice the rights hereby created by any such
action, or to enforce any right hereunder or under the Voting Rights, the
Exchange Right or the Automatic Exchange Rights, except subject to the
conditions and in the manner herein provided, and that all powers and trusts
hereunder shall be exercised and all proceedings at law shall be instituted, had
and maintained by the Trustee, except only as herein provided, and in any event
for the equal benefit of all Holders.

7.8      RELIANCE UPON DECLARATIONS

         The Trustee shall not be considered to be in contravention of any of
its rights, powers, duties and authorities hereunder if, when required, it acts
and relies in good faith upon lists, mailing labels, notices, statutory
declarations, certificates, opinions, reports or other papers or documents
furnished pursuant to the provisions hereof or required by the Trustee to be
furnished to it in the exercise of its rights, powers, duties and authorities
hereunder, and such lists, mailing labels, notices, statutory declarations,
certificates, opinions, reports or other papers or documents comply with the
provisions of Section 7.9 hereof, if applicable, and with any other applicable
provisions of this agreement.

7.9      EVIDENCE AND AUTHORITY TO TRUSTEE

         PTI Holdco and/or OSI shall furnish to the Trustee evidence of
compliance with the conditions provided for in this agreement relating to any
action or step required or permitted to be taken by PTI Holdco and/or OSI or the
Trustee under this agreement or as a result of any obligation imposed under this
agreement, including, without limitation, in respect of the Voting Rights or the
Exchange Right or the Automatic Exchange Rights and the taking of any other
action to be taken by the Trustee at the request of or on the application of PTI
Holdco and/or OSI forthwith if and when:

         (a)   such evidence is required by any other section of this agreement
               to be furnished to the Trustee in accordance with the terms of
               this Section 7.9; or

         (b)   the Trustee, in the exercise of its rights, powers, duties and
               authorities under this agreement, gives PTI Holdco and/or OSI
               written notice requiring it to furnish such evidence in relation
               to any particular action or obligation specified in such notice.

                                      D-21
<PAGE>   22

         Such evidence shall consist of an Officer's Certificate of PTI Holdco
and/or OSI or a statutory declaration or a certificate made by persons entitled
to sign an Officer's Certificate stating that any such condition has been
complied with in accordance with the terms of this agreement.

         Whenever such evidence relates to a matter other than the Voting Rights
or the Exchange Right or the Automatic Exchange Rights, and except as otherwise
specifically provided herein, such evidence may consist of a report or opinion
of any solicitor, auditor, accountant, appraiser, valuer, engineer or other
expert or any other person whose qualifications give authority to a statement
made by him, provided that, if such report or opinion is furnished by a
director, officer or employee of PTI Holdco and/or OSI, it shall be in the form
of an Officer's Certificate or a statutory declaration.

         Each statutory declaration, certificate, opinion or report furnished to
the Trustee as evidence of compliance with a condition provided for in this
agreement shall include a statement by the person giving the evidence:

               (i)   declaring that such person has read and understands the
                     provisions of this agreement relating to the condition in
                     question;

               (ii)  describing the nature and scope of the examination or
                     investigation upon which such person based the statutory
                     declaration, certificate, statement or opinion; and

               (iii) declaring that such person has made such examination or
                     investigation as such person believes is necessary to
                     enable such person to make the statements or give the
                     opinions contained or expressed therein.

7.10     EXPERTS, ADVISERS AND AGENTS

         The Trustee may:

         (a)   in relation to these presents act and rely on the opinion or
               advice of or information obtained from or prepared by any
               solicitor, auditor, accountant, appraiser, valuer, engineer or
               other expert, whether retained by the Trustee or by PTI Holdco
               and/or OSI or otherwise, and may employ such assistants as may be
               necessary to the proper determination and discharge of its powers
               and duties and determination of its rights hereunder and may pay
               proper and reasonable compensation for all such legal and other
               advice or assistance as aforesaid; and

         (b)   employ such agents and other assistants as it may reasonably
               require for the proper determination and discharge of its powers
               and duties hereunder, and may pay reasonable remuneration for all
               services performed for it (and shall be entitled to receive
               reasonable remuneration for all services performed by it) in the
               discharge of the trusts hereof and compensation for all
               disbursements, costs and expenses made or incurred by it in the
               determination and discharge of its duties hereunder and in the
               management of the Trust.

                                      D-22
<PAGE>   23
7.11     INVESTMENT OF MONEYS HELD BY TRUSTEE

         Unless otherwise provided in this agreement, any moneys held by or on
behalf of the Trustee which under the terms of this agreement may or ought to be
invested or which may be on deposit with the Trustee or which may be in the
hands of the Trustee, may be invested and reinvested in the name or under the
control of the Trustee in securities in which, under the laws of the Province of
Alberta, trustees are authorized to invest trust moneys; provided that such
securities are stated to mature within two years after their purchase by the
Trustee, and the Trustee shall so invest such moneys on the written direction of
PTI Holdco. Pending the investment of any moneys as hereinbefore provided, such
moneys may be deposited in the name of the Trustee in any chartered bank in
Canada or, with the consent of PTI Holdco, in the deposit department of the
Trustee or any other loan or trust company authorized to accept deposits under
the laws of Canada or any province thereof at the rate of interest then current
on similar deposits.

7.12     TRUSTEE NOT REQUIRED TO GIVE SECURITY

         The Trustee shall not be required to give any bond or security in
respect of the execution of the trusts, rights, duties, powers and authorities
of this agreement or otherwise in respect of the premises.

7.13     TRUSTEE NOT BOUND TO ACT ON REQUEST

         Except as in this agreement otherwise specifically provided, the
Trustee shall not be bound to act in accordance with any direction or request of
PTI Holdco and/or OSI or of the directors thereof until a duly authenticated
copy of the instrument or resolution containing such direction or request shall
have been delivered to the Trustee, and the Trustee shall be empowered to act
and rely upon any such copy purporting to be authenticated and believed by the
Trustee to be genuine.

7.14     AUTHORITY TO CARRY ON BUSINESS

         The Trustee represents to PTI Holdco and OSI that at the date of
execution and delivery by it of this agreement it is authorized to carry on the
business of a trust company in the Province of Alberta but if, notwithstanding
the provisions of this Section 7.14, it ceases to be so authorized to carry on
business, the validity and enforceability of this agreement and the Voting
Rights, the Exchange Right and the Automatic Exchange Rights shall not be
affected in any manner whatsoever by reason only of such event; provided,
however, the Trustee shall, within 90 days after ceasing to be authorized to
carry on the business of a trust company in the Province of Alberta, either
become so authorized or resign in the manner and with the effect specified in
Article 10 hereof.

7.15     CONFLICTING CLAIMS

         If conflicting claims or demands are made or asserted with respect to
any interest of any Holder in any Exchangeable Shares, including any
disagreement between the heirs, representatives, successors or assigns
succeeding to all or any part of the interest of any Holder in any Exchangeable
Shares resulting in conflicting claims or demands being made in connection with
such interest, then the Trustee shall be entitled, at its sole discretion, to
refuse to recognize

                                      D-23
<PAGE>   24

or to comply with any such claim or demand. In so refusing, the Trustee may
elect not to exercise any Voting Rights, Exchange Right or Automatic Exchange
Rights subject to such conflicting claims or demands and, in so doing, the
Trustee shall not be or become liable to any person on account of such election
or its failure or refusal to comply with any such conflicting claims or demands.
The Trustee shall be entitled to continue to refrain from acting and to refuse
to act until:

         (a)   the rights of all adverse claimants with respect to the Voting
               Rights, Exchange Right or Automatic Exchange Rights subject to
               such conflicting claims or demands have been adjudicated by a
               final judgment of a court of competent jurisdiction; or

         (b)   all differences with respect to the Voting Rights, Exchange Right
               or Automatic Exchange Rights subject to such conflicting claims
               or demands have been conclusively settled by a valid written
               agreement binding on all such adverse claimants, and the Trustee
               shall have been furnished with an executed copy of such
               agreement.

         If the Trustee elects to recognize any claim or comply with any demand
made by any such adverse claimant, it may in its discretion require such
claimant to furnish such surety bond or other security satisfactory to the
Trustee as it shall deem appropriate fully to indemnify it as between all
conflicting claims or demands.

7.16     ACCEPTANCE OF TRUST

         The Trustee hereby accepts the Trust created and provided for by and in
this agreement and agrees to perform the same upon the terms and conditions
herein set forth and to hold all rights, privileges and benefits conferred
hereby and by law in trust for the various persons who shall from time to time
be Holders, subject to all the terms and conditions herein set forth.

                                   ARTICLE 8
                                  COMPENSATION

OSI and PTI Holdco jointly and severally agree to pay to the Trustee reasonable
compensation for all of the services rendered by it under this agreement and
will reimburse the Trustee for all reasonable expenses (including but not
limited to taxes, compensation paid to experts, agents and advisors, and travel
expenses) and disbursements, including the cost and expense of any suit or
litigation of any character and any proceedings before any governmental agency,
reasonably incurred by the Trustee in connection with its rights and duties
under this agreement; provided that OSI and PTI Holdco shall have no obligation
to reimburse the Trustee for any expenses or disbursements paid, incurred or
suffered by the Trustee in any suit or litigation in which the Trustee is
determined to have acted in bad faith or with negligence or willful misconduct.

                                      D-24
<PAGE>   25

                                   ARTICLE 9
                   INDEMNIFICATION AND LIMITATION OF LIABILITY

9.1      INDEMNIFICATION OF THE TRUSTEE

         OSI and PTI Holdco jointly and severally agree to indemnify and hold
harmless the Trustee and each of its directors, officers, employees and agents
appointed and acting in accordance with this agreement (collectively, the
"Indemnified Parties") against all claims, losses, damages, costs, penalties,
fines and reasonable expenses (including reasonable expenses of the Trustee's
legal counsel) which, without fraud, negligence, willful misconduct or bad faith
on the part of such Indemnified Party, may be paid, incurred or suffered by the
Indemnified Party by reason of or as a result of the Trustee's acceptance or
administration of the Trust, its compliance with its duties set forth in this
agreement, or any written or oral instructions delivered to the Trustee by OSI
or PTI Holdco pursuant hereto. In no case shall OSI or PTI Holdco be liable
under this indemnity for any claim against any of the Indemnified Parties unless
OSI and PTI Holdco shall be notified by the Trustee of the written assertion of
a claim or of any action commenced against the Indemnified Parties, promptly
after any of the Indemnified Parties shall have received any such written
assertion of a claim or shall have been served with a summons or other first
legal process giving information as to the nature and basis of the claim.
Subject to (ii) below, OSI and PTI Holdco shall be entitled to participate at
their own expense in the defense and, if OSI or PTI Holdco so elect at any time
after receipt of such notice, either of them may assume the defense of any suit
brought to enforce any such claim. The Trustee shall have the right to employ
separate counsel in any such suit and participate in the defense thereof, but
the fees and expenses of such counsel shall be at the expense of the Trustee
unless: (i) the employment of such counsel has been authorized by OSI or PTI
Holdco, such authorization not to be unreasonably withheld; or (ii) the named
parties to any such suit include both the Trustee and OSI or PTI Holdco and the
Trustee shall have been advised by counsel acceptable to OSI or PTI Holdco that
there may be one or more legal defenses available to the Trustee that are
different from or in addition to those available to OSI or PTI Holdco and that
an actual or potential conflict of interest exists (in which case OSI and PTI
Holdco shall not have the right to assume the defense of such suit on behalf of
the Trustee, but shall be liable to pay the reasonable fees and expenses of
counsel for the Trustee). This indemnity shall survive the resignation or
removal of the Trustee and the termination of the trust.

9.2      LIMITATION OF LIABILITY

         The Trustee shall not be held liable for any loss which may occur by
reason of depreciation of the value of any part of the Trust Estate or any loss
incurred on any investment of funds pursuant to this agreement, except to the
extent that such loss is attributable to the fraud, negligence, willful
misconduct or bad faith on the part of the Trustee.

                                   ARTICLE 10
                                CHANGE OF TRUSTEE

10.1     RESIGNATION

         The Trustee, or any trustee hereafter appointed, may at any time resign
by giving written notice of such resignation to OSI and PTI Holdco specifying
the date on which it desires to

                                      D-25
<PAGE>   26

resign, provided that such notice shall never be given less than 60 days before
such desired resignation date unless OSI and PTI Holdco otherwise agree and
provided further that such resignation shall not take effect until the date of
the appointment of a successor trustee and the acceptance of such appointment by
the successor trustee. Upon receiving such notice of resignation, OSI and PTI
Holdco shall promptly appoint a successor trustee by written instrument, in
duplicate, one copy of which shall be delivered to the resigning trustee and one
copy to the successor trustee. Failing acceptance by a successor trustee, a
successor trustee may be appointed by an order of the superior court of the
province in which PTI Holdco has its registered office upon application of one
or more of the parties hereto.

10.2     REMOVAL

         The Trustee, or any trustee hereafter appointed, may be removed with or
without cause, at any time on 60 days prior notice by written instrument
executed by OSI and PTI Holdco, in duplicate, one copy of which shall be
delivered to the trustee so removed and one copy to the successor trustee;
provided that, in connection with such removal, provision is made for a
replacement trustee similar to that contemplated in Section 10.1.

10.3     SUCCESSOR TRUSTEE

         Any successor trustee appointed as provided under this agreement shall
execute, acknowledge and deliver to OSI and PTI Holdco and to its predecessor
trustee an instrument accepting such appointment. Thereupon the resignation or
removal of the predecessor trustee shall become effective and such successor
trustee, without any further act, deed or conveyance, shall become vested with
all the rights, powers, duties and obligations of its predecessor under this
agreement, with like effect as if originally named as trustee in this agreement.
However, on the written request of OSI and PTI Holdco or of the successor
trustee, the trustee ceasing to act shall, upon payment of any amounts then due
it pursuant to the provisions of this agreement, execute and deliver an
instrument transferring to such successor trustee all the rights and powers of
the trustee so ceasing to act. Upon the request of any such successor trustee,
OSI, PTI Holdco and such predecessor trustee shall execute any and all
instruments in writing for more fully and certainly vesting in and confirming to
such successor trustee all such rights and powers.

10.4     NOTICE OF SUCCESSOR TRUSTEE

         Upon acceptance of appointment by a successor trustee as provided
herein, OSI and PTI Holdco shall cause to be mailed notice of the succession of
such trustee hereunder to each Holder specified in a List. If OSI or PTI Holdco
shall fail to cause such notice to be mailed within 10 days after acceptance of
appointment by the successor trustee, the successor trustee shall cause such
notice to be mailed at the expense of OSI and PTI Holdco.

                                   ARTICLE 11
                                   SUCCESSORS

11.1     CERTAIN REQUIREMENTS IN RESPECT OF COMBINATION, ETC.

         Neither OSI nor PTI Holdco shall enter into any transaction (whether by
way of reconstruction, reorganization, consolidation, merger, transfer, sale,
lease or otherwise) whereby

                                      D-26
<PAGE>   27

all or substantially all of its undertaking, property and assets would become
the property of any other Person or, in the case of a merger, of the continuing
corporation resulting therefrom, but may do so if:

         (a) (i)  such other Person or continuing corporation (the "Successor"),
                  by operation of law, becomes, without further action, bound by
                  the terms and provisions of this agreement or, if not so
                  bound, executes, prior to or contemporaneously with the
                  consummation of such transaction an agreement supplemental
                  hereto and such other instruments (if any) as are satisfactory
                  to the Trustee and in the opinion of legal counsel to the
                  Trustee are necessary or advisable to evidence the assumption
                  by the Successor of liability for all moneys payable and
                  property deliverable hereunder, the covenant of such Successor
                  to pay and deliver or cause to be delivered the same and its
                  agreement to observe and perform all the covenants and
                  obligations of OSI or PTI Holdco, as the case may be, under
                  this agreement; and

             (ii) such transaction shall, to the satisfaction of the Trustee, be
                  upon such terms which substantially preserve and do not impair
                  in any material respect any of the rights, duties, powers and
                  authorities of the Trustee or of the Holders hereunder; or

         (b) all Exchangeable Shares are redeemed or repurchased pursuant to
             Article 7 of the Exchangeable Share Provisions or under the
             Redemption Call Rights prior to or concurrently with the
             consummation of such transactions.

11.2     VESTING OF POWERS IN SUCCESSOR

         Whenever the conditions of Section 11. 1 hereof have been duly observed
and performed, the Trustee, if required by Section 11.1 hereof, the Successor
and OSI or PTI Holdco, as the case may be, shall execute and deliver the
supplemental agreement provided for in Article 12 hereof, and thereupon the
Successor shall possess and from time to time may exercise each and every right
and power of OSI or PTI Holdco, as the case may be, under this agreement in the
name of OSI or PTI Holdco, as the case may be, or otherwise and any act or
proceeding by any provision of this agreement required to be done or performed
by the board of directors or any officers of OSI or PTI Holdco may be done and
performed with like force and effect by the directors or officers of such
Successor.

11.3     WHOLLY-OWNED SUBSIDIARIES

         Nothing herein shall be construed as preventing: (a) the amalgamation
or merger of any wholly-owned subsidiary of OSI with or into OSI; or (b) the
winding-up, liquidation or dissolution of any wholly-owned subsidiary of OSI
provided that all of the assets of such subsidiary are transferred to OSI or
another wholly-owned subsidiary of OSI, and any such transactions are hereby
expressly permitted.

                                      D-27
<PAGE>   28

                                   ARTICLE 12
                     AMENDMENTS AND SUPPLEMENTAL AGREEMENTS

12.1     AMENDMENTS, MODIFICATIONS, ETC.

         Subject to Sections 12.2 and 12.4, this agreement may not be amended,
modified or waived except by an agreement in writing executed by PTI Holdco, OSI
and the Trustee and approved by the Holders in accordance with Section 9.2 of
the Exchangeable Share Provisions. No amendment to or modification or waiver of
any of the provisions of this agreement otherwise permitted hereunder shall be
effective unless made in writing and signed by all of the parties hereto.

12.2     MINISTERIAL AMENDMENTS

         Notwithstanding the provisions of Section 12.1 hereof, the parties to
this agreement may in writing, at any time and from time to time, without the
approval of the Holders, amend or modify this agreement for the purposes of:

         (a)   adding to the covenants of any or all of the parties hereto for
               the protection of the Holders hereunder subject to the receipt by
               the Trustee of an opinion of its counsel that the addition of the
               proposed covenant is not prejudicial to the interests of the
               Holders as a whole or the Trustee;

         (b)   making such amendments or modifications not inconsistent with
               this agreement as may be necessary or desirable with respect to
               matters or questions which, in the opinion of the board of
               directors of each of OSI and PTI Holdco and in the opinion of the
               Trustee and its counsel, having in mind the best interests of the
               Holders as a whole, it may be expedient to make, provided that
               such boards of directors and the Trustee and its counsel shall be
               of the opinion that such amendments and modifications will not be
               prejudicial to the interests of the Holders as a whole;

         (c)   making such changes or corrections which, on the advice of
               counsel to PTI Holdco, OSI and the Trustee, are required for the
               purpose of curing or correcting any ambiguity or defect or
               inconsistent provision or clerical omission or mistake or
               manifest error; provided that the Trustee and its counsel and the
               board of directors of each of PTI Holdco and OSI shall be of the
               opinion that such changes or corrections will not be prejudicial
               to the interests of the Holders as a whole; or

         (d)   making such changes as may be necessary or appropriate to
               implement or give effect to any assignment or assumption made
               pursuant to Section 14.9 hereof.

12.3     MEETING TO CONSIDER AMENDMENTS

         PTI Holdco, at the request of OSI, shall call a meeting or meetings of
the Holders for the purpose of considering any proposed amendment or
modification requiring approval pursuant hereto. Any such meeting or meetings
shall be called and held in accordance with the by-laws of PTI Holdco, the
Exchangeable Share Provisions and all applicable laws.

                                      D-28
<PAGE>   29
12.4     CHANGES IN CAPITAL OF OSI AND PTI HOLDCO

         At all times after the occurrence of any event effected pursuant to
Section 2.7 or Section 2.8 of the Support Agreement, as a result of which either
OSI Common Stock or the Exchangeable Shares or both are in any way changed, this
agreement shall forthwith be amended and modified as necessary in order that it
shall apply with full force and effect, mutatis mutandis, to all new securities
into which OSI Common Stock or the Exchangeable Shares or both are so changed,
and the parties hereto shall execute and deliver a supplemental agreement giving
effect to and evidencing such necessary amendments and modifications.

12.5     EXECUTION OF SUPPLEMENTAL AGREEMENTS

         From time to time, PTI Holdco (when authorized by a resolution of its
Board of Directors), OSI (when authorized by a resolution of its board of
directors) and the Trustee may, subject to the provisions of these presents, and
they shall, when so directed by these presents, execute and deliver by their
proper officers, agreements or other instruments supplemental hereto, which
thereafter shall form part hereof, for any one or more of the following
purposes:

         (a)   evidencing the succession of any Successors to OSI and the
               covenants of and obligations assumed by each such Successor in
               accordance with the provisions of Article 11 and the successor of
               any successor trustee in accordance with the provisions of
               Article 10;

         (b)   making any additions to, deletions from or alterations of the
               provisions of this agreement or the Voting Rights, the Exchange
               Right or the Automatic Exchange Rights which, in the opinion of
               the Trustee and its counsel, will not be prejudicial to the
               interests of the Holders as a whole or are in the opinion of
               counsel to the Trustee necessary or advisable in order to
               incorporate, reflect or comply with any legislation the
               provisions of which apply to OSI, PTI Holdco, the Trustee or this
               agreement;

         (c)   to implement or give effect to any assignment or assumption made
               pursuant to Section 14.9 hereof; and

         (d)   for any other purposes not inconsistent with the provisions of
               this agreement, including without limitation to make or evidence
               any amendment or modification to this agreement as contemplated
               hereby, provided that, in the opinion of the Trustee and its
               counsel, the rights of the Trustee and the Holders as a whole
               will not be prejudiced thereby.

                                   ARTICLE 13
                                   TERMINATION

13.1     TERM

         The Trust created by this agreement shall continue until the earliest
to occur of the following events:

         (a)   no outstanding Exchangeable Shares are held by a Holder;

                                      D-29
<PAGE>   30
         (b)   each of PTI Holdco and OSI elects in writing to terminate the
               Trust and such termination is approved by the Holders of the
               Exchangeable Shares in accordance with Section 9.1 of the
               Exchangeable Share Provisions; and

         (c)   21 years after the death of the last survivor of the descendants
               of Her Majesty Queen Elizabeth II of the United Kingdom of Great
               Britain and Northern Ireland living on the date of the creation
               of the Trust;

whereupon OSI may repurchase the Voting Share for cancellation, at par value.

13.2     SURVIVAL OF AGREEMENT

         This agreement shall survive any termination of the Trust and shall
continue until there are no Exchangeable Shares outstanding held by a Holder;
provided, however, that the provisions of Articles 8 and 9 hereof shall survive
any such termination of this agreement.

                                   ARTICLE 14
                                     GENERAL

14.1     SEVERABILITY

         If any provision of this agreement is held to be invalid, illegal or
unenforceable, the validity, legality or enforceability of the remainder of this
agreement shall not in any way be affected or impaired thereby, and the
agreement shall be carried out as nearly as possible in accordance with its
original terms and conditions.

14.2     INUREMENT

         This agreement shall be binding upon and inure to the benefit of the
parties hereto and their respective successors and permitted assigns and to the
benefit of the Holders.

14.3     NOTICES TO PARTIES

         All notices and other communications between the parties hereunder
shall be in writing and shall be deemed to have been given if delivered
personally or by confirmed telecopy to the parties at the following addresses
(or at such other address for such party as shall be specified in like notice):

(a)      if to OSI:

         Oil States International, Inc.
         Three Allen Center
         333 Clay Street, Suite 333460
         Houston, Texas 77002

         Attention:  Cindy B. Taylor
         Fax:  (713) 652-0499

                                      D-30
<PAGE>   31

                  with a copy to:

                  Donahue, Ernst & Young LLP
                  1000 Ernst & Young Tower
                  440 - 2nd Avenue S.W.
                  P.O. Box 2258, Station M
                  Calgary, Alberta  T2P 5E5

                  Attention:  Richard Peters
                  Fax:  (403) 206-5525

         (b)      if to PTI Holdco to:

                  Three Allen Center
                  333 Clay Street, Suite 333460
                  Houston, Texas 77002

                  Attention:  Cindy B. Taylor
                  Fax:  (713) 652-0499

         (c)      if to the Trustee to:

                  Montreal Trust Company of Canada
                  Suite 600, 530 - 8th Avenue S.W.
                  Calgary, Alberta
                  T2P 3S8

                  Attention:  Manager, Stock Transfer Services
                  Fax:  (403) 267-6529

         Any notice or other communication given personally shall be deemed to
have been given and received upon delivery thereof, and if given by telecopy
shall be deemed to have been given and received on the date of receipt thereof
unless such day is not a Business Day in which case it shall be deemed to have
been given and received upon the immediately following Business Day.

14.4     NOTICE TO HOLDERS

         Any and all notices to be given and any documents to be sent to any
Holders may be given or sent to the address of such Holder shown on the register
of Holders of Exchangeable Shares in any manner permitted by the Exchangeable
Share Provisions and shall be deemed to be received (if given or sent in such
manner) at the time specified in such Exchangeable Share Provisions, the
provisions of which Exchangeable Share Provisions shall apply mutatis mutandis
to notices or documents as aforesaid sent to such Holders.

14.5     RISK OF PAYMENTS BY POST

         Whenever payments are to be made or documents are to be sent to any
Holder by the Trustee, by PTI Holdco or by OSI or by such Holder to the Trustee
or to OSI or PTI Holdco, the

                                      D-31
<PAGE>   32

making of such payment or sending of such document sent through the mail shall
be at the risk of PTI Holdco or OSI, in the case of payments made or documents
sent by the Trustee or PTI Holdco or OSI, and the Holder, in the case of
payments made or documents sent by the Holder.

14.6     COUNTERPARTS

         This agreement may be executed in counterparts, each of which shall be
deemed an original, but all of which taken together shall constitute one and the
same instrument.

14.7     JURISDICTION

         This agreement shall be construed and enforced in accordance with the
laws of the Province of Alberta and the federal laws of Canada applicable
therein.

14.8     ATTORNMENT

         OSI agrees that any action or proceeding arising out of or relating to
this agreement may be instituted in the courts of Alberta, waives any objection
which it may have now or hereafter to the venue of any such action or
proceeding, irrevocably submits to the jurisdiction of such courts in any such
action or proceeding, agrees to be bound by any judgment of such courts and
agrees not to seek, and hereby waives, any review of the merits of any such
judgment by the courts of any other jurisdiction and hereby appoints PTI Holdco
at its registered office in the Province of Alberta as OSI's attorney for
service of process.

14.9     PERMITTED ASSIGNMENT

         OSI may assign any or all of its rights and obligations under this
Agreement to OSI ULC, provided that each of OSI and OSI ULC shall thereafter,
jointly and severally, be liable for the performance by OSI ULC of the
obligations of OSI pursuant to this Agreement. Any and all of the obligations of
OSI may be performed and satisfied by OSI ULC, except that nothing in this
Section 14.9 will permit any change to the rights, privileges, restrictions and
conditions attaching to the Voting Share or Exchangeable Shares or to the
Exchange Right or Automatic Exchange Rights.

         IN WITNESS WHEREOF, the parties hereby have caused this agreement to be
duly executed as of the date first above written.

                                        OIL STATES INTERNATIONAL, INC.

                                        Per:
                                            --------------------------------
                                        Per:
                                            --------------------------------

                                        MONTREAL TRUST COMPANY OF CANADA

                                        Per:
                                            --------------------------------
                                        Per:
                                            --------------------------------

                                      D-32
<PAGE>   33
                                   APPENDIX A

                   TO THE VOTING AND EXCHANGE TRUST AGREEMENT

                            [ARTICLES OF PTI HOLDCO]

                                      D-33

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