VOTING AGREEMENT


         VOTING  AGREEMENT  ("Agreement")  dated  as of June 30,  1996,  between
Halliburton  Company,  a  Delaware  corporation  (the  "Acquiror"),  and S. Rutt
Bridges  and  Barbara Ann  Bridges  (the  "Stockholders"),  holders of shares of
common stock,  par value $0.05 per share, of Landmark  Graphics  Corporation,  a
Delaware corporation (the "Company").

                                    RECITALS:

         The  Stockholders  beneficially  own an aggregate  of 1,971,263  shares
(together  with any  additional  shares  as to  which  beneficial  ownership  is
acquired by any member of the Stockholder  Group described  below,  the "Company
Shares") of common stock, par value $0.05 per share ("Company Common Stock"), of
the Company.

         The Acquiror is prepared to enter into an Agreement  and Plan of Merger
with the  Company  (the  "Merger  Agreement")  providing  for the  merger of the
Company  with  and  into a  wholly-owned  subsidiary  of the  Acquiror  and  the
conversion in such merger of each share of Company  Common Stock into the number
of shares of the Common  Stock,  par value $2.50 per share,  of the Acquiror set
forth in the Merger Agreement (the "Merger").

         To facilitate the Merger,  the  Stockholders  are willing to enter into
certain arrangements with respect to the Company Shares.

         NOW,  THEREFORE,  in consideration of the premises set forth above, the
mutual promises set forth below, and other good and valuable consideration,  the
receipt and  sufficiency  of which are hereby  acknowledged,  the parties hereto
agree as follows:

1.       Stockholders' Support of the Merger.  From the date hereof until 
February 28, 1997, or, if earlier, termination of the Merger Agreement:

                  (a) Except as  contemplated by the Merger  Agreement,  neither
         the Stockholders nor any Person controlled by either Stockholder or any
         Affiliate  or  Associate  thereof,  other  than  the  Company  and  its
         subsidiaries (collectively, the "Stockholder Group"), will, directly or
         indirectly,  sell, transfer, pledge or otherwise dispose of, or grant a
         proxy with respect to, any Company  Shares to any Person other than any
         member of the  Stockholder  Group or the Acquiror or its  designee,  or
         grant an option with respect to any of the Company Shares or enter into
         any other  agreement or arrangement  with respect to any of the Company
         Shares.

                  (b) The Stockholders  agree that the  Stockholders  will vote,
         and will  cause  each  member  of the  Stockholder  Group to vote,  all
         Company Shares  beneficially  owned by such Persons (i) in favor of the
         Merger and (ii), subject to the provisions of paragraph (c) below,

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         against any combination  proposal or other matter that may interfere or
         be  inconsistent  with  the  Merger  (including  without  limitation  a
         Competing Transaction).

                  (c) The  Stockholders  agree that, if reasonably  requested by
         the Acquiror in order to facilitate the Merger, they will not, and they
         will cause each member of the Stockholder  Group not to, attend or vote
         any Company Shares  beneficially owned by any such Person at any annual
         or special  meeting of  stockholders  or execute any written consent of
         stockholders.

                  (d)  The   Stockholders   hereby  consent  to  the  Acquiror's
         announcement  in any press  release,  public filing,  advertisement  or
         other document, that the Stockholders have entered into this Agreement.

                  (e) To the extent  inconsistent  with the  provisions  of this
         Section 1, each member of the Stockholder  Group hereby revokes any and
         all proxies with respect to such member's  Company  Shares or any other
         voting securities of the Company.

         2.       Miscellaneous

                  (a) The  Stockholders,  on the one hand, and the Acquiror,  on
         the other, acknowledge and agree that irreparable damage would occur if
         any  of  the  provisions  of  this  Agreement  were  not  performed  in
         accordance with their specific terms or were otherwise breached.  It is
         accordingly  agreed  that the  parties  hereto  shall be entitled to an
         injunction or injunctions to prevent breaches of the provisions of this
         Agreement and to enforce  specifically the terms and provisions  hereof
         in  any  court  of  the  United  States  or any  state  thereof  having
         jurisdiction,  in addition  to any other  remedies to which they may be
         entitled at law or equity.

                  (b) Descriptive headings are for convenience only and shall 
         not control or affect the meaning or construction of any provision of 
         this Agreement.

                  (c) All notices, consents, requests,  instructions,  approvals
         and other  communications  provided for herein shall be validly  given,
         made or served, if in writing and delivered  personally,  by telecopier
         (subject to receipt of electronic  confirmation)  or sent by registered
         mail, postage prepaid:


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                  If to the Acquiror:

                           Halliburton Company
                           3600 Lincoln Plaza
                           500 North Akard Street
                           Dallas, Texas  75201-3391
                           Attention:  Lester L. Coleman, Executive 
                                          Vice President and General Counsel
                           Telecopier No.: (214) 978-2658

                  with a copy to:

                           Vinson & Elkins L.L.P.
                           First City Tower
                           1001 Fannin
                           Houston, Texas  77002-6760
                           Attention:  William E. Joor III
                           Telecopier No.:  (713) 758-2346

                  If to the Stockholders:

                           S. Rutt Bridges
                           34 Silver Fox Circle
                           Greenwood Village, Colorado  80121

                  and

                           Barbara Ann Bridges
                           4200 East Plum Court
                           Greenwood Village, Colorado  80121

         or to such other  address or  telecopier  number as any party may, from
         time to time,  designate  in a written  notice  given in a like manner.
         Notice  given by  telecopier  shall be deemed  delivered on the day the
         sender receives  telecopier  confirmation that such notice was received
         at the telecopier number of the addressee.  Notice given by mail as set
         out above shall be deemed  delivered three days after the date the same
         is postmarked.

                  (d) From and  after the  termination  of this  Agreement,  the
         covenants of the parties set forth herein shall be of no further  force
         or effect and the  parties  shall be under no further  obligation  with
         respect thereto.


                                VOTING AGREEMENT
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                  (e) Definitions.  For purposes of this Agreement, the 
         following terms shall have the following meanings:

                           (i) Affiliate.  "Affiliate" shall have the meaning 
                  ascribed to it in Rule 12b-2 of the General Rules and 
                  Regulations under the Exchange Act, as in effect on the date
                  hereof.

                           (ii) Associate.  "Associate" shall have the meaning 
                  ascribed to it in Rule 12b-2 of the General Rules and 
                  Regulations under the Exchange Act, as in effect on the date
                  hereof.

                           (iii)  Beneficial  Owner.  A person shall be deemed a
                  "beneficial  owner" of or to have  "beneficial  ownership"  of
                  Company Shares in accordance with the  interpretations  of the
                  term  "beneficial  ownership" as defined in Rule 13-d(3) under
                  the Exchange  Act, as in effect on the date  hereof,  provided
                  that a Person shall be deemed to be the  beneficial  owner of,
                  and to have beneficial  ownership of, Company Shares that such
                  Person  or any  Affiliate  of such  Person  has the  right  to
                  acquire (whether such right is exercisable immediately or only
                  after  the  passage  of  time)   pursuant  to  any  agreement,
                  arrangement   or   understanding   or  upon  the  exercise  of
                  conversion  rights,  exchange  rights,  warrant,   options  or
                  otherwise.

                           (iv) Exchange Act.  "Exchange Act" shall mean the 
                  Securities Exchange Act of 1934, as amended.

                           (v) Person.  A "Person" shall mean any individual, 
                  firm, corporation, partnership, trust, limited liability 
                  company or other entity.

                           (vi) Significant Subsidiary.  "Significant 
                  Subsidiary" shall have the meaning ascribed to it in
                  Rule 1-02 of SEC Regulation S-X as in effect on the date
                  hereof.

                  (g) Due Authorization;  No Conflicts.  The Stockholders hereby
         represent and warrant to the Acquiror as follows: The Stockholders have
         full power and  authority  to enter into this  Agreement;  neither  the
         execution or delivery of this  Agreement  nor the consum  mation of the
         transactions  contemplated herein will (a) conflict with or result in a
         breach,  default or  violation of (i) any of the terms,  provisions  or
         conditions of the certificate of  incorporation or bylaws of any member
         of the  Stockholder  Group  or (ii)  any  agreement,  proxy,  document,
         instrument,  judgment, decree, order, governmental permit, certificate,
         license,  law,  statute,  rule or regulation to which any member of the
         Stockholder  Group is a party or to which it is subject,  (b) result in
         the creation of any lien, charge or other encum brance on any shares of
         Company Common Stock or (c) require any member of the Stockholder Group
         to obtain the consent of any private nongovernmental third party; no

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         consent,   action,  approval  or  authorization  of,  or  registration,
         declaration or filing with, any  governmental  department,  commission,
         agency  or other  instrumentality  or any  other  person  or  entity is
         required to authorize, or is otherwise required in connection with, the
         execution  and  delivery of this  Agreement  (with the  exception of an
         Amended  Schedule 13D to be filed by the  Stockholders  pursuant to the
         Securities  Exchange  Act of 1934,  as  amended)  or the  Stockholders'
         performance  of  the  terms  of  this  Agreement  or  the  validity  or
         enforceability of this Agreement;  neither  Stockholder has any plan or
         intention to sell or otherwise dispose of any shares of Acquiror Common
         Stock to be received by the undersigned pursuant to the Merger.

                  (h)  Successors and Assigns.  This Agreement  shall be binding
         upon,  and  inure to the  benefit  of,  the  parties  hereto  and their
         respective heirs,  personal  representatives,  successors,  assigns and
         Affiliates,  but shall not be assignable by either party hereto without
         the prior written consent of the other party hereto.

                  (i)  Waiver.  No party may waive any of the terms or
         conditions of this Agreement except by a duly signed writing referring
         to the specific provision to be waived.

                  (j) Governing  Law. This  Agreement  shall be governed by, and
         construed  in  accordance  with,  the  laws  of  the  State  of  Texas,
         regardless  of the laws that might  otherwise  govern under  applicable
         principles  of conflicts  of law;  provided,  however,  that any matter
         involving the internal  corporate  affairs of any party hereto shall be
         governed by the provisions of the General  Corporation Law of the State
         of Delaware.

                  (k) Entire Agreement.  This Agreement constitutes the entire 
         agreement and supersedes all other and prior agreements and 
         understandings, both written and oral, among the parties hereto and 
         their Affiliates.

                  (l) Counterparts.  This Agreement may be executed in two or 
         more counterparts, each of which shall be deemed an original but all 
         of which shall constitute one and the same instrument.


                                VOTING AGREEMENT
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         IN WITNESS WHEREOF,  the Stockholders have each executed this Agreement
and the  Acquiror has caused this  Agreement to be duly  executed by an officer,
thereunto duly authorized, all as of the day and year first above written.

                                      HALLIBURTON COMPANY


                                      By:_________________________________
                                        Lester L. Coleman
                                        Executive Vice President 
                                          and General Counsel


                                      STOCKHOLDERS


                                      ____________________________________  
                                      S. Rutt Bridges

                                      ____________________________________  
                                      Barbara Ann Bridges




VEHOU05:17947.1

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