SHEFFIELD EXPLORATION COMPANY, INC.
 
          THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS
            FOR THE SPECIAL MEETING OF STOCKHOLDERS ON JUNE 3, 1996.
 
  THE BOARD OF DIRECTORS RECOMMENDS A VOTE "FOR" ITEM 1 BELOW.
 
  As evidenced by the signature(s) on the reverse side hereof, the undersigned
hereby appoints J. Samuel Butler and David L. Milanesi, and any one of them, as
Proxies, each with full power of substitution, to represent and vote all shares
of the Common Stock of Sheffield Exploration Company, Inc. ("Sheffield") which
the undersigned would be entitled to vote if personally present at the Special
Meeting of Stockholders of Sheffield to be held at the Forum Room, Norwest Bank
Building, 1740 Broadway, Denver, Colorado, on June 3, 1996, at 2:00 P.M., and
at any adjournments thereof, with all power the undersigned would possess if
personally present.
 
ITEM 1.  APPROVAL OF THE RESTATED AGREEMENT AND PLAN OF MERGER BETWEEN
     SHEFFIELD AND TRANSMONTAIGNE OIL COMPANY AS MORE FULLY SET FORTH IN THE
     ACCOMPANYING JOINT PROXY STATEMENT/PROSPECTUS.
 
                      [_] FOR   [_] AGAINST   [_] ABSTAIN
 
ITEM 2. ON ANY OTHER MATTERS THAT MAY PROPERLY COME BEFORE THE MEETING.
 
                   (continued and to be signed on other side)

  THIS PROXY WILL BE VOTED IN THE MANNER DIRECTED. IN THE ABSENCE OF DIRECTION,
THIS PROXY WILL BE VOTED "FOR" ITEM 1 AND IN THE DISCRETION OF THE WITHIN NAMED
PROXIES WITH RESPECT TO OTHER BUSINESS THAT MAY PROPERLY COME BEFORE THE
MEETING OR ANY ADJOURNMENT THEREOF.
 
  When signing as attorney, executor, administrator, trustee, or guardian, or
in other representative capacities, please give your full title as such. A
Proxy for shares held in joint ownership should be signed by EACH owner. If
account is registered in the name of a corporation, partnership or other
entity, a duly authorized individual must sign on its behalf and give title.
 
                                           Date___________________________

                                           _______________________________
                                            Signature(s) of Stockholder(s)

                                           _______________________________
                                            Signature(s) of Stockholder(s)
 
  PLEASE SIGN EXACTLY AS YOUR NAME APPEARS ABOVE, MARK ANY ADDRESS CORRECTION,
DATE, AND RETURN THIS PROXY USING THE ENCLOSED ENVELOPE.