Exhibit 10.11

               [LETTERHEAD OF PETRIE PARKMAN & CO. APPEARS HERE]



                               December 15, 1995




Sheffield Exploration Company, Inc.
1801 Broadway, Suite 600
Denver, CO 80202

Attn: J. Samuel Butler
      President and Chief Executive Officer

Gentlemen:

      This letter confirms our understanding that Sheffield Exploration Company,
Inc. (the "Company") has engaged Petrie Parkman & Co., Inc. ("Petrie Parkman")
as financial advisor to render financial advisory and investment banking
services to the Company in connection with a possible transaction involving the
Company and TransMontaigne Oil Company ("TMOCO") which transaction is presently
expected to take the form of a merger or similar transaction between the Company
and TMOCO (a "Transaction").

     In connection with serving in our role of financial advisor to the Company,
Petrie Parkman will be available to:

1.   assist the Company in developing the Company's valuation of TMOCO;

2.   assist the Company in developing and presenting, if appropriate, the 
     Company's valuation of the Company;

3.   assist the Company by developing its own view of reference values for the
     Company and TMOCO;

4.   assist the Company in developing an initial offering price and the
     structure of an offer, if appropriate,

5.   assist the Company in developing the Company's negotiating strategy;

6.   assist the Company in considering and evaluating alternate transaction
     structures;

7.   assist the Company in pursuing negotiations with TMOCO, including the 
     signing of a definitive agreement;


 
 
8.   assist the Company in its due diligence on TMOCO and the due diligence by 
     TMOCO on the Company;

9.   assist the Company in preparing presentations for the Company's Board of 
     Directors concerning the Transaction;

10.  assist the Company in preparing presentations for analysts and 
     shareholders;

11.  provide other advisory services that may be requested by the Company in 
     connection with this assignment.

     In consideration for our role as financial advisor, the Company agrees to 
compensate Petrie Parkman as follows:

          (a)   A financial advisory fee of $50,000 which shall be payable upon
          the execution of a merger agreement or other definitive documentation
          of a Transaction, plus

          (b)   An additional financial advisory fee of $50,000 payable upon the
          closing of a Transaction, plus

          (c)   If, during the twelve-month period from the date of termination
          of this engagement, the Company has entered into a letter of intent or
          a definitive agreement or is engaged in substantive negotiations which
          lead to a Transaction which is consummated within six months following
          the end of such 12-month period, the Company agrees to pay Petrie
          Parkman, at closing, a transaction fee consisting of 30,000 fully-
          registered shares of the common stock of the Company.

          (d)   If a Transaction does not occur and, at any time hereafter, the
          Company receives any payment from TMOCO as a result of the termination
          or cancellation of the Company's efforts to effect a Transaction, the
          Company shall pay Petrie Parkman a participation fee in an amount
          equal to 10% of such payment.

     The Company also agrees to reimburse Petrie Parkman for its out-of-pocket
expenses, including fees and expenses of counsel.

     Since Petrie Parkman will be acting on behalf of the Company in connection
with its engagement hereunder, the Company and Petrie Parkman have entered into 
a separate letter agreement, dated the date hereof, providing for the 
indemnification by the Company of Petrie Parkman and certain related entities.

     It is understood that our services may be terminated with or without cause 
by us or by you upon notice to the other party at any time and without liability
or continuing obligation to us or to you (except for any compensation earned and
expenses incurred by us up to the date of


 
termination).  Notwithstanding the foregoing, the indemnity provisions of this 
agreement shall remain operative regardless of any such termination.

     If the foregoing is in accordance with your understanding, I would 
appreciate your signing and returning to us the enclosed duplicate of this 
letter.

     We sincerely look forward to working with you on this assignment.


                                            Very truly yours,

                                            PETRIE PARKMAN & CO., INC.
                       
                                            By [Signature Appears Here]
                                              --------------------------

AGREED TO AND ACCEPTED

SHEFFIELD EXPLORATION COMPANY, INC.

By [Signature Appears Here]
  ----------------------------

 
                               December 15, 1995

Petrie Parkman & Co., Inc.
6350 Texas Commerce Tower
Houston, Texas 77002

Gentlemen:

     In connection with your engagement to advise and assist us pursuant to the 
engagement letter dated the date hereof, Sheffield Exploration Company, Inc. 
(the "Company") hereby agrees to indemnify and hold harmless Petrie Parkman & 
Co., Inc. ("Petrie Parkman") and its affiliates, the respective directors, 
officers, partners, agents and employees of Petrie Parkman and its affiliates 
and each other person, if any, controlling Petrie Parkman or any of its 
affiliates, to the full extent lawful, from and against all losses, claims, 
damages, liabilities and expenses incurred by them (including fees and 
disbursements of counsel) which (A) are related to or arise out of (i) actions 
taken or omitted to be taken (including any untrue statements made or any 
statements omitted to be made) by the Company or (ii) actions taken or omitted 
to be taken by an indemnified person with our consent or in conformity with our 
actions or omissions or (B) are otherwise related to or arise out of Petrie 
Parkman's activities on our behalf under Petrie Parkman's engagement, and we 
will reimburse Petrie Parkman and any other person indemnified hereunder for all
expenses (including fees and disbursements of counsel) as they are incurred by 
Petrie Parkman or such other indemnified person in connection with 
investigating, preparing or defending any such action or claim, whether or not
in connection with pending or threatened litigation in which Petrie Parkman or
any other indemnified person is a party. We will not be responsible, however,
for any losses, claims, damages, liabilities or expenses pursuant to clause (B)
of the preceding sentence which are finally judicially determined to have
resulted primarily from the bad faith or gross negligence of the person seeking
indemnification hereunder. We also agree that neither Petrie Parkman, or any of
its affiliates, nor any director, officer, partner, agent or employee of Petrie
Parkman or any of its affiliates, nor any person controlling Petrie Parkman or
any of its affiliates, shall have any liability to us for or in connection with
such engagement except for such liability for losses, claims, damages,
liabilities or expenses incurred by us which is finally judicially determined to
have resulted primarily from Petrie Parkman's bad faith or gross negligence. We
also agree that we will not, without the prior written consent of Petrie
Parkman, settle or compromise or consent to the entry of any judgment in any
pending or threatened claim, action, suit or proceeding in respect of which
indemnification may be sought hereunder (whether or not Petrie Parkman or any
other indemnified person is an actual or potential party to such claim, action,
suit or proceeding) unless such settlement, compromise or consent includes an
unconditional release of Petrie Parkman and each other indemnified person
hereunder from all liability arising out of such claim, action, suit or
proceeding. The foregoing agreement shall be in addition to any rights that
Petrie Parkman or any other indemnified person may have at common law or
otherwise, including, but not limited to, any right to contribution. We hereby
consent to personal jurisdiction and service and venue in any court in which any
claim which is subject to this agreement is brought against Petrie Parkman or
any other indemnified person. 
     It is understood that, in connection with Petrie
Parkman's above-mentioned engagement. Petrie Parkman may also be engaged to act
for us in one or more additional capacities, and that the terms of the original
engagement or any such additional engagement may be embodied in one or more
separate written agreements. This indemnification shall apply to the original
engagement, any such additional engagement and any modification of the original
engagement or such additional engagement and shall remain in full force and
effect following the completion or termination of Petrie Parkman's
engagement(s).
     We further understand that if Petrie Parkman is asked to act for us in any 
other formal capacity, such further action may be subject to a separate 
agreement containing provisions and terms to be mutually agreed upon.

                                            Very truly yours,
                                            SHEFFIELD EXPLORATION COMPANY, INC.
                                            By: [Signature Appears Here]
                                               -------------------------------- 

Agreed to and Accepted:
PETRIE PARKMAN & CO., INC.
By: [Signature Appears Here]
   -------------------------------- 


 
 
               [LETTERHEAD OF PETRIE PARKMAN & CO. APPEARS HERE]

                                March 21, 1996


Sheffield Exploration Company, Inc.
1801 Broadway, Suite 600
Denver, CO 80202

Attn: J. Samuel Butler
      President and Chief Executive Officer

Dear Gentlemen:

The purpose of this letter is to amend that certain letter agreement between 
Sheffield Exploration Company, Inc. (the "Company") and Petrie Parkman & Co. 
("Petrie Parkman") dated December 15, 1995 (the "Letter Agreement").

Item (c) on the second page of the Letter Agreement is hereby deleted in its 
entirety and replaced with the following:

(c)         "If, during the twelve-month period from the date of this
            engagement, the Company has entered into a letter of intent or a
            definitive agreement or is engaged in substantive negotiations which
            lead to a Transaction which is consummated during, or within six
            months following the end of, such 12-month period, the Company
            agrees to pay Petrie Parkman, at closing, a transaction fee
            consisting of 30,000 fully-registered shares of the common stock of
            the Company."

Except as modified above, the Letter agreement shall remain in full force and 
effect as originally executed.

                                             Very Truly Yours,

                                             PETRIE PARKMAN & CO., INC.

                                             By /s/ Signature Appears Here
                                                --------------------------

AGREED TO AND ACCEPTED:

SHEFFIELD EXPLORATION, INC.

By /s/ Signature Appears Here
   --------------------------