DAVID A. RAPAPORT
                            333 SANDY SPRINGS CIRCLE
                                   SUITE 230
                                ATLANTA, GA 30328
                      TEL (404)-257-9150 FAX (404)-257-9125


March 1, 2001

VIA FACSIMILE
281/272-2987

John N. Ehrman, J.D. S.P.E., President
Vulcan Minerals & Energy, Inc.
650 North Sam Houston Parkway E., Suite 500
Houston, TX 77060

Dear John:

         This letter sets forth the  agreement  by and among  Vulcan  Minerals &
Energy, Inc. (Vulcan),  John N. Ehrman (Ehrman) and David A. Rapaport, as escrow
agent for Generation  Capital  Associates and others (Escrow Agent) with respect
to Escrow Agent providing $800,000 of substitute collateral (Collateral) to Bank
One, Texas,  National  Association (Bank One) for the benefit of Vulcan pursuant
to a Credit  Agreement dated November 14, 2000 between Bank One and Vulcan (Bank
One Credit Facility).

         In  consideration  of Escrow Agent  pledging the Collateral to Bank One
for the benefit of Vulcan, Vulcan and Ehrman agree:

         1. The Collateral is partial security to Bank One for a $6,000,000 take
down by Vulcan  under  the  Credit  Agreement  for the  acquisition  on or about
November  14, 2000 by Vulcan of the  "Marathon  Acquisition"  being the Marathon
interest in OCS-G 4243,  OCS-G 2934,  OCS-G 4895,  OCS-G 2136, OCS-G 1989, OCS-G
1874, OCS-G 1449, OCS-g 2572 and OCS-G 5438 (Marathon Properties).

         2.  Simultaneous  with the execution hereof, a promissory note shall be
executed by Vulcan, and unconditionally  guaranteed by Ehrman personally,  which
shall provide for repayment  and/or  replacement  of the Collateral on or before
the  earlier  of  (i)  the  closing  of  the  initial  $800,000  of  convertible
subordinated notes pursuant to a Financing Terms Agreement,  a draft of which is
attached  hereto  (Financing  Terms  Agreement)  (First  Traunch  Closing) to be
entered  into by and among  Vulcan,  Generation  Capital  Associates  and others
(Purchasers) and Escrow Agent; or (ii) August 28, 2001. (Except as otherwise set
forth herein all capitalized  terms have the meanings set forth in the Financing
Terms Agreement.)

         3. From March 1, 2001,  until the earlier of the First Traunch  Closing
or the release to the Escrow  Agent of the  Collateral  by Bank One,  Purchasers
shall be  entitled  to a ten percent  (10%) net  profits  interest  (NPI) in the
Marathon  Properties,  payable to Escrow Agent  monthly in arrears.  The initial
payment  shall be made to  Escrow  Agent on or about  April 6,  2001;  provided,
however, that no NPI shall be payable to Purchasers if the First Traunch Closing
occurs on or before  March 31,  2001.  An NPI shall be defined as an interest in
the net  proceeds  of  production  after  deduction  of all costs of  operation,
capital  expense and financing of the Marathon  Properties  pursuant to the Bank
One Credit Facility on November 14, 2000; and shall not include any financing of
the  Marathon   Properties  in  excess  of  the  present  principal  balance  of
$5,300,000.

         4. Vulcan shall use its best efforts to have the Collateral released by
Bank One as soon as possible;  and shall not seek or permit the Collateral to be
used as  security  for any  property  or  properties  other  than  the  Marathon
Properties.

         5. As additional consideration for pledging the Collateral to Bank One,
Purchasers  shall receive  200,000 Vulcan  Warrants.  At the time of the Closing
Vulcan shall be given credit for such 200,000 Vulcan Warrants against the number
of Vulcan Warrants issuable pursuant to the Financing Terms Agreement.

         6. Vulcan and Purchasers  acknowledge  that Bathgate  McColley  Capital
Group,  LLC (BM) has  acted as the sole  placement  agent  (Placement  Agent) in
arranging this collateral  substitution.  Vulcan shall issue to BM 80,000 Vulcan
Warrants  and shall pay BM $40,000  in full  payment  of BM's  services  in this
transaction. The compensation paid to BM hereunder shall be credited against any
compensation earned by BM under the Financing Terms Agreement.

         7. The  Purchasers  and BM shall have the  registration  rights for the
Vulcan Warrants and Vulcan Warrants Shares as are set forth in Section 11 of the
Financing Terms Agreement.

         8. If  Vulcan,  Purchasers  and  Escrow  Agent  do not  enter  into the
Financing Terms Agreement,  or a substantially  similar agreement,  on or before
March 31, 2001, Vulcan shall pay the NPI to Escrow Agent on behalf of Purchasers
for a minimum of six months.


Very truly yours,


David A. Rapaport, Escrow Agent



/s/ David A. Rapaport               March 1, 2001
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                                    Date

Accepted and agreed:

Vulcan Minerals & Energy, Inc.

By: /s/ John N. Ehrman              March 1, 2001
    ---------------------------------------------
           John N. Ehrman           Date
         President

John N. Ehrman, individually



/s/ John N. Ehrman                  March 1, 2001
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                                    Date