FOURTH AMENDMENT OF CREDIT AGREEMENT

         THIS FOURTH AMENDMENT OF CREDIT AGREEMENT (this "Amendment"),  dated as
of  June  30,  2000,  is by  and  between  COLUMBUS  ENERGY  CORP.,  a  Colorado
corporation  (herein  called  "Borrower"),  and WELLS FARGO BANK WEST,  NATIONAL
ASSOCIATION,  a  national  banking  association  ("WFBW"),  f/k/a  NORWEST  BANK
COLORADO, NATIONAL ASSOCIATION ("Norwest").

                                    RECITALS

         A.  Borrower and Norwest  entered  into an Amended and Restated  Credit
Agreement  dated as of October 23,  1996,  as  previously  amended  (the "Credit
Agreement"),  in order to set forth the terms  upon  which  Norwest  would  make
available  to Borrower a line of credit and by which the line of credit would be
governed.  Capitalized terms used herein without  definition shall have the same
meanings as set forth in the Credit Agreement.

         B. WFBW is the successor to Norwest.

         C.  Borrower  and WFBW desire to enter into this  Amendment in order to
amend further certain terms and provisions of the Credit Agreement.


                                    AGREEMENT

         NOW, THEREFORE,  in consideration of $10.00 and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereby agree as follows:

         1.  Credit  Agreement.  The Credit  Agreement  shall be, and hereby is,
amended as follows as of the date hereof:

                  (a) All  references  in the Credit  Agreement to "Norwest Bank
Colorado,  National  Association"  shall be changed to be  references  to "Wells
Fargo Bank West,  National  Association".  The definition of "WFBW" contained in
the first  paragraph  of this  Amendment  shall be  incorporated  in the  Credit
Agreement,  and all  references  in the Credit  Agreement to "Norwest"  shall be
changed to be references to "WFBW".

                  (b) The following  shall be substituted  for the definition of
"Borrowing Base Period" in Section 1.1 on page 2 of the Credit Agreement:


<PAGE>


                          "Borrowing Base Period" means: (a) the period from the
date of this Agreement  through March 31, 1997; (b)  thereafter,  until April 1,
2002, each  twelve-month  period  beginning on April 1 of each year; and (c) the
period from April 1, 2002 to July 1, 2002.

                  (c) The following  shall be substituted  for the definition of
"Maturity Date" in Section 1.1 on page 7 of the Credit Agreement:

                          "Maturity Date" means July 1, 2006.

                  (d) The following  shall be substituted  for the definition of
"Principal Payment Date" in Section 1.1 on page 8 of the Credit Agreement:

                          "Principal Payment Date" means: (a) the first Business
Day  of  each  calendar  month,  commencing  August  1,  2002,  and  (b)  if all
Obligations  due and payable on any such date are not then paid, each succeeding
day until all due and payable Obligations are paid in full.

                  (e) The following  shall be substituted  for the definition of
"Revolving Period" in Section 1.1 on page 8 of the Credit Agreement:

                          "Revolving  Period"   means the time  period  from the
date of this Agreement to July 1, 2002.

         2. The Note.  The Note shall be amended,  such amendment to be effected
by an Allonge (the "Allonge") to be attached to the Note and to be substantially
in the form of Exhibit A attached hereto and made a part hereof.

         3.  Loan  Documents.  All  references  in any  document  to the  Credit
Agreement  and the Note shall  refer to the Credit  Agreement  and the Note,  as
amended pursuant to this Amendment and the Allonge.

         4.  Conditions  Precedent.  The  obligations  of the parties under this
Amendment  and under the foregoing  amendments  to the Credit  Agreement and the
Note are  subject,  at the  option  of WFBW,  to the prior  satisfaction  of the
condition  that Borrower shall have executed and delivered to WFBW the following
(all documents to be satisfactory in form and substance to WFBW):

                  (a)  This Amendment.


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<PAGE>

                  (b)  The Allonge.

                  (c)  A Consent of Guarantor and Amendment of Guaranty execute
by CGSI in the form of Exhibit B attached hereto and made a part hereof.

         5.  Representations  and Warranties.  Borrower hereby certifies to WFBW
that as of the date of this Amendment: (a) all of Borrower's representations and
warranties  contained in the Credit Agreement are true, accurate and complete in
all material  respects,  and (b) no Default or Event of Default has occurred and
is continuing under the Credit Agreement.

         6.  Continuation of the Credit  Agreement.  Except as specified in this
Amendment and the Allonge,  the provisions of the Credit  Agreement and the Note
shall  remain in full force and effect,  and if there is a conflict  between the
terms of this Amendment or the Allonge and those of the Credit  Agreement or the
Note, the terms of this Amendment and the Allonge shall control.

         7.  Expenses.  Borrower  shall pay all expenses  incurred in connection
with  the  transactions  contemplated  by  this  Amendment,   including  without
limitation all fees and expenses of WFBW's attorney.

         8.  Miscellaneous.  This  Amendment  shall be governed by and construed
under the laws of the State of Colorado  and shall be binding  upon and inure to
the  benefit  of the  parties  hereto and their  successors  and  assigns.  This
Amendment may be executed in any number of counterparts,  each of which shall be
an original, but all of which together shall constitute one instrument.

         Executed as of the date first above written.

                              COLUMBUS ENERGY CORP.


                              By: /s/ Michael M. Logan
                                  -----------------------
                                  Michael M. Logan,
                                  Vice President

                              WELLS FARGO BANK WEST, NATIONAL ASSOCIATION
                              f/k/a NORWEST BANK COLORADO, NATIONAL ASSOCIATION


                              By: /s/ J. Thomas Reagan
                                  ----------------------------
                                  J. Thomas Reagan,
                                  Vice President



                                      -3-
<PAGE>

                                    EXHIBIT A

                                     ALLONGE

         FOR VALUE  RECEIVED,  COLUMBUS  ENERGY  CORP.,  a Colorado  corporation
("Columbus"),  and WELLS  FARGO  BANK  WEST,  NATIONAL  ASSOCIATION,  a national
banking association ("WFBW"), f/k/a NORWEST BANK COLORADO, NATIONAL ASSOCIATION,
a national banking association ("Norwest"), hereby agree to amend the Promissory
Note dated July 1, 1992, as previously amended (the "Note"),  in the face amount
of $10,000,000, made by Columbus, payable to the order of Norwest, as follows:

         1. All  references  in the Note to  "Norwest  Bank  Colorado,  National
Association"  or "Payee"  shall be deemed to be  references  to Wells Fargo Bank
West, National Association.

         2. By  substituting  the following for the first  sentence of the third
paragraph on page 1 of the Note:

                  The outstanding principal amount of this Note shall be payable
                  as provided in the Credit Agreement,  in monthly  installments
                  due  on  the  first  Business  Day  of  each  calendar  month,
                  commencing  August 1,  2002,  as more fully  described  in the
                  Credit Agreement.

         3. By  substituting  the following for the third  sentence of the third
paragraph on page 1 of the Note:

                  The entire outstanding principal balance of this Note shall be
                  due and  payable  on  July  1,  2006  (unless  payable  sooner
                  pursuant to the terms of the Credit Agreement).

         4. By  substituting  the following for the first  sentence of the fifth
paragraph on page 1 of the Note:

                  Interest  on Prime  Rate  Advances  shall  be due and  payable
                  monthly on the first Business Day of each calendar month, from
                  the date hereof through July 1, 2006.

         5. By  substituting  the following for the third  sentence of the fifth
paragraph on page 1 of the Note:

                  All  accrued and unpaid  interest  will be due and payable not
                  later than July 1, 2006.

                                      A-1
<PAGE>

                DATED as of June 30, 2000.

                              COLUMBUS ENERGY CORP.


                              By:
                                  -----------------------
                                  Michael M. Logan,
                                  Vice President

                              WELLS FARGO BANK WEST, NATIONAL ASSOCIATION
                              f/k/a NORWEST BANK COLORADO, NATIONAL ASSOCIATION


                              By:
                                  ----------------------------
                                  J. Thomas Reagan,
                                  Vice President










                                      A-2

<PAGE>

                                    EXHIBIT B

                              CONSENT OF GUARANTOR
                            AND AMENDMENT OF GUARANTY

         THIS CONSENT OF GUARANTOR AND AMENDMENT OF GUARANTY  (this "Consent and
Amendment"), dated as of June 30, 2000, is by and between WELLS FARGO BANK WEST,
NATIONAL  ASSOCIATION,  a national banking association  ("WFBW"),  f/k/a NORWEST
BANK COLORADO, NATIONAL ASSOCIATION ("Norwest"), and COLUMBUS GAS SERVICES, INC.
("Guarantor").

                                    RECITALS

         A. Guarantor  executed and delivered a Guaranty Agreement dated July 1,
1992, as amended (the "Guaranty"),  to guaranty certain  obligations of Columbus
Energy Corp. ("Borrower").

         B.  Borrower  and WFBW are entering  into a Fourth  Amendment of Credit
Agreement dated as of June 30, 2000 (the "Amendment"), in order to amend further
the Amended and  Restated  Credit  Agreement  dated as of October 23,  1996,  as
previously amended (the "Credit Agreement"), between Borrower and Norwest.

         C. One of the conditions to the  effectiveness of the Amendment is that
Guarantor deliver this Consent and Amendment to WFBW.

         D. Guarantor will benefit from the financial success of Borrower.

                                    GUARANTY

         NOW, THEREFORE,  in consideration of $10.00 and other good and valuable
consideration,  the receipt and  sufficiency  of which are hereby  acknowledged,
Guarantor and WFBW agree as follows:

         1. Amendment of Guaranty. The Guaranty shall be, and hereby is, amended
by changing all references in the Guaranty to "Norwest Bank  Colorado,  National
Association"  or "Bank" to be  references  to Wells  Fargo Bank  West,  National
Association.

         2. Consent of Guarantor.  Guarantor hereby consents to the transactions
set forth in and contemplated by the Amendment, including without limitation the
extension  of the  end of the  "Revolving  Period"  (as  defined  in the  Credit
Agreement) to July 1, 2002 and the extension of the "Maturity  Date" (as defined
in the Credit Agreement) to July 1, 2006.

                                      B-1
<PAGE>

         3.  Miscellaneous.  This Consent and  Amendment  may be executed in any
number of  counterparts,  each of which shall be an original and no one of which
need be signed by all of the parties, but all of which together shall constitute
one and the same instrument.  Guarantor hereby ratifies the Guaranty, as amended
hereby.

                EXECUTED as of the date first above written.

                              COLUMBUS GAS SERVICES, INC.


                              By:
                                  -----------------------
                                  Michael M. Logan,
                                  Executive Vice President

                              WELLS FARGO BANK WEST, NATIONAL ASSOCIATION
                              f/k/a NORWEST BANK COLORADO, NATIONAL ASSOCIATION


                              By:
                                  ----------------------------
                                  J. Thomas Reagan,
                                  Vice President






                                       B-2