Document:

<PAGE>

                                                                EXHIBIT 10.5 (e)

                  FOURTH AMENDMENT TO CREDIT AGREEMENT BY AND
                          BETWEEN INDIAN OIL COMPANY
                         AND BANK ONE, OKLAHOMA, N.A.

     THIS FOURTH AMENDMENT TO CREDIT AGREEMENT (the "Amendment") is made
effective the 1st day of November, 1999 by and between INDIAN OIL COMPANY, an
Oklahoma corporation. (the "Borrower") and BANK ONE, OKLAHOMA, N.A. (the
"Lender").

                             W I T N E S S E T H:

     WHEREAS, on December 22, 1997, Borrower and Lender entered into that
certain Credit Agreement (the "Original Agreement") whereby Lender provided
Borrower with a reducing, revolving line of credit in an amount, subject to a
Borrowing Base, which shall not exceed $50,000,000.00 as evidenced by the Note.

     WHEREAS, on August 10, 1998 Borrower and Lender amended the Original
Agreement for the first time (the "First Amendment") in order to: (i) change the
Debt Service Coverage ratio calculation; (ii) waive the occurrence of certain
events of default; and (iii) certain other changes more particularly set forth
therein.

     WHEREAS, on February 26, 1999, Borrower and Lender amended the Original
Agreement for the second time (the "Second Amendment") in order to (i) reduce
the Borrower's Borrowing Base availability from $24,000,000.00 to
$20,000,000.00; (ii) extend the deadline for Borrower to have completed a
$12,000,000.00 equity offering until March 1, 1999; (iii) extend the deadline
for Borrower to provide an audited financial statement for the fiscal year
ending December 31, 1997 until April 10, 1999; and  (iv) waive the occurrence of
certain events of default.

     WHEREAS, on March 31, 1999, Borrower and Lender amended the Agreement for
the third time (the "Third Amendment") in order to: (i) reset the Borrowing
Base, (ii) reset the Monthly Borrowing Base Reduction, (iii) restate the Debt
Service Coverage Ratio, and (iv) document such other amendments and waivers as
set forth therein (the Original Agreement as amended by the First, Second, and
Third Amendments is referred to herein as the "Agreement")

     WHEREAS, the obligations described in the Agreement are secured by, among
other things not specifically set forth herein, certain Oil and Gas Properties;
and

     WHEREAS, all capitalized terms not otherwise defined herein shall have
those meanings assigned to such terms in the Agreement;
<PAGE>

     WHEREAS, Borrower and Lender now desire to amend the Agreement for the
fourth time in order to (i) permit additional subordinated debt, as described
herein,  (ii) to provide for Unscheduled Redeterminations (defined herein),
(iii) to include commodity rate management language and (iv) to document such
other amendments, extensions and waivers as set forth herein.

     NOW THEREFORE, in consideration of the mutual covenants and agreements
herein contained and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Borrower and the Lender hereby
agree to amend  the agreement as follows:

     A.   CHANGES TO THE AGREEMENT.  The Agreement is hereby amended as follows:

          1.   The definition of "Affiliate" at Section 1.2 of the Agreement,
                                  ---------
Additional Defined Terms, is hereby amended to specifically include "INDCO,
------------------------
L.C.C." by inserting the following sentence at the end of said definition:

     The term "Affiliates" is also understood to include, but is not limited to,
               ----------
     INDCO, L.L.C.

          2.   The definition of "Obligations" at Section 1.2 of the Agreement,

Additional Defined Terms, is hereby amended and restated in its entirety as
------------------------
follows:

          "Obligations" shall mean, without duplication, (a) all
           -----------
     Indebtedness evidenced by the Note, (b) the obligation of the
     Borrower for the payment of any fees required herein, (c) any and
     all obligations, contingent or otherwise, whether now existing or
     hereafter arising, of Borrower to Lender arising under or in
     connection with Rate Management Transactions, and (d) all other
     obligations and liabilities of the Borrower to the Lender, now
     existing or hereafter incurred, under, arising out of or in
     connection with any Loan Document, and with respect to all of the
     foregoing to the extent that any of the same includes or refers
     to the payment of amounts deemed or constituting interest, only
     so much thereof as shall have accrued, been earned and remains
     unpaid at each relevant time of determination.

          3.   The definition of "Tangible Net Worth" at Section 1.2 of the
Agreement, Additional Defined Terms, is hereby amended and restated in its
           ------------------------
entirety as follows:

          "Tangible Net Worth" shall mean, on any date as of which the
           ------------------
     amount thereof is to be determined, the sum of the following for
     Borrower calculated in accordance with GAAP: (i) the amount of
     stated capital (less cost of treasury shares), plus (ii) the
                                                    ----
     amount of surplus and retained earnings (or in the case of a

                                       2
<PAGE>

     surplus or retained earnings deficit, minus the amount of such
                                           -----
     deficit), plus (iii) all debt owed to shareholders and/or
               ----
     Affiliates subordinated to the Obligations, minus (iv) all debt
                                                 -----
     owed to Borrower by shareholders and/or Affiliates.

          4.   A new definition shall be added to Section 1.2 of the Agreement,
Additional Defined Terms, for the term "Rate Management Transaction" which shall
-------------------------
be inserted in Section 1.2 in its alphabetical location and which shall state as
follows:

          "Rate Management Transaction" shall mean any transaction
           ---------------------------
     (including an agreement with respect thereto) now existing or
     hereafter entered into between Borrower and Lender which is a
     rate swap, basis swap, forward transaction, commodity swap,
     commodity option, equity or equity index swap, equity or equity
     index option, bond option, interest rate option, foreign exchange
     transaction, cap transaction, floor transaction, collar
     transaction, forward transaction, currency swap transaction,
     cross-currency rate swap transaction, currency option or any
     other similar transaction (including any option with respect to
     any of these transactions) or any combination thereof, whether
     linked to one or more interest rates, foreign currencies,
     commodity prices, equity prices or other financial measures.

          5.   A new definition shall be added to Section 1.2 of the Agreement,
Additional Defined Terms, for the term "Unscheduled Redetermination" which shall
-------------------------
be inserted in Section 1.2 in its alphabetical location and which shall state as
follows:

          "Unscheduled Redetermination" shall mean a redetermination
           ---------------------------
     of the Maximum Borrowing Base made at any time other than on the
     dates set for the regular semi-annual redetermination of the
     Maximum Borrowing Base which is made (A) at the reasonable
     request of a Borrower, (B) at any time it appears to the Lender,
     in the exercise of its reasonable discretion, that either (i)
     there has been a material decrease in the value of the Oil and
     Gas Properties, or (ii) an event has occurred which is reasonably
     expected to have a Material Adverse Effect.

          6.   Paragraph (b) of Section 2.9 of the Agreement, Borrowing Base
                                                              --------------
Determinations and Monthly Borrowing Base Reductions, is hereby amended and
----------------------------------------------------
restated in its entirety as follows:

          (b)  Subsequent Borrowing Base Determinations shall be made
     by the Lender at least semi-annually on March 1 and September 1
     (each a "Determination Date") of each year beginning September 1,
     1999 or at any other time as an Unscheduled Borrowing Base
     Determination. In connection with, and as of, each Borrowing Base
     Determination, the Lender shall also determine the Monthly
     Borrowing Base Reduction and Half Life of the Borrower's Oil and
     Gas

                                       3
<PAGE>

     Properties. Borrower shall provide Lender with engineering
     information pursuant to the terms of Section 6.4 below. Lender
     shall, by notice to the Borrower by March 1 and September 1 of
     each year, or within a reasonable time thereafter (herein called
     the "Determination Date"), notify the Borrower of the designation
     by the Lender of the new Borrowing Base, Monthly Borrowing Base
     Reduction and Half Life of the Borrower's Oil and Gas Properties
     for the period beginning on such Determination Date and
     continuing until, but not including, the next Determination Date.
     If an Unscheduled Borrowing Base Determination is made by the
     Lender, the Lender shall notify the Borrower within a reasonable
     time after receipt of all requested information of the new
     Borrowing Base, Monthly Borrowing Base Reduction, and Half Life
     of the Borrower's Oil and Gas Properties and such new Borrowing
     Base, Monthly Borrowing Base Reduction, and Half Life of the
     Borrower's Oil and Gas Properties shall continue until the next
     Borrowing Base Determination. If the Borrower does not furnish
     all such information, reports and data by any date specified in
     this Section 2.9.2 or Section 6.4, the Lender may nonetheless
     designate the Borrowing Base, Monthly Borrowing Base Reduction,
     and Half Life of the Borrower's Oil and Gas Properties at any
     amounts which the Lender in its discretion determines and may
     redesignate the Borrowing Base, Monthly Borrowing Base Reduction,
     and Half Life of the Borrower's Oil and Gas Properties from time
     to time thereafter until the Lender receives all such
     information, reports and data, whereupon the Lender shall
     designate a new Borrowing Base, Monthly Borrowing Base Reduction,
     and Half Life of the Borrower's Oil and Gas Properties as
     described above. At each Borrowing Base Determination Lender
     shall determine the amount of the Borrowing Base, Monthly
     Borrowing Base Reduction, and Half Life of the Borrower's Oil and
     Gas Properties based upon the Lender's evaluation of the
     Collateral which Lender in its discretion (using such
     methodology, assumptions and discounts rates as Lender
     customarily uses in assigning collateral value to oil and gas
     properties, oil and gas gathering systems, gas processing and
     plant operations) assigns to such Oil and Gas Properties and
     other Collateral of the Borrower at the time in question and
     based upon such other credit factors consistently applied
     (including, without limitation, the assets, liabilities, cash
     flow, business, properties, prospects, management and ownership
     of the Borrower and its Affiliates) as Lender customarily
     considers in evaluating similar oil and gas loans. If at any time
     any of the Oil and Gas Properties are sold, the Borrowing Base
     then in effect shall automatically be reduced by a sum equal to
     the amount of prepayment required to be made pursuant to Section
     8.4 hereof. It is expressly understood that the Lender has no
     obligation to designate the Borrowing Base, Monthly Borrowing
     Base Reduction or Half Life of the Borrower's Oil and Gas
     Properties at any particular amounts, except in the exercise of
     its discretion, whether in relation to the Commitment or
     otherwise. Provided, however, that the Lender shall not have the
     obligation to designate a

                                       4
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     Borrowing Base in an amount in excess of the Commitment or its
     legal or internal lending limits.

          7.   Article III of the Agreement, COLLATERAL AND OTHER FORMS OF
                                             -----------------------------
CREDIT ENHANCEMENT, is hereby amended to include a new section at Section 3.7
------------------
entitled, INDCO, L.L.C. Collateral, which shall state as follows:
          ------------------------

          3.7  INDCO, L.L.C. Collateral. As further security for the
               ------------------------
     Obligations, Borrower shall pledge to Lender its $960,000.00 note
     from INDCO, L.L.C. and upon request by Lender, INDCO, L.L.C.
     shall pledge and/or grant Lender a security interest in and to
     all assets transferred to INDCO, L.L.C. by Borrower, and any
     consideration received by INDCO, L.L.C. for the sale or transfer
     of the aforementioned assets.

          8.   Section 6.5 of the Agreement, Reserve Reports, is hereby  amended
                                             ---------------
and restated in its entirety to allow for Unscheduled Redeterminations as
follows:

          6.4  Reserve Reports.
               ---------------

          (a)  Deliver to the Lender no later than February 1, 2000,
     and each February 1 thereafter during the term of this Agreement
     and, upon request, in conjunction with any Unscheduled
     Redetermination, engineering reports prepared by an independent
     third party engineer approved by Lender (and/or such other
     appropriate information acceptable to Lender) covering or
     pertaining to Borrower's Oil and Gas Properties in form and
     substance acceptable to Lender setting forth (i) the proven
     producing and proven non-producing oil and gas reserves
     (separately classified as such) attributable to the Oil and Gas
     Properties as of each January 1 of each year for which the
     Reserve Reports are furnished, (ii) the aggregate present value
     determined on the basis of stated pricing assumptions, of the
     future net income with respect to such Oil and Gas Properties,
     discounted at a stated per annum discount rate of proven and
     producing reserves, and (iii) projections of the annual rate of
     production, gross income and net income with respect to such
     proven and producing reserves.

          (b)  The report provided pursuant to this Section 6.4 shall
                                                    -----------
     be submitted to the Lender together with additional data as the
     Lender may reasonably request concerning pricing, quantities of
     production from the Oil and Gas Properties, purchasers of
     production and engineering and geological data. By August 1 of
     each year and, upon request, in conjunction with Unscheduled
     Redeterminations, Borrower shall provide Lender with such other
     reserve information as Lender may reasonably request to complete
     its semi annual redetermination of the Borrowing Base, Monthly
     Borrowing Base Reduction, and Half Life of the Borrower's Oil and
     Gas Properties.

                                       5
<PAGE>

          (c)  In conjunction with the Reserve Report, Borrower shall furnish
     Lender a report on the status of all gas balancing affecting any of the Oil
     and Gas Properties.

          9.   Section 8.1 of the Agreement, Indebtedness, is hereby amended and
                                             ------------
restated in its entirety in order to permit certain of Borrower's obligations to
INDCO, L.L.C. as a permitted indebtedness as follows:

          8.1  Indebtedness. Create, incur, assume or suffer to exist
               ------------
     any Indebtedness that exceed, in the aggregate, the sum of
     $100,000.00, whether by way of loan or otherwise; provided
                                                       --------
     however, the foregoing restriction shall not apply to (a) the
     -------
     Obligations; (b) unsecured current accounts payable incurred in
     he ordinary course of business; (c) the MidFirst Debt; or (d)
     that certain $500,000.00 note payable to INDCO, L.L.C., which
     such note shall be expressly subordinate to the Obligations.

          10.  Section 8.13 of the Agreement, Limitation of Hedging Activities,
                                              --------------------------------
is hereby amended and restated in its entirety, in order to provide for Rate
Management Transactions as follows:

          8.13  Limitation of Hedging Activities. The Borrower will
                --------------------------------
     not enter into any transaction providing (i) for the hedging,
     forward sale, swap or any derivation thereof of crude oil or
     natural gas or other commodities; or (ii) for a swap, collar,
     floor, cap, option, corridor or other contract which is intended
     to reduce or eliminate risk of fluctuation of interest rates, as
     such terms are referred in the capital markets, except the
     foregoing prohibitions shall not apply to: (a) transactions
     consented to in writing by the Lender which are on terms
     acceptable to the Lender; or (b) Pre-Approved Contracts. The term
     "Pre-Approved Contracts" as used herein shall mean (i) any
     physical delivery contract or agreement with an oil and gas
     purchaser under which the Borrower agrees to sell its oil and gas
     at an agreed upon price for an agreed upon period of time and for
     volume amounts which do not exceed the monthly production
     forecast for all of the Borrower's proved developed producing
     reserves; and/or (ii) any financial contract or agreement entered
     into between the Borrower and an affiliate of the Lender or such
     other counterparty as is acceptable to Lender and which is
     consistent with the following: (a) the sales price is at or above
     the Bank's oil and gas pricing then in effect; (b) the volume
     amounts do not exceed 75% of the Borrower's monthly production
     forecast for all of the Borrower's proved developed producing
     reserves; (c) the term does not extend beyond an twelve month
     period. Upon entering into any such contract allowed hereunder,
     Borrower agrees to notify Bank so as to allow for an adjustment
     to the Maximum Borrowing Base if and when deemed appropriate by
     the Bank in its sole discretion.

                                       6
<PAGE>

          11.  The Event of Default set forth at Section 9.1 of the Agreement,
Enumeration of Events of Default, at paragraph (c) is hereby amended and
---------------------------------
restated in its entirety in order to include Rate Management Transactions as
follows:

          (c) default shall be made by Borrower in the due observance
     or performance of any of its obligations, covenants or agreements
     (for payment or otherwise) contained in any of the Loan Documents
     or pursuant to any Rate Management Transaction and such default
     could be expected to have a Material Adverse Effect;

     B.   NOTICES.  Borrower is hereby notified of the following occurrences:

          1.   Borrowing Base Determinations.  Pursuant to Section 2.9 and
               -----------------------------
Section 7.2 of the Agreement, Borrower and Lender hereby affirm the Borrowing
Base at $18,292,000.00 until December 1, 1999 at which time the Monthly
Borrowing Base Reduction shall resume at $244,000.00.  Borrower and Bank
acknowledge that the aforementioned sentence effectively provides a waiver of
the $244,000.00 Monthly Borrowing Base reduction otherwise scheduled for
November 1, 1999. Borrower and Bank further acknowledge that the regularly
scheduled Borrowing Base Determination dates are March 1 and September 1.  The
Borrowing Base Determination Dates set forth in Section 2.9 of the Agreement
notwithstanding, the September 1, 1999 Borrowing Base Determination Date is
hereby extended until December 15, 1999.

          2.   Debt Service Coverage Ratio.  For the quarterly reporting period
               ---------------------------
ending September 30, 1999 and only for the quarterly reporting period ending
September 30, 1999, the denominator of the Debt Service Coverage Ratio shall be
$488,000.00 (which such amount equates to the Monthly Borrowing Base Reduction
for two months - not three- in order to offset the $250,000.00 payment to Reid
Investments incurred during the month of September, 1999) plus interest expense
                                                          ----
(less any accrued and unpaid interest on subordinated debt ) for the quarter
then ended, plus any other current maturities of long term debt.   The
            ----
calculation of the Debt Service Coverage Ratio as set forth in the Agreement
shall continue and be reinstated for all quarters subsequent to September 30,
1999.

          3.   Tangible Net Worth.  Lender hereby waives the default created by
               ------------------
Borrower's failure to maintain the level of Tangible Net Worth required pursuant
to Section 7.3 of the Agreement, Tangible Net Worth, for the quarterly reporting
                                 ------------------
periods ending March 31, 1999 and June 30, 1999. This waiver is on a one-time
basis and is specifically not intended to waive any future violations of Section
7.3 of the Agreement or any other terms, covenants or conditions of the
Agreement.

     C.   REPRESENTATIONS AND WARRANTIES

                                       7
<PAGE>

     Borrower hereby represents and warrants to Lender that:

          1.   Borrower is a corporation, duly organized, legally existing, and
in good standing under the laws of the State of Oklahoma, and is duly qualified
as a foreign corporation and in good standing in all other states wherein the
nature of its business or its assets make such qualification necessary.

          2.   Borrower's execution and delivery of this Amendment and
performance of its obligations hereunder: (a) are and will be within its
corporate powers; (b) are duly authorized by its board of directors; (c) are not
and will not be in contravention of any law, statute, rule or regulation, the
terms of its articles or certificates of incorporation and bylaws, nor of any
preferred stock provision, indenture, agreement or undertaking to which
Corporation or any of its properties are bound; (d) do not require any consent
or approval (including governmental) which has not been given; and (e) will not
result in the imposition of Liens, charges or encumbrances on any of its
properties or assets, except those in favor of Lender hereunder.

          3.   This Amendment, when duly executed and delivered, will constitute
the legal, valid and binding obligations of each Borrower, enforceable in
accordance with its terms.

          4.   All financial statements, balance sheets, income statements and
other financial data which have been or are hereafter furnished to Lender by
each Borrower to induce Lender to make the loans hereunder due, and as to
subsequent financial statements will, fairly represent each Borrower's financial
condition as of the dates for which the same are furnished. All such financial
statements, reports, papers and other data furnished to Lender are and will be,
when furnished: prepared in accordance with generally accepted accounting
principles consistently applied; accurate and correct in all material respects;
and complete insofar as completeness may be necessary to give Lender a true and
accurate knowledge of the subject matter.  Since the date of the last such
financial statements, no material adverse change has occurred in the operations
or condition, financial or otherwise and other financial data provided to
Lender; of either Borrower, nor, to the best of their knowledge, has either
Borrower incurred, any material liabilities or made any material investment or
guarantees, direct or contingent, in any single case or in the aggregate, which
has not been disclosed to Lender.

          5.   The Borrower is the sole and lawful owner of the Collateral,
pledged, mortgaged or assigned by it, and Borrower has, and as to after acquired
property or New Properties will have, good right to cause the Collateral to be
hypothecated to Lender as security for the Obligations.

                                       8
<PAGE>

          6.   All of Borrower's other representations and warranties set forth
in Sections 5.1 through 5.22 of the Agreement are true and correct on and as of
the date hereof with the same effect as though made and repeated by Borrower as
of the date hereof.

     D.   CONDITIONS

     Lender's obligations under the Agreement, as hereby amended, is subject to
the following conditions:

          1.   Lender and Borrower shall have executed and delivered this
Amendment.

          2.   Lender shall have executed and delivered such endorsements and
assignments necessary, in the discretion of Bank, to pledge the $960,000.00
promissory note from INDCO, L.L.C. to Borrower.

          3.   INDCO, L.L.C. and Borrower shall have executed and delivered to
Lender for its execution an agreement, satisfactory to Lender, subordinating
INDCO, L.L.C.'s $500,000.00 promissory note from the Borrower (principal and
interest) to the Obligations.

          4.   Borrower's representations and warranties set forth in Section
C hereof shall be true and correct on and as of the date hereof, and the date of
any subsequent advance with the same effect as though such representation and
warranty had been on and as of such date.

          5.   Borrower shall have satisfied all conditions set forth in Section
4.1 of the Agreement.

          6.   Except for the default created by Borrower's failure to provide
Bank with a copy of its audited financial statements for year ending December
31, 1998, as of the date hereof, and the date of any subsequent Advance, no
Event of Default nor any event which, with the giving of notice or lapse of
time, would constitute an Event of Default shall have occurred and be
continuing.

     E.   OTHER COVENANTS AND MISCELLANEOUS TERMS

          1.   Except as expressly amended and supplemented hereby, the
Agreement shall remain unchanged and in full force and effect, and the same is
hereby ratified and extended.

                                       9
<PAGE>

          2.   The Obligations, including but not limited to the indebtedness
evidenced by the Note executed in conjunction with the Agreement, shall continue
to be secured by the Collateral, without interruption or impairment of any kind.

          3.   Borrower shall make, execute or endorse, and acknowledge and
deliver or file or cause the same to be done, all such vouchers, invoices,
notices, certifications and additional agreements, undertakings, conveyances,
deeds of trusts, mortgages, transfers, assignments, financing statements or
other assurances, and take any and all such other action, as Lender may, from
time to time, deem reasonably necessary or proper in connection with any of the
Loan Documents and the obligations of Borrower assuring and confirming unto
Lender all or any part of the security for any such obligation.  In connection
herewith, Lender may require Borrower to execute additional mortgages or deeds
of trust pursuant to the terms of the Agreement.

          4.   The Borrower hereby agrees to pay all reasonable attorney fees
and legal expenses incurred by Lender in preparation, execution and
implementation of this Amendment and any mortgages, deeds of trust, security
agreements, pledge agreements or any amendments thereto.

          5.   This Amendment shall be construed in accordance with and governed
by the laws of the State of Oklahoma, and shall be binding on and inure to the
benefit of the Borrower and Lender, and their respective successors and assigns.
All obligations of the Borrower under the Agreement and all rights of Lender and
any other holder of the Notes, whether expressed herein or in any Note, shall be
in addition to and not in limitation of those provided by applicable law.
Borrower irrevocably agrees that, subject to Lender's sole election, all suits
or proceedings arising from or related to the Agreement, as amended, or the
Notes may be litigated in courts (whether State or Federal) sitting in Oklahoma
City, Oklahoma, and the Borrower hereby irrevocably waives any objection to such
jurisdiction and venue.

          6.   This Amendment may be executed in as many counterparts as are
deemed necessary or convenient, and it shall not be necessary for the signature
of more than any one party to appear on any single counterpart.  Each
counterpart shall be deemed an original, but all shall be construed together as
one and the same instrument.  The failure of any party to sign shall not affect
or limit the liability of any party executing any such counterpart.

     BORROWER:                INDIAN OIL COMPANY,
                              an Oklahoma corporation

                              __________________________________________
                              By:  Richard R. Dunning
                              Title:  Chief Executive Officer

                                       10
<PAGE>

     LENDER:                  BANK ONE, OKLAHOMA, N.A.

                              __________________________________________
                              By: John K. Slay, Jr.
                              Title: Vice President

                                       11
<PAGE>

                        INDCO, L.L.C. JOINDER

     INDCO, L.L.C., for good and valuable consideration the receipt and
sufficiency of which are hereby acknowledged, certify that it is familiar with,
has read, and is bound by applicable provisions concerning it contained therein.
Further, INDCO, L.L.C. hereby acknowledges and ratifies its agreements set forth
that certain letter agreement with Bank One, Oklahoma, N.A. and Indian Oil
Company dated as of September 20, 1999.

                                    INDCO, L.L.C.,

                                    ____________________________________
                                    By:  Richard R. Dunning
                                    Title:  Manager

                                       12<PAGE>

                                                                EXHIBIT 10.5 (f)

                            INTERCREDITOR AGREEMENT

     This Intercreditor Agreement is dated as of this 31st day of March, 1999 by
and among BANK ONE, OKLAHOMA, N.A. and its successors and assigns ("Bank One"),
MIDFIRST BANK, a federally chartered savings association and its successors and
assigns ("MidFirst"), and INDIAN OIL COMPANY, an Oklahoma corporation (the
"Borrower").

                                   RECITALS:
                                   ---------

     WHEREAS, On December 17, 1997, Borrower and MidFirst entered that certain
Loan Agreement (the "MidFirst Loan Agreement") and that certain promissory note
in the principal amount of $12,000,000.00 (the "MidFirst Note") and such other
documents executed in conjunction with the MidFirst Loan Agreement (the
"MidFirst Loan Documents").

     WHEREAS, on December 17, 1997, Borrower and Bank One entered into that
certain Credit Agreement (the "Bank One Loan Agreement") and that certain
revolving promissory note in the principal amount of $50,000,000.00 (the "Bank
One Note") and such other documents executed in conjunction with the Bank One
Loan Agreement (the "Bank One Loan Documents").

     WHEREAS, all indebtedness evidenced by the Bank One Loan Agreement, the
Bank One Note and the Bank One Loan Documents is referred to herein as the "Bank
One Debt."

     WHEREAS, all indebtedness evidenced by the MidFirst Loan Agreement, the
MidFirst Note and the MidFirst Loan Documents is referred to herein as the
"MidFirst Debt."

     WHEREAS, MidFirst and Bank One entered into and executed that certain
Intercreditor Agreement on December 17, 1997 (the "1997 Intercreditor
Agreement") in conjunction with the execution of both the Bank One Loan
Agreement and the MidFirst Loan Agreement, wherein MidFirst and Bank One agreed
to certain procedures to follow concerning collateral shared by both lenders.

     WHEREAS, both the Bank One Loan Agreement and the MidFirst Loan Agreement
have been amended from time to time after the date of the original execution
thereof.

     WHEREAS, contemporaneously herewith, Borrower has agreed to make a six
million dollar ($6,000,000.00) payment to reduce its total outstanding
indebtedness;

     WHEREAS, Bank One, MidFirst, and Indian desire that the entire
$6,000,000.00 be applied against the MidFirst Debt in consideration for, among
other things, the execution of this Intercreditor Agreement.

                                       1
<PAGE>

     WHEREAS, it is the intent hereof and the parties hereto agree that this
Intercreditor Agreement shall replace and be substituted for, in its entirety,
the 1997 Intercreditor Agreement.

     NOW, THEREFORE, in consideration of the mutual promises herein contained
and such other good and valuable consideration the sufficiency of which is
hereby acknowledged, the parties hereby agree as follows:

     I.   REPRESENTATIONS AND WARRANTIES.  MidFirst and Borrower represent and
          ------------------------------
warrant to Bank One that:

          (a) MidFirst Loan.  As of the date hereof, the total indebtedness
              -------------
owing by Borrower to MidFirst is $12,000,000.00 of which such amount shall be
contemporaneously reduced to $6,000,000.00.

          (b) Default.  There is no default in the indebtedness from Borrower to
              -------
MidFirst or under any other agreements between Borrower and third parties.

     II.  JUNIOR PRIORITY OF MIDFIRST DEBT.  In order to induce Bank One to
          --------------------------------
extend a loan to Borrower, it is agreed as follows:

          (a) Junior Priority.   MidFirst agrees that the outstanding principal
              ----------------
indebtedness of the MidFirst Debt together with all interest obligations and the
payment therefor shall be and hereby are inferior and junior to the Bank One
Debt, unless otherwise agreed to in writing by Bank One, and MidFirst shall be
entitled to no payments of either principal or interest of any nature whatsoever
until the full cash payment of any and all indebtedness (including all interest
after the date of filing of a petition by or against Borrower under any
bankruptcy act) now due to Bank One from Borrower pursuant to the Bank One Loan
Agreement, as same may be amended from time to time hereafter.  Provided,
however, notwithstanding the above, MidFirst may accept monthly payments of
interest only on the MidFirst Debt so long as Borrower  is not in default on the
Bank One Loan Agreement. Upon the occurrence of an Event of Default under the
Bank One Loan Agreement, payments of interest on the MidFirst Debt by Borrower
shall be suspended and not made until such Event of Default has been cured to
Bank One's satisfaction; provided MidFirst shall have the right to collect the
principal and interest of the MidFirst Debt from its guarantors or the
liquidation of its collateral as provided in Section II(b) hereof.

          (b) No Action by MidFirst.  MidFirst will not, without Bank One's
              ---------------------
prior written consent,  collect or enforce the MidFirst Debt or any part thereof
out of the assets of Borrower or otherwise exercise its remedies against
Borrower under the MidFirst Loan Documents, except as provided below, until the
Bank One Debt has been paid in full.  MidFirst shall be entitled to exercise its
remedies against the collateral securing the MidFirst

                                       2
<PAGE>

Debt and against any guarantors of the MidFirst Debt at any time. MidFirst shall
have the right to initiate collection activities and seek a judgment against
Borrower upon the initiation by Bank One of litigation to enforce Borrower's
obligations to Bank One, but not before. Bank One hereby agrees that upon its
transmission of any notification to Borrower of the occurrence of any event of
default thereby triggering any applicable cure period, it will forward MidFirst
a copy of this notice. Bank One also agrees to promptly forward MidFirst notice
of any litigation filed by it against Borrower. In no event shall MidFirst file
a judgment lien against the assets of Borrower prior to the filing by Bank One
of such a judgment lien. It is the intent hereof that MidFirst shall have the
right to obtain repayment of the MidFirst Debt pursuant to the MidFirst Loan
Documents from guarantors of the MidFirst Debt and from and against any
collateral securing the MidFirst Debt at any time, and, it is the intent hereof
that MidFirst shall have the right to obtain repayment of the MidFirst Debt
pursuant to the MidFirst Loan Documents against Borrower after repayment of the
Bank One Debt.

          (c) Amendment of MidFirst Loan.  So long as the Bank One Debt shall
              --------------------------
remain outstanding, MidFirst shall not make or permit any amendment to the
MidFirst Loan Documents without the prior written consent of Bank One which
would (i) extend the maturity date past September 1,2000, (ii) encumber the
collateral securing the Bank One Debt or any other assets owned by the Borrower
or (iii) increase the MidFirst Debt.

          (d) Payments Held in Trust.  In the event that any payment of
              ----------------------
principal or interest or other payment or distribution of assets of Borrower
shall be received by any holder of the MidFirst Debt, notwithstanding the
foregoing, in violation of the provisions hereof, and before payment in full of
the Bank One Debt, such payment or distribution shall be held by such holder of
the MidFirst Debt in trust for the holder of the Bank One Debt by such holder of
the MidFirst Debt to the extent necessary to make payment of any unpaid Bank One
Debt.

          (e) Permissive Payments.  Borrower agrees with Bank One that after the
              -------------------
execution hereof, it will make no payments of principal or interest to MidFirst
on the MidFirst Loan; provided, however, Bank One agrees that Borrower shall be
allowed to make monthly payments of interest only to MidFirst on the MidFirst
Loan, as long as such payment does not cause the Borrower to violate Section 7.2
of the Bank One Loan Agreement (the "Debt Service Coverage Ratio") and  so long
as no "Event of Default"  has occurred or is continuing under the Bank One Loan
Agreement. In the event that making the monthly interest payment due to MidFirst
would cause the Borrower to violate the Debt Service Coverage Ratio, and as a
result anything less than the full interest payment is made, Bank One agrees
that such payments may be made up at such point in time and to the extent that
no violation of the Debt Service Coverage Ratio would result.

          (f) Amendment of Bank One Loan.   So long as the MidFirst Debt shall
              --------------------------
remain outstanding, Bank One shall not make or permit any amendment to the Bank
One Loan Documents without the prior written consent of MidFirst which would (i)
extend the maturity date past September 1, 2000, (ii) encumber the collateral
securing the MidFirst Debt or (iii) increase the Bank One commitment amount
beyond $20,000,000.00.

                                       3
<PAGE>

          (g) Discontinuance of Bank One Debt.  If, at any time hereafter, Bank
              -------------------------------
One shall, in its own judgment determine to discontinue the extension of credit
to Borrower, Bank One may do so.  This Agreement shall continue in full force
and effect until Borrower shall have satisfied all obligations and Bank One
shall have been paid in full on all indebtedness, of any nature whatsoever that
may be due on the Bank One Loan Agreement  or any amendments thereto to Bank One
from Borrower.

     III  MISCELLANEOUS
          -------------

          (a) Insolvency.  In the event of any liquidation, dissolution or
              ----------
winding up of the Borrower, or any execution sale, receivership, insolvency,
bankruptcy, liquidation, readjustment, reorganization or other similar
proceeding relative to the Borrower or its property, all principal, interest and
other amounts owing on the Bank One Debt shall first be paid in full in cash
before any payment is made upon the MidFirst Debt; and in any such event, and in
the event of any payment in violation of this Intercreditor Agreement, any
payment or distribution of any kind or character, whether in cash, property or
securities which shall be made upon or in respect of the MidFirst Debt shall be
paid over to Bank One for application in payment thereof unless and until the
Bank One Debt shall have been paid or satisfied in full in cash.

          (b) Proof and Vote of Claims.  MidFirst hereby appoints, which
              ------------------------
appointment is irrevocable and coupled with an interest, Bank One, its
successors and assigns, as MidFirst's true and lawful attorney, with full power
of substitution, in the name of MidFirst, Bank One or otherwise.  Such
appointment shall be for the sole use and benefit of Bank One, to the extent
permitted by law, to prove and vote all claims relating to the MidFirst Debt,
and to receive and collect all distributions and payments to which MidFirst
would be otherwise entitled on any liquidation of Borrower or in any proceeding
affecting Borrower or its property under any bankruptcy or insolvency laws or
any laws or proceedings relating to the relief of the Borrower, readjustment,
composition or extension of indebtedness or reorganization.

          (c) Release of Oil and Gas Collateral.  MidFirst will forthwith
              ---------------------------------
release its second mortgage on Borrower's oil and gas properties.

          (d) Release of MidFirst Collateral.  Bank One will forthwith release
              ------------------------------
its liens against the MidFirst Collateral.

          (e)  Administrative Proceedings.  Except as permitted in Section
               --------------------------
II(b), MidFirst agrees that it will not commence, prosecute or participate in
any administrative, legal, or equitable action against Borrower or in any
administrative, legal or equitable action that might adversely affect Borrower
or its interest, without Bank One's prior written consent.

          (f) No Interference.  MidFirst agrees that it will not take any action
              ---------------
that will impede, interfere with or restrict or restrain the exercise by Bank
One of its rights and

                                       4
<PAGE>

remedies under the Bank One Loan Documents and, upon the commencement of any
bankruptcy of the Borrower, will take such actions as may be reasonably
necessary or appropriate to effectuate the subordination provided hereby. In
furtherance thereof, MidFirst hereby agrees not to oppose any motion filed or
supported by Bank One for relief from the automatic stay, for adequate
protection in respect of the Bank One Debt, and/or for the Borrower's use of
cash collateral or post-petition borrowing from Bank One.

          (g) Collection Actions.  If MidFirst, in violation of this Agreement,
              ------------------
shall commence, prosecute or participate in any suit, action or proceeding
against Borrower, Borrower may interpose as a defense or plea the making of this
Agreement and Bank One may intervene and interpose such defense or plea in Bank
One's name or in the name of Borrower.  If MidFirst shall attempt to enforce any
security agreements, real estate mortgages or any lien instrument or other
encumbrances in violation of this Agreement, Bank One or Borrower may by virtue
of this Agreement restrain the enforcement thereof in Bank One's name or in the
name of Borrower.  If MidFirst obtains any assets of the Borrower as a result of
any administrative, legal, or equitable action, or otherwise, MidFirst agrees to
forthwith pay, deliver, and assign to Bank One any such assets for application
upon the amount now or hereafter owing to Bank One by Borrower.

          (h) MidFirst Rights.  Nothing contained in this Subordination
              ---------------
Agreement is intended to or shall impair, as between Borrower and the holder of
the MidFirst Debt, the obligation of Borrower, which is absolute and
unconditional, to pay to the holder of the MidFirst Debt the principal of and
interest on such indebtedness.

          (i) Limitation Assignments.  MidFirst shall not sell, assign or
              ----------------------
transfer any of the MidFirst Debt, unless the buyer, assignee or transferee
thereof shall agree in writing to become bound by the provisions of this
Agreement and the holders of the Bank One Debt shall have been furnished with
the original copies of such agreement.

          (j) Borrower Agreement.  Borrower agrees, for the benefit of the
              ------------------
holder of the Bank One Debt, that, in the event that any note evidencing the
MidFirst Debt is declared due and payable before its expressed maturity,
Borrower will give prompt notice in writing of such happening to the holder of
the Bank One Debt.  Borrower further agrees and covenants not to make any
distribution or payment to MidFirst in violation of the terms hereof.

          (k) Governing Law.  This Agreement and the obligations which it
              -------------
secures and all rights and liabilities of the parties shall be governed as to
validity, interpretation, enforcement and effect by the laws of the State of
Oklahoma.

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of this 31st day of March, 1999.

                    BORROWER:

                                       5
<PAGE>

                                        INDIAN OIL COMPANY

                                        _____________________________________
                                        By: Richard R. Dunning
                                        Title: Chief Executive Officer

                              MIDFIRST:

                                        MIDFIRST BANK:

                                        ______________________________________
                                        By: Alan H. Kraft
                                        Title: Sr. Vice President

                              BANK ONE:

                                        BANK ONE, OKLAHOMA, N.A.

                                        ______________________________________
                                        By: John K. Slay, Jr.
                                        Title: Sr. Vice President

                                       6

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