Document:

<PAGE>

                                                                 Exhibit 10.6(c)

                            INTERCREDITOR AGREEMENT
                            -----------------------

          THIS INTERCREDITOR AGREEMENT is dated this ___ day of March, 1999 by
and among MidFirst BANK and its successors and assigns ("MidFirst"), CORAL
RESERVES, INC., an Oklahoma corporation ("Coral Reserves"), CORAL RESERVES
ENERGY CORP., an Oklahoma corporation ("Coral Energy"), CORAL RESERVES GROUP,
LTD., an Oklahoma corporation ("Coral Ltd.") (collectively, Coral Reserves,
Coral Energy, and Coral Ltd. are referred to herein as the "Coral Group"), and
INDIAN OIL COMPANY, an Oklahoma corporation (the "Borrower").

                                   RECITALS:
                                   --------

          WHEREAS, on December 22, 1997, Borrower and MidFirst entered into that
certain Credit Agreement and other loan documents providing for a loan in the
principal amount of $12,000,000.

          WHEREAS, on February 15, 1999, the Coral Group and Borrower entered
into that certain Agreement and Plan of Merger ("Merger Agreement").

          WHEREAS, pursuant to the Merger Agreement, the Coral Group purchased
or shall purchase from Borrower, for $6,000,000, an unsecured contingent
production payment.

          WHEREAS, in return for such $6,000,000 purchase, Borrower has agreed
to make a production payment to the Coral Group from proceeds received from
Borrower's interests in oil and gas properties in the amount of $56,250 per
month (the "Contingent Production Payment").

          WHEREAS, Borrower intends to pay $6,000,000 against the indebtedness
owing to MidFirst.

          WHEREAS, Borrower and MidFirst intend to enter into a Credit Agreement
(the "MidFirst Loan Agreement") and promissory note in the principal amount of
$6,000,000 (the "MidFirst Note") and other loan documents (the "MidFirst Loan
Documents") providing for a loan by MidFirst to Borrower in the amount of
$6,000,000.

          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, this Intercreditor Agreement sets forth the subordination of
the payment of the Contingent Production Payment to the MidFirst Debt.

          NOW, THEREFORE, in consideration of the mutual promises herein
contained and such other good and valuable consideration
<PAGE>

the sufficiency of which is hereby acknowledged, the parties hereby agree as
follows:

          I.   REPRESENTATIONS AND WARRANTIES.  The Coral Group and Borrower
               ------------------------------
represent and warrant to MidFirst that:

               (a)  The Contingent Production Payment.  As of the date hereof,
                    ---------------------------------
the total indebtedness owing by Borrower to the Coral Group is evidenced by the
Contingent Production Payment.

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

          II.  JUNIOR PRIORITY OF CONTINGENT PRODUCTION PAYMENT.  In order to
               ------------------------------------------------
induce MidFirst to extend a loan to Borrower, it is agreed as follows:

               (a)  Junior Priority.  The Coral Group agrees that the Contingent
                    ---------------
Production Payment shall be and hereby is inferior and junior to the MidFirst
Debt, unless otherwise agreed to in writing by MidFirst, and the Coral Group
shall be entitled to no payments pursuant to the Contingent Production Payment
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) of any nature whatsoever now due to MidFirst from Borrower
pursuant to the MidFirst Loan, as the same may be amended from time to time.
Notwithstanding the above, the Coral Group shall be entitled to the monthly
Contingent Production Payment so long as Borrower is not in default of the
MidFirst Loan Agreement.  Upon the occurrence of a Default or an Event of
Default under the MidFirst Loan Agreement, the Contingent Production Payment
shall be suspended and not made until such Default or Event of Default has been
cured to MidFirst's satisfaction.

               (b)  No Action by the Coral Group.  The Coral Group will not,
                    ----------------------------
without MidFirst's prior written consent, accelerate, assert, collect or enforce
the Contingent Production Payment or any part thereof and/or otherwise exercise
its remedies pursuant to the Contingent Production Payment and the Merger
Agreement until the MidFirst Debt has been paid in full.

               (c)  No Amendment.  The Coral Group shall not amend or permit
                    ------------
amendment of the terms of any instrument or agreement evidencing the Contingent
Production Payment without the prior written consent of MidFirst.

               (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

                                      -2-
<PAGE>

of the Contingent Production Payment in violation of the provisions hereof, and
before payment in full of the MidFirst Debt, such payment or distribution shall
be held by such holder of the Contingent Production Payment in trust for the
holder of the MidFirst Debt by such holder of the Contingent Production Payment
(subject to the rights of Bank One Oklahoma, N.A. under its Intercreditor
Agreement with the Coral Group and Borrower of even date (the "Bank One
Agreement")) to the extent necessary to make payment of any unpaid MidFirst
Debt.

               (e)  Permissive Payments.  Borrower agrees with MidFirst that,
                    -------------------
after the execution hereof, it will not pay the Contingent Production Payment to
the Coral Group until the MidFirst Debt is paid in full; provided, however, as
long as no Default or Event of Default under the MidFirst Credit Agreement has
occurred or is continuing under the MidFirst Loan, MidFirst agrees that Borrower
shall be allowed to service the monthly Contingent Production Payment.

               (f)  MidFirst Modifications.  With respect to the MidFirst Debt,
                    ----------------------
the Coral Group agrees that MidFirst may grant extensions of the time of payment
or performance, make compromises, including releases of collateral and
settlements with Borrower, or otherwise modify the MidFirst Debt without
affecting the agreements of the Coral Group or Borrower hereunder.

               (g)  Discontinuance of MidFirst Debt.  If, at any time hereafter,
                    -------------------------------
MidFirst shall determine to discontinue the extension of credit to Borrower,
MidFirst may do so.  This Agreement shall continue in full force and effect
until Borrower shall have satisfied all obligations and MidFirst shall have been
paid in full on all indebtedness, of any nature whatsoever that may be due on
the MidFirst Loan Agreement or any amendments thereto to MidFirst 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 MidFirst Debt shall first be paid in full in cash
before any payment is made upon the Contingent Production Payment; 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
Contingent Production Payment shall (subject to the rights of Bank One under the
Bank One Agreement) be paid over to MidFirst for application in payment thereof
unless and until the MidFirst Debt

                                      -3-
<PAGE>

shall have been paid or satisfied in full in cash.

               (b)  Proof and Vote of Claims.  The Coral Group hereby appoints,
                    ------------------------
which appointment is irrevocable and coupled with an interest, MidFirst, its
successors and assigns, as the Coral Group's true and lawful attorney, with full
power of substitution, in the name of the Coral Group, MidFirst or otherwise.
Such appointment shall be for the sole use and benefit of MidFirst, to the
extent permitted by law, to prove and vote all claims relating to the Contingent
Production Payment, and to receive and collect all distributions and payments to
which the Coral Group 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, subject to the rights of Bank One under the Bank One Agreement.

               (c)  Administrative Proceedings.  The Coral Group 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 arising out of Borrower's failure to make the Contingent Production
Payment that might adversely affect Borrower or its interest, without MidFirst's
prior written consent.

               (d)  No Interference.  The Coral Group agrees that it will not
                    ---------------
take any action that will impede, interfere with or restrict or restrain the
exercise by MidFirst of its rights and remedies under the MidFirst 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, the Coral Group
hereby agrees not to oppose any motion filed or supported by MidFirst for relief
from the automatic stay, for adequate protection in respect of the MidFirst
Debt, and/or for the Borrower's use of cash collateral or post-petition
borrowing from MidFirst.

               (e)  Collection Actions.  If the Coral Group, 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 MidFirst may intervene and interpose such defense
or plea in MidFirst's name or in the name of Borrower.  If the Coral Group shall
attempt to enforce any security agreements, real estate mortgages or any lien
instrument or other encumbrances, MidFirst or Borrower may by virtue of this
Agreement restrain the enforcement thereof in MidFirst's name or in the name of
Borrower.  If the Coral Group obtains any assets of the Borrower as a result of
any administrative, legal, or equitable action, or otherwise,

                                      -4-
<PAGE>

the Coral Group agrees to forthwith pay, deliver, and assign to MidFirst any
such assets for application upon the amount now or hereafter owing to MidFirst
by Borrower, subject to the rights of Bank One under the Bank One Agreement.

               (f)  The Coral Group Rights.  Nothing contained in this
                    ----------------------
Agreement is intended to or shall impair, as between Borrower and the holder of
the Contingent Production Payment, the obligation of Borrower, which is absolute
and unconditional, to pay to the holder of the Contingent Production Payment
such indebtedness.

               (g)  Limitation on Assignments.  The Coral Group shall not sell,
                    -------------------------
assign or transfer any of the Contingent Production Payment, 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 MidFirst Debt shall have
been furnished with original copies of such agreement.

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

               (i)  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 ____ day of March, 1999.

BORROWER:                        INDIAN OIL COMPANY

                                 By_______________________________

CORAL GROUP:                     CORAL RESERVES, INC.

                                 By_______________________________
                                  Name:__________________________
                                  Title:_________________________

                                      -5-
<PAGE>
                                 CORAL RESERVES ENERGY CORP.

                                 By_______________________________
                                  Name:__________________________
                                  Title:_________________________

                                 CORAL RESERVES GROUP, LTD.

                                 By_______________________________
                                  Name:__________________________
                                  Title:_________________________

MidFirst:                        MidFirst BANK

                                 By_______________________________
                                  Alan H. Kraft
                                  Senior Vice President

                                      -6-<PAGE>

                                                                 EXHIBIT 10.6(d)

                     SECOND AMENDMENT TO CREDIT AGREEMENT
                     ------------------------------------

          This SECOND AMENDMENT TO CREDIT AGREEMENT is entered into as of
February 1, 2000, by INDIAN OIL COMPANY ("Borrower"), CIBOLA CORPORATION
("Guarantor"), RICHARD R. DUNNING, LARRY D HARTZOG, MICHAEL C. BLACK, DUNNING
FAMILY LIMITED PARTNERSHIP, and MICHAEL C. BLACK, TRUSTEE OF THE MICHAEL C.
BLACK REVOCABLE TRUST ("Pledgors"), and MIDFIRST BANK ("Lender"), with respect
to the following:

          A.   Borrower, Guarantor, Pledgors and Lender entered into a Credit
Agreement on March 31, 1999, as amended by First Amendment to Credit Agreement
dated as of May ___, 1999 (the "Agreement") with respect to a certain extension
of credit by Lender to Borrower in the form of a Term Loan in the principal
amount of $6,000,000 due on March 1, 2000.

          B.   Borrower, Guarantor and Pledgors have requested that the Loan
amount be increased in an amount sufficient to capitalize accrued and unpaid
interest on the Loan (in the maximum additional amount of $425,000), and that
the Maturity Date of the Loan be extended until March 1, 2001, and have agreed
to make a principal and interest payment on July 1, 2000 and to pay interest
quarterly as it accrues thereafter, and Lender has agreed to such increase and
extension, subject to the terms and conditions contained herein, and the parties
desire to amend the Agreement to set forth their agreements.

          NOW THEREFORE, in consideration of the recitals and the mutual
covenants and agreements herein contained, the parties hereto agree as follows:

          1.   Definitions of Terms.  The definitions of terms contained in the
               --------------------
Agreement and not otherwise defined herein shall define the terms used in this
Amendment, except as follows:

               "Maturity Date" means March 1, 2001.
                -------------

          2.   Interest; Payments of Principal and Interest.  Section 2.2 of the
               --------------------------------------------
Agreement is amended to read as follows:

               "The Loan (exclusive of any past due principal or
               interest) shall bear interest on each day at the
               Base Rate in effect on such date. All past due
               principal and interest on the Loan shall bear
               interest on each day outstanding at the Late
               Payment Rate in effect on such day, and such
               interest shall be due and payable immediately as
               it accrues. The following payments shall be made
               on July 1, 2000:

                    (a)  a principal payment in an amount
                    sufficient to reduce the outstanding
                    principal balance of the Loan to $6,000,000;
                    and
<PAGE>

                    (b)  all accrued and unpaid interest.

               Thereafter, accrued interest on the Loan shall be
               payable quarterly, with the first payment to be
               made on September 30, 2000 and thereafter on the
               last day of each quarter until the Maturity Date,
               at which time all remaining accrued but unpaid
               interest and all principal shall be due and
               payable."

          3.   Events of Default.  Section 7.1(a) of the Agreement is amended to
               -----------------
read as follows:

               "(a) Borrower shall fail to pay within ten (10)
               days of any due date the Obligations, or any part
               thereof, including, without limitation, any
               principal of, or interest on, the Note, any Fee,
               any Expenses or other payment under the Loan
               Documents; or"

          4.   Conditions to Effectiveness.  The effectiveness of this Amendment
               ---------------------------
is subject to receipt by Lender of the following, each in form and substance
satisfactory to Lender:

               (a)  this Amendment executed by Borrower, Guarantor and Pledgors.

               (b)  the Promissory Note in the form of Exhibit 2.1 executed by
                                                       -----------
Borrower.

               (c)  documentation executed by Bank One, Oklahoma, N.A.
consenting to the amendments contained herein, and extending the maturity of the
Other Loan until January 15, 2001.

               (d)  An amendment to the Intercreditor Agreement with respect to
the Production Payment executed by the parties thereto, together with evidence
that the Coral Agreement is in full force and effect and there are no defaults
or events of default thereunder.

               (e)  a certificate of the president and of the secretary or an
assistant secretary of Borrower and Guarantor, certifying, inter alia (i) true
and complete copies of the resolutions adopted by the board of directors of
Borrower and Guarantor authorizing the execution, delivery and performance by
Borrower and Guarantor of this Amendment and (ii) the incumbency and specimen
signatures of the officers of Borrower and Guarantor executing this Amendment on
their behalf.

               (f)  the payment to Lender of all reasonable fees and expenses
(including the reasonable fees and disbursements of McAfee & Taft) incurred in
connection with this Amendment.

                                       2
<PAGE>

          5.   Substitution of Exhibit.  Exhibit 2.1 attached hereto shall be
               -----------------------   -----------
substituted for Exhibit 2.1 attached to the original Credit Agreement.
                -----------

          6.   Increase in Loan.  The Guaranty, the Pledgor Guaranty, the
               ----------------
Account Pledge Agreement, the Individual Pledge Agreement and each other Loan
Document is hereby amended to reflect a Loan in the increased principal amount
set forth in the Note, each of which Loan Documents shall cover such principal
amount, which is hereby incorporated therein, and each of the Loan Documents, as
amended, is hereby ratified and confirmed in all respects.

          7.   Representations True; No Default.  Borrower, Guarantor and
               --------------------------------
Pledgors represent and warrant that:

               (a)  this Amendment has been duly authorized, executed and
delivered on behalf of each of them and the Agreement, as amended hereby,
constitutes a valid and legally binding agreement of Borrower, Guarantor and
Pledgors enforceable in accordance with its terms, except as enforceability
thereof may be limited by bankruptcy, insolvency reorganization or moratorium or
other similar laws relating to creditors' rights and by general equitable
principles which may limit the right to obtain equitable remedies (regardless of
whether such enforceability is considered in a proceeding, in equity or at law);

               (b)  the representations and warranties of Borrower, Guarantor
and Pledgors contained in the Agreement are true and correct in all material
respects on and as of the date hereof as though made on and as of the date
hereof, except to the extent such representations and warranties relate solely
to an earlier date; and

               (c)  after giving effect to this Amendment, no Default or Event
of Default under the Agreement has occurred and is continuing.

          8.   Expenses.  Borrower shall pay to Lender all reasonable expenses
               --------
in connection with preparation of this Amendment, including reasonable fees and
expenses of counsel to Lender.

          9.   Continuation; Ratification.  Except as amended by this Amendment,
               --------------------------
the Agreement and the Loan Documents, including each Guaranty, shall continue in
full force and effect and are ratified and confirmed in all respects. Any
reference to the Credit Agreement in any Loan Document shall be deemed a
reference to the Agreement, as amended.

                                       3
<PAGE>

          IN WITNESS WHEREOF, the parties have caused this Second Amendment to
Credit Agreement to be duly executed as of the date first set forth above.

                                    INDIAN OIL COMPANY, an Oklahoma corporation

                                    By__________________________________________
                                      _______________________________, President

                                    Notice Address:

                                    9400 North Broadway
                                    One Benham Place, Suite 800
                                    Oklahoma City, Oklahoma 73114
                                    Fax: (405) 475-7777
                                                                    ("Borrower")

                                    CIBOLA CORPORATION, a Wyoming corporation

                                    By__________________________________________
                                      Michael C. Black, President

                                    Notice Address:

                                    1131 13th Street, Suite 206
                                    Cody, Wyoming 82414
                                                                   ("Guarantor")

                                    ____________________________________________
                                    Richard R. Dunning

                                    ____________________________________________
                                    Larry D. Hartzog

                                    ____________________________________________
                                    Michael C. Black

                                       4
<PAGE>

                                    DUNNING FAMILY LIMITED PARTNERSHIP,
                                    an Oklahoma limited partnership
                                        By   Dunning Management L.L.C., an
                                             Oklahoma limited liability company,
                                             General Partner

                                             By_________________________________
                                               Richard R. Dunning, Manager

                                    ____________________________________________
                                    MICHAEL C. BLACK, Trustee of the Michael C.
                                    Black Revocable Trust

                                                                    ("Pledgors")

                                    MIDFIRST BANK

                                    By__________________________________________
                                      W. Thomas Portman, Vice President

                                    Notice Address:

                                    501 West I-44 Service Road
                                    Oklahoma City, Oklahoma 73118
                                    Fax: (405) 879-6155
                                                                      ("Lender")

                                       5
<PAGE>

                                  EXHIBIT 2.1

                            RENEWAL PROMISSORY NOTE
                            -----------------------

$____________________                                    Oklahoma City, Oklahoma
                                                             February ____, 2000

          FOR VALUE RECEIVED, the undersigned, INDIAN OIL COMPANY, an Oklahoma
corporation ("Borrower"), promises to pay to the order of MIDFIRST BANK
("Lender"), the principal sum of ________________________________________ AND
NO/100 DOLLARS ($______________), together with interest on the unpaid principal
balance thereof as hereinafter set forth, both principal and interest payable in
lawful money of the United States of America at the office of MidFirst Bank, at
501 West I-44 Service Road, Oklahoma City, Oklahoma 73118, or such other place
as from time to time may be designated in writing by Lender.  Borrower promises
to pay interest on the unpaid principal balance of this Note until said
principal amount is paid in full, at the times and at the rate or rates
specified in the Credit Agreement (as hereafter defined).  If not paid earlier
as herein required, all unpaid principal and accrued interest thereon shall be
due and payable on the Maturity Date.

          This Note is the Note referred to in, and is subject to the terms and
provisions of, the Credit Agreement dated as of March 31, 1999, amended by First
Amendment to Credit Agreement dated as of May ___, 1999, amended by Second
Amendment to Credit Agreement dated as of the date hereof, among Borrower,
Cibola Corporation, as Guarantor and Lender (herein, as from time to time
supplemented, modified, amended or restated, called the "Credit Agreement").

          The Credit Agreement, among other things, (i) provides for the making
of the Loan by Lender to Borrower, the indebtedness of Borrower to Lender being
evidenced by this Note, (ii) contains provisions for acceleration of the
maturity hereof upon the happening of certain stated events and also for
prepayments on account of principal hereof prior to the maturity hereof upon the
terms and conditions therein specified, (iii) provides for installments of
interest to be made hereunder and (iv) provides for collateral to secure payment
of this Note. Reference is hereby made to the Credit Agreement for a description
of the rights, limitations of rights, obligations and duties of the parties
hereto. All terms not expressly defined herein shall have the same definitions
as set forth in the Credit Agreement.

          The makers, endorsers, sureties, guarantors, and all other persons who
may become liable for all or any part of this obligation severally waive demand,
presentment for payment, protest, notice of nonpayment and notice of intention
to accelerate the maturity hereof. Such parties consent to any extension of time
(whether one or more) of payment hereof, any renewal (whether one or more)
hereof, release of all or any part of the security for payment hereof and any
release of any party liable for payment of this obligation. Any such extension,
renewal or release may be made at any time and from time to time without notice
to any such party and without discharging such party's liability hereunder.

                                       1
<PAGE>

          If this Note is placed in the hands of an attorney for collection
after default, or if all or any part of the indebtedness represented hereby is
proved, established or collected in any court or in any bankruptcy,
receivership, debtor relief, probate or other court proceedings, Borrower and
all endorsers, sureties and guarantors of this Note jointly and severally agree
to pay reasonable attorneys' fees and collection costs to the holder hereof in
addition to the principal and interest payable hereunder.

          This Note and the rights and duties of the parties hereto shall be
governed by the laws of the State of Oklahoma.

          IN WITNESS WHEREOF, the undersigned has executed this instrument of
the day and year first above written.

                                        INDIAN OIL COMPANY, an Oklahoma
                                        corporation

                                        By_____________________________________,
                                          _____________________________President

                                       2

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