<PAGE>   1


                                                                    EXHIBIT 10.1

                                 Amendment No. 1




AMENDMENT NO. 1 dated as of December 1, 2000 (this AMENDMENT NO. 1) between:
GREKA AM, INC., a corporation duly organized and validly existing under the laws
of the State of Colorado (the BORROWER); GREKA ENERGY CORPORATION, a corporation
duly organized and validly existing under the laws of the State of Colorado (the
GUARANTOR or GREKA ENERGY); CIBC, INC., as lender (the LENDER), CANADIAN
IMPERIAL BANK OF COMMERCE (CIBC), as administrative agent (the AGENT) and CIBC
WORLD MARKETS CORP., as arranger (the ARRANGER).

WHEREAS

The Borrower, the Guarantor, the Lender, the Agent and the Arranger are parties
to a Credit and Guarantee Agreement dated as of June 19, 2000, as amended by a
letter agreement dated August 18, 2000 (as in effect on the date hereof, the
CREDIT AGREEMENT), providing, subject to the terms and conditions thereof, for
extensions of credit to be made by the Lender to the Borrower in an aggregate
principal amount not exceeding $47.5 million;

the Borrower and the Guarantor wish to extend the Maturity Date (as defined in
the Credit Agreement); and

the Borrower, the Guarantor, the Lender, the Agent and the Arranger wish to
amend the Credit Agreement in certain other respects, and accordingly, the
parties hereto hereby agree as follows:

Section 1. DEFINITIONS. Except as otherwise defined in this Amendment No. 1,
terms defined in the Credit Agreement are used herein as defined therein.

Section 2. AMENDMENTS. Subject to the satisfaction of the conditions precedent
set forth in Section 4 below, the Credit Agreement shall be amended as follows
effective immediately on the date hereof upon the execution and delivery of this
Amendment No. 1 by the parties hereto:

A.       References in the Credit Agreement to "this Agreement" (and indirect
         references such as "hereunder", "hereby", "herein" and "hereof") shall
         be deemed to be references to the Credit Agreement, as amended hereby
         and as the same may from time to time be further amended or
         supplemented.

B.       The definition of MATURITY DATE in the Credit Agreement is amended by
         replacing the reference therein to "December 1, 2000" with "February
         28, 2001".

C.       The definition of MAXIMUM AVAILABLE AMOUNT in the Credit Agreement is
         deleted and replaced as follows:

         MAXIMUM AVAILABLE AMOUNT means, (i) for the period from December 1,
         2000 to but excluding December 29, 2000, $9,700,000; (ii) for the
         period from and including December 29, 2000 to but excluding January
         31, 2001, $8,700,000; and (iii) for the period from and including
         January 31, 2001 through the Maturity Date, $7,700,000, in each case as
         such amount may be reduced from time to time pursuant to Section 2.2 or
         terminated pursuant to Section 9.3.

D.       The reference in Section 2.7 of the Credit Agreement to "$14,200,000"
         is deleted and replaced with "$9,700,000".

<PAGE>   2

E.       Section 6.3 of the Credit Agreement is deleted in its entirety.

Section 3. REPRESENTATIONS AND WARRANTIES. Each of the Borrower and the
Guarantor represents and warrants to the Lender, the Agent and the Arranger that
(a) (unless specifically limited to an earlier date) the representations and
warranties set forth in Section 7 of the Credit Agreement are true and complete
on and as of the date hereof with the same force and effect as if made on and as
of such date, and as if each reference in said Section 7 to "this Agreement"
included reference to this Amendment No. 1 and (b) no Default has occurred and
is continuing and neither the Borrower nor the Guarantor are in violation of any
law or governmental regulation or court order or decree except for such
violations as could not reasonably be expected to have a Material Adverse
Effect.

Section 4. CONDITIONS PRECEDENT. As provided in Section 2, the amendments to the
Credit Agreement set forth in said Section 2 shall become effective, as of the
date hereof, upon the satisfaction of the following conditions precedent:

A.       EXECUTION BY ALL PARTIES. This Amendment No. 1 shall have been executed
         and delivered by each of the parties hereto.

B.       DOCUMENTS. The Agent shall have received the following documents, which
         shall be satisfactory to the Agent in form and substance:

             (i)  a certificate of the Secretary or Assistant Secretary of each
                  of the Borrower and the Guarantor (A) that since June 19,
                  2000, there have been no changes to the charter and by-laws
                  (or equivalent documents) of each Obligor and (B) as to all
                  corporate authority for such Obligor (including, without
                  limitation, board of director resolutions) with respect to the
                  execution, delivery and performance of this Amendment No. 1
                  and the Credit Agreement as amended hereby and the extensions
                  of credit under the Credit Agreement as amended hereby and
                  each other document to be delivered by such Obligor from time
                  to time in connection with the Credit Agreement as amended
                  hereby (and the Lender, the Agent and the Arranger may
                  conclusively rely on such certificate until it receives notice
                  in writing from the relevant Obligor to the contrary); and

            (ii)  sufficient copies of Amendment No. 1 to the Line of Credit
                  Mortgage, Deed of Trust, Assignment of Production, Security
                  Agreement and Financing Agreement dated as of December 1,
                  2000, signed by the Borrower, for filing in each of the
                  counties and parishes where the Mortgage was filed.

Section 5. FEES; EXPENSES. The Obligors agree to pay all reasonable
out-of-pocket costs and expenses of the Lender, the Agent and the Arranger
(including, without limitation, the reasonable fees and expenses of Freshfields
Bruckhaus Deringer LLP, special New York counsel to the Agent and any local
counsel to the Agent) in connection with the negotiation, preparation, execution
and delivery of this Amendment No. 1.

Section 6. MISCELLANEOUS. Except as herein provided, the Credit Agreement shall
remain unchanged and in full force and effect. This Amendment No. 1 may be
executed in any number of counterparts, all of which taken together shall
constitute one and the same amendatory instrument and any of the parties hereto
may execute this Amendment No. 1 by signing any such counterpart. This Amendment
No. 1 shall be governed by, and construed in accordance with, the law of the
State of New York.


            [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

<PAGE>   3


         IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1
to be duly executed and delivered as of the day and year first above written.


GREKA AM, INC.,
  as Borrower

By /s/ Randeep S. Grewal
   -------------------------------------
   Title: Ch., CEO & President

GREKA ENERGY CORPORATION,
  as Guarantor

By /s/ Randeep S. Grewal
   -------------------------------------
   Title: Ch., CEO & President

CIBC, INC.,
  as Lender

By /s/ Ian Schottlaender
   -------------------------------------
   Title: Managing Director

CANADIAN IMPERIAL BANK OF COMMERCE,
  as Agent

By /s/ Ian Schottlaender
   -------------------------------------
   Title: Managing Director

CIBC WORLD MARKETS CORP.,
  as Arranger

By /s/ Ian Schottlaender
   -------------------------------------
   Title: Managing Director