<PAGE>
                                                                   EXHIBIT 10.12

                        [BANK OF TEXAS, N.A. LETTERHEAD]

November 8, 2001

TOREADOR RESOURCES CORPORATION
TOREADOR EXPLORATION & PRODUCTION INC.
TOREADOR ACQUISITION CORPORATION
TORMIN, INC.
4809 Cole Avenue, Suite 108
Dallas, Texas 75205

         Re:      First Amendment to Loan Agreement

Ladies and Gentlemen:

         This letter (this "Amendment") amends the loan agreement (the "Loan
Agreement") dated February 16, 2001, among TOREADOR RESOURCES CORPORATION, a
Delaware corporation, TOREADOR EXPLORATION & PRODUCTION INC., a Texas
corporation, TOREADOR ACQUISITION CORPORATION, a Delaware corporation, and
TORMIN, INC., a Delaware corporation (collectively "Borrowers"), and BANK OF
TEXAS, NATIONAL ASSOCIATION ("Bank"), a national banking association.
Capitalized terms below have the meanings assigned in the Loan Agreement.

         1. Tranches and Rates. Subsection (a) of Section 1 of the Loan
Agreement is amended to create tranches and to create a new tier of interest
rates and thus to read as follows:

                  "(a) (i) Subject to the terms and conditions set forth in the
         Loan Agreement and the other agreements, instruments, and documents
         executed and delivered in connection with the Loan Agreement
         (collectively the "Loan Documents"), Bank agrees to make a revolving
         loan in the face amount of $75,000,000.00 to Borrowers (the "Revolving
         Loan") on the terms set forth in the Revolving Promissory Note attached
         as Exhibit A to this Amendment (the "Revolving Note"), for the purposes
         set forth in the Loan Agreement. Effective on the date of this
         Amendment, the Revolving Loan will consist of two tranches: Tranche A
         and Tranche B. "Tranche A" is defined as an amount determined by Bank,
         in its sole discretion, based on Bank's valuation of Borrower's proved
         developed producing reserves and proved developed non-producing
         reserves. The initial amount of Tranche A as of the date of this
         Amendment is $18,024,750.00. "Tranche B" is defined as all amounts in
         excess of Tranche A owed under the Revolving Loan.


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TOREADOR RESOURCES CORPORATION, et al
November 8, 2001
Page 2 of 7

                           (ii) All amounts owed on Tranche B shall bear
         interest from the date advanced until paid or until default or maturity
         at a fluctuating rate equal to the sum of the Stated Rate (as defined
         below), plus one percent (1.0%), but subject to the default rate set
         forth in the Revolving Note. All amounts owed on Tranche A (and after
         Tranche B is paid in full, all amounts owed on the Revolving Loan)
         shall bear interest from the date advanced until paid or until default
         or maturity at the rates elected by Borrowers from the following
         options under the terms of the Revolving Note: (i) the difference
         between the Stated Rate less the Applicable Margin, or (ii) the sum of
         the LIBOR Rate plus the LIBOR Spread. The Applicable Margin and the
         LIBOR Spread will vary as set forth below based on the ratio, expressed
         as a percentage, of (i) the sum of the average principal balance owing
         on the Revolving Note for the prior quarter, plus the face amount of
         all outstanding Letters of Credit, to (ii) the then-current Borrowing
         Base:

<Table>
<Caption>
                  % of Borrowing Base                Applicable Margin   LIBOR Spread
                  -------------------                -----------------   -------------
<S>                                                  <C>                 <C>
                  Greater than or equal to 85%        0.25%                  2.75%
                  Between 75% and 85% inclusive       1.00%                  2.00%
                  Less than 75%                       1.25%                  1.75%
</Table>

         The "Stated Rate" shall be equal to the greater of (i) the rate of
         interest per annum then most recently published by The Wall Street
         Journal as the "prime rate" on corporate loans for large U.S.
         commercial banks, or (ii) the sum of the rate of interest, then most
         recently published by The Wall Street Journal as the "federal funds"
         rate for reserves traded among commercial banks for overnight use, plus
         one half of one percent (0.5 %), both as published in the Money Rates
         section of The Wall Street Journal. The "LIBOR Rate" means the rate of
         interest per annum at which deposits in U.S. dollars are offered by the
         major London clearing banks, as reported by Reuters news service (or
         such other similar news reporting service as Bank may subscribe to at
         the time such LIBOR Rate is determined), in the London interbank
         Eurodollar market for a period of time equal or comparable to a 30, 60,
         or 90 day interest period, as elected by Borrowers, and in an amount
         equal to or comparable to the principal amount of the LIBOR balance to
         which such interest period relates."

         2. Borrowing Base. (a) Subsection (b) of Section 1 of the Loan
Agreement is amended to change the Borrowing Base and to add a due date for
Tranche B and thus to read as follows:

                  "(b) Subject to the terms and conditions of the Loan
         Agreement, Borrowers may borrow, repay and reborrow on a revolving
         basis from time to time during the period commencing on the date hereof
         and continuing through 11:00 a.m. (Dallas, Texas time) on February 16,
         2006 (the "Termination Date"), such amounts as Borrowers may request
         under the Revolving Loan; provided, however, the total principal amount
         outstanding at

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TOREADOR RESOURCES CORPORATION, et al
November 8, 2001
Page 3 of 7

         any time shall not exceed the lesser of (i) the aggregate sums
         permitted under the Borrowing Base, which is set at $21,850,000.00 as
         of the date of this Amendment, (ii) after May 8, 2002, the aggregate
         sums permitted under Tranche A, or (iii) $75,000,000. Notwithstanding
         any provision in the Loan Agreement or the Revolving Note to the
         contrary, all amounts outstanding on Tranche B must be paid in full on
         or before May 8, 2002; and all sums advanced under the Revolving Loan,
         together with all accrued but unpaid interest thereon, shall be due and
         payable in full on the Termination Date."

                  (b) Effective as of the date of this Amendment, Bank has set
the Borrowing Base at $21,850,000.00, and the MCR shall continue to be $0, until
reset by Bank. The next scheduled redetermination of the Borrowing Base will be
April 1, 2002.

         3. Acquisition. (a) Toreador Resources Corporation has agreed to
acquire Madison Oil Company, a Delaware corporation, through a merger with a new
subsidiary of Toreador Resources Corporation. Borrowers have requested that Bank
permit an advance on the Revolving Loan of an amount up to $3,000,000.00, for
the purpose of this acquisition and merger, and Bank has agreed on the terms set
forth in this Amendment.

                  (b) Subsection (k) of Section 6 of the Loan Agreement is
amended to permit the distribution for the Madison Oil Company acquisition and
merger and thus to read as follows:

                  "(k) Not make any loans, advances, dividends, or other
         distributions to any party, including without limitation, shareholders,
         officers, directors, and affiliates, and any profit sharing or
         retirement plan, except so long as there is not a default under this
         Loan Agreement or any other Loan Documents, (i) Borrowers may
         distribute to their shareholders an amount not to exceed $100,000 in
         the aggregate, and (ii) Borrowers may distribute an amount not to
         exceed $5,000,000 for the acquisition and merger of Madison Oil Company
         and the development of the Madison Oil Company oil and gas properties;
         and not purchase, acquire, redeem, or retire any stock of Borrowers;
         and not permit any transaction or contract with any affiliates or
         related parties, except at arms length and on market terms."

         4. Collateral. (a) As security for the Notes, Borrowers previously
executed the Security Documents. Borrowers ratify and confirm the Security
Documents, acknowledge that they are valid, subsisting, and binding, and agree
that the Security Documents secure payment of the Notes and Loans.

                  (b) As additional security for the Notes, Toreador Exploration
& Production Inc. will execute and deliver a Deed of Trust and Security
Agreement in Proper Form, covering oil and gas properties located in Meade
County, Kansas. This additional deed of trust will constitute one of the
"Security Documents" as defined in the Loan Agreement.


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TOREADOR RESOURCES CORPORATION, et al
November 8, 2001
Page 4 of 7

         5. Fees. In connection with Tranche B, Borrowers will pay to Bank an
arrangement fee in the amount of $200,000.00. This fee is non-refundable and
earned by Bank upon execution of this Amendment.

         6. Conditions Precedent. (a) The obligation of Bank to make any further
advance on the Revolving Loan is subject to Borrower's satisfaction, in Bank's
sole discretion, of the following conditions precedent:

                          (1) the negotiation, execution, and delivery of Loan
Documents in Proper Form, including, but not limited to, the following:

                                    (i)    this Amendment;
                                    (ii)   the Revolving Note; and
                                    (iii)  the Kansas Deed of Trust.

                          (2) satisfactory evidence that Bank holds perfected
liens and security interests in all collateral for the Loans, subject to no
other liens or security interests.

                          (3) there being no order or injunction or other
pending or threatened litigation in which there is a reasonable possibility, in
Bank's judgment, of a decision which could materially adversely affect the
ability of Borrowers to perform under the Loan Documents.

                          (4) Bank shall have completed and approved a review of
title to, and the status of the environmental condition of, Borrower's oil and
gas properties, and the results of such review shall be acceptable to Bank in
its sole discretion.

                          (5) Bank's receipt and review, with results
satisfactory to Bank and its counsel, of information regarding litigation, tax,
accounting, insurance, pension liabilities (actual or contingent), real estate
leases, material contracts, debt agreements, property ownership, and contingent
liabilities of Borrowers and any subsidiaries.

                  (b) Bank will not be obligated to make any advance on the
Loans, if, prior to the time that a loan or advance is made, (i) there has been
any material adverse change in any Borrowers' financial condition since the
most-recent financial statements furnished to Bank, (ii) any representations or
warranties made by any Borrowers in the Loan Agreement or the other Loan
Documents is untrue or incorrect as of the date of the advance or loan, (iii)
Bank has not received all Loan Documents appropriately executed by Borrowers and
all other proper parties, (iv) Bank has requested that Borrowers execute
additional loan or security documents and those documents have not yet been
properly executed, delivered, and recorded, or (v) an Event of Default has
occurred.


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TOREADOR RESOURCES CORPORATION, et al
November 8, 2001
Page 5 of 7


         7. Confirmations. Borrowers hereby represent to Bank that all
representations and warranties of Borrowers set forth in Section 5 of the Loan
Agreement are true and correct as of the date of execution of this Amendment;
and that Borrowers are in compliance as of the date of execution of this
Amendment with all covenants set forth in Section 6 of the Loan Agreement, all
financial covenants set forth in Section 7 of the Loan Agreement, and all
reporting requirements set forth in Section 8 of the Loan Agreement.

         8. Validity and Defaults. The Loan Agreement, as amended, remains in
full force and effect. Borrowers acknowledge that the Loan Agreement, the Notes,
and the Security Documents are valid, subsisting, and binding upon Borrowers; no
uncured breaches or defaults exist under the Loan Agreement, as amended; and no
event has occurred or circumstance exists which, with the passing of time or
giving of notice, will constitute a default or breach under the Loan Agreement,
as amended. Borrowers ratify the Loan Agreement, as amended.

         9. Fax Provision. This Amendment and the related Loan Documents may be
executed in counterparts, and Bank is authorized to attach the signature pages
from the counterparts to copies for Bank and Borrowers and filing counterparts.
At Bank's option, this Amendment and the related Loan Documents may also be
executed by Borrowers in remote locations with signature pages faxed to Bank.
Borrowers agree that the faxed signatures are binding upon Borrowers, and
Borrowers further agree to promptly deliver the original signatures for this
Amendment and the related Loan Documents by overnight mail or expedited
delivery. It will be an Event of Default if they fail to promptly deliver all
required original signatures.

         10. Captions. Captions are for convenience only and should not be used
in interpreting this Amendment.

         11. Final Agreement. (a) In connection with the Loans, Borrowers and
Bank have executed and delivered this Amendment and the Loan Documents
(collectively the "Written Loan Agreement").

                  (b) It is the intention of Borrowers and Bank that this
paragraph be incorporated by reference into each of the Loan Documents.
Borrowers and Bank each warrant and represent that their entire agreement with
respect to the Loans is contained within the Written Loan Agreement, and that no
agreements or promises have been made by, or exist by or among, Borrowers and
Bank that are not reflected in the Written Loan Agreement.


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TOREADOR RESOURCES CORPORATION, et al
November 8, 2001
Page 6 of 7


                  (c) THE LOAN AGREEMENT, AS AMENDED, REPRESENTS THE FINAL
AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO
UNWRITTEN AGREEMENTS BETWEEN THE PARTIES.

         If the foregoing correctly sets forth your understanding of our
agreement, please sign and return one copy of this letter.

                                        Yours very truly,

                                        BANK OF TEXAS, NATIONAL ASSOCIATION
                                        By:  /s/ Timothy E. Merrell
                                             ----------------------------------
                                             Timothy E. Merrell,
                                             Senior Vice President

Agreed on this 8th day of November, 2001:

BORROWERS:

TOREADOR RESOURCES CORPORATION

By:      /s/ Douglas W. Weir, Vice President
         ------------------------------------
         Douglas W. Weir, Vice President

TOREADOR EXPLORATION & PRODUCTION INC.

By:      /s/ Douglas W. Weir, Vice President
         ------------------------------------
         Douglas W. Weir, Vice President

TOREADOR ACQUISITION CORPORATION

By:      /s/ Douglas W. Weir, Vice President
         ------------------------------------
         Douglas W. Weir, Vice President

TORMIN, INC.

By:      /s/ Douglas W. Weir, Vice President
         ------------------------------------
         Douglas W. Weir, Vice President



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TOREADOR RESOURCES CORPORATION, et al
November 8, 2001
Page 7 of 7


         Exhibits:
         --------
         A - Revolving Note