Document:

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                                                                     Exhibit 4.1

                               ELEVENTH AMENDMENT
                                       TO
              FIRST AMENDED, RESTATED, AND COMBINED LOAN AGREEMENT
                              DATED AUGUST 28, 1997
                     BY AND BETWEEN CARRIZO OIL & GAS, INC.
                                AND COMPASS BANK

         This Eleventh Amendment to the Loan Agreement (this "Eleventh
Amendment") by and between CARRIZO OIL & GAS, INC., a Texas corporation (the
"Borrower"), and COMPASS BANK, an Alabama state chartered bank, formerly a Texas
chartered bank (the "Bank"), is entered into on this _____ day of April 2001.

                              W I T N E S S E T H:

         Borrower and Bank entered into a First Amended, Restated, and Combined
Loan Agreement dated August 28, 1997, as amended by the First Amendment thereto
dated December 23, 1997, the Second Amendment thereto dated December 30, 1997,
the Third Amendment thereto dated July 30, 1998, the Fourth Amendment thereto
dated September 24, 1998, the Fifth Amendment thereto dated March 22, 1999, the
Sixth Amendment thereto dated April 23, 1999, the Seventh Amendment thereto
dated August 27, 1999, the Eighth Amendment thereto dated November 11, 1999, the
Ninth Amendment thereto dated December 15, 1999 and the Tenth Amendment thereto
dated November 3, 2000 (collectively, the "Loan Agreement").

         Borrower has requested, among other things, that Bank extend the
maturity date of certain indebtedness under the Loan Agreement, and Bank has
agreed to such requests, subject to the terms and conditions set forth in this
Eleventh Amendment.

         Capitalized terms used, but not defined herein, shall have the meanings
prescribed therefor in the Loan Agreement.

         NOW, THEREFORE, in consideration of the mutual promises herein
contained, and for other good and valuable consideration, the receipt and
sufficiency of which are acknowledged by Borrower and Bank, and each intending
to be legally bound hereby, the parties agree as follows:

1.       Specific Amendments to Loan Agreement.

         Article I, Definitions, is hereby amended by adding the following
definition thereto:

                  "Eleventh Amendment" means the Eleventh Amendment to this
         Agreement executed by Borrower and Bank on April ___ 2001.

         Article I, Definitions, is hereby further amended by revising the
following definition in its entirety to read as follows:
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                  "Maturity Date" means April 1, 2003.

                           "Second Term Loan Maturity Date" means the earlier
                  of: (1) the date of closing of the issuance of additional
                  equity of Borrower, other than with regard to the Chase
                  Transaction, if the net proceeds of such issuance are
                  sufficient to repay in full the Second Term Loan; (2) the date
                  of closing of the issuance of convertible subordinated debt of
                  Borrower, other than with regard to the Chase Transaction, if
                  the proceeds of such issuance are sufficient to repay in full
                  the Second Term Loan; (3) the date of repayment of the
                  Revolving Loan and the termination of the Revolving
                  Commitment; and (4) December 1, 2001.

2. Conditions Precedent in Connection with the Eleventh Amendment. The Eleventh
Amendment shall not be binding on the Bank until satisfaction of the following
conditions precedent:

                  (a) Receipt of Eleventh Amendment and Compliance Certificate.
         Bank shall have received multiple fully executed counterparts of the
         Eleventh Amendment, as requested by Bank, and the Compliance
         Certificate duly executed by an authorized officer for Borrower.

                  (b) Receipt of Additional Security Instruments. Bank shall
         have received multiple fully executed counterparts of the additional
         Security Instruments described on Exhibit "A" attached to this Eleventh
         Amendment, as requested by Bank, duly executed by an authorized officer
         for Borrower.

                  (c) Receipt of Extension Fee. Bank shall have received a fee
         equal to $5,000 in consideration for extending the Second Term Loan
         Maturity Date.

                  (d) Accuracy of Representations and Warranties and No Event of
         Default. After giving effect to the Eleventh Amendment, the
         representations and warranties contained in Article IV of the Loan
         Agreement shall be true and correct in all material respects on the
         date of the Eleventh Amendment with the same effect as though such
         representations and warranties had been made on such date; and after
         giving effect to the Eleventh Amendment, no Event of Default shall have
         occurred and be continuing or will have occurred upon the execution of
         the Eleventh Amendment.

                  (e) Legal Matters Satisfactory to Special Counsel to Bank. All
         legal matters incident to the consummation of the
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         transactions contemplated by the Eleventh Amendment shall be
         satisfactory to the firm of Porter & Hedges, L.L.P., special counsel
         for Bank.

                  (f) Legal Fees. All reasonable legal fees and expenses owed by
         Bank to Porter & Hedges, L.L.P. in connection with the Loan Agreement
         shall have been paid by Borrower.

                  (g) No Material Adverse Change. No material adverse change
         shall have occurred since the date of the Loan Agreement in the
         condition, financial or otherwise, of Borrower.

3. Reaffirmation of Representations and Warranties. To induce Bank to enter into
this Eleventh Amendment, Borrower hereby reaffirms, as of the date hereof, after
giving effect to the Eleventh Amendment, its representations and warranties
contained in Article IV of the Loan Agreement and in all other documents
executed pursuant thereto, and additionally represents and warrants as follows:

                  A. The execution and delivery of this Eleventh Amendment and
         the performance by Borrower of its obligations under this Eleventh
         Amendment are within Borrower's power, have been duly authorized by all
         necessary corporate action, have received all necessary governmental
         approval (if any shall be required), and do not and will not contravene
         or conflict with any provision of law or of the articles of
         incorporation, charter or bylaws of Borrower or of any agreement
         binding upon Borrower.

                  B. The Loan Agreement as amended by this Eleventh Amendment,
         represents the legal, valid and binding obligations of Borrower,
         enforceable against Borrower in accordance with its terms, subject as
         to enforcement only to bankruptcy, insolvency, reorganization,
         moratorium or other similar laws affecting the enforcement of
         creditors' rights generally.

                  C. No Event of Default or Unmatured Event of Default has
         occurred and is continuing as of the date hereof.

4. Defined Terms. Except as amended hereby, terms used herein that are defined
in the Loan Agreement shall have the same meanings in this Eleventh Amendment.

5. Reaffirmation of Loan Agreement. This Eleventh Amendment shall be deemed to
be an amendment to the Loan Agreement, and the Loan Agreement, as further
amended hereby, is hereby ratified, approved and confirmed in each and every
respect. All references

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to the Loan Agreement herein and in any other document, instrument, agreement or
writing shall hereafter be deemed to refer to the Loan Agreement as amended
hereby.

6. Entire Agreement. The Loan Agreement, as hereby further amended, embodies the
entire agreement between Borrower and Bank and supersedes all prior proposals,
agreements and understandings relating to the subject matter hereof. Borrower
certifies that it is relying on no representation, warranty, covenant or
agreement except for those set forth in the Loan Agreement as hereby further
amended and the other documents previously executed or executed of even date
herewith.

7. Governing Law. THIS ELEVENTH AMENDMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS AND THE APPLICABLE LAWS OF THE
UNITED STATES OF AMERICA. This Eleventh Amendment has been entered into in
Harris County, Texas, and it shall be performable for all purposes in Harris
County, Texas. Courts within the State of Texas shall have jurisdiction over any
and all disputes between Borrower and Bank, whether in law or equity, including,
but not limited to, any and all disputes arising out of or relating to this
Eleventh Amendment or any other Loan Document; and venue in any such dispute
whether in federal or state court shall be laid in Harris County, Texas.

8. Severability. Whenever possible each provision of this Eleventh Amendment
shall be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Eleventh Amendment shall be
prohibited by or invalid under applicable law, such provision shall be
ineffective to the extent of such prohibition or invalidity, without
invalidating the remainder of such provision or the remaining provisions of this
Eleventh Amendment.

9. Execution in Counterparts. Each party hereto acknowledges that this Agreement
may be executed in several counterparts by each party at different times and in
different locations; that each separate counterpart bearing the signature of any
party may be effectively delivered to the other parties by the delivery of an
electronic facsimile sent via telecopier; that each party so delivering any such
counterpart shall be bound by its facsimile signature thereon; and that the
signature pages from counterparts signed by each party may be collated into one
or more copies of this agreement, which shall constitute one and the same
agreement among all parties hereto.

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10. Section Captions. Section captions used in this Eleventh Amendment are for
convenience of reference only, and shall not affect the construction of this
Eleventh Amendment.

11. Successors and Assigns. This Eleventh Amendment shall be binding upon
Borrower and Bank and their respective successors and assigns, and shall inure
to the benefit of Borrower and Bank, and the respective successors and assigns
of Bank.

12. Non-Application of Chapter 346 of Texas Finance Codes. In no event shall
Chapter 346 of the Texas Finance Code (which regulates certain revolving loan
accounts and revolving tri-party accounts) apply to this Loan Agreement as
hereby further amended or any other Loan Documents or the transactions
contemplated hereby.

13. Notice. THIS ELEVENTH AMENDMENT TOGETHER WITH THE LOAN AGREEMENT, AND THE
OTHER LOAN DOCUMENTS REPRESENT 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 ORAL AGREEMENTS BETWEEN THE
PARTIES.

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         IN WITNESS WHEREOF, the parties hereto have caused this Eleventh
Amendment to be duly executed as of the day and year first above written.

BANK                                        BORROWER

COMPASS BANK                                CARRIZO OIL & GAS, INC.

By:                                         By:
   --------------------------                  -----------------------------
      Kathleen J. Bowen                             Frank A. Wojtek
       Vice President                                Vice President
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                                   EXHIBIT "A"

                         ADDITIONAL SECURITY INSTRUMENTS

1.       Third Amendment to Deed of Trust, Mortgage, Security Agreement,
         Financing Statement and Assignment of Production dated September 29,
         1998 covering Borrower's interest in the Neblett #3 Well.

2.       Second Amendment to Deed of Trust, Mortgage, Security Agreement,
         Financing Statement and Assignment of Production dated November 11,
         1999 covering Borrower's interest in the Luker #2 Well.

3.       Sixth Amendment to Security Agreement covering the collateral described
         in items #1 and #2 above.

4.       UCC Financing Statement Amendment covering the collateral described in
         items #1 and #2 above.
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                             COMPLIANCE CERTIFICATE

                  I, Frank A. Wojtek, Vice President of CARRIZO OIL & GAS, INC.
(the "Company"), pursuant to Article II(a) of the Eleventh Amendment to the
First Amended, Restated, and Combined Loan Agreement dated as of August 28,
1997, by and among COMPASS BANK ("Bank") and the Company (the "Agreement") do
hereby certify, as of the date hereof, that to my knowledge:

         1.       After giving effect to the Eleventh Amendment, no Event of
                  Default (as defined in the Agreement) has occurred and is
                  continuing, and no Unmatured Event of Default (as defined in
                  the Agreement) has occurred and is continuing;

         2.       No material adverse change has occurred in the business
                  prospects, financial condition, or the results of operations
                  of the Company since the date of the previous Financial
                  Statements (as defined in the Agreement) provided to Bank;

         3.       After giving effect to the Eleventh Amendment, each of the
                  representations and warranties of the Company contained in
                  Article IV of the Agreement is true and correct in all
                  respects.

                  This certificate is executed this ______ day of April 2001.

                                           -----------------------------
                                                 Frank A. Wojtek<PAGE>   1

                                                                    EXHIBIT 10.1

                                  AMENDMENT TO
                SECOND AMENDED AND RESTATED PRODUCTION AGREEMENT

          This Amendment to Second Amended and Restated Production Agreement
(this "Amendment") made effective as of March 1, 2001 is by and between BP
Chemicals Inc., an Ohio corporation ("BP"), and Sterling Chemicals, Inc., a
Delaware corporation ("SCI"), with reference to the following facts:

     A.   BP and SCI are parties to a Second Amended and Restated Production
          Agreement dated effective as of August 1, 1996 (as amended, the
          "Acetic Acid Production Agreement").

     B.   BP and SCI wish to amend the Acetic Acid Production Agreement in
          certain respects.

THE PARTIES THEREFORE AGREE THAT:

          1. Amendment of Section 6.6(a) of the Acetic Acid Production
Agreement. Section 6.6(a) of the Acetic Acid Production Agreement is hereby
amended to read in its entirety as follows:

               (a) For the period of time from December 12, 1988 through the end
          of the First Additional Term, BP shall pay to the Company in cash an
          amount equal to ******** of any Profit for each Contract Year as an
          additional fee hereunder (such ********* share being the "Company
          Profit Share"), payable as follows:

               (i)  for each Contract Year ending prior to or on December 31,
                    2000, BP shall pay the Company the Company Profit Share
                    within ninety (90) Days after the end of such Contract Year;
                    and

               (ii) for each Contract Year during the period commencing on
                    January 1, 2001 and ending at the end of the First
                    Additional Term, BP shall, on or before the last Business
                    Day of the first Month following the end of each Quarter of
                    such Contract Year (with the exception that the first such
                    last Business Day shall be March 30, 2001 rather than April
                    30, 2001), (A) prepare in good faith and deliver to the
                    Company an estimate of the Company Profit Share, if any,
                    which will be payable to the Company with respect to such
                    Contract Year (the "Estimated Company Profit Share") , and
                    (B) pay the Company an amount

******* - CONFIDENTIAL TREATMENT HAS BEEN REQUESTED FROM THE SECURITIES AND
EXCHANGE COMMISSION WITH RESPECT TO THE OMITTED MATERIAL. THE OMITTED MATERIAL
HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

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                    equal to (x) such Estimated Company Profit Share times a
                    fraction, the numerator of which is the number of Quarters
                    elapsed in such Contract Year and the denominator of which
                    is four (4) minus (y) the aggregate amount of payments
                    previously made by BP to the Company under this clause (ii)
                    with respect to such Contract Year.

                    After the end of each Contract Year, BP shall calculate the
          actual Company Profit Share for such Contract Year and the difference
          between such Company Profit Share and the aggregate amount of payments
          made to the Company with respect to such Contract Year based on
          Estimated Company Profit Share. On or before March 1 of each year,
          commencing with March 1, 2002, BP shall send to the Company a
          reconciliation statement showing (1) the additional amount to be paid
          by BP, if Company Profit Share for the immediately preceding Contract
          Year exceeded the aggregate amount of payments made to the Company
          with respect to such Contract Year based on Estimated Company Profit
          Share, or (2) the amount to be refunded by the Company, if Company
          Profit Share for the immediately preceding Contract Year was less than
          the aggregate amount of payments made to the Company with respect to
          such Contract Year based on Estimated Company Profit Share. BP or the
          Company, as appropriate, shall pay the amount indicated on the
          reconciliation statement on or before March 31 of such year following
          the relevant Contract Year.

                    The period from January 1, 2006 through July 31, 2006 shall
          be considered a Contract Year and the period from July 1, 2006 through
          July 31, 2006 shall be considered a Quarter. All Estimated Company
          Profit Share payments during such period shall be appropriately
          prorated (e.g., the Estimated Company Profit Share payment for the
          first and second Quarters of 2006 would each be 3/7s of the Estimated
          Company Profit Share for the period from January 1, 2006 through July
          31, 2006 and the Estimated Company Profit Share payment for July 1,
          2006 would be 1/7 of the Estimated Company Profit Share for such
          period). BP will send the reconciliation statement for such
          seven-month period on or before October 1, 2006 and BP or the Company,
          as appropriate, shall pay the amount indicated on the reconciliation
          statement on or before October 31, 2006.

          2. No Other Changes. Except as expressly amended in this Amendment,
the terms and conditions of the Acetic Acid Production Agreement shall remain in
full force and effect. Upon the effectiveness of this Amendment, each reference
in the Acetic Acid Production Agreement to "this Agreement" shall mean and be a
reference to the Acetic Acid Production Agreement as amended hereby.

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          3. Binding Effect. This Amendment shall inure to the benefit of, and
shall be binding upon, the parties and their respective successors and permitted
assigns.

          4. Counterparts. This Amendment may be executed in two or more
counterparts, each of which shall be deemed an original but all of which taken
together shall constitute one and the same agreement. It shall not be necessary
in making proof of this Amendment to produce or account for more than one such
counterpart.

          5. Severability. Should any clause, sentence, paragraph, subsection or
Section of this Amendment be judicially declared to be invalid, unenforceable or
void, such decision will not have the effect of invalidating or voiding the
remainder of this Amendment, and the parties agree that the part or parts of
this Amendment so held to be invalid, unenforceable or void will be deemed to
have been stricken herefrom as if such stricken part or parts had never been
included herein.

          6. Governing Law. THIS AMENDMENT SHALL BE CONSTRUED AND ENFORCED IN
ACCORDANCE WITH, AND THE RIGHTS OF THE PARTIES SHALL BE GOVERNED BY, THE
INTERNAL LAWS OF THE STATE OF TEXAS, WITHOUT REFERENCE TO PRINCIPLES OF
CONFLICTS OF LAW.

          7. Entire Agreement. This Amendment and the Acetic Acid Production
Agreement set forth all of the promises, agreements, conditions, understandings,
warranties and representations between the parties with respect to the matters
cover hereby, and supersede all prior agreements, arrangements and
understandings between the parties, whether written, oral or otherwise. There
are no promises, agreements, conditions, understandings, warranties or
representations, oral or written, express or implied, between the parties
concerning the subject matter hereof or thereof except as set forth herein or
therein.

          INTENDING TO BE LEGALLY BOUND, the parties have execute this Agreement
through their duly authorized representatives effective as of the date specified
above.

BP CHEMICALS INC.

By: /s/ D. R. Sourwine
   -------------------

STERLING CHEMICALS, INC.

By: /s/ Robert W. Fransham
   -----------------------

                                      -3-

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