<PAGE>
                                                                    EXHIBIT 4.18



                                 NINTH AMENDMENT



         NINTH AMENDMENT, dated as of November 28, 2001 (this "Agreement" or the
"Ninth Amendment"), to the Amended and Restated Credit Agreement, dated as of
May 22, 1998 (as amended, supplemented or otherwise modified prior to the date
hereof, the "Credit Agreement"), among The Meridian Resource Corporation, a
Texas corporation (the "Borrower"), the several lenders from time to time
parties thereto (the "Lenders"), JPMorgan Chase Bank (formerly The Chase
Manhattan Bank), as the Administrative Agent for the Lenders (in such capacity,
the "Administrative Agent"), Toronto Dominion (Texas), Inc. and Fortis Capital
Corp. (formerly Mees Pierson N.V.), as co-arrangers (each in such capacity, a
"Co-Arranger"), and Toronto Dominion (Texas), Inc., as documentation agent (in
such capacity, the "Documentation Agent").

                                   WITNESSETH:

         WHEREAS, the Borrower, the Lenders and the Administrative Agent are
parties to the Credit Agreement;

         WHEREAS, the Borrower, the Lenders and the Administrative Agent intend
to redetermine the Borrowing Base in accordance with Section 4.9 at
$190,000,000, such redetermination constituting the September 2001
Redetermination;

         WHEREAS, the Borrower has requested and the Administrative Agent and
the Lenders have agreed to certain modifications as set forth herein;

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

         1. Defined Terms. Terms defined in the Credit Agreement and used herein
shall, unless otherwise indicated, have the meanings given to them in the Credit
Agreement.

         2. Amendments to Section 1.1 of the Credit Agreement. (a) Section 1.1
of the Credit Agreement is hereby amended by deleting therefrom the definitions
of "Applicable Margin", "Applicable Redetermination" and "Borrowing Base"
contained therein in their entirety and substituting in lieu thereof the
following definition:

         "Applicable Margin": for any day with respect to Eurodollar Loans and
ABR Loans, the applicable per annum rate set forth below:

<Table>
<Caption>

                                 Eurodollar            ABR
                                   Margin             Margin
                                 ----------           ------
<S>                                                   <C>
                                   2.75%              1.75%
</Table>





<PAGE>

         provided, if there is no Borrowing Base Deficiency on the first to
occur of (i) the effective date of the March 2002 Redetermination or (ii) any
Special Redetermination (after giving effect thereto, or if there is such a
Borrowing Base Deficiency, such deficiency is cured within 30 days as
contemplated herein), then commencing on the later of such effective date or
cure date, if applicable, the Applicable Margin thereafter, for any day with
respect to Eurodollar Loans and ABR Loans shall be the applicable per annum rate
set forth below opposite the Borrowing Base Usage in effect on any such day:

<Table>
<Caption>

      Borrowing Base                 Eurodollar              ABR
          Usage                        Margin               Margin
      --------------                 ----------             ------
<S>                                  <C>                    <C>
Less than or equal to 25%              1.25%                 .25%

Greater than 25% and less              1.50%                 .50%
than or equal to 50%

Greater than 50% and less              1.75%                 .75%
than or equal to 75%

Greater than 75%                       2.00%                 1.00%
</Table>

                  As used herein, "Borrowing Base Usage" on any day means the
                  percentage equivalent to the ratio of (i) the sum of the
                  aggregate principal amount of the Loans then outstanding and
                  Letter of Credit Outstandings on such day to (ii) the
                  Borrowing Base in effect on such day.

         "Applicable Redetermination": any redetermination of the Borrowing Base
effectuated from the Ninth Amendment Effective Date through and including the
March 2002 Redetermination (including, without limitation, any Special
Redetermination).

         "Borrowing Base": at any time of determination, the amount then in
effect as determined in accordance with Section 4.9. For the period from the
Ninth Amendment Effective Date through the March 2002 Redetermination, the
Borrowing Base shall be $190,000,000; provided, however, that the Borrowing Base
may be redetermined during such period as provided by Sections 4.9(c) and
4.9(f).

         (b) Section 1.1 of the Credit Agreement is hereby amended by deleting
the definitions of "September 2001 Redetermination" and "Eighth Amendment
Effective Date" and adding thereto the following new definitions in alphabetical
order:

         "March 2002 Redetermination": the redetermination of the Borrowing Base
scheduled for March 31, 2002, pursuant to subsection 4.9(c), utilizing the
Reserve Report dated as of December 31, 2001 and required to be delivered prior
to March 1, 2002.



                                      -2-
<PAGE>

         "Ninth Amendment Effective Date": the date upon which the Ninth
Amendment, dated as of November 28, 2001, to this Agreement became effective in
accordance with the terms therein.

         3. Amendments to Subsection 4.9 of the Credit Agreement. (a) Subsection
4.9(c) of the Credit Agreement is hereby amended by deleting such subsection in
its entirety and substituting in lieu thereof the following:

         "(c) Redetermination of the Borrowing Base. The Borrowing Base shall be
redetermined (i) after receipt by the Administrative Agent of each scheduled
Reserve Report, commencing with the Reserve Report prepared as of December 31,
2001, (ii) upon the delivery of a Lender Redetermination Notice to the Borrower
and (iii) upon the delivery of a Borrower Redetermination Notice (which, except
as provided in paragraph (f) below, shall not be delivered until after the March
2002 Redetermination) to the Administrative Agent, all as provided in this
subsection 4.9. Within 15 days after the delivery of a Borrower Redetermination
Notice or a Lender Redetermination Notice, the Borrower shall furnish to the
Administrative Agent and to each Lender a Reserve Report as of the most recent
practicable date. If the Borrower fails to deliver a Reserve Report within the
time period provided for in the preceding sentence, then the Administrative
Agent shall have the right to rely on the last Reserve Report previously
delivered by the Borrower with any such adjustments and taking into account any
additional information as the Administrative Agent may deem appropriate, in its
sole discretion. On or before the date which is 30 days after receipt (i) of a
scheduled semi-annual Reserve Report or (ii) of a Reserve Report in connection
with a Lender Redetermination Notice or a Borrower Redetermination Notice, the
Administrative Agent shall redetermine the Borrowing Base in its sole
discretion, and the Administrative Agent shall notify the Borrower and the
Lenders of its redetermination of the Borrowing Base. Within 10 Business Days
after receipt from the Administrative Agent of the amount of its redetermination
of the Borrowing Base, each Lender shall notify the Administrative Agent stating
whether or not such Lender agrees with that redetermination. Failure of any
Lender to give such notice within such period of time shall be deemed to
constitute an acceptance of such redetermination. If the Supermajority Lenders
(or, with respect to any Applicable Redetermination, all of the Lenders) agree
with that redetermination, then the Administrative Agent promptly shall notify
the Borrower of the Borrowing Base as so redetermined, whereupon that
redetermined value shall automatically become effective (and shall remain
effective until the Borrowing Base is again redetermined as provided in this
subsection (c)). If the Supermajority Lenders (or, with respect to any
Applicable Redetermination, all of the Lenders) have not approved or are not
deemed to have approved the Borrowing Base within the 10 Business Day period
following their receipt of the proposed amount from the Administrative Agent,
the Borrowing Base shall be set at the amount of the then current Borrowing Base
and the Borrowing Base shall remain at such level until the Supermajority
Lenders (or, with respect to any Applicable Redetermination, all of the
Lenders), utilizing the procedure outlined herein, agree on a new Borrowing
Base; provided, that if a new Borrowing Base has not been agreed upon for the
March 2002 Redetermination by all of the Lenders (i) during such 10 Business Day
period or (ii) in any event, by no later than March 31, 2002, then the Borrowing
Base shall automatically be redetermined to equal $180,000,000 until a new
Borrowing Base has been agreed upon for the March 2002 Redetermination by all of
the Lenders. Each redetermination provided for by this subsection 4.9(c) shall
be made in accordance with the provisions of subsection 4.9(d). It is the
intention of the Borrower and the




                                      -3-
<PAGE>

Lenders that the Borrowing Base be redetermined within 45 days after the
furnishing of each Reserve Report, subject to the provisions of this paragraph
(c)."

         (b) Section 4.9(f) of the Credit Agreement is hereby amended by
deleting the term "September 2001 Redetermination" in the first sentence thereof
and substituting therefore the term "March 2002 Redetermination."

         4. Amendments to Subsections 7.12 and 7.13 of the Credit Agreement.
Subsections 7.12 and 7.13 of the Credit Agreement are hereby amended by deleting
such subsections in their entirety and substituting in lieu thereof the
following:

          "7.12 Maintenance of Mortgages. Beginning on the Ninth Amendment
Effective Date, cause to be performed any and all acts to ensure that Mortgages
are recorded in the appropriate recording offices such that the Administrative
Agent, for the ratable benefit of the Lenders, shall have by December 31, 2001
and at all times thereafter first priority perfected liens on, and security
interests in, Oil and Gas Properties of the Borrower or its consolidated
Subsidiaries, equal to at least ninety percent (90%) of the Present Value."

         5. Waiver of Subsections 4.9(c) and 4.10 of the Credit Agreement. The
Administrative Agent and the Lenders hereby waive compliance with the provisions
of (i) Subsection 4.9(c) of the Credit Agreement as such provisions specifically
relate to the automatic redetermination of the Borrowing Base on October 31,
2001, the Administrative Agent and the Lenders hereby agreeing that no automatic
redetermination of the Borrowing Base shall occur or is required as of such
date, and (ii) Subsection 4.10 of the Credit Agreement as such provisions
specifically relate to any mandatory prepayment required as a result of the
automatic redetermination of the Borrowing Base on October 31, 2001.

         6. Conditions to Effectiveness. The amendment provided for in this
Agreement shall become effective on the date upon which the following conditions
precedent are satisfied and the Administrative Agent notifies the Borrower and
the Lenders of the occurrence of such date:

                  (a) the Administrative Agent shall have received counterparts
         of this Agreement, duly executed by the Borrower and each of the
         Lenders listed in the signature pages hereof;

                  (b) the Administrative Agent shall have received counterparts
         of the Acknowledgment and Consent, confirming and agreeing that the
         Second Amended and Restated Guarantee, dated as of June 30, 1998, is
         and shall continue to be, in full force and effect, duly executed by
         the Guarantors attached hereto;

                  (c) the Administrative Agent shall have received a copy of the
         resolutions, in form and substance satisfactory to the Administrative
         Agent, of the Board of Directors of each applicable Loan Party
         authorizing the execution, delivery and performance of this Agreement,
         certified by its Secretary or Assistant Secretary as of the Ninth
         Amendment Effective Date, which certificate shall state that the
         resolutions thereby certified have not been amended, modified, revoked
         or rescinded as of the date of such certificate; and



                                      -4-
<PAGE>

                  (d) the Administrative Agent shall have received from the
         Borrower written confirmation that the Subordinated Indebtedness of the
         Borrower has been refinanced or replaced on terms identical to the
         existing terms thereof or on terms otherwise acceptable to the Required
         Lenders, including in either case a maturity date of no earlier than
         December 31, 2002.

         7. Representations and Warranties. The Borrower, as of the date hereof
and after giving effect to the amendment contained herein, hereby (i) represents
and warrants to the administrative Agent and each Lender that the Lenders have a
first priority lien on, and security interest in, Oil and Gas Properties of the
Borrower constituting at least 80% of the Present Value of the Oil and Gas
Properties of the Borrower and its consolidated Subsidiaries as reflected in the
Reserve Reported dated June 30, 2001, and delivered to the Lenders and (ii)
confirms, reaffirms and restates that (a) representations and warranties made by
it in Section 5 of the Credit Agreement are true and correct on and as of the
date hereof (except to the extent such representations and warranties are stated
to relate to a specific earlier date) and (b) no Default or Event of Default has
occurred and is continuing on the date hereof; provided, that each reference to
the Credit Agreement therein shall be deemed to be a reference to the Credit
Agreement after giving effect to this Agreement.

         8. Payment of Expenses. The Borrower agrees to pay or reimburse the
Administrative Agent for all of its reasonable out-of-pocket costs and
reasonable expenses incurred in connection with this Agreement, any other
documents prepared in connection herewith and the transactions contemplated
hereby, including, without limitation, the reasonable fees and disbursements of
counsel to the Administrative Agent.

         9. Reference to and Effect on the Loan Documents; Limited Effect. On
and after the date hereof and the satisfaction of the conditions contained in
paragraph 6 of this Agreement, each reference in the Credit Agreement to "this
Agreement", "hereunder", "hereof" or words of like import referring to the
Credit Agreement, and each reference in the other Loan Documents to "the Credit
Agreement", "thereunder", "thereof" or words of like import referring to the
Credit Agreement, shall mean and be a reference to the Credit Agreement as
amended hereby. The execution, delivery and effectiveness of this Agreement
shall not, except as expressly provided herein, operate as a waiver of any
right, power or remedy of any Lender or the Agent under any of the Loan
Documents, nor constitute a waiver of any provisions of any of the Loan
Documents. Except as expressly amended herein, all of the provisions and
covenants of the Credit Agreement and the other Loan Documents are and shall
continue to remain in full force and effect in accordance with the terms thereof
and are hereby in all respects ratified and confirmed.

         10. Counterparts. This Agreement may be executed by one or more of the
parties hereto in any number of separate counterparts (which may include
counterparts delivered by facsimile transmission) and all of said counterparts
taken together shall be deemed to constitute one and the same instrument. Any
executed counterpart delivered by facsimile transmission shall be effective as
for all purposes hereof.

         11. Severability. Any provision of this Agreement which is prohibited
or unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any



                                      -5-
<PAGE>


such prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction.

         12. Integration. This Agreement and the other Loan Documents represent
the agreement of the Loan Parties, the Administrative Agent and the Lenders with
respect to the subject matter hereof, and there are no promises, undertakings,
representations or warranties by the Administrative Agent or any Lender relative
to the subject matter hereof not expressly set forth or referred to herein or in
the other Loan Documents.

         13. GOVERNING LAW. THIS AGREEMENT AND THE RIGHTS AND OBLIGATIONS OF THE
PARTIES UNDER THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED AND INTERPRETED
IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.


                  [remainder of page intentionally left blank]



                                      -6-
<PAGE>


         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed and delivered by their respective proper and duly authorized
officers as of the day and year first above written.

BORROWER:                                      THE MERIDIAN RESOURCE CORPORATION


                                               By:       /s/ MICHAEL MAYELL
                                                   ----------------------------
                                                   Name:  Michael Mayell
                                                   Title: President


                                               By:    /s/  JAMES H. SHONSEY
                                                   ----------------------------
                                                   Name:  James H. Shonsey
                                                   Title: V.P.-Finance &
                                                          Capital Markets



                                               JPMORGAN CHASE BANK (formerly The
                                               Chase Manhattan Bank), as
                                               Administrative Agent, Issuing
                                               Lender and as a Lender


                                               By:       /s/ STEVEN WOOD
                                                   ----------------------------
                                                   Name:  Steven Wood
                                                   Title: Vice President



                                               TORONTO DOMINION (TEXAS), INC.,
                                               as Arranger, Documentation Agent
                                               and as a Lender


                                               By:       /s/ ANN S. SLANIS
                                                   ----------------------------
                                                   Name:  Ann S. Slanis
                                                   Title: Vice President



                                               SOCIETE GENERALE, SOUTHWEST
                                               AGENCY, as a Lender


                                               By:        /s/ CARY HUGHES
                                                   ----------------------------
                                                   Name:  Cary Hughes
                                                   Title: Director



                                               FORTIS CAPITAL CORP. (formerly
                                               MeesPierson N.V.), as a Lender


                                               By:     /s/ DARRELL W. HOLLEY
                                                   ----------------------------
                                                   Name:  Darrell W. Holley
                                                   Title: Managing Director


                                               By:      /s/ M.F.E. DE HAAN
                                                   ----------------------------
                                                   Name:  M.F.E. de Haan
                                                   Title: Associate



                                               ROYAL BANK OF CANADA, as a Lender


                                               By:       /s/ JASON YORK
                                                   ----------------------------
                                                   Name:  Jason York
                                                   Title: Vice President



                                               BNP PARIBAS, as a Lender


                                               By:       /s/ BRIAN MALONE
                                                   ----------------------------
                                                   Name:  Brian Malone
                                                   Title: Managing Director


                                               By:       /s/ J. ONLSCHUK
                                                   ----------------------------
                                                   Name:  J. Onlschuk
                                                   Title: Director



                                               CREDIT AGRICOLE INDOSUEZ, as a
                                               Lender


                                               By:      /s/ BRIAN KNEZEAK
                                                   ----------------------------
                                                   Name:  Brian Knezeak
                                                   Title: FVP, Manager


                                               By:     /s/ MICHAEL D. WILLIS
                                                   ----------------------------
                                                   Name:  Michael D. Willis
                                                   Title: VP, Credit Analysis
<PAGE>




                           ACKNOWLEDGMENT AND CONSENT

         Each of the undersigned corporations, as a guarantor under that certain
Second Amended and Restated Guarantee, dated as of June 30, 1998 (as amended,
supplemented or otherwise modified from time to time, the "Guarantee") made by
each of such entities in favor of the Administrative Agent, confirms and agrees
that the Guarantee is, and shall continue to be, in full force and effect and is
hereby ratified and confirmed in all respects and the Guarantee and all of the
Collateral (as defined in the Guarantee Agreement), do, and shall continue to,
secure the payment of all of the Obligations (as defined in the Guarantee
Agreement) pursuant to the terms of the Guarantee. Capitalized terms not
otherwise defined herein shall have the meanings assigned to them in the Credit
Agreement referred to in the Agreement to which this Acknowledgment and Consent
is attached.

                                               CAIRN ENERGY USA, INC.


                                               By:    /s/ MICHAEL MAYELL
                                                   ----------------------------
                                                   Name:  Michael Mayell
                                                   Title: President


                                               By:    /s/ JAMES H. SHONSEY
                                                   ----------------------------
                                                   Name:  James H. Shonsey
                                                   Title: Vice President


                                               Address for Notices:
                                               1401 Enclave Parkway, Suite 300
                                               Houston, Texas 77077
                                               Fax: (281) 558-5744





<PAGE>



                                               THE MERIDIAN RESOURCE &
                                               EXPLORATION, LLC


                                               By:    /s/ MICHAEL MAYELL
                                                   ----------------------------
                                                   Name:  Michael Mayell
                                                   Title: President


                                               By:    /s/ JAMES H. SHONSEY
                                                   ----------------------------
                                                   Name:  James H. Shonsey
                                                   Title: Vice President

                                               Address for Notices:
                                               1401 Enclave Parkway, Suite 300
                                               Houston, Texas 77077
                                               Fax: (281) 558-5744


                                               THE MERIDIAN PRODUCTION
                                               CORPORATION


                                               By:    /s/ MICHAEL MAYELL
                                                   ----------------------------
                                                   Name:  Michael Mayell
                                                   Title: President


                                               By:    /s/ JAMES H. SHONSEY
                                                   ----------------------------
                                                   Name:  James H. Shonsey
                                                   Title: Vice President

                                               Address for Notices:
                                               1401 Enclave Parkway, Suite 300
                                               Houston, Texas 77077
                                               Fax: (281) 558-5744


<PAGE>



                                               THE MERIDIAN RESOURCE CORPORATION
                                               (Delaware Subsidiary)


                                               By:    /s/ MICHAEL MAYELL
                                                   ----------------------------
                                                   Name:  Michael Mayell
                                                   Title: President


                                               By:    /s/ JAMES H. SHONSEY
                                                   ----------------------------
                                                   Name:  James H. Shonsey
                                                   Title: Vice President


                                               Address for Notices:
                                               1401 Enclave Parkway, Suite 300
                                               Houston, Texas 77077
                                               Fax: (281) 558-5744


                                               LOUISIANA ONSHORE PROPERTIES, LLC


                                               By:    /s/ MICHAEL MAYELL
                                                   ----------------------------
                                                   Name:  Michael Mayell
                                                   Title: President


                                               By:    /s/ JAMES H. SHONSEY
                                                   ----------------------------
                                                   Name:  James H. Shonsey
                                                   Title: Vice President


                                               Address for Notices:
                                               1401 Enclave Parkway, Suite 300
                                               Houston, Texas 77077
                                               Fax: (281) 558-5744