<PAGE>

          SECOND AMENDMENT TO CREDIT AND SECURITY AGREEMENT

 PREAMBLE. This Second Amendment to Credit and Security Agreement (this
 "Amendment") dated as of August 27, 2004, is made among (i) OMNI ENERGY
 SERVICES CORP., a Louisiana corporation "Parent Company"); AMERICAN
 HELICOPTERS INC., a Texas corporation ("AHI"); and OMNI ENERGY SERVICES
 CORP.-MEXICO, a Louisiana corporation ("Mexico"; Mexico, AHI and Parent Company
 herein sometimes called individually, "Initial Borrower" and, collectively, the
 "Initial Borrowers"); (ii) TRUSSCO, INC., a Louisiana corporation ("Trussco")
 and TRUSSCO PROPERTIES, LLC, a Louisiana limited liability company ("Trussco
 Properties"; Trussco Properties and Trussco herein sometimes called,
 individually, "New Borrower" and, collectively, the "New Borrowers"; each New
 Borrower and each Initial Borrower herein sometimes called, individually, a
 "Borrower" and, collectively, the "Borrowers"); and (iii) WEBSTER BUSINESS
 CREDIT CORPORATION, a corporation organized under the laws of the State of New
 York ("WBCC"), individually, as lender hereunder and as agent for itself and
 each other Lender Party (as hereinafter defined) (WBCC, acting in both such
 capacities, herein called "Lender"), for the purpose of amending the Credit and
 Security Agreement, dated December 23, 2003, between Initial Borrowers and
 Lender (the "Credit Agreement"), as amended by that certain First Amendment to
 Credit and Security Agreement, dated as of June 30, 2 004, among the parties
 hereto (the "Trussco Amendment"), in order to reflect, among other things,
 Lender's approval to incorporate the financial performance and condition of the
 New Borrowers into the Financial Covenants.

      1.  Definitions. Capitalized terms used in this Amendment, but not
expressly defined herein, shall have the same meanings as given to such terms in
the Credit Agreement and/or, as appropriate, the Trussco Amendment.

      2.  Amendments. Retroactive to June 30, 2004, EBITDA of the Borrowers, as
defined in Section 8.1 of the Credit Agreement, and used in the computation of
the Fixed Charge Coverage Ratio and the leverage Ratio in Sections 8.2 and 8.4
of the Credit Agreement, respectively, shall expressly include EBITDA of the New
Borrowers for all applicable fiscal periods (including those beginning prior to
the Trussco Acquisition).

      3.  Conditions to Effectiveness. The amendments set forth hereinabove are
further made contingent upon, and shall not become effective, unless and until:
Borrowers shall have executed and delivered to WBCC this Amendment binding
themselves to all agreements (including amendments) set forth herein.

      4.  Effective Date. The amendments and modifications to the Credit
Agreement set forth in this Amendment shall be effective as of the date hereof
(except as otherwise expressly provided hereinabove).

      5.  No Other Changes. Except as expressly amended and modified hereby, the
terms of the Credit Agreement shall remain unchanged and continue in full force
and effect.

      6.  Other Document. This Amendment constitutes an Other Document and shall
be governed and construed accordingly.

<PAGE>

Each of the parties has signed this Amendment as of the day and year first above
written.

                                     "BORROWERS"
                                     OMNI ENERGY SERVICES CORP.

                                     By: /s/ G. Darcy Klug
                                         ---------------------------------------
                                         G. Darcy Klug
                                         Chief Financial Officer

                                     AMERICAN HELICOPTERS INC.

                                     By: /s/ G. Darcy Klug
                                         ---------------------------------------
                                         G. Darcy Klug
                                         Chief Financial Officer

                                     OMNI ENERGY SERVICES CORP.-MEXICO

                                     By: /s/ G. Darcy Klug
                                         ---------------------------------------
                                         G. Darcy Klug
                                         Chief Financial Officer

                                     TRUSSCO, INC.

                                     By: /s/ G. Darcy Klug
                                         ---------------------------------------
                                         G. Darcy Klug
                                         Chief Financial Officer

                                     TRUSSCO PROPERTIES, LLC

                                     By: /s/ G. Darcy Klug
                                         ---------------------------------------
                                         G. Darcy Klug
                                         Chief Financial Officer

                                        2

<PAGE>

                                     "LENDER"

                                     WEBSTER BUSINESS CREDIT
                                     CORPORATION

                                     By: /s/ Webster Officer
                                         -------------------------------
                                         Authorized Officer

                                        3