FOURTH AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT

This Fourth Amendment to Amended and Restated Credit Agreement (hereinafter referred to as the “ Amendment ”) executed as of July 28, 2006, by and among Clayton Williams Energy Inc., a Delaware corporation (“ CWEI ”), Southwest Royalties, Inc. (successor by merger to CWEI-SWR, Inc.), a Delaware corporation (“ SWR ”, and together with CWEI and each of their respective successors and permitted assigns, the “ Borrowers ” and each a “ Borrower ”), Warrior Gas Co., a Texas corporation (“ Warrior ”), CWEI Acquisitions, Inc. a Delaware corporation (“ CWEI Acquisitions ”), Romere Pass Acquisition L.L.C., a Delaware limited liability company (“ Romere ”), CWEI Romere Pass Acquisition Corp., a Delaware corporation (“ Romere Corp ”), Blue Heel Company, a Delaware corporation (“ Blue Heel ”), and Tex-Hal Partners, Inc., a Delaware corporation (“ Tex-Hal ,” and together with Warrior, CWEI Acquisitions, Romere, Romere Corp and Blue Heel and each of their successors and permitted assigns, the “ Guarantors ” and each a “ Guarantor ”), JPMorgan Chase Bank, N.A. (successor by merger to Bank One, N.A. (Illinois)), a national banking association (“ JPMorgan Chase ”), each of the financial institutions which is a party hereto (as evidenced by the signature pages to this Amendment) or which may from time to time become a party to the Agreement pursuant to the provisions of Section 14.3 thereof or any successor or permitted assignee thereof (hereinafter collectively referred to as “ Lenders ”, and individually, “ Lender ”), JPMorgan Chase, as Administrative Agent (in its capacity as Administrative Agent and together with its successors in such capacity, “ Administrative Agent ”).  Capitalized terms used but not defined in this Amendment have the meanings assigned to such terms in that certain Amended and Restated Credit Agreement dated as of May 21, 2004, by and among Borrowers, Guarantors, Administrative Agent and Lenders (as amended, supplemented or otherwise modified from time to time, the “ Agreement ”).

WHEREAS, the Borrowers and the Guarantors have requested that the Administrative Agent and the Lenders amend the Agreement to permit the investment of up to $10,000,000 in a newly formed partnership with a unit of General Electric Corporation through West Coast Energy Properties GP, LLC, a newly formed subsidiary of CWEI and the general partner of such partnership; and the Administrative Agent and the Lenders (or at least the requisite percentage thereof) have agreed to do so on the terms and conditions hereinafter set forth; and

NOW, THEREFORE, for and in consideration of the mutual covenants and agreements herein contained and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged and confessed, the Borrowers, the Guarantors, the Administrative Agent and the Lenders, hereby agree as follows:

SECTION 1.         Amendments to the Agreement.   Subject to the satisfaction or waiver in writing of each condition precedent set forth in Section 2 hereof, and in reliance on the representations, warranties, covenants and agreements contained in this Amendment, the Agreement shall be amended in the manner provided in this Section 1 .

1.1             Additional Definitions. Article I of the Agreement shall be and it hereby is amended by adding the following definition in the correct alphabetical order:

“West Coast Properties” means West Coast Energy Properties, L.P., a Texas limited partnership and its successors.

1.2             Investments.    Section 8.15 of the Agreement shall be and it hereby is amended by replacing clause (ix) of such Section with the following clauses (ix) and (x):

(ix)           Investments in West Coast Properties, including equity contributions, and loans, advances or other extensions of credit to West Coast Properties; provided that the amount of such Investments made pursuant to this clause (ix) of Section 8.15 does not exceed in the aggregate, $10,000,000 and the proceeds of such Investments are used by West Coast Properties to acquire and develop Oil and Gas Interests.

(x)           Other Investments not otherwise described in clauses (i) through (ix) above; provided that, the aggregate amount of all other Investments made pursuant to this clause (x) outstanding at any time shall not exceed $1,000,000 (calculated based on the original cost of such Investment).

SECTION 2.         Conditions.   The amendments to the Agreement contained in Section 1 of this Amendment shall be effective upon the satisfaction of each of the conditions set forth in this Section 2 .

2.1             Execution and Delivery.   Each Borrower and each Guarantor shall have executed and delivered this Amendment.

2.2             Representations and Warranties.   The representations and warranties of each Borrower under the Agreement, as amended by the Amend