| American Exploration Company Apache Corporation Applied Drilling Technology, Inc. Basic Resources Int'l (Bahamas) Ltd. D. B. Baxter, Inc. Black Stone Energy Company Blue Ridge Directional Cabot Oil & Gas Carrizo Oil & Gas Chevron U.S.A., Inc. Coastal Oil & Gas Corporation Cobra Oil & Gas Corporation Continental Operating Company Cox & Perkins Exploration, Inc. Cougar Directional Drilling Dailey Drilling Systems Denbury Management, Inc. Diamondback Directional, Inc. Drilling Measurements, Inc. Enco Exploration Company Enron Oil & Gas Company Forcenergy Gas Exploration, Inc. Forney & McCombs Gardes Directional Drilling Granstaff Directional Drilling Co., Inc. Griffith Directional H.S. Resources Halliburton Drilling Systems Helmer Directional Drilling, Inc. Howell Petroleum Corporation Leam Directional Drilling Leam Horizontal, Inc. Legacy Resources Co., L.P. Mandalay Oil & Gas Matrix Oil & Gas, Inc. Mobil Exploration & Producing U.S., Inc. | National Energy Group, Inc. Neumin Production Company Oxy, U.S.A. Pecos Petroleum Company Pennzoil Exploration & Production Company Petroleum Management, Inc. Petroleum Resource Management Company Philliber Directional Drilling, Inc. Phoenix Drilling Services Pioneer Natural Resources U.S.A., Inc. Prime Directional Systems Prime Natural Resources Ramco Directional Drilling Ridgelake Energy Scientific Drilling International, Inc. Shell Western Exploration & Producing Co. Sperry Sun Drilling Services Spirit Energy Strata Directional Swift Energy Company 3-D Directional Drilling Taylor Directional & Horizontal Drilling Services Tesoro Petroleum Corporation Texaco Exploration & Production, Inc. Texas Meridian Resources Corporation Torch Energy Advisors, Inc. Trans Texas Gas Corporation Tri-City Services, Inc. Union Pacific Resources Unit Petroleum Company United Geocom Drilling Services, L.L.C. U.S. Steel Mining Company Keith F. Walker Oil & Gas, L.L.C. Whitmar Exploration Co., Inc. James A. Whitson, Jr. Wilson Downhole Services |