- Ambar Drilling Fluids
- Amerada Hess Corporation
- Anadarko Petroleum Corporation
- Apache Corporation
- Arkla Gas
- Ashland Oil Inc.
- Baker Hughes
- Baroid Fluids Services
- BP America">
- BP Exploration & Production Inc.
- Chesapeake Energy Corp.
- Chevron U.S.A. Inc
- Texaco
- ConocoPhillips
- Devon Energy Corporation
- Dominion Exploration & Production
- Elf - Yemen
- Eni US Operating Co. Inc.
- EOG Resources
- Exxon Mobil Corporation
- Forest Oil Corporation
- Hunt Oil Company
- Kerr-McGee Oil & Gas
- Marathon Oil Company
- Mariner Energy, Inc.
- McMoran Oil and Gas
- Meridan Resources Corp
- M-I Drilling Fluids
- Mudman Consulting Engineers, LLC
- Murphy Exploration & Production
- Newfield Exploration Company
- Newpark Drilling Fluids
- Nexen Petroleum U.S.A. Inc.
- Noble Energy, Inc.
- Occidental Petroleum, Inc.
- Ocean Energy Inc
- Petrobras America Inc.
- Petrocanada - Yemen
- Petrohawk Energy Corp.
- Pioneer Natural Resources USA, Inc.
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