Anadarko Petroleum Corp.

Apache Deepwater LLC

ATP Oil & Gas Corp.

BHP Billiton ( Americas) Inc.

Century Exploration

Cobalt International Energy LP

Deep Gulf Energy LP/Deep Gulf Energy II, LLC

ENI U.S. Operating Company

Energy Resources Technology

Hess Corporation LLOG Exploration Co. LLC

Marathon Oil Company

Marubeni Oil & Gas (USA) Inc.

Murphy Oil Corporation

Newfield Exploration Company

Nexen Petroleum USA Inc.

Noble Energy, Inc.

Plains Exploration & Production

Repsol E&P USA, Inc.

Statoil Gulf of Mexico LLC

Stone Energy Corp.

Walter Oil & Gas Corp.

Woodside Energy (USA) Inc.

W&T Offshore, Inc.