Abarta Oil & Gas Abraxas Petroleum Corp. Adams Resources Adexco Operating Co. AEDC (USA) Inc. Amrican Oil & Gas Inc. Anadarko Petroleum Corp. Apache Corp. Arena Resources Artex Ol Co. Aspect Energy, LLC Aspen Exploration Corp. Aspen Integrated Oil & Gas Atlas Energy Resources ATP Oil & Gas Aurora Oil & Gas Corp. Barrow-Shaver Resources Co. Basic Earth Science Sys., Inc. Belden & Blake Corp. Berexco, Inc. Berry Petroleum Bill Barrett Corp. <...> Co. Black Diamond Energy, Inc. Black Hills Corp. Bow Valley Energy Ltd. BrateBurn Energy & Energy Partners Brigham Exploration Co. Cabot Oil & Gas Corp. Callon Petroleum Co. Cano Petroleum Carrizo Oil & Gas Inc. Century Offshore Mgmt. <...> A. Anadarko Petroleum Corp. Antrim Energy Inc. Anzon Australia Apache Corp. Aspect Energy, LLC ATP Oil & Gas Bashneft Bow Valley Energy Ltd. BP BG Group Plc Pertamina Burren Energy Cairn Energy Plc CGX Energy Inc. Chevron CNOOC CNPC ConocoPhillips Dana Petroleum Canadian Natural Res. <...>