ATNA RESOURCES Advantage Oil & Gas Ltd. Alon USA Energy, Inc. Anadarko Petroleum Corp. Apache Corp. Approach Resources, Inc. Atlas Pipeline Partners L.P. Atwood Oceanics, Inc. BP PLC ADS BPZ Resources Baker Hughes, Inc. Bill Barrett Corp. BreitBurn Energy Partners, L.P. CAMAC Energy, Inc. CNOOC Ltd. ADS Cabot Oil & Gas Corp. Cameron International Corp. Carrizo Oil & Gas, Inc. Cenovus Energy, Inc. Cheniere Energy Partners L.P. Cheniere Energy, Inc. Chesapeake Energy Corp. Chevron Cimarex Energy Co. Cobalt International Energy Comstock Resources, Inc. Concho Resources ConocoPhillips Constellation Energy Partners LLC Continental Resources OK Core Laboratories N.V. Crimson Exploration, Inc. Crosstex Energy, Inc. Dawson Geophysical Co Dejour Energy Ltd. Denbury Resources, Inc. Devon Energy Corp. Diamond Offshore Drilling, Inc. Dril-Quip, Inc. ENERGY USD UNRESTR ENHANCED OIL RES EOG Resources, Inc. EQT Corporation EXCO Resources Eagle Rock Energy Partners, L.P. Ecopetrol S.A. ADS EnCana Corp. Enbridge, Inc. Equal Energy Ltd. Exxon Mobil FX Energy, Inc. Flotek Industries, Inc. Forest Oil Corp. Gasco Energy Gastar Exploration GeoGlobal Resources Goodrich Petroleum Corp. Gran Tierra Energy Halliburton Co. Helix Energy Solutions Group Helmerich Payne Hercules Offshore, Inc. Hess Corp. Hyperdynamics Corp. Imperial Oil Ltd. InterOil Kinder Morgan Management L.L.C. Legacy Reserves LP Linn Energy, LLC MDU Resources Group, Inc. Magellan Petroleum Corp Magnum Hunter Resources Corp Marathon Oil Corp. MarkWest Energy Partners LP McMoRan Exploration Co. Miller Energy Resources Murphy Oil Corp. NIGHTHAWK ENERGY Nabors Industries Ltd. National-Oilwell, Inc. Newfield Exploration Co. Newpark Resources, Inc. Nexen, Inc. Noble Corp. Noble Energy, Inc. Northern Oil And Gas ORY INTER GR GBP-AC Oasis Petroleum Occidental Petroleum Corp. Oceaneering International, Inc. Oil States International, Inc. Parker Drilling Co. Patterson-UTI Energy, Inc. Penn Virginia Corp. Petrobras - Petroleo Brasileiro S.A. Pioneer Natural Resources Co. Plains Exploration & Production Co. Precision Drilling Corp. QEP Resources Questar Corp. Range Resources Corp. Rex Energy Corporation Rosetta Resources, Inc. Royale Energy, Inc. SM Energy SandRidge Energy Schlumberger Ltd. SeaDrill Ltd. Sinopec Shanghai Petrochemical Co. Ltd. ADS Sonde Resources Corp Southwestern Energy Co. Spectra Energy Statoil ASA ADS Stone Energy Corp. Superior Energy Services, Inc. Swift Energy Co. TRANSGLOBE ENERGY CORP Talisman Energy, Inc. Taubman Centers, Inc. Tengasco, Inc. Tesco Corp Tesoro Corp. Total S.A. ADS TransAtlantic Petroleum Ltd. Transocean US Energy Corp Wyoming Ultra Petroleum Corp. Unit Corp. Valero Energy Corp. Vantage Drilling Co WT Offshore Warren Resources, Inc. Weatherford International Ltd. Western Refining Whiting Petroleum Corp. Williams Cos.