O'Neal Resources Corp. O.I.L. Energy Corp. Oakmont Corp. Obow Exploration Inc. Ocean Energy Inc. ODG Private Equity Group ODYSSEY Petroleum Corp. Officer Basin Energy Inc. Offshore Development Inc. OGR 96 Ltd. Oil & Gas Investment Corp. Oilexco Inc. OJSC Tambeyneftegas Oklahoma Oil & Gas Management Inc. Olympic Peru Omimex Petroleum Onebane, Donohoe, Bernard, Torian Oneok Inc. Online Resources Operations Management Ltd. Opon Development Co. Optima Petroleum Corp. Ore and Petrol Partners LLC. Orient Petroleum (Central Asia) Osborne Oil Co. Overseas Private Investment Corp. Oxbow Energy Inc. Oxy USA Inc. |
O'Brien Resources LLC. O'Sullivan Oil & Gas Co. Inc. Oakland Petroleum Oaktree Capital Partners Occidental Petroleum Corp. Oculus Energy Co. ODIN Capital Inc. Oedekoven Water Hot Oil Service Offset Energy Corp. Offshore Energy Development Corp. OGY Petroleum Oil City Petroleum Inc. OJSC MMC Norslik Nickel OJSC Yamal LNG Old Oak Capital LLC. Omimex Canada Ltd. OMV (Pakistan) Exploration GMBH Oneida and Western Energy Co. ONGC Videsh Ltd. Opal Resources LLC. Opicoil America Ltd. OPT Inc. Orbis Energy LLC. Oregon Natural Gas Development Corp. Orion Securities Inc. Output Exploration LLC. Owen Inc. Oxy Services Inc. |