| Company Name | Company Location | Company Type | Most Recent Production | |
|---|---|---|---|---|
| 1 | O'Brien Operating Company | Oil & Gas Operator | Dec 2004 | |
| 2 | O'Malley Production Co. Inc. | Oil & Gas Operator | Mar 1988 | |
| 3 | Oakland Corporation | Oil & Gas Operator | Dec 1981 | |
| 4 | Oilwell Acquisition Co. | Oil & Gas Operator | Jun 1999 | |
| 5 | Okkatahula, Inc. | Oil Operator | Nov 1978 | |
| 6 | Owl Creek Production Co., Inc. | Houston, TX 77027 | Oil & Gas Operator | Apr 2006 |