| Company Name | Company Location | Company Type | Most Recent Production | |
|---|---|---|---|---|
| 1 | O'Brien Operating Company | Shreveport, LA 71164 | Oil & Gas Operator | Dec 2004 |
| 2 | O. B. Mobley | Oil & Gas Operator | Jul 1989 | |
| 3 | Oakland Corporation | Oil & Gas Operator | Dec 1981 | |
| 4 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2025 |
| 5 | Orx Resources, L.L.C. | Houston, TX 77067 | Oil & Gas Operator | Oct 2025 |
| 6 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 7 | Owl Creek Production Co., Inc. | Houston, TX 77027 | Oil & Gas Operator | Apr 2006 |
| 8 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |