| 1 | O G & E | Oklahoma City, OK 73124 | Oil & Gas Operator | Feb 2014 |
| 2 | O K Swabbing Inc | Hennessey, OK 73742 | Oil & Gas Operator | Nov 2025 |
| 3 | O'Brien Oil Corporation | Guthrie, OK 73044-3154 | Oil & Gas Operator | Nov 2025 |
| 4 | O'Brien Oil LLC | Guthrie, OK 73044-3154 | Oil & Gas Operator | Apr 2020 |
| 5 | O'Neal Oil & Gas Co | Fort Worth, TX 76107-1479 | Oil & Gas Operator | Dec 2025 |
| 6 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Feb 2026 |
| 7 | Oex-1 LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Mar 2024 |
| 8 | Ofs-Tulsa Corporation | Fort Worth, TX 76102 | Oil & Gas Operator | Feb 1997 |
| 9 | Oil Investors Inc | Crescent, OK 73028 | Oil & Gas Operator | Dec 2025 |
| 10 | Oil Ventures LTD | | Oil & Gas Operator | Jan 2013 |
| 11 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Nov 2025 |
| 12 | Oklahoma Energy Acquisitions LP | Houston, TX 77094-1900 | Oil & Gas Operator | Nov 2025 |
| 13 | Oklahoma Equipment & Salvage | Oklahoma City, OK 73120-5903 | Oil & Gas Operator | Mar 2015 |
| 14 | Oklahoma Liquid Resources Inc | Collinsville, OK 74021 | Oil & Gas Operator | Oct 2025 |
| 15 | Oklahoma Oil & Gas MGMT Inc | Edmond, OK 73083-6786 | Oil & Gas Operator | Nov 2025 |
| 16 | Oklahoma Oil And Gas Resources LLC | Guthrie, OK 73044-8095 | Oil & Gas Operator | Dec 2025 |
| 17 | Oklahoma Plugging & Equip Inc | | Oil & Gas Operator | Nov 2000 |
| 18 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 19 | Omimex International Corp | Fort Worth, TX 76103-2300 | Oil & Gas Operator | Nov 2025 |
| 20 | Oneok Gas Transportation Co | Tulsa, OK 74121-2089 | Oil & Gas Operator | Oct 2014 |
| 21 | Oneok Resources Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 22 | Optima Exploration LLC | Tulsa, OK 74116-5664 | Oil & Gas Operator | Mar 2015 |
| 23 | Opubco Resources Of TX Inc | Dallas, TX 75231 | Oil & Gas Operator | Sep 2005 |
| 24 | Orason Resources Inc | Tulsa, OK 74169-1225 | Oil & Gas Operator | Nov 2006 |
| 25 | Orion Exploration LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Apr 2015 |
| 26 | Orion Exploration Partners LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Nov 2025 |
| 27 | Osage Exploration & Development Inc | San Diego, CA 92131-3807 | Oil & Gas Operator | Oct 2016 |
| 28 | Oso Resources LLC | Edmond, OK 73003 | Oil & Gas Operator | Nov 2025 |
| 29 | Osterhout Phillip L | Drumright, OK 74030-0693 | Oil & Gas Operator | Jan 2014 |
| 30 | Ovintiv Mid-Continent Inc. | The Woodlands, TX 77380-2764 | Oil & Gas Operator | Dec 2025 |