| 1 | O.G.P. Operating, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Apr 2024 |
| 2 | Oak Hills Drilling & Oper., LLC | Holdenville, OK 74848 | Oil & Gas Operator | May 2013 |
| 3 | Oak Hills Energy Inc | Holdenville, OK 74848-0470 | Oil & Gas Operator | Sep 2014 |
| 4 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Apr 2024 |
| 5 | Oasis Energy Resources LLC | | Oil & Gas Operator | Dec 2023 |
| 6 | Octagon Resources LLC | Norman, OK 73071-1295 | Oil & Gas Operator | May 2015 |
| 7 | Odessa Oil Investment Co., Inc. | Odessa, TX 79762 | Oil & Gas Operator | Nov 2016 |
| 8 | Oil Center Operating Inc | Fort Worth, TX 76102-5108 | Oil & Gas Operator | Apr 2014 |
| 9 | Oil Production Systems Inc | Cushing, OK 74023 | Oil & Gas Operator | Jan 2013 |
| 10 | Okla Sub-Surface Pump & Supply Co | Seminole, OK 74818-2248 | Oil & Gas Operator | Jan 2024 |
| 11 | Oklahoma Basic Economy Corp | Houston, TX 77002-6003 | Oil & Gas Operator | Apr 2020 |
| 12 | Oklahoma Equipment & Salvage | Oklahoma City, OK 73120-5903 | Oil & Gas Operator | Mar 2015 |
| 13 | Oklahoma Liquid Resources Inc | Owasso, OK 74055-0841 | Oil & Gas Operator | Dec 2023 |
| 14 | Oklahoma Oil & Gas MGMT Inc | | Oil & Gas Operator | Dec 2023 |
| 15 | Oklahoma Petroleum Allies LLC | Ardmore, OK 73401 | Oil Operator | Oct 2023 |
| 16 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Jan 2024 |
| 17 | Onshore Royalties LLC | Houston, TX 77269 | Oil & Gas Operator | Feb 2024 |
| 18 | Orca Operating Company LLC | Houston, TX 77056 | Oil & Gas Operator | Jan 2024 |
| 19 | Ovintiv Mid-Continent Inc. | The Woodlands, TX 77380-2764 | Oil & Gas Operator | Jan 2024 |