| 1 | O'Donnell Bill C | Tulsa, OK 74135-4241 | Oil & Gas Operator | Oct 2014 |
| 2 | O'Neal Oil & Gas Co | Fort Worth, TX 76107-1479 | Oil & Gas Operator | Feb 2024 |
| 3 | O'Neal Oil Company | Nocona, TX 76255 | Oil & Gas Operator | May 2024 |
| 4 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | May 2024 |
| 5 | Octagon Resources LLC | Norman, OK 73071-1295 | Oil & Gas Operator | May 2015 |
| 6 | Oil Lift, Incorporated | Metairie, LA 70002 | Oil & Gas Operator | Apr 2020 |
| 7 | Oil Operations Inc | | Oil & Gas Operator | Apr 2011 |
| 8 | Oil Patch Energy LLC | Broken Arrow, OK 74014 | Oil & Gas Operator | Jan 2024 |
| 9 | Oil Producers, Inc. Of Kansas | Wichita, KS 67206 | Oil & Gas Operator | May 2024 |
| 10 | Oilfield Operating Company | Cushing, OK 74023-1347 | Oil & Gas Operator | Jan 2018 |
| 11 | Okc Energy Corporation | Oklahoma City, OK 73120-3119 | Oil & Gas Operator | Nov 2014 |
| 12 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2024 |
| 13 | Oklahoma & Northwestern Co. | Oklahoma City, OK 73102 | Oil & Gas Operator | Jan 1997 |
| 14 | Oklahoma Cellulose Inc | Cleveland, OK 74020-0193 | Oil Operator | Jan 2024 |
| 15 | Oklahoma Crude Reclaimers, LLC | | Oil Operator | Feb 2024 |
| 16 | Oklahoma Energy LLC | Skiatook, OK 74070-3998 | Oil Operator | Aug 2023 |
| 17 | Oklahoma Liquid Resources Inc | Owasso, OK 74055-0841 | Oil & Gas Operator | Jan 2024 |
| 18 | Oklahoma Oil & Gas MGMT Inc | | Oil & Gas Operator | Jan 2024 |
| 19 | Oklahoma Petroleum Allies LLC | Ardmore, OK 73401 | Oil Operator | Oct 2023 |
| 20 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 21 | Ole Crow Operating | Wichita Falls, TX 76308-0072 | Oil Operator | Feb 2024 |
| 22 | Oliphant Operating LTD LLC | Tulsa, OK 74159-4529 | Oil Operator | Jan 2024 |
| 23 | Oneok Gas Transportation Co | Tulsa, OK 74121-2089 | Oil & Gas Operator | Oct 2014 |
| 24 | Orion Exploration LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Apr 2015 |
| 25 | Orion Exploration Partners LLC | | Oil & Gas Operator | Jul 2020 |
| 26 | Osage Energy LLC | Colony, KS 66015 | Oil Operator | Nov 2023 |
| 27 | Osage Energy Resources LLC | Bartlesville, OK 74005-2527 | Oil & Gas Operator | Jan 2024 |
| 28 | Osage Operating | Virginia Beach, VA 23452 | Oil & Gas Operator | Oct 2003 |
| 29 | Otc Investors Inc | Locust Grove, OK 74352 | Oil Operator | Dec 2023 |
| 30 | Otc/Occ Not Assigned | | Oil & Gas Operator | Nov 2023 |
| 31 | Ovintiv USA Inc. | Denver, CO 80202 | Oil & Gas Operator | May 2024 |
| 32 | Oxco LLC | Pawhuska, OK 74056 | Oil & Gas Operator | Feb 2015 |
| 33 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | May 2024 |