| 1 | O K Swabbing Inc | Hennessey, OK 73742 | Oil & Gas Operator | Sep 2024 |
| 2 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Dec 2024 |
| 3 | O'Neill Properties, LTD. | Midland, TX 79702 | Oil & Gas Operator | Dec 2024 |
| 4 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Dec 2024 |
| 5 | Oakwood Resources, Inc. | Dallas, TX 75374 | Oil & Gas Operator | May 1998 |
| 6 | Occidental Energy MKT Inc | Houston, TX 77001 | Oil & Gas Operator | Jan 2011 |
| 7 | Oexco, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2015 |
| 8 | Oil Producers, Inc. Of Kansas | Wichita, KS 67206 | Oil & Gas Operator | Dec 2024 |
| 9 | Oil Property Management, Inc. | Attica, KS 67009 | Oil & Gas Operator | Feb 2021 |
| 10 | Oil Recovery Systems Inc | Tulsa, OK 74145-4619 | Oil & Gas Operator | Sep 2024 |
| 11 | Oilsearch Corporation | Albuquerque, NM 87109 | Oil & Gas Operator | Feb 1994 |
| 12 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Sep 2024 |
| 13 | Oklahoma Energy Acquisitions LP | Houston, TX 77094-1900 | Oil & Gas Operator | Sep 2024 |
| 14 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Oct 2024 |
| 15 | Olympic Petroleum Company | Tulsa, OK 74114 | Oil & Gas Operator | Jun 1998 |
| 16 | Omimex International Corporation | Fort Worth, TX 76103-2300 | Oil & Gas Operator | Sep 2024 |
| 17 | Oneok Exploration Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 18 | Oneok Field Services Company | Tulsa, OK 74103 | Oil & Gas Operator | Jul 2022 |
| 19 | Oneok Resources Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 20 | Opal Operating Company LLC | Oklahoma City, OK 73142 | Oil & Gas Operator | Dec 2024 |
| 21 | Oryx Crude Trading & Transporation LP | Dallas, TX 75221 | Oil & Gas Operator | Jun 1999 |
| 22 | Osterhout Phillip L | Drumright, OK 74030-0693 | Oil & Gas Operator | Jan 2014 |
| 23 | Otc Petroleum Corporation | Nichols Hill, OK 73116 | Oil & Gas Operator | Mar 2015 |
| 24 | Overflow Energy, LLC | Booker, TX 79005 | Oil & Gas Operator | Dec 2024 |
| 25 | Ovintiv Mid-Continent Inc. | The Woodlands, TX 77380-2764 | Oil & Gas Operator | Oct 2024 |
| 26 | Oxford Oil Inc | Cleveland, OK 74020 | Oil & Gas Operator | Feb 1997 |
| 27 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Dec 2024 |