| 1 | Oak Dale Drilling Co | Logan, OH 43138-1851-1851 | Oil & Gas Operator | Dec 2015 |
| 2 | Obermiller Clarence Trust | Creston, OH 44217 | Oil & Gas Operator | Dec 1987 |
| 3 | Obermiller Paul J | Creston, OH 44217 | Oil & Gas Operator | Dec 2014 |
| 4 | Og Co., Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2024 |
| 5 | Ohio Energy Assets, Inc. | Laurelville, OH 43135 | Oil & Gas Operator | Dec 2014 |
| 6 | Ohio Energy Operators LLC | Colorado Spring, CO 80908 | Oil Operator | Dec 2018 |
| 7 | Ohio L & M Company Inc | Marietta, OH 45750 | Oil & Gas Operator | Dec 2008 |
| 8 | Ohio Natural Fuel Co | Canton, OH 44718 | Oil & Gas Operator | Dec 1985 |
| 9 | Ohio Oil & Gas | Fowler, OH 44418 | Oil & Gas Operator | Dec 1988 |
| 10 | Ohio Production Corp | Westerville, OH 43081 | Oil & Gas Operator | Dec 2001 |
| 11 | Ohio Production* | Newark, OH 43055 | Oil & Gas Operator | Dec 1987 |
| 12 | Ohio Valley Energy Systems Corp | Austintown, OH 44515 | Oil & Gas Operator | Dec 2023 |
| 13 | Oil & Gas Solutions LTD | Wooster, OH 44691 | Oil & Gas Operator | Dec 2007 |
| 14 | Oil & Realty Devlop Inc | Columbus, OH 43212 | Oil Operator | Dec 1986 |
| 15 | Oil Enterprises | Logan, OH 43138 | Oil & Gas Operator | Dec 2022 |
| 16 | Oil Search Inc | Brookfield, OH 44403 | Oil & Gas Operator | Dec 2022 |
| 17 | Oiltech Inc | Yuba City, CA 95991 | Oil & Gas Operator | Dec 1984 |
| 18 | Oiltex, Inc. | Baltimore, MD 21221 | Oil & Gas Operator | Dec 2013 |
| 19 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 20 | Old South Oil LLC | Marietta, OH 45750 | Oil & Gas Operator | Dec 2023 |
| 21 | Ole Miss Oil & Gas Inc | New Bremen, OH 45689 | Oil & Gas Operator | Dec 1985 |
| 22 | Olympic Resources Co | Wooster, OH 44691 | Oil & Gas Operator | Dec 2000 |
| 23 | Omac Oil & Gas Co | Newark, OH 43055 | Oil & Gas Operator | Dec 1990 |
| 24 | Omega Oil Corp | Lafayette, IN 47903 | Oil & Gas Operator | Dec 1987 |
| 25 | Orion Energy Corp | MT Vernon, IL 62864 | Oil & Gas Operator | Dec 1984 |
| 26 | Orion Petro Corp | MT Vernon, IL 62864 | Oil & Gas Operator | Dec 2016 |
| 27 | Orr Robert W Jr | Zanesville, OH 43702-2683-2683 | Oil & Gas Operator | Dec 2022 |
| 28 | Orwig Oil Company Inc | Bradenton, FL 34212 | Oil & Gas Operator | Dec 2022 |
| 29 | Osair Inc | Mentor, OH 44061 | Oil & Gas Operator | Dec 2021 |
| 30 | Otex Inc | N Canton, OH 44720 | Oil & Gas Operator | Dec 1988 |
| 31 | Ows Acquisition Co LLC | Bolivar, OH 44612 | Oil & Gas Operator | Dec 2022 |
| 32 | Oxford Oil | Zanesville, OH 43702-0910-0910 | Oil & Gas Operator | Dec 2012 |