| 1 | C & B Oil Company | Drumright, OK 74030 | Oil & Gas Operator | May 2025 |
| 2 | C & F Oil Company, Inc. | | Oil Operator | Jan 2025 |
| 3 | C & R Oil | | Oil Operator | Jun 2025 |
| 4 | C.T.R. Oil, Inc. | | Oil & Gas Operator | Jan 2025 |
| 5 | Campground Corporation | | Oil Operator | Nov 2023 |
| 6 | Candleridge Oil, Inc. | Fort Worth, TX 76109 | Oil & Gas Operator | Jun 2003 |
| 7 | Cardinal Petroleum Corp Of La | | Oil Operator | May 2003 |
| 8 | Caroline Hunt Trust Estate | | Oil & Gas Operator | Mar 1987 |
| 9 | Castor Production, L.L.C. | | Oil Operator | Dec 2024 |
| 10 | Cavalcade Operating Company LLC | Kilgore, TX 75663 | Oil & Gas Operator | Dec 2017 |
| 11 | Cavenham Energy Resources Inc. | | Oil & Gas Operator | Apr 1991 |
| 12 | Cavenham Forest Ind., Inc. | | Oil & Gas Operator | Nov 1987 |
| 13 | Cedar Creek Consulting Inc | | Oil Operator | Jan 2025 |
| 14 | Cenla Oil Company, LLC | | Oil Operator | Dec 2024 |
| 15 | Chadco, Inc. | | Oil Operator | Dec 2024 |
| 16 | Channel Exploration Company | | Oil & Gas Operator | Feb 1997 |
| 17 | Charles B. Bice | | Oil & Gas Operator | Jul 1983 |
| 18 | Cities Service Company | | Oil & Gas Operator | Mar 1983 |
| 19 | Cities Service Oil & Gas Corp | | Oil & Gas Operator | Mar 1988 |
| 20 | Cities Service Oil Co. | | Oil & Gas Operator | Dec 1986 |
| 21 | Consolidated Energy Res., Inc. | | Oil Operator | Jun 1992 |
| 22 | Coquina Oil Corporation | Houston, TX 77227 | Oil & Gas Operator | Mar 2015 |
| 23 | Cross Development Co. | | Oil Operator | Dec 1989 |
| 24 | Cross Development-MMHS PRTSHP. | | Oil Operator | May 1987 |
| 25 | Cross Development1984-1 PRTSHP | | Oil & Gas Operator | Sep 1990 |
| 26 | Crossroads Energy Development, LLC | | Oil Operator | Mar 2018 |
| 27 | Crosstex Treating Services, L.P. | | Oil Operator | Sep 2009 |
| 28 | Crown Zellerbach | | Oil & Gas Operator | May 1986 |
| 29 | CSC, Inc. | | Oil Operator | Jan 2000 |
| 30 | Curtis Beard & Huston P. Ganey | | Oil Operator | Mar 1987 |