| 1 | C & K Petroleum | | Oil & Gas Operator | Jan 1984 |
| 2 | Cabot Oil & Gas Corporation | Houston, TX 77024 | Oil & Gas Operator | Nov 2025 |
| 3 | Caerus Northern Rockies LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2021 |
| 4 | Cambria Oil Company | Casper, WY 82601 | Oil & Gas Operator | Dec 1996 |
| 5 | Carol-Holly Oil Corporation | Denver, CO 80237 | Oil & Gas Operator | Dec 2025 |
| 6 | Carolla And Hay | | Gas Operator | Aug 1983 |
| 7 | Celsius Energy Company | Denver, CO 80202-1558 | Oil & Gas Operator | Mar 2000 |
| 8 | Cenex | | Oil & Gas Operator | Dec 1996 |
| 9 | Chaco Energy Company | Denver, CO 80201 | Oil & Gas Operator | Jan 2026 |
| 10 | Chambers Jerry | Denver, CO 80237 | Oil & Gas Operator | Dec 1993 |
| 11 | Chaparral Energy, L.L.C. | Oklahoma City, OK 73142 | Oil & Gas Operator | Feb 2026 |
| 12 | Chevron USA Inc | Midland, TX 79706 | Oil & Gas Operator | Feb 2026 |
| 13 | Chriscor Oil & Gas | Plana, TX 75075 | Oil & Gas Operator | Jul 1987 |
| 14 | Christmann John J | Lubbock, TX 79401 | Oil & Gas Operator | Dec 1994 |
| 15 | Cig Exploration | Denver, CO 80201 | Oil & Gas Operator | Sep 1999 |
| 16 | Coastal Chem Inc | Midvale, UT 84047 | Oil & Gas Operator | Aug 2003 |
| 17 | Coastal Oil & Gas Corp | Houston, TX 77252 | Oil & Gas Operator | Dec 2009 |
| 18 | Cobra Oil & Gas Corporation | Wichita Falls, TX 76307 | Oil & Gas Operator | Feb 2026 |
| 19 | Cody Energy, Inc. | Houston, TX 77077 | Oil & Gas Operator | Dec 2025 |
| 20 | Cohort Energy Company | Centennial, CO 80112 | Oil & Gas Operator | Feb 2007 |
| 21 | Coleman Oil & Gas Inc | Farmington, NM 87499 | Oil & Gas Operator | Jan 2023 |
| 22 | Colt Resources Corporation | Billings, MT 59103 | Oil & Gas Operator | Feb 2013 |
| 23 | Columbine Exploration Corp | Englewood, CO 80111 | Oil & Gas Operator | Aug 1998 |
| 24 | Conoco Inc | Houston, TX 77252 | Oil & Gas Operator | Mar 2015 |
| 25 | ConocoPhillips Company | Midland, TX 79701 | Oil & Gas Operator | Feb 2026 |
| 26 | Contango Resources LLC | Andrews, TX 79714 | Oil & Gas Operator | Feb 2026 |
| 27 | Continental Industries LC | Casper, WY 82602 | Oil & Gas Operator | Feb 2008 |
| 28 | Cotton Petroleum Corporation | Tulsa, OK 74102 | Oil & Gas Operator | Jan 2005 |
| 29 | Crowheart Energy LLC | Baggs, WY 82321 | Oil & Gas Operator | Nov 2025 |
| 30 | Crown Energy Partners LLC | Englewood, CO 80112 | Oil & Gas Operator | Sep 2013 |
| 31 | Crown Oil & Gas Co Inc | Labarge, WY 83123 | Oil & Gas Operator | Jan 2023 |