| 1 | C & K Petroleum Inc | Denver, CO 80202 | Oil & Gas Operator | Apr 1984 |
| 2 | C&M Operating Company, LLC | | Oil & Gas Operator | Apr 2011 |
| 3 | Callon Petroleum Company | Natchez, MS 39120 | Oil & Gas Operator | Jan 2000 |
| 4 | Calpine Natural Gas Company | Houston, TX 77002 | Oil & Gas Operator | Apr 2002 |
| 5 | Carl Oil & Gas Co. | Bakersfield, CA 93309 | Oil & Gas Operator | Dec 1995 |
| 6 | Ceka Gas, Div Of GTC | | Oil & Gas Operator | May 1988 |
| 7 | Celeron Oil & Gas Company | | Oil & Gas Operator | Dec 1987 |
| 8 | Chesapeake Operating, Inc. | Oklahoma City, OK 73154 | Oil & Gas Operator | Jun 2025 |
| 9 | Chevron Pipe Line Company | Houston, TX 77001 | Oil Operator | Feb 2015 |
| 10 | Chevron USA Inc | Midland, TX 79706 | Oil & Gas Operator | Oct 2025 |
| 11 | Coalinga Corporation | Houston, TX 77002 | Oil & Gas Operator | May 1999 |
| 12 | Crosstex Lig, LLC | | Oil Operator | Mar 2014 |
| 13 | Crosstex Treating Services, L.P. | | Oil Operator | Sep 2009 |
| 14 | Cypress Gas Pipeline Company | | Oil Operator | Dec 1998 |
| 15 | Cypress Gas Pipeline, LLC | | Oil Operator | Sep 2019 |