| 1 | C & K Petroleum Inc | Denver, CO 80202 | Oil & Gas Operator | Apr 1984 |
| 2 | Cajun Minerals, Inc. | | Oil & Gas Operator | Mar 1997 |
| 3 | California Time Petroleum, Inc | | Oil Operator | Mar 1986 |
| 4 | Carrollton Resources Corp. | | Oil & Gas Operator | Sep 2000 |
| 5 | Castle Exploration Company Inc | Blue Bell, PA 19422 | Oil & Gas Operator | May 2018 |
| 6 | Castlerock Oil Company, Inc. | Addison, TX 75001 | Oil & Gas Operator | Feb 2006 |
| 7 | Chaparral Energy, Inc. | Oklahoma City, OK 73114 | Oil & Gas Operator | Dec 2009 |
| 8 | Chaparral Energy, L.L.C. | Oklahoma City, OK 73142 | Oil & Gas Operator | Oct 2025 |
| 9 | Chesapeake Operating, Inc. | Oklahoma City, OK 73154 | Oil & Gas Operator | Jun 2025 |
| 10 | Chevron USA Inc | Midland, TX 79706 | Oil & Gas Operator | Oct 2025 |
| 11 | Cities Service Company | | Oil & Gas Operator | Mar 1983 |
| 12 | Cities Service Oil & Gas Corp | | Oil & Gas Operator | Mar 1988 |
| 13 | Cities Service Oil Co. | | Oil & Gas Operator | Dec 1986 |
| 14 | Clayton W. Williams, Jr. | | Oil & Gas Operator | Sep 1986 |
| 15 | Clayton W. Williams, Jr., Inc. | | Oil & Gas Operator | May 1993 |
| 16 | Clayton Williams Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | Apr 2017 |
| 17 | Coastal Oil & Gas Corporation | Houston, TX 77252 | Oil & Gas Operator | Dec 2009 |
| 18 | Coastal Plains Exploration, LLC | Port Lavaca, TX 77979 | Oil & Gas Operator | Oct 2025 |
| 19 | Coastal States Gas Prod. Co. | | Oil & Gas Operator | Jun 1996 |
| 20 | Cody Energy, Inc. | Houston, TX 77077 | Oil & Gas Operator | Aug 2025 |
| 21 | Creek Operating Company, Inc. | Dallas, TX 75205 | Oil & Gas Operator | Sep 1998 |
| 22 | Crosstex Lig, LLC | | Oil Operator | Mar 2014 |
| 23 | Cypress Gas Pipeline Company | | Oil Operator | Dec 1998 |
| 24 | Cypress Gas Pipeline, LLC | | Oil Operator | Sep 2019 |
| 25 | Cypress Operating, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Oct 2025 |