| 1 | D & G Operating Company, Inc. | Houston, TX 77056 | Oil & Gas Operator | Oct 2025 |
| 2 | D & P Operating & Prod. Corp. | Cedar Park, TX 78613 | Oil & Gas Operator | Dec 2003 |
| 3 | D-Mil Production Inc | Argyle, TX 76226 | Oil & Gas Operator | Oct 2025 |
| 4 | Daf Operating, LLC | Houston, TX 77005 | Oil & Gas Operator | Oct 2025 |
| 5 | Dallas Operating Corp. | Dallas, TX 75205 | Oil & Gas Operator | Nov 2006 |
| 6 | Daniels Corporation, The | Seabrook, TX 77586 | Oil & Gas Operator | Oct 2025 |
| 7 | Daubert Operating, L.L.C. | San Antonio, TX 78209 | Oil Operator | Oct 2025 |
| 8 | Davis Bros. Oil Producers, Inc. | Tulsa, OK 74119 | Oil & Gas Operator | Apr 2020 |
| 9 | Daylight Petroleum LLC | Houston, TX 77052 | Oil & Gas Operator | Oct 2025 |
| 10 | Daystar Operating Company, LLC | Austin, TX 78750 | Oil & Gas Operator | Apr 2008 |
| 11 | Delta Exploration Company Inc | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 12 | Denbury Onshore, LLC | Plano, TX 75024 | Oil & Gas Operator | Oct 2025 |
| 13 | Devon Energy Operating Corp | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2013 |
| 14 | Devon Energy Production Company LP | Oklahoma City, OK 73102 | Oil & Gas Operator | Oct 2025 |
| 15 | Devon Louisiana Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2019 |
| 16 | Diamond S Energy Company | Fort Worth, TX 76132 | Oil & Gas Operator | Oct 2025 |
| 17 | DJH Investments, Inc. | Houston, TX 77024 | Oil Operator | Oct 2025 |
| 18 | DKM Resources, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Sep 2011 |
| 19 | DKW Energy, Inc. | Sherman Oaks, CA 91403 | Oil & Gas Operator | Oct 2025 |
| 20 | Dominion Oklahoma Texas E&P, Inc | Richmond, VA 23219 | Oil & Gas Operator | Sep 2018 |
| 21 | Douglas Petroleum Inc. | Spring, TX 77379 | Oil & Gas Operator | Nov 2010 |
| 22 | Dreyfus, Louis Natural Gas Corp | Oklahoma City, OK 73134 | Oil & Gas Operator | Nov 2001 |
| 23 | Duncan Energy LLC | Dallas, TX 75231 | Oil & Gas Operator | Oct 2025 |
| 24 | Dyersdale Energy, L.P. | Kilgore, TX 75663 | Oil & Gas Operator | Oct 2025 |