| 1 | D K Cook Heirs LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2011 |
| 2 | D90 Energy, LLC | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 3 | Dalen Resources Oil & Gas Co. | Dallas, TX 75206 | Oil & Gas Operator | Jun 2010 |
| 4 | Damson Oil Corporation | Houston, TX 77210 | Oil & Gas Operator | Mar 2005 |
| 5 | Daube Company The | Ardmore, OK 73401 | Oil & Gas Operator | Jul 2025 |
| 6 | Davey Corporation | Golden, CO 80401 | Oil & Gas Operator | Aug 2025 |
| 7 | Davis Exploration | | Oil Operator | Dec 2007 |
| 8 | Davis Oil Company | Denver, CO 80202 | Oil & Gas Operator | Jun 1988 |
| 9 | DCD Inc | Gillette, WY 82716 | Oil & Gas Operator | Aug 2003 |
| 10 | Deca Energy Corporation | | Oil & Gas Operator | Aug 1986 |
| 11 | Decalta International Corp | Denver, CO 80202 | Oil & Gas Operator | Mar 2015 |
| 12 | Dekalb Energy Company | Oklahoma City, OK 73134 | Oil & Gas Operator | Oct 1996 |
| 13 | Denbury Onshore, LLC | Plano, TX 75024 | Oil & Gas Operator | Oct 2025 |
| 14 | Devon Energy Operating Corp | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2013 |
| 15 | Devon Energy Production Company LP | Oklahoma City, OK 73102 | Oil & Gas Operator | Oct 2025 |
| 16 | Devon SFS Operating Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | Mar 2008 |
| 17 | Diamond Oil & Gas LLC | Casper, WY 82604 | Oil & Gas Operator | Aug 2025 |
| 18 | Diasu Oil & Gas Co., Inc. | Houston, TX 77002 | Oil & Gas Operator | Mar 2016 |
| 19 | Dietrich Resources Corporation | | Oil & Gas Operator | Jun 2007 |
| 20 | DKM Resources, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Sep 2011 |
| 21 | DNR Oil And Gas, Inc. | Englewood, CO 80155 | Oil & Gas Operator | Aug 2025 |
| 22 | Dol Resources Inc | Rowlett, TX 75088 | Oil & Gas Operator | Aug 2025 |
| 23 | Dome Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2016 |
| 24 | Dominion Exploration & Production Inc | Houston, TX 77060 | Oil & Gas Operator | Apr 2015 |
| 25 | Duncan Energy Company | Denver, CO 80202 | Oil & Gas Operator | Mar 2008 |
| 26 | Duncan Oil Inc | Denver, CO 80210 | Oil & Gas Operator | Jun 2016 |
| 27 | Dyco Petroleum Corporation | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2015 |