| 1 | Damson Oil Corporation | Houston, TX 77210 | Oil & Gas Operator | Mar 2005 |
| 2 | Daniel Oil Company | | Oil & Gas Operator | Jan 1983 |
| 3 | Davis Oil Company | Denver, CO 80202 | Oil & Gas Operator | Jun 1988 |
| 4 | Dawson Exploration, Inc. | | Oil & Gas Operator | Jun 1986 |
| 5 | Daylight Petroleum LLC | Houston, TX 77052 | Oil & Gas Operator | Oct 2025 |
| 6 | DBL DRLG.&Prod. Services, Inc. | | Oil & Gas Operator | Jul 1997 |
| 7 | Dean Enterprises, Inc. | | Oil & Gas Operator | Jun 2019 |
| 8 | Deck Oil Company | Tulsa, OK 74101 | Oil & Gas Operator | Jun 2020 |
| 9 | Delta Energy Resources, Inc. | | Oil & Gas Operator | Jun 1990 |
| 10 | Deltaus Corporation | | Oil & Gas Operator | Oct 1985 |
| 11 | Denali Oil & Gas Management, LLC | Houston, TX 77060 | Oil & Gas Operator | Dec 2012 |
| 12 | Denovo Oil & Gas, Inc. | Houston, TX 77210 | Oil & Gas Operator | May 1995 |
| 13 | Devon Energy Operating Co., L.P. | Oklahoma City, OK 73102 | Oil & Gas Operator | Jun 2009 |
| 14 | Di Energy Inc. | Houston, TX 77067 | Oil & Gas Operator | Jan 2004 |
| 15 | Diamond D Operating | | Oil & Gas Operator | Apr 1995 |
| 16 | Dimension Energy Co., L.L.C. | | Oil & Gas Operator | Dec 2024 |
| 17 | Discovery Energy, LLC | | Oil Operator | Jan 2007 |
| 18 | Discovery Operating, LLC | | Oil & Gas Operator | Oct 2023 |
| 19 | Dome De Sel LLC | | Oil & Gas Operator | Nov 2024 |
| 20 | Dome Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2016 |
| 21 | Dow Intrastate Gas Company | | Oil Operator | Dec 2023 |
| 22 | Duer Wagner & Company | Fort Worth, TX 76102 | Oil & Gas Operator | Dec 1998 |
| 23 | Duncan Oil Inc | Denver, CO 80210 | Oil & Gas Operator | Jun 2016 |
| 24 | Dune Operating Company | Dallas, TX 75201 | Oil & Gas Operator | Jun 2016 |
| 25 | Dunn Exploration Company, LLC | | Oil & Gas Operator | Jan 2025 |
| 26 | Dynaco, Incorporated | | Oil & Gas Operator | Dec 1980 |