| 1 | D & W Oil & Gas Co. | | Gas Operator | Jan 1990 |
| 2 | D-Ram Construction Co., Inc. | | Gas Operator | Dec 1990 |
| 3 | D. J. Simmons & Co. Of La. | | Gas Operator | Nov 1996 |
| 4 | Daleco Resources | | Gas Operator | Dec 2000 |
| 5 | David L. Whittington | | Gas Operator | Dec 1998 |
| 6 | David L. Whittington Inc | | Gas Operator | Sep 2022 |
| 7 | DCP Midstream, LLC | | Oil Operator | Jun 2016 |
| 8 | Delhi Gas Pipeline Corporation | Palestine, TX 75802 | Oil & Gas Operator | Feb 1998 |
| 9 | Devon Energy Corporation | Oklahoma City, OK 73102 | Oil & Gas Operator | Dec 2009 |
| 10 | Devon Energy Operating Co., L.P. | Oklahoma City, OK 73102 | Oil & Gas Operator | Jun 2009 |
| 11 | Devon Energy Production Company LP | Oklahoma City, OK 73102 | Oil & Gas Operator | Oct 2025 |
| 12 | Devon Louisiana Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2019 |
| 13 | Diablo Oil Corp. | | Oil & Gas Operator | Apr 1989 |
| 14 | Diamond Shamrock Corp | Amarillo, TX 79105 | Oil & Gas Operator | Jan 1987 |
| 15 | Diamond Shamrock Expl. Co. | | Oil & Gas Operator | Jun 1987 |
| 16 | Ditta Exploration Co., Inc. | | Oil & Gas Operator | Feb 1990 |
| 17 | Drake Energy Corporation | | Gas Operator | Dec 2024 |
| 18 | DRD Operating Company | | Oil & Gas Operator | Feb 2014 |
| 19 | Drum Energy, L.L.C. | | Gas Operator | Dec 2016 |
| 20 | Dubach Gas Company | | Oil Operator | May 2003 |
| 21 | Duke Energy Field Services LLC | | Oil Operator | Dec 2006 |