| 1 | D C Energy, Inc. | Oklahoma City, OK 73134 | Oil & Gas Operator | Apr 2020 |
| 2 | D&H-S-S Production Co.,Inc | Corpus Chrsti, TX 78409 | Oil & Gas Operator | Aug 2003 |
| 3 | Dale Operating Company | Dallas, TX 75201 | Oil & Gas Operator | Oct 2025 |
| 4 | Dalen Resources Oil & Gas Co. | Dallas, TX 75206 | Oil & Gas Operator | Jun 2010 |
| 5 | Dartex Energy Corporation | Austin, TX 78746 | Oil & Gas Operator | Oct 2025 |
| 6 | Daylight Petroleum LLC | Houston, TX 77052 | Oil & Gas Operator | Oct 2025 |
| 7 | DCP Operating Co LP | Houston, TX 77042 | Oil & Gas Operator | May 2025 |
| 8 | Decker Operating Co., L.L.C. | Houston, TX 77008 | Oil & Gas Operator | Oct 2025 |
| 9 | Dekalb Energy Company | Oklahoma City, OK 73134 | Oil & Gas Operator | Oct 1996 |
| 10 | Delaware Davis Petroleum Corp. | Houston, TX 77056 | Oil & Gas Operator | Jan 2000 |
| 11 | Delray Oil, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Oct 2025 |
| 12 | Delta Exploration Company Inc | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 13 | Denali Oil & Gas Management, LLC | Houston, TX 77060 | Oil & Gas Operator | Dec 2012 |
| 14 | Devon Energy Production Company LP | Oklahoma City, OK 73102 | Oil & Gas Operator | Oct 2025 |
| 15 | Devon Gas Services, L.P. | Oklahoma City, OK 73102 | Oil & Gas Operator | Nov 2015 |
| 16 | Devon Louisiana Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2019 |
| 17 | Dewbre Petroleum Corporation | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Oct 2025 |
| 18 | Discovery Energy Corp. CC | Corpus Chrsti, TX 78403 | Oil & Gas Operator | Oct 2025 |
| 19 | DMS Oil Company | Houston, TX 77042 | Oil & Gas Operator | Aug 2025 |
| 20 | Dominion Exploration & Production Inc | Houston, TX 77060 | Oil & Gas Operator | Apr 2015 |
| 21 | Dominion Oklahoma Texas E&P, Inc | Richmond, VA 23219 | Oil & Gas Operator | Sep 2018 |
| 22 | Dorado Drilling, Inc. | Gulfport, MS 39501 | Oil & Gas Operator | Oct 2025 |
| 23 | Double Eagle Petroleum Corp | Evansville, IN 47725 | Oil & Gas Operator | Oct 2025 |
| 24 | Double Play Oil & Gas, Inc | Portland, TX 78374 | Oil & Gas Operator | Oct 2025 |
| 25 | Dreyfus, Louis Natural Gas Corp | Oklahoma City, OK 73134 | Oil & Gas Operator | Nov 2001 |
| 26 | Duster Production, Inc. | Refugio, TX 78377 | Oil & Gas Operator | Oct 2011 |
| 27 | Dynamic Petroleum Res., Inc. | Houston, TX 77068 | Oil & Gas Operator | Jul 1994 |
| 28 | Dynamic Production, Inc. | Fort Worth, TX 76106 | Oil & Gas Operator | Oct 2025 |