| 1 | D. G. Oil Co. | Dennis, TX 76439 | Oil & Gas Operator | Oct 2025 |
| 2 | D. Shel Oil, Inc. | Gonzales, TX 78629 | Oil Operator | Oct 2025 |
| 3 | Dakota Resources, Inc. (I) | Midland, TX 79707 | Oil & Gas Operator | Oct 2025 |
| 4 | Dantex Oil & Gas, Inc. | Dallas, TX 75225 | Oil & Gas Operator | Aug 2003 |
| 5 | Davenport Oil Company | Luling, TX 78648 | Oil & Gas Operator | Dec 1996 |
| 6 | DCP Operating Co LP | Houston, TX 77042 | Oil & Gas Operator | May 2025 |
| 7 | Dee-Jay Exploration Company | Nichols Hill, OK 73116 | Oil & Gas Operator | Oct 2025 |
| 8 | Delcar, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Oct 1995 |
| 9 | Delco Operating Company LP | Houston, TX 77056 | Oil & Gas Operator | May 2020 |
| 10 | Delong, Horace | Pleasanton, TX 78064 | Oil & Gas Operator | Oct 2025 |
| 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 | Di Energy Inc. | Houston, TX 77067 | Oil & Gas Operator | Jan 2004 |
| 17 | Diamond M DRLG & Expl Co. | San Antonio, TX 78217 | Oil & Gas Operator | Oct 2025 |
| 18 | Dinero Oil Corporation | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Nov 1999 |
| 19 | Dirnett, Inc. | Tuleta, TX 78162 | Oil & Gas Operator | Oct 2025 |
| 20 | Dolch Production, Inc. | San Antonio, TX 78248 | Oil & Gas Operator | Jul 1996 |
| 21 | Dominion Minerals Corporation | Houston, TX 77014 | Oil & Gas Operator | Nov 2009 |
| 22 | Dominion Production Company, LLC | Tampa, FL 33606 | Oil & Gas Operator | Oct 2025 |
| 23 | Dorado Oil Company | Corpus Chrsti, TX 78403 | Oil & Gas Operator | Oct 2013 |
| 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 | Driscoll S.W.D. Inc. | San Antonio, TX 78229 | Oil & Gas Operator | Oct 2025 |