| 1 | T & L Production Company | | Oil Operator | Feb 1984 |
| 2 | T. L. James & Co., Inc. | | Oil & Gas Operator | Oct 1992 |
| 3 | T. M. Hopkins | | Oil & Gas Operator | Aug 2007 |
| 4 | T. N. T. Energy Co. | Belcher, LA 71004 | Oil Operator | May 1991 |
| 5 | T.O.I. | Midland, TX 79710 | Oil & Gas Operator | Mar 2001 |
| 6 | Taggart Oil Co., Inc. | | Oil Operator | Oct 1992 |
| 7 | Tanos Exploration II, LLC | Tyler, TX 75701 | Oil & Gas Operator | Sep 2023 |
| 8 | TDX Energy, LLC | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2024 |
| 9 | Tellurian Operating LLC | | Oil & Gas Operator | Jun 2024 |
| 10 | Tensas Delta Expl Co., LLC | Shreveport, LA 71101-5323 | Oil & Gas Operator | Jul 2021 |
| 11 | Texas Eastern Transm. Corp. | | Oil & Gas Operator | Dec 2002 |
| 12 | Texas Oil & Gas Corporation | Dallas, TX 75201 | Oil & Gas Operator | Feb 2001 |
| 13 | Texex Petroleum Corporation | | Oil & Gas Operator | Dec 2024 |
| 14 | The Maurice L. Brown Company | | Oil & Gas Operator | Aug 1987 |
| 15 | Thomas E. Slack | | Oil Operator | Mar 2003 |
| 16 | Tierra Petroleum Corp. | | Oil & Gas Operator | Jun 1987 |
| 17 | Tigner Walker | | Oil & Gas Operator | Dec 2021 |
| 18 | Tipco Operating Co. | Marshall, TX 75671 | Oil & Gas Operator | Dec 2025 |
| 19 | Tma Production, LLC | | Oil Operator | Dec 2024 |
| 20 | TMR Exploration, Inc. | Bossier City, LA 71171 | Oil & Gas Operator | Dec 2025 |
| 21 | Total E&P USA, Inc. | Houston, TX 77210 | Oil & Gas Operator | May 2025 |
| 22 | Totalfinaelf E&P USA Inc | Houston, TX 77024 | Oil & Gas Operator | Jul 2007 |
| 23 | Trafalgar House Oil & Gas Inc | Houston, TX 77002-7346 | Oil & Gas Operator | Jan 1992 |
| 24 | Transcontinental Oil Corp. | | Oil & Gas Operator | Sep 1985 |
| 25 | Triple L Oil Company | Corpus Chrsti, TX 78469 | Oil & Gas Operator | Jan 1998 |
| 26 | Tristate Nla, LLC | | Oil Operator | Dec 2024 |
| 27 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |