| 301 | Trident Oil & Gas Corp. | | Oil & Gas Operator | Sep 2000 |
| 302 | Trigon Exploration, Inc. | | Oil & Gas Operator | Jan 1999 |
| 303 | Trinidad Petroleum Corporation | | Oil & Gas Operator | Apr 1990 |
| 304 | Trinity Operating (Usg), LLC | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 305 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 306 | Trinity River Energy Oper, LLC | Houston, TX 77008 | Oil & Gas Operator | May 2018 |
| 307 | Triple J Investments Inc | Longview, TX 75606 | Oil & Gas Operator | Feb 2023 |
| 308 | Triple J Oil Co. | Pampa, TX 79065 | Oil & Gas Operator | Aug 1996 |
| 309 | Triple L Oil Company | Corpus Chrsti, TX 78469 | Oil & Gas Operator | Jan 1998 |
| 310 | Triple L Operating Company LLC | Kilgore, TX 75663 | Oil Operator | Feb 2026 |
| 311 | Triple S Oil Company | | Oil & Gas Operator | Feb 1979 |
| 312 | Tripower Resources, Inc. | Ardmore, OK 73402 | Oil & Gas Operator | Mar 2020 |
| 313 | Tristar Energy 1 | | Oil Operator | Sep 1987 |
| 314 | Tristate Nla, LLC | | Oil Operator | Dec 2024 |
| 315 | Triton Oil & Gas Corp. | Houston, TX 77002 | Oil & Gas Operator | Nov 2014 |
| 316 | Triumph Energy Inc | Lafayette, LA 70505 | Oil & Gas Operator | Nov 2015 |
| 317 | Triumph Energy Inc-P B Berry | | Oil & Gas Operator | Jun 1986 |
| 318 | Troy E. Boyd | | Oil Operator | Oct 1998 |
| 319 | Trunkline Gas Company | | Oil Operator | Mar 2008 |
| 320 | Tryvest, Inc. | | Oil & Gas Operator | Sep 1991 |
| 321 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Feb 2026 |
| 322 | Tulip Industries, Inc. | | Oil & Gas Operator | Feb 2024 |
| 323 | Tundra Energy | | Oil Operator | Jan 2025 |
| 324 | Tundra Operating LLC | Spring, TX 77386 | Oil Operator | May 2017 |
| 325 | Turnkey E&P Corporation | | Oil & Gas Operator | Dec 2010 |
| 326 | TWC Oil Company, Inc. | | Oil Operator | Jan 2025 |
| 327 | Twin City Gas | | Gas Operator | Nov 1997 |
| 328 | Twiner Oil & Gas Corporation | | Oil & Gas Operator | Oct 1988 |
| 329 | Two Bayous, Inc. | | Oil & Gas Operator | Dec 2024 |
| 330 | Txla Energy, Inc. | Houston, TX 77018 | Oil & Gas Operator | Feb 2026 |
| 331 | Txo Prod Corp.-Arkla Expl. Co. | | Oil & Gas Operator | Dec 1990 |
| 332 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 333 | Txo Production Corp/Amh O&G Co | | Oil & Gas Operator | Dec 1990 |
| 334 | TXP Operating Co. | | Oil & Gas Operator | Jul 1992 |
| 335 | TXX Operating LLC | Shreveport, LA 71133 | Oil & Gas Operator | Feb 2026 |
| 336 | Ty-Tex Exploration, Inc. | Tyler, TX 75711 | Oil Operator | Dec 2000 |
| 337 | Tygr Operating Company, LLC | | Oil & Gas Operator | Nov 2024 |
| 338 | Tyler Production, LLC | | Oil & Gas Operator | Jul 2013 |
| 339 | Tysco Oil And Gas Corp. | | Oil & Gas Operator | Dec 2024 |
| 340 | Tyson Oil Co. | | Oil Operator | Jan 2025 |