| 301 | Southwestern Energy Prod Co | Houston, TX 77032 | Oil & Gas Operator | Jun 2015 |
| 302 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Jul 2025 |
| 303 | SRP Production Corp. | | Oil & Gas Operator | Nov 1997 |
| 304 | Sun Exploration-Production Co. | | Oil & Gas Operator | Jan 1990 |
| 305 | SV Energy Company, LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Mar 2017 |
| 306 | Swift Energy Operating, LLC | Houston, TX 77079 | Oil & Gas Operator | Jun 2017 |
| 307 | Synergy Oil & Gas, L.P. | Houston, TX 77024 | Oil & Gas Operator | May 2012 |
| 308 | Taurus Petroleum | | Oil & Gas Operator | Jul 1987 |
| 309 | Taylor Energy Co. | | Oil & Gas Operator | May 1991 |
| 310 | Tee Operating Company | | Oil & Gas Operator | Jun 1989 |
| 311 | Tejas Production Company | | Oil Operator | Nov 1979 |
| 312 | Tenison Oil Company | Abilene, TX 79605 | Oil & Gas Operator | Jul 2025 |
| 313 | Tenneco Oil Company | Oklahoma City, OK 73125 | Oil & Gas Operator | Apr 2025 |
| 314 | Terrier Oil Company | | Oil & Gas Operator | Feb 2015 |
| 315 | Tesoro Petroleum Corporation | | Oil & Gas Operator | May 1982 |
| 316 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Jul 2025 |
| 317 | Texaco Inc | Kingfisher, OK 73750 | Oil & Gas Operator | Dec 2017 |
| 318 | Texaco Oils, Inc. | Tulsa, OK 74102-2420 | Oil & Gas Operator | Jan 2003 |
| 319 | Texaco Producing Inc. | Rock Springs, WY 82901 | Oil & Gas Operator | Dec 2000 |
| 320 | Texas Eastern Transm. Corp. | | Oil & Gas Operator | Dec 2002 |
| 321 | Texas General Petroleum Corp | | Oil & Gas Operator | Aug 1984 |
| 322 | Texas Meridian Operating Co. Inc | Houston, TX 77079 | Oil & Gas Operator | Oct 1993 |
| 323 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Jul 2025 |
| 324 | Texegy Operating Company LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Dec 2024 |
| 325 | TGX Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2004 |
| 326 | The Southern Louisiana Expl. Company LLC | | Oil & Gas Operator | Nov 2024 |
| 327 | Three Sisters Investments, LTD | | Oil & Gas Operator | Oct 1989 |
| 328 | Todd Oil Corp. Of La. Inc. | | Oil & Gas Operator | Jul 2000 |
| 329 | Tom West | | Oil & Gas Operator | Nov 1989 |
| 330 | Trace Operators, Inc. | | Oil & Gas Operator | Nov 2024 |
| 331 | Traillour Oil Co. | | Oil & Gas Operator | Mar 1990 |
| 332 | Trans-Sabine Pipeline Corp | | Oil Operator | Mar 2009 |
| 333 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Jul 2025 |
| 334 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 335 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 336 | Triumph Energy, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Nov 2015 |
| 337 | Trunkline Gas Company | | Oil Operator | Mar 2008 |
| 338 | Tryvest, Inc. | | Oil & Gas Operator | Sep 1991 |
| 339 | Tundra Energy | | Oil Operator | Jan 2025 |
| 340 | Turnkey E&P Corporation | | Oil & Gas Operator | Dec 2010 |
| 341 | Txla Energy, Inc. | Houston, TX 77018 | Oil & Gas Operator | Jul 2025 |
| 342 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 343 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Jul 2025 |
| 344 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 345 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Jul 2025 |
| 346 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Jul 2025 |
| 347 | Vetra Exploration And Production LLC | | Oil & Gas Operator | Aug 2012 |
| 348 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Apr 2025 |
| 349 | W. B. McCarter, Jr., Inc. | | Oil & Gas Operator | Dec 1995 |
| 350 | W. G. Darsey, III | | Oil & Gas Operator | Nov 1981 |
| 351 | W. M. Morgan | | Oil Operator | Jan 1985 |
| 352 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 353 | Warhorse Oil & Gas, LLC | | Oil & Gas Operator | Dec 2018 |
| 354 | Weeks Exploration Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 355 | Wheeler Oil Company | Sperry, OK 74073-9417 | Oil & Gas Operator | Mar 2025 |
| 356 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Jul 2025 |
| 357 | Wilcox Operating Corporation | Shreveport, LA 71115 | Oil & Gas Operator | Jul 2025 |
| 358 | Will-Drill Operating, L.L.C. | Shreveport, LA 71105 | Oil & Gas Operator | Jul 2025 |
| 359 | Will-Drill Production Co., Inc. | Shreveport, LA 71105 | Oil & Gas Operator | Jul 2025 |
| 360 | William F. Powell | | Oil & Gas Operator | Jun 1979 |
| 361 | Wintershall Oil & Gas Corp | Houston, TX 77027 | Oil & Gas Operator | Jul 1989 |
| 362 | Woolf & Magee, Inc. | | Oil & Gas Operator | Oct 1991 |
| 363 | World Producers, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Nov 1994 |
| 364 | Worldwide Energy Corp. | Freer, TX 78357 | Oil & Gas Operator | Jan 1997 |
| 365 | WRT Energy Corporation | Oklahoma City, OK 73118 | Oil & Gas Operator | May 1998 |
| 366 | Wynn-Crosby Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2005 |
| 367 | Wynn-Crosby Operating, LTD. | Dallas, TX 75201 | Oil & Gas Operator | Jul 2025 |
| 368 | Yuma E & P Company, Inc. | Houston, TX 77027 | Oil & Gas Operator | Jul 2025 |
| 369 | Zadeck Energy Group Inc | | Oil & Gas Operator | Dec 2011 |