| 501 | TGX Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2004 |
| 502 | Three C Exploration, LLC | Hebbronville, TX 78361 | Oil & Gas Operator | Apr 2026 |
| 503 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Apr 2026 |
| 504 | Tierra Mineral Development, L.C. | Dallas, TX 75244 | Oil & Gas Operator | Oct 1994 |
| 505 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 506 | TR Offshore, LLC | Corpus Christ, TX 78413 | Oil & Gas Operator | Apr 2026 |
| 507 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Apr 2026 |
| 508 | Traton Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Mar 2019 |
| 509 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 510 | Triple L Oil Company | Corpus Christ, TX 78469 | Oil & Gas Operator | Jan 1998 |
| 511 | Tschoepe, Arthur J. | Leakey, TX 78873 | Oil & Gas Operator | Jun 2001 |
| 512 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2026 |
| 513 | Tuthill & Barbee | Amarillo, TX 79101 | Oil & Gas Operator | Nov 1994 |
| 514 | TX Petroleum Company | Corpus Christ, TX 78412 | Oil & Gas Operator | Apr 1996 |
| 515 | Txco Resources Inc. | San Antonio, TX 78280 | Oil & Gas Operator | Apr 2026 |
| 516 | Txla Energy, Inc. | Houston, TX 77018 | Oil & Gas Operator | Apr 2026 |
| 517 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | Apr 2026 |
| 518 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 519 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 520 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 521 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 522 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 523 | Uphill Consulting LLC | Pearland, TX 77584 | Oil & Gas Operator | Apr 2026 |
| 524 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Apr 2026 |
| 525 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Apr 2026 |
| 526 | Valerius, Inc. & Zine, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Jul 1994 |
| 527 | Valerius, Robert D. Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Aug 2003 |
| 528 | Vanguard Permian, LLC | Houston, TX 77057 | Oil & Gas Operator | Nov 2018 |
| 529 | Vantage Operating, LLC | San Antonio, TX 78230 | Oil & Gas Operator | Apr 2026 |
| 530 | Vector Energy Corporation | Houston, TX 77060 | Oil & Gas Operator | Apr 2026 |
| 531 | Ventex Operating Corp. | Addison, TX 75001 | Oil & Gas Operator | Apr 2026 |
| 532 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 533 | Victoria Operating, Inc. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2026 |
| 534 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Jan 2026 |
| 535 | Viper S.W.D., LLC | El Campo, TX 77437 | Oil & Gas Operator | Apr 2026 |
| 536 | Virtex Operating Company, Inc. | Corpus Christ, TX 78401 | Oil & Gas Operator | Oct 2023 |
| 537 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 538 | Vision Oil And Gas LLC | Laredo, TX 78041 | Oil & Gas Operator | Apr 2026 |
| 539 | Vtex Energy, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2026 |
| 540 | Wadi Operating, LLC | Houston, TX 77079 | Oil & Gas Operator | Apr 2026 |
| 541 | Wadi Petroleum Inc | Houston, TX 77014 | Oil & Gas Operator | May 2018 |
| 542 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2026 |
| 543 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 544 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | Apr 2026 |
| 545 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Apr 2026 |
| 546 | Warren American Oil Co | Tulsa, OK 74147 | Oil & Gas Operator | Feb 2026 |
| 547 | Waters Eng. & Operating, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Sep 2013 |
| 548 | Welder Exploration & Prod., Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Dec 2022 |
| 549 | Western Gulf Oil & Gas Inc. | Dallas, TX 75360 | Oil & Gas Operator | Jul 2000 |
| 550 | Western Gulf Oil & Gas, LLC | Bishop, TX 78343 | Oil & Gas Operator | Apr 2026 |
| 551 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 552 | White Marlin Operating Company, LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2026 |
| 553 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Apr 2026 |
| 554 | Whitehead Prod. Co., Inc. | Humble, TX 77338 | Oil & Gas Operator | Feb 2026 |
| 555 | Whitfield Energy | Midland, TX 79702 | Oil & Gas Operator | Jan 1999 |
| 556 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Apr 2026 |
| 557 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Jan 2025 |
| 558 | Whittington Operating Company | Houston, TX 77069 | Oil & Gas Operator | Apr 2026 |
| 559 | Williams, Clayton Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | Apr 2026 |
| 560 | Wilson Hydrocarbon Inc. | Houston, TX 77066 | Oil & Gas Operator | Apr 2026 |
| 561 | Wind River Resources Inc | Tulsa, OK 74136-6381 | Oil & Gas Operator | Jun 2010 |
| 562 | Winn Exploration Co., Inc. | Corpus Christ, TX 78401 | Oil & Gas Operator | Apr 2026 |
| 563 | Wood Energy Corporation | Baytown, TX 77520 | Oil & Gas Operator | Jun 1999 |
| 564 | WRT Energy Corporation | Oklahoma City, OK 73118 | Oil & Gas Operator | May 1998 |
| 565 | Wynn-Crosby Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2005 |
| 566 | Wynne Petroleum Co. | Fort Worth, TX 76116 | Oil & Gas Operator | Nov 1997 |
| 567 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 568 | Xog Operating LLC | Midland, TX 79702 | Oil & Gas Operator | Apr 2026 |
| 569 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Apr 2026 |
| 570 | Yordes Energy, LLC | El Campo, TX 77437 | Oil Operator | Apr 2026 |