| 501 | Texas-Ohio Producing Company | Spring, TX 77383 | Oil & Gas Operator | Jul 1995 |
| 502 | Thalmann Oilfield | Carrizo SPGS, TX 78834 | Oil Operator | Dec 2025 |
| 503 | Thomas Exploration & Devel., Inc | Jourdanton, TX 78026 | Oil & Gas Operator | Dec 2025 |
| 504 | Three Forks Operating Co, LLC | Flatonia, TX 78941 | Oil & Gas Operator | Dec 2025 |
| 505 | Three J Energy, Inc. | Seguin, TX 78155 | Oil & Gas Operator | Dec 2025 |
| 506 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Dec 2025 |
| 507 | Tide West Oil Company | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2021 |
| 508 | Tidelands Oil Corporation | Crystal City, TX 78839 | Oil & Gas Operator | Aug 2003 |
| 509 | Tiki Oil & Gas, LLC | Cisco, TX 76437 | Oil & Gas Operator | Dec 2025 |
| 510 | TKL Oil Properties Inc | Konawa, OK 74849 | Oil & Gas Operator | Oct 2025 |
| 511 | Townsend Company | Abilene, TX 79608 | Oil & Gas Operator | Dec 2021 |
| 512 | Trailblazer Energy Resources, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Dec 2025 |
| 513 | Transamerica Energy Corp. | Atlanta, GA 30356 | Oil & Gas Operator | Dec 2025 |
| 514 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Dec 2025 |
| 515 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 516 | Trident Corporation | Woodsboro, TX 78393 | Oil & Gas Operator | Dec 2025 |
| 517 | Trinity Operating (Usg), LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 518 | Trio Production Company, LLC | Stephens, AR 71764 | Oil Operator | Jan 2025 |
| 519 | Tristar Oil & Gas | Freer, TX 78357 | Oil & Gas Operator | Dec 2025 |
| 520 | Tug Hill Operating, LLC | Fort Worth, TX 76107 | Oil & Gas Operator | Dec 2021 |
| 521 | Tundra Operating LLC | Spring, TX 77386 | Oil Operator | May 2017 |
| 522 | Turner, M. O. | San Antonio, TX 78278 | Oil & Gas Operator | Apr 2003 |
| 523 | TX Petroleum Company | Corpus Chrsti, TX 78412 | Oil & Gas Operator | Apr 1996 |
| 524 | U. D. Man, Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Dec 2025 |
| 525 | U.S.A. Plugging Company | Pearsall, TX 78061 | Oil & Gas Operator | Dec 2025 |
| 526 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 527 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Dec 2025 |
| 528 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Dec 2025 |
| 529 | Vanguard Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Aug 2019 |
| 530 | Vargas Oil & Gas | San Antonio, TX 78240 | Oil Operator | Dec 2025 |
| 531 | Vastar Resources Inc | Houston, TX 77253 | Oil & Gas Operator | Sep 2025 |
| 532 | Venado Operating Company LLC | Austin, TX 78738 | Oil & Gas Operator | Mar 2022 |
| 533 | Venus Exploration, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2013 |
| 534 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 535 | Verdun Oil & Gas LLC | Houston, TX 77024 | Oil & Gas Operator | Dec 2025 |
| 536 | Verdun Oil Ef II LLC | Houston, TX 77024 | Oil & Gas Operator | Dec 2025 |
| 537 | Vermillion Production, Inc. | Pearsall, TX 78061 | Oil & Gas Operator | Dec 2025 |
| 538 | Viceroy Petroleum, LP | College Sta, TX 77845 | Oil & Gas Operator | Dec 2025 |
| 539 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Dec 2025 |
| 540 | Virtex Operating Company, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2023 |
| 541 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 542 | Voyager Gas Corporation | Spring, TX 77379 | Oil & Gas Operator | Feb 2012 |
| 543 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Dec 2025 |
| 544 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 545 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | Dec 2025 |
| 546 | Wapiti Operating, LLC | Houston, TX 77043 | Oil & Gas Operator | Dec 2025 |
| 547 | Warwick-Artemis, LLC | Nichols Hill, OK 73116 | Oil & Gas Operator | Dec 2025 |
| 548 | Waters Eng. & Operating, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Sep 2013 |
| 549 | Watson Energy Investments, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Dec 2025 |
| 550 | Wen-Be | Jourdanton, TX 78026 | Oil & Gas Operator | Dec 2025 |
| 551 | White Creek Energy | Three Rivers, TX 78071 | Oil & Gas Operator | Dec 2025 |
| 552 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Dec 2025 |
| 553 | Wilbanks, Bruce A. Company | Midland, TX 79702 | Oil & Gas Operator | Dec 2025 |
| 554 | Wiley Lease Co., LTD. | Jourdanton, TX 78026 | Oil Operator | Dec 2025 |
| 555 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2023 |
| 556 | WJC, Inc. | Post, TX 79356 | Oil & Gas Operator | Dec 2025 |
| 557 | Wofford, C. J. | El Campo, TX 77437 | Oil & Gas Operator | Dec 2025 |
| 558 | WSM | New Braunfels, TX 78132 | Oil Operator | Dec 2025 |
| 559 | WTXR Operating (Texas), Inc. | Carrollton, TX 75007 | Oil Operator | Dec 2025 |
| 560 | Wynn-Crosby Operating, LTD. | Dallas, TX 75201 | Oil & Gas Operator | Dec 2025 |
| 561 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Dec 2025 |
| 562 | York & Price Petroleum Corp. | San Antonio, TX 78218 | Oil & Gas Operator | Jul 2004 |
| 563 | Zapata-Fender, L. L. C. | Tyler, TX 75710 | Oil & Gas Operator | Apr 2001 |
| 564 | Zavala Independent Gas, Inc. | San Antonio, TX 78217 | Oil & Gas Operator | Oct 2007 |