| 501 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | Jul 2025 |
| 502 | Texas Crude Energy, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 2012 |
| 503 | Texas Crude, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 1995 |
| 504 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | Jul 2025 |
| 505 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 506 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 507 | Texas Meridian Res. Expl., Inc. | Houston, TX 77079 | Oil & Gas Operator | Jun 1998 |
| 508 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Jul 2025 |
| 509 | Texas Standard Oil Operating Co. | Midland, TX 79705 | Oil & Gas Operator | Oct 2019 |
| 510 | Texcal Energy (GP) LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2016 |
| 511 | Tharp Operating Company | Houston, TX 77070 | Oil & Gas Operator | Nov 2014 |
| 512 | Thorp Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2014 |
| 513 | Timberwolf Energy, Inc. | Houston, TX 77042 | Oil & Gas Operator | Jul 2025 |
| 514 | Titan Allen Dome LLC | Houston, TX 77056 | Oil Operator | Feb 2015 |
| 515 | Titan Energy Operating LLC | Houston, TX 77056 | Oil Operator | Jan 2016 |
| 516 | TMR Exploration, Inc. | Bossier City, LA 71171 | Oil & Gas Operator | Jul 2025 |
| 517 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 518 | Torrent Oil LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 519 | Transfuel Resources Co | Houston, TX 77215 | Oil & Gas Operator | Aug 2013 |
| 520 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 521 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 522 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 523 | Tri-Union Development Corp. | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 524 | Triangle Development Co | Mahtomedi, MN 55115 | Gas Operator | Feb 1982 |
| 525 | Trinidad Resources, LLC | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2025 |
| 526 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 527 | Trio Operating Company, Inc. | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2006 |
| 528 | Triple J Investments Inc | Longview, TX 75606 | Oil & Gas Operator | Feb 2023 |
| 529 | Tristar Exploration, Inc | Pflugerville, TX 78660 | Oil & Gas Operator | Jul 2025 |
| 530 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Jul 2025 |
| 531 | TX Lone Star Operating Co, LLC | Sulphur SPGS, TX 75483 | Oil & Gas Operator | Jul 2025 |
| 532 | Txla Energy, Inc. | Houston, TX 77018 | Oil & Gas Operator | Jul 2025 |
| 533 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 534 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | Jul 2025 |
| 535 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 536 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 537 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 538 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 539 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Jul 2025 |
| 540 | Vandeveer Energy, LLC | Dallas, TX 75225 | Oil & Gas Operator | Jul 2016 |
| 541 | Ventex Operating Corp. | Addison, TX 75001 | Oil & Gas Operator | Jul 2025 |
| 542 | Ventum Oil And Gas, LP | Northbrook, IL 60062 | Oil & Gas Operator | Mar 2010 |
| 543 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 544 | Viceroy Petroleum, LP | College Sta, TX 77845 | Oil & Gas Operator | Jul 2025 |
| 545 | Viesca Gas Co. | Spring, TX 77379 | Oil & Gas Operator | Jul 2025 |
| 546 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Apr 2025 |
| 547 | Wacker Oil Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 1996 |
| 548 | Wadi Petroleum Inc | Houston, TX 77014 | Oil & Gas Operator | May 2018 |
| 549 | Wagner & Brown, LTD. | Midland, TX 79702 | Oil & Gas Operator | Aug 2014 |
| 550 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Jul 2025 |
| 551 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 552 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 553 | Warbonnet Exploration Company | Houston, TX 77056 | Oil & Gas Operator | Apr 2016 |
| 554 | Weber Energy Corporation | Dallas, TX 75219 | Oil & Gas Operator | Feb 2017 |
| 555 | Welder Exploration & Prod., Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Dec 2022 |
| 556 | Wheeler Operating Corporation | Fort Worth, TX 76101 | Oil & Gas Operator | Jul 2025 |
| 557 | White Marlin Operating Company, LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 558 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Jul 2025 |
| 559 | Whitehead Prod. Co., Inc. | Humble, TX 77338 | Oil & Gas Operator | May 2025 |
| 560 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 561 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Jan 2025 |
| 562 | Whitson, James A., Jr. | Houston, TX 77063 | Oil & Gas Operator | Nov 2011 |
| 563 | Wild Cat Operating Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 564 | Williams, Clayton Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | Jul 2025 |
| 565 | Williams, Clayton Energy, L.L.C | Midland, TX 79705 | Oil & Gas Operator | May 1993 |
| 566 | Williams, Clayton W., Jr., Inc. | Midland, TX 79705 | Oil & Gas Operator | Mar 2008 |
| 567 | Williams-Cody, Inc. | Houston, TX 77060 | Oil & Gas Operator | May 1994 |
| 568 | Wimco | Dallas, TX 75229 | Oil & Gas Operator | Jul 2008 |
| 569 | Wing Corporation | Houston, TX 77002 | Oil & Gas Operator | Jun 2000 |
| 570 | Winn Exploration Co., Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Jul 2025 |
| 571 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2023 |
| 572 | Wolverine Exploration Company | Houston, TX 77002 | Oil & Gas Operator | May 2019 |
| 573 | Woodard Energy Company | Houston, TX 77042 | Oil & Gas Operator | Mar 2010 |
| 574 | WRT Energy Corporation | Oklahoma City, OK 73118 | Oil & Gas Operator | May 1998 |
| 575 | Wynn-Crosby Operating, LTD. | Dallas, TX 75201 | Oil & Gas Operator | Jul 2025 |
| 576 | Xog Resources, LLC | Spring, TX 77379 | Oil & Gas Operator | Jul 2025 |
| 577 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Jul 2025 |
| 578 | Yordes Energy, LLC | El Campo, TX 77437 | Oil Operator | Jul 2025 |
| 579 | Yuma Petroleum Company | Houston, TX 77027 | Oil & Gas Operator | Aug 2002 |
| 580 | Zachry Exploration, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | Jul 2025 |
| 581 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | Jul 2025 |
| 582 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |
| 583 | Zenergy Inc | Tulsa, OK 74136 | Oil & Gas Operator | May 2025 |
| 584 | Zinke & Trumbo, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2007 |
| 585 | Zinn Petroleum Co. | Houston, TX 77024 | Oil & Gas Operator | Nov 2021 |