| 501 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 502 | Tag Operating Company, Inc. | Houston, TX 77092 | Oil & Gas Operator | Jul 2025 |
| 503 | Talos Gulf Coast Onshore LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2024 |
| 504 | Tap Operating Company, Inc. | Mexia, TX 76667 | Oil & Gas Operator | May 1995 |
| 505 | Tartan Resources Corporation | Houston, TX 77251 | Oil & Gas Operator | Oct 1995 |
| 506 | Taylor-McIlhenny Oper. Co., Inc. | Lewisville, TX 75029 | Oil & Gas Operator | Jan 1996 |
| 507 | TC Oil And Gas, LLC | Denton, TX 76205 | Oil Operator | Jul 2025 |
| 508 | Te-Ray Resources, Inc. | Oklahoma City, OK 73108 | Oil & Gas Operator | Mar 2015 |
| 509 | Tema Oil And Gas Company | Houston, TX 77084 | Oil & Gas Operator | Jul 2025 |
| 510 | Tema Oil And Gas, LLC | Houston, TX 77040 | Oil & Gas Operator | Apr 2000 |
| 511 | Templeton Oil, Inc. | Houston, TX 77002 | Oil & Gas Operator | Nov 1994 |
| 512 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 513 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Jul 2025 |
| 514 | Texakota, Inc. | Houston, TX 77098 | Oil & Gas Operator | Mar 2021 |
| 515 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | Jul 2025 |
| 516 | Texas American Resources Company | Austin, TX 78701 | Oil & Gas Operator | Jul 2025 |
| 517 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | Jul 2025 |
| 518 | Texas Land & Trading Co, Inc. | Austin, TX 78734 | Oil & Gas Operator | Mar 2008 |
| 519 | Texas Oil Company, The | Houston, TX 77018 | Oil & Gas Operator | Aug 2006 |
| 520 | Texas, Les & Co. | Austin, TX 78746 | Oil & Gas Operator | Jul 2025 |
| 521 | Texcal Energy (GP) LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2016 |
| 522 | Texian Operating Company, LLC | Irving, TX 75063 | Oil & Gas Operator | Jul 2025 |
| 523 | Thornberry Oilfield Service, Inc | Conroe, TX 77302 | Oil & Gas Operator | Aug 2003 |
| 524 | Threshold Development Company | Fort Worth, TX 76109 | Oil & Gas Operator | Aug 2016 |
| 525 | Titus Liberty Multi Well 2, LLC | Irving, TX 75063 | Oil & Gas Operator | Jul 2025 |
| 526 | Tomlinson, Thomas K. Inc. | Port Lavaca, TX 77979 | Oil & Gas Operator | Jul 2003 |
| 527 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 528 | Torrent Oil LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 529 | Transoil, Inc. | Oklahoma City, OK 73129 | Oil & Gas Operator | Jul 2025 |
| 530 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 531 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 532 | Tri-Union Development Corp. | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 533 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 534 | Trinity River Operating Company | Oklahoma City, OK 73147 | Oil & Gas Operator | Jul 2025 |
| 535 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 536 | Union Crude Operating Co. | Baytown, TX 77521 | Oil Operator | Aug 2003 |
| 537 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 538 | Union Seaboard Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 539 | Upstream Properties, LLC | Southlake, TX 76092 | Oil & Gas Operator | Jul 2025 |
| 540 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Jul 2025 |
| 541 | Utility Ventures Company | Pasadena, TX 77504 | Oil & Gas Operator | Jul 2025 |
| 542 | Valley Gathering Company | Midland, TX 79702 | Oil & Gas Operator | Feb 1997 |
| 543 | Vantage Operating, LLC | San Antonio, TX 78230 | Oil & Gas Operator | Jul 2025 |
| 544 | Vanya Oil & Gas, Inc. | Hardin, TX 77561 | Oil & Gas Operator | Jul 2025 |
| 545 | Veracity Energy LLC | The Woodlands, TX 77380 | Oil & Gas Operator | Aug 2023 |
| 546 | Viesca Gas Co. | Spring, TX 77379 | Oil & Gas Operator | Jul 2025 |
| 547 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Apr 2025 |
| 548 | Virlar Exploration, Inc. | Houston, TX 77227 | Oil & Gas Operator | Aug 1995 |
| 549 | Votaw Production Company LLC | Houston, TX 77007 | Oil Operator | Jul 2025 |
| 550 | W & T Offshore, L.L.C. | Houston, TX 77046 | Gas Operator | Jan 1999 |
| 551 | Wadi Petroleum Inc | Houston, TX 77014 | Oil & Gas Operator | May 2018 |
| 552 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Jul 2025 |
| 553 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 554 | Waldrop, L. E. | Houston, TX 77024 | Oil & Gas Operator | Jun 1996 |
| 555 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 556 | Weatherly Oil & Gas, LLC | Dallas, TX 75206 | Oil & Gas Operator | Jul 2025 |
| 557 | Weber Energy Corporation | Dallas, TX 75219 | Oil & Gas Operator | Feb 2017 |
| 558 | Well-Co Solutions, LLC | Batson, TX 77519 | Oil Operator | Jul 2025 |
| 559 | Western Energy Group, LLC | Leander, TX 78641 | Oil & Gas Operator | Jul 2025 |
| 560 | Western Gulf Oil & Gas Inc. | Dallas, TX 75360 | Oil & Gas Operator | Jul 2000 |
| 561 | Westhall Associates, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Aug 1997 |
| 562 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 563 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 564 | Weststar Oil & Gas Inc | Edmond, OK 73013 | Oil & Gas Operator | May 2025 |
| 565 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Jul 2025 |
| 566 | Whitson, James A., Jr. | Houston, TX 77063 | Oil & Gas Operator | Nov 2011 |
| 567 | Whittington Operating Company | Houston, TX 77069 | Oil & Gas Operator | Jul 2025 |
| 568 | Wild Cat Operating Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 569 | Willow Creek Resources, Inc. | Midland, TX 79702 | Oil & Gas Operator | Feb 2009 |
| 570 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2023 |
| 571 | WJH Energy, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Jul 2025 |
| 572 | Wolfson, I. J. | Wichita Falls, TX 76301 | Oil & Gas Operator | Apr 2002 |
| 573 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Jul 2025 |
| 574 | Yordes Energy, LLC | El Campo, TX 77437 | Oil Operator | Jul 2025 |
| 575 | York E & P, LLC | Boling, TX 77420 | Oil & Gas Operator | Jul 2025 |
| 576 | Young, John H., Inc. | Houston, TX 77027 | Oil & Gas Operator | Jul 2025 |
| 577 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |
| 578 | Zackson Resources, Inc. | Houston, TX 77063 | Oil & Gas Operator | Jul 2025 |
| 579 | Zilkha Energy Company | Houston, TX 77046 | Oil & Gas Operator | Oct 2002 |
| 580 | Zinn Petroleum Co. | Houston, TX 77024 | Oil & Gas Operator | Nov 2021 |