| 601 | Synergy Production Company | Houston, TX 77024 | Oil & Gas Operator | Jan 1996 |
| 602 | Tag Operating Company, Inc. | Houston, TX 77092 | Oil & Gas Operator | May 2025 |
| 603 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 604 | Talos Gulf Coast Onshore LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2024 |
| 605 | Tartan Resources Corporation | Houston, TX 77251 | Oil & Gas Operator | Oct 1995 |
| 606 | Taylor-Link Operating Co. | Midland, TX 79702 | Oil & Gas Operator | Apr 2017 |
| 607 | TBC Petroleum | Cuero, TX 77954 | Oil & Gas Operator | Sep 2023 |
| 608 | TC Oil And Gas, LLC | Denton, TX 76205 | Oil Operator | May 2025 |
| 609 | TDC Engineering, Inc. | Abilene, TX 79604 | Oil & Gas Operator | May 2025 |
| 610 | Te-Ray Resources, Inc. | Oklahoma City, OK 73108 | Oil & Gas Operator | Mar 2015 |
| 611 | Tend Oil Inc. | Tyler, TX 75703 | Oil & Gas Operator | Jul 1995 |
| 612 | Tenex Corporation | Houston, TX 77227 | Oil & Gas Operator | Dec 2007 |
| 613 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 614 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | May 2025 |
| 615 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | May 2025 |
| 616 | Texas Consolidated Pet. Corp. | Fort Worth, TX 76109 | Oil & Gas Operator | May 2025 |
| 617 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 618 | Texas Standard Oil Operating Co. | Midland, TX 79705 | Oil & Gas Operator | Oct 2019 |
| 619 | Texasgulf Inc. | Newgulf, TX 77462 | Oil & Gas Operator | Jul 1994 |
| 620 | Texcal Energy (GP) LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2016 |
| 621 | Texokan Energy Corporation | Scroggins, TX 75480 | Oil & Gas Operator | Jul 1996 |
| 622 | Texploration | Rosharon, TX 77583 | Oil Operator | May 2025 |
| 623 | Texstar North America, Inc. | Waynesboro, MS 39367 | Oil & Gas Operator | Aug 1994 |
| 624 | The Termo Company | Long Beach, CA 90801 | Oil & Gas Operator | Mar 2025 |
| 625 | Thorp Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2014 |
| 626 | Titan Resources I, Inc. | Midland, TX 79701 | Oil & Gas Operator | Jun 2000 |
| 627 | TMR Exploration, Inc. | Bossier City, LA 71171 | Oil & Gas Operator | May 2025 |
| 628 | Tomlinson, Thomas K. Inc. | Port Lavaca, TX 77979 | Oil & Gas Operator | Jul 2003 |
| 629 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 630 | Touchstone Resources USA, Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2006 |
| 631 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 632 | Transfuel Resources Co | Houston, TX 77215 | Oil & Gas Operator | Aug 2013 |
| 633 | Transpacific Energy, LLC | Katy, TX 77450 | Oil & Gas Operator | May 2025 |
| 634 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 635 | Traton Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Mar 2019 |
| 636 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 637 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | May 2025 |
| 638 | Trident Corporation | Woodsboro, TX 78393 | Oil & Gas Operator | May 2025 |
| 639 | Triple L Oil Company | Corpus Chrsti, TX 78469 | Oil & Gas Operator | Jan 1998 |
| 640 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 641 | Tuskar (Texas), Inc. | Nichols Hill, OK 73116 | Oil & Gas Operator | Jan 2016 |
| 642 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 643 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | May 2025 |
| 644 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 645 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 646 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | May 2025 |
| 647 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 648 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 649 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 650 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | May 2025 |
| 651 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 652 | Unoso Operating Company L.L.C. | Georgetown, TX 78633 | Oil & Gas Operator | May 2025 |
| 653 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | May 2025 |
| 654 | Us Petro LP | Amarillo, TX 79106 | Oil & Gas Operator | Apr 2020 |
| 655 | Valley Gathering Company | Midland, TX 79702 | Oil & Gas Operator | Feb 1997 |
| 656 | Vantage Operating, LLC | San Antonio, TX 78230 | Oil & Gas Operator | May 2025 |
| 657 | Vastar Resources Inc | Houston, TX 77253 | Oil & Gas Operator | Jan 2025 |
| 658 | Ventum Oil And Gas, LP | Northbrook, IL 60062 | Oil & Gas Operator | Mar 2010 |
| 659 | Venus Exploration, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2013 |
| 660 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 661 | Verus Energy, Inc | Houston, TX 77098 | Oil & Gas Operator | Sep 2004 |
| 662 | Viceroy Petroleum, LP | College Sta, TX 77845 | Oil & Gas Operator | May 2025 |
| 663 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Feb 2025 |
| 664 | Viper S.W.D., LLC | El Campo, TX 77437 | Oil & Gas Operator | May 2025 |
| 665 | Virlar Exploration, Inc. | Houston, TX 77227 | Oil & Gas Operator | Aug 1995 |
| 666 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 667 | Voight Oil Company | Tyler, TX 75703 | Oil & Gas Operator | Aug 2001 |
| 668 | Votaw Production Company LLC | Houston, TX 77007 | Oil Operator | May 2025 |
| 669 | W. R. G. Oil & Gas, Inc. | Arlington, TX 76013 | Oil & Gas Operator | Dec 1993 |
| 670 | Wadi Petroleum Inc | Houston, TX 77014 | Oil & Gas Operator | May 2018 |
| 671 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | May 2025 |
| 672 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 673 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 674 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | May 2025 |
| 675 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | May 2025 |
| 676 | Weber Energy Corporation | Dallas, TX 75219 | Oil & Gas Operator | Feb 2017 |
| 677 | Weiser-Brown Operating Company | Magnolia, AR 71754 | Oil & Gas Operator | May 2025 |
| 678 | Welder Exploration & Prod., Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Dec 2022 |
| 679 | Welderxp LTD. | San Antonio, TX 78212 | Oil & Gas Operator | May 2025 |
| 680 | Westco Oil Company | Ozona, TX 76943 | Oil & Gas Operator | May 2025 |
| 681 | Western Energy Group, LLC | Leander, TX 78641 | Oil & Gas Operator | May 2025 |
| 682 | Westhall Associates, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Aug 1997 |
| 683 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 684 | Westridge Oil & Gas Properties | Mineral Wells, TX 76068 | Oil & Gas Operator | May 2025 |
| 685 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | May 2025 |
| 686 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Jan 2025 |
| 687 | Williams, Clayton Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | May 2025 |
| 688 | Wilson Hydrocarbon Inc. | Houston, TX 77066 | Oil & Gas Operator | May 2025 |
| 689 | Windrush Operating Co., L.L.C. | Longville, LA 70652 | Oil & Gas Operator | May 2025 |
| 690 | Wofford, C. J. | El Campo, TX 77437 | Oil & Gas Operator | May 2025 |
| 691 | Wynn-Crosby Operating, LTD. | Dallas, TX 75201 | Oil & Gas Operator | May 2025 |
| 692 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 693 | Xog Operating LLC | Midland, TX 79702 | Oil & Gas Operator | May 2025 |
| 694 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | May 2025 |
| 695 | York E & P, LLC | Boling, TX 77420 | Oil & Gas Operator | May 2025 |
| 696 | Yuma E & P Company, Inc. | Houston, TX 77027 | Oil & Gas Operator | May 2025 |
| 697 | Yuma Petroleum Company | Houston, TX 77027 | Oil & Gas Operator | Aug 2002 |
| 698 | Zachry Exploration, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | May 2025 |
| 699 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | May 2025 |
| 700 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |