| 501 | South Texas Operating Company | San Antonio, TX 78217 | Oil & Gas Operator | Sep 2026 |
| 502 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 503 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 504 | Spiller Operating Co., Inc. | Round Rock, TX 78665 | Oil & Gas Operator | May 2015 |
| 505 | Spur Operating Co. | Austin, TX 78701 | Oil & Gas Operator | Sep 2026 |
| 506 | Square One Corporation | Giddings, TX 78942 | Oil & Gas Operator | Dec 2012 |
| 507 | SSC, Inc. | Lubbock, TX 79408 | Oil & Gas Operator | Sep 2026 |
| 508 | Starr Operating Company | Austin, TX 78759 | Oil & Gas Operator | Sep 2026 |
| 509 | Sto Operating Company | San Antonio, TX 78258 | Oil & Gas Operator | Sep 2026 |
| 510 | Stoneburner Exploration, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Oct 1997 |
| 511 | Stonegate Operators, Inc. | Addison, TX 75001 | Oil Operator | Sep 2026 |
| 512 | Stonegate Production Company,LLC | Houston, TX 77024 | Oil & Gas Operator | Sep 2026 |
| 513 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Sep 2026 |
| 514 | Stratco Operating Co., Inc. | Austin, TX 78701 | Oil & Gas Operator | Sep 2026 |
| 515 | Stubbs, J. W. | Suwanee, GA 30024 | Oil & Gas Operator | Mar 2008 |
| 516 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 517 | Sun-Key Oil Co., Inc. | Dublin, TX 76446 | Oil & Gas Operator | Sep 2026 |
| 518 | Sunburst, Inc. | Wheat Ridge, CO 80033 | Oil & Gas Operator | Jun 2026 |
| 519 | Suncoast Investments Co., Inc. | Plano, TX 75074 | Oil & Gas Operator | Oct 2001 |
| 520 | Sutton Producing Corp. | San Antonio, TX 78270 | Oil & Gas Operator | Sep 2026 |
| 521 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 522 | Sydri Operating, LLC | Dallas, TX 75231 | Oil & Gas Operator | Sep 2026 |
| 523 | T & T Production Co. | Victoria, TX 77902 | Oil & Gas Operator | Feb 1995 |
| 524 | Tamarack Petroleum Company, Inc. | Midland, TX 79701 | Oil & Gas Operator | Sep 2026 |
| 525 | Targa Midstream Services LLC | Tulsa, OK 74103 | Oil Operator | Mar 2023 |
| 526 | Targa Pipeline Mid-Continent LLC | Houston, TX 77002 | Oil & Gas Operator | Jun 2018 |
| 527 | Tech Resources, Inc. | Georgetown, TX 78628 | Oil & Gas Operator | Dec 2001 |
| 528 | Tekna Synergy Corporation | Midland, TX 79702 | Oil & Gas Operator | Sep 2026 |
| 529 | Terrafina Energy, LLC | San Antonio, TX 78280 | Oil & Gas Operator | Sep 2026 |
| 530 | Texaco E & P Inc. | Houston, TX 77099 | Oil & Gas Operator | Sep 2026 |
| 531 | Texakoma Oil & Gas Corp | Dallas, TX 75240 | Oil & Gas Operator | Sep 2014 |
| 532 | Texan Production | Pearsall, TX 78061 | Oil & Gas Operator | Aug 2003 |
| 533 | Texan Production Company, Inc. | Canyon Lake, TX 78133 | Oil & Gas Operator | Sep 2026 |
| 534 | Texas American Resources Company | Austin, TX 78701 | Oil & Gas Operator | Sep 2026 |
| 535 | Texas Crude, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 1995 |
| 536 | Texas International Resource LLC | Allen, TX 75013 | Oil Operator | Sep 2026 |
| 537 | Texas Oil And Gas Operating, LLC | Friendswood, TX 77546 | Oil & Gas Operator | Sep 2026 |
| 538 | Texas Southern Petroleum Corp. | Corpus Christ, TX 78410 | Oil & Gas Operator | Sep 2026 |
| 539 | Texas Sunset Energy And Ent Inc | Victoria, TX 77904 | Oil Operator | Aug 2003 |
| 540 | Texas, Les & Co. | Brenham, TX 77833 | Oil & Gas Operator | Sep 2026 |
| 541 | Texas-Ohio Producing Company | Spring, TX 77383 | Oil & Gas Operator | Jul 1995 |
| 542 | Texokan Operating, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Sep 2026 |
| 543 | Texstar North America, Inc. | Waynesboro, MS 39367 | Oil & Gas Operator | Aug 1994 |
| 544 | Thalmann Oil Field Service, Inc. | Carrizo SPGS, TX 78834 | Oil & Gas Operator | Mar 2008 |
| 545 | Thalmann, David Vac Service Inc | Carrizo SPGS, TX 78834 | Oil & Gas Operator | Sep 2026 |
| 546 | Thunder Oil & Gas, LLC | Ardmore, OK 73402 | Oil & Gas Operator | Jun 2026 |
| 547 | Tide West Oil Company | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2021 |
| 548 | Tipperary Oil & Gas Corporation | Denver, CO 80202 | Oil & Gas Operator | May 2014 |
| 549 | Tiza Energy, Inc. | Austin, TX 78715 | Oil & Gas Operator | Sep 2026 |
| 550 | Trailblazer Energy Resources, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Sep 2026 |
| 551 | Traton Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Mar 2019 |
| 552 | Tree Operating, LLC | Graham, TX 76450 | Oil & Gas Operator | Sep 2026 |
| 553 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Sep 2026 |
| 554 | Trinity Operating (Usg), LLC | Houston, TX 77002 | Oil & Gas Operator | Sep 2026 |
| 555 | Triton Oil & Gas Corp. | Houston, TX 77002 | Oil & Gas Operator | Nov 2014 |
| 556 | Trump Energy | Austin, TX 78734 | Oil & Gas Operator | Mar 2008 |
| 557 | Tularosa Operating Company | Kerrville, TX 78029 | Oil & Gas Operator | Mar 2024 |
| 558 | Tulsa Minerals Inc | Tulsa, OK 74136-1045 | Oil & Gas Operator | May 2013 |
| 559 | Turner, M. O. | San Antonio, TX 78278 | Oil & Gas Operator | Apr 2003 |
| 560 | TX Petroleum Company | Corpus Christ, TX 78412 | Oil & Gas Operator | Apr 1996 |
| 561 | U. S. Energy Development Corporation | Fort Worth, TX 76164 | Oil & Gas Operator | Sep 2026 |
| 562 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 563 | U.S.A. Plugging Company | Pearsall, TX 78061 | Oil & Gas Operator | Sep 2026 |
| 564 | Union Pacific Austin Chalk Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 565 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 566 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Sep 2026 |
| 567 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Sep 2026 |
| 568 | V/J Oil Company | Yancey, TX 78886 | Oil & Gas Operator | Oct 2015 |
| 569 | Vac-U-Lift Production Co.,Inc. | Lake Forest, CA 92630 | Oil & Gas Operator | Sep 2026 |
| 570 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Sep 2026 |
| 571 | Vanco Oil & Gas Corp. | Abilene, TX 79604 | Oil & Gas Operator | Sep 2026 |
| 572 | Venado Operating Company LLC | Austin, TX 78738 | Oil & Gas Operator | Mar 2022 |
| 573 | Verdun Oil Ef II LLC | Houston, TX 77024 | Oil & Gas Operator | Sep 2026 |
| 574 | Vermillion Production, Inc. | Pearsall, TX 78061 | Oil & Gas Operator | Sep 2026 |
| 575 | Viceroy Petroleum GP, LLC | Rockdale, TX 76567 | Oil & Gas Operator | Feb 2010 |
| 576 | Viceroy Petroleum, LP | College Sta, TX 77845 | Oil & Gas Operator | Sep 2026 |
| 577 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Sep 2026 |
| 578 | Virtex Operating Company, Inc. | Corpus Christ, TX 78401 | Oil & Gas Operator | Oct 2023 |
| 579 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 580 | W. E. B. Well Tending Service, Inc. | Vienna, WV 26105 | Oil & Gas Operator | Nov 2011 |
| 581 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Sep 2026 |
| 582 | Warren American Oil Co | Tulsa, OK 74147 | Oil & Gas Operator | Jun 2026 |
| 583 | Watco Energy, Inc. | Tyler, TX 75713 | Oil & Gas Operator | Apr 1996 |
| 584 | Waters Eng. & Operating, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Sep 2013 |
| 585 | Watson Energy Investments, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Sep 2026 |
| 586 | Wayne E. Glenn Associates, Inc. | Dickinson, TX 77539 | Oil & Gas Operator | Jan 2016 |
| 587 | WCS Oil & Gas Corporation | Dallas, TX 75209 | Oil & Gas Operator | Aug 2021 |
| 588 | Weber Energy Corporation | Dallas, TX 75219 | Oil & Gas Operator | Feb 2017 |
| 589 | Wen-Be | Jourdanton, TX 78026 | Oil & Gas Operator | Sep 2026 |
| 590 | Western Field Exploration, Inc. | Dilley, TX 78017 | Oil & Gas Operator | Sep 2026 |
| 591 | Wetzel Oil Company | Austin, TX 78738 | Oil & Gas Operator | May 2007 |
| 592 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Sep 2026 |
| 593 | Wild Cat Operating Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 594 | Wiley Lease Co., LTD. | Jourdanton, TX 78026 | Oil Operator | Sep 2026 |
| 595 | Williams, Clayton Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | Sep 2026 |
| 596 | Williams, Clayton Energy, L.L.C | Midland, TX 79705 | Oil & Gas Operator | May 1993 |
| 597 | Williams, Clayton W., Jr., Inc. | Midland, TX 79705 | Oil & Gas Operator | Mar 2008 |
| 598 | Windsor Exploration Company | Dallas, TX 75204 | Oil & Gas Operator | Jan 1994 |
| 599 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2023 |
| 600 | World Energy Corporation | Laredo, TX 78041 | Oil & Gas Operator | Aug 2003 |