| 501 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | Feb 2026 |
| 502 | Sandstone Resources, Inc. | Houston, TX 77043 | Oil & Gas Operator | Feb 2026 |
| 503 | Satex Energy, Inc. | San Antonio, TX 78216 | Oil & Gas Operator | Aug 2003 |
| 504 | Scana Petroleum Resources Inc | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 505 | Scoggins Oil & Gas Co. | Seabrook, TX 77586 | Oil & Gas Operator | Jun 2000 |
| 506 | Scully And Smith Oil Corporation | Salado, TX 76571 | Oil & Gas Operator | Feb 1995 |
| 507 | Scully Energy Corporation | Salado, TX 76571 | Oil & Gas Operator | Mar 2012 |
| 508 | Se USA Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2009 |
| 509 | Seagull Energy E & P Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2015 |
| 510 | Sedona Oil & Gas Corporation | Dallas, TX 75231 | Oil & Gas Operator | Feb 2026 |
| 511 | Seguro Well Service, Inc. | Gonzales, TX 78629 | Oil & Gas Operator | Feb 2026 |
| 512 | Seisgen Exploration, Inc | Houston, TX 77024 | Gas Operator | Aug 2005 |
| 513 | Sequoia Fossil Fuels, Inc. | Albany, TX 76430 | Oil & Gas Operator | Feb 2026 |
| 514 | Shanghai Energy Corporation | Houston, TX 77027 | Oil & Gas Operator | Apr 2003 |
| 515 | Shell Western E&P | Houston, TX 77001 | Oil & Gas Operator | Feb 2026 |
| 516 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 517 | Sheridan Energy,Inc. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 518 | Shidler, Mark L., Inc. | Houston, TX 77055 | Oil & Gas Operator | Feb 2026 |
| 519 | Signal Oil And Gas Company | Colleyville, TX 76034 | Oil & Gas Operator | Feb 2026 |
| 520 | Sisters Operating Company | Victoria, TX 77904 | Oil & Gas Operator | Nov 2010 |
| 521 | Snyder Oil Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 522 | Sonterra Oil & Gas, Inc. | Wichita, KS 67217 | Oil & Gas Operator | Feb 2026 |
| 523 | South Texas Operating Company | San Antonio, TX 78217 | Oil & Gas Operator | Feb 2026 |
| 524 | Southcoast Production Inc | Houston, TX 77010 | Oil & Gas Operator | Feb 2026 |
| 525 | Southern G Holdings, LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2007 |
| 526 | Southern Royalty Inc. | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Feb 1997 |
| 527 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 528 | Spindletop Oil & Gas Co. | Dallas, TX 75230 | Oil & Gas Operator | Feb 2026 |
| 529 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Feb 2026 |
| 530 | Star Of Texas Energy SRVS, Inc. | Austin, TX 78702 | Oil & Gas Operator | Feb 2026 |
| 531 | Star Production, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Feb 2026 |
| 532 | Starco Exploration, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Feb 2026 |
| 533 | Statoil Oil & Gas LP | Austin, TX 78730 | Oil & Gas Operator | Oct 2018 |
| 534 | STB Energy Inc. | Tulsa, OK 74105 | Oil & Gas Operator | Jul 2008 |
| 535 | Stealth Onsite Solutions LLC | Pasadena, TX 77505 | Oil Operator | Feb 2026 |
| 536 | Stone Edge Energy, LLC | El Campo, TX 77437 | Oil & Gas Operator | Feb 2026 |
| 537 | Stone, J. G. Oil Co. | Victoria, TX 77904 | Oil & Gas Operator | Sep 2018 |
| 538 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 539 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Feb 2026 |
| 540 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Feb 2026 |
| 541 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 542 | Sundown Energy LP | Dallas, TX 75248 | Oil & Gas Operator | Feb 2026 |
| 543 | Sundown Energy, Inc. | Dallas, TX 75240 | Oil & Gas Operator | May 2025 |
| 544 | Superior Midstream, LLC | Tulsa, OK 74170 | Oil & Gas Operator | Feb 2020 |
| 545 | Sure Flow Oil & Gas Company | Victoria, TX 77902 | Oil & Gas Operator | Mar 2008 |
| 546 | SV Energy Company, LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Mar 2017 |
| 547 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 548 | Sydri Operating, LLC | Dallas, TX 75231 | Oil & Gas Operator | Feb 2026 |
| 549 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 550 | Tag Operating Company, Inc. | Houston, TX 77092 | Oil & Gas Operator | Feb 2026 |
| 551 | Tal-Con, Inc. | Houston, TX 77279 | Oil & Gas Operator | Feb 2026 |
| 552 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 553 | Talos Gulf Coast Onshore LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2024 |
| 554 | TBC Petroleum | Cuero, TX 77954 | Oil & Gas Operator | Sep 2023 |
| 555 | TC Oil And Gas, LLC | Denton, TX 76205 | Oil Operator | Feb 2026 |
| 556 | TDC Engineering, Inc. | Abilene, TX 79604 | Oil & Gas Operator | Feb 2026 |
| 557 | Team Operating, L.L.C. | Pinehurst, TX 77362 | Oil & Gas Operator | Feb 2026 |
| 558 | Tejones Operating Corporation | San Antonio, TX 78217 | Oil & Gas Operator | Feb 2026 |
| 559 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | Feb 2026 |
| 560 | Texas American Resources Company | Austin, TX 78701 | Oil & Gas Operator | Feb 2026 |
| 561 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | Feb 2026 |
| 562 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Feb 2026 |
| 563 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 564 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Feb 2026 |
| 565 | Texinia Corp | Dallas, TX 75201 | Oil & Gas Operator | Jun 2015 |
| 566 | Texokan Energy Corporation | Scroggins, TX 75480 | Oil & Gas Operator | Jul 1996 |
| 567 | Texron Operating, LLC | Bulverde, TX 78163 | Oil & Gas Operator | Feb 2026 |
| 568 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Feb 2026 |
| 569 | Tide Energy, Inc. | Dallas, TX 75206 | Gas Operator | Oct 1994 |
| 570 | Tidemark Petroleum, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2002 |
| 571 | Tidewater Minerals Corporation | Orange Grove, TX 78372 | Oil & Gas Operator | Feb 2026 |
| 572 | Titan Resources I, Inc. | Midland, TX 79701 | Oil & Gas Operator | Jun 2000 |
| 573 | Toma Oil & Gas, Inc. | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Oct 1997 |
| 574 | Tomlinson, Thomas K. Inc. | Port Lavaca, TX 77979 | Oil & Gas Operator | Jul 2003 |
| 575 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Feb 2026 |
| 576 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 577 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Feb 2026 |
| 578 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 579 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | Feb 2026 |
| 580 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 581 | Trinidad Resources, LLC | San Antonio, TX 78217 | Oil & Gas Operator | Feb 2026 |
| 582 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 583 | Trump Energy | Austin, TX 78734 | Oil & Gas Operator | Mar 2008 |
| 584 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Feb 2026 |
| 585 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 586 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Jul 2025 |
| 587 | Union Gas Operating Company | Spring, TX 77391 | Oil & Gas Operator | Feb 2026 |
| 588 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 589 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 590 | United Energy Partners, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Mar 2008 |
| 591 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 592 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 593 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Feb 2026 |
| 594 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 595 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Feb 2026 |
| 596 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 597 | Unoso Operating Company L.L.C. | Georgetown, TX 78633 | Oil & Gas Operator | Feb 2026 |
| 598 | Vaquero Operating | FT Stockton, TX 79735 | Oil & Gas Operator | Feb 2026 |
| 599 | Ventex Operating Corp. | Addison, TX 75001 | Oil & Gas Operator | Feb 2026 |
| 600 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |