| 501 | San Patricio Corporation | Dinero, TX 78350 | Oil & Gas Operator | Sep 2003 |
| 502 | Sanchez Exploration Company LLC | Houston, TX 77056 | Oil & Gas Operator | Oct 2024 |
| 503 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | Apr 2025 |
| 504 | Sanchez-O'Brien Oil & Gas Corp | Houston, TX 77057 | Oil & Gas Operator | May 1998 |
| 505 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | Apr 2025 |
| 506 | Sandstone Resources, Inc. | Houston, TX 77043 | Oil & Gas Operator | Apr 2025 |
| 507 | Satex Energy, Inc. | San Antonio, TX 78216 | Oil & Gas Operator | Aug 2003 |
| 508 | Scana Petroleum Resources Inc | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 509 | Scoggins Oil & Gas Co. | Seabrook, TX 77586 | Oil & Gas Operator | Jun 2000 |
| 510 | Scully And Smith Oil Corporation | Salado, TX 76571 | Oil & Gas Operator | Feb 1995 |
| 511 | Scully Energy Corporation | Salado, TX 76571 | Oil & Gas Operator | Mar 2012 |
| 512 | Se USA Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2009 |
| 513 | Seagull Energy E & P Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2015 |
| 514 | Sedona Oil & Gas Corporation | Austin, TX 78746 | Oil & Gas Operator | Apr 2025 |
| 515 | Seguro Well Service, Inc. | Gonzales, TX 78629 | Oil & Gas Operator | Apr 2025 |
| 516 | Seisgen Exploration, Inc | Houston, TX 77024 | Gas Operator | Aug 2005 |
| 517 | Sequoia Fossil Fuels, Inc. | Albany, TX 76430 | Oil & Gas Operator | Apr 2025 |
| 518 | Shanghai Energy Corporation | Houston, TX 77027 | Oil & Gas Operator | Apr 2003 |
| 519 | Shell Trading Us Company | Houston, TX 77210 | Oil & Gas Operator | Jan 2025 |
| 520 | Shell Western E&P | Houston, TX 77001 | Oil & Gas Operator | Apr 2025 |
| 521 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 522 | Sheridan Energy,Inc. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 523 | Shidler, Mark L., Inc. | Houston, TX 77055 | Oil & Gas Operator | Apr 2025 |
| 524 | Signal Oil And Gas Company | Colleyville, TX 76034 | Oil & Gas Operator | Apr 2025 |
| 525 | Sir Drake Oil And Gas Company | Corpus Chrsti, TX 78413 | Oil & Gas Operator | Sep 2022 |
| 526 | Sisters Operating Company | Victoria, TX 77904 | Oil & Gas Operator | Nov 2010 |
| 527 | Snyder Oil Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 528 | Sonterra Oil & Gas, Inc. | Wichita, KS 67217 | Oil & Gas Operator | Apr 2025 |
| 529 | South Texas Operating Company | San Antonio, TX 78217 | Oil & Gas Operator | Apr 2025 |
| 530 | Southcoast Production Inc | Houston, TX 77010 | Oil & Gas Operator | Apr 2025 |
| 531 | Southern G Holdings, LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2007 |
| 532 | Southern Royalty Inc. | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Feb 1997 |
| 533 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 534 | Spindletop Oil & Gas Co. | Dallas, TX 75230 | Oil & Gas Operator | Apr 2025 |
| 535 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Apr 2025 |
| 536 | Star Of Texas Energy SRVS, Inc. | Austin, TX 78702 | Oil & Gas Operator | Apr 2025 |
| 537 | Star Production, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Apr 2025 |
| 538 | Starco Exploration, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Apr 2025 |
| 539 | Statoil Oil & Gas LP | Austin, TX 78730 | Oil & Gas Operator | Oct 2018 |
| 540 | STB Energy Inc. | Tulsa, OK 74105 | Oil & Gas Operator | Jul 2008 |
| 541 | Stealth Onsite Solutions LLC | Pasadena, TX 77505 | Oil Operator | Apr 2025 |
| 542 | Stone Edge Energy, LLC | Georgetown, TX 78633 | Oil & Gas Operator | Apr 2025 |
| 543 | Stone, J. G. Oil Co. | Victoria, TX 77904 | Oil & Gas Operator | Sep 2018 |
| 544 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Apr 2025 |
| 545 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Apr 2025 |
| 546 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2025 |
| 547 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 548 | Sundown Energy LP | Dallas, TX 75248 | Oil & Gas Operator | Apr 2025 |
| 549 | Sundown Energy, Inc. | Dallas, TX 75240 | Oil & Gas Operator | Dec 2024 |
| 550 | Superior Midstream, LLC | Tulsa, OK 74170 | Oil & Gas Operator | Feb 2020 |
| 551 | Sure Flow Oil & Gas Company | Victoria, TX 77902 | Oil & Gas Operator | Mar 2008 |
| 552 | SV Energy Company, LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Mar 2017 |
| 553 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 554 | Sydri Operating, LLC | Dallas, TX 75231 | Oil & Gas Operator | Apr 2025 |
| 555 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 556 | Tag Operating Company, Inc. | Houston, TX 77092 | Oil & Gas Operator | Apr 2025 |
| 557 | Tal-Con, Inc. | Houston, TX 77279 | Oil & Gas Operator | Apr 2025 |
| 558 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 559 | Talos Gulf Coast Onshore LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2024 |
| 560 | TBC Petroleum | Cuero, TX 77954 | Oil & Gas Operator | Sep 2023 |
| 561 | TC Oil And Gas, LLC | Denton, TX 76205 | Oil Operator | Apr 2025 |
| 562 | TDC Engineering, Inc. | Abilene, TX 79604 | Oil & Gas Operator | Apr 2025 |
| 563 | Team Operating, L.L.C. | Pinehurst, TX 77362 | Oil & Gas Operator | Apr 2025 |
| 564 | Tejones Operating Corporation | San Antonio, TX 78217 | Oil & Gas Operator | Apr 2025 |
| 565 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | Apr 2025 |
| 566 | Texas American Resources Company | Austin, TX 78701 | Oil & Gas Operator | Apr 2025 |
| 567 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | Apr 2025 |
| 568 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Apr 2025 |
| 569 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 570 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Apr 2025 |
| 571 | Texinia Corp | Dallas, TX 75201 | Oil & Gas Operator | Jun 2015 |
| 572 | Texokan Energy Corporation | Scroggins, TX 75480 | Oil & Gas Operator | Jul 1996 |
| 573 | Texron Operating, LLC | Bulverde, TX 78163 | Oil & Gas Operator | Apr 2025 |
| 574 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Apr 2025 |
| 575 | Tidemark Petroleum, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2002 |
| 576 | Tidewater Minerals Corporation | Orange Grove, TX 78372 | Oil & Gas Operator | Apr 2025 |
| 577 | Titan Resources I, Inc. | Midland, TX 79701 | Oil & Gas Operator | Jun 2000 |
| 578 | Toma Oil & Gas, Inc. | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Oct 1997 |
| 579 | Tomlinson, Thomas K. Inc. | Port Lavaca, TX 77979 | Oil & Gas Operator | Jul 2003 |
| 580 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Apr 2025 |
| 581 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 582 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Apr 2025 |
| 583 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 584 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | Apr 2025 |
| 585 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 586 | Trinidad Resources, LLC | San Antonio, TX 78217 | Oil & Gas Operator | Apr 2025 |
| 587 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 588 | Trump Energy | Austin, TX 78734 | Oil & Gas Operator | Mar 2008 |
| 589 | Truth Resources LP | Houston, TX 77090 | Oil Operator | Sep 2021 |
| 590 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2025 |
| 591 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 592 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Apr 2025 |
| 593 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Apr 2025 |
| 594 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 595 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 596 | United Energy Partners, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Mar 2008 |
| 597 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 598 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 599 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Apr 2025 |
| 600 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |