| 501 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2025 |
| 502 | San Patricio Corporation | Dinero, TX 78350 | Oil & Gas Operator | Sep 2003 |
| 503 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | Jul 2025 |
| 504 | Sanchez-O'Brien Oil & Gas Corp | Houston, TX 77057 | Oil & Gas Operator | May 1998 |
| 505 | Sandel Energy, Inc. | Huntsville, TX 77342 | Oil & Gas Operator | Apr 2004 |
| 506 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | Jul 2025 |
| 507 | Sandia Operating Corp. | San Antonio, TX 78270 | Oil & Gas Operator | May 2010 |
| 508 | Santos USA Corp. | Houston, TX 77042 | Oil & Gas Operator | Dec 2008 |
| 509 | Saxet Energy, LTD. | Houston, TX 77057 | Oil & Gas Operator | Mar 2004 |
| 510 | Scope Operating Company | Fort Worth, TX 76102 | Oil & Gas Operator | Aug 2003 |
| 511 | Senora Resources, Inc. | Dime Box, TX 77853 | Oil & Gas Operator | Jul 2025 |
| 512 | Shanghai Energy Corporation | Houston, TX 77027 | Oil & Gas Operator | Apr 2003 |
| 513 | Sharon Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Aug 2010 |
| 514 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 515 | Sheridan Production Company, LLC | Houston, TX 77056 | Oil & Gas Operator | Apr 2025 |
| 516 | Shiner Exploration, LLC | Houston, TX 77091 | Oil & Gas Operator | Jul 2025 |
| 517 | Silverbow Resources Oper, LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 518 | SM Energy Company | Midland, TX 79707 | Oil & Gas Operator | Jul 2025 |
| 519 | Smith Petroleum Company | Spring, TX 77389 | Oil & Gas Operator | Jul 2025 |
| 520 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Jul 2025 |
| 521 | Snyder Oil Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 522 | Sonat Exploration Co. | Houston, TX 77251 | Oil & Gas Operator | Dec 2021 |
| 523 | Sonat Exploration Co. - Houston | Houston, TX 77251 | Oil & Gas Operator | Dec 1999 |
| 524 | Sounion Petroleum Incorporated | Baltimore, MD 21218 | Oil & Gas Operator | Aug 1994 |
| 525 | Southern Mineral Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2001 |
| 526 | Southern Resource Company | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Mar 2022 |
| 527 | Southstone Energy, LLC | Austin, TX 78735 | Oil Operator | Jul 2025 |
| 528 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 529 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 530 | Southwest Operating, Inc.-Tyler | Tyler, TX 75701 | Oil & Gas Operator | Jul 2025 |
| 531 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Jul 2025 |
| 532 | Stallion Oil Company | Lafayette, LA 70505 | Oil & Gas Operator | Jun 2004 |
| 533 | Statoil Texas Onshore Prop LLC | Austin, TX 78730 | Oil & Gas Operator | Dec 2018 |
| 534 | STB Energy Inc. | Tulsa, OK 74105 | Oil & Gas Operator | Jul 2008 |
| 535 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | May 2025 |
| 536 | Stone & Webster Oil Company, Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 1995 |
| 537 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 538 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Jul 2025 |
| 539 | STS Petroleum LLC | Houston, TX 77289 | Oil & Gas Operator | Jul 2025 |
| 540 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Jul 2025 |
| 541 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 542 | Suemaur Expl. & Prod., LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Jun 2024 |
| 543 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 544 | Sundown Energy LP | Dallas, TX 75248 | Oil & Gas Operator | Jul 2025 |
| 545 | Sure Flow Oil & Gas, Inc. | Victoria, TX 77902 | Oil & Gas Operator | Jul 2025 |
| 546 | SV Energy Company, LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Mar 2017 |
| 547 | Talisman Energy USA Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | May 2016 |
| 548 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 549 | TBC Petroleum | Cuero, TX 77954 | Oil & Gas Operator | Sep 2023 |
| 550 | TD Natural Resources LLC | Cuero, TX 77954 | Oil & Gas Operator | Jul 2025 |
| 551 | Teal Operating, LLC | Dallas, TX 75225 | Oil & Gas Operator | Oct 2021 |
| 552 | Tejas Operating LLC | Houston, TX 77056 | Oil & Gas Operator | Jul 2025 |
| 553 | Tempest Energy Resources, LP | Houston, TX 77251 | Oil & Gas Operator | Jun 2013 |
| 554 | Tenex Corporation | Houston, TX 77227 | Oil & Gas Operator | Dec 2007 |
| 555 | Terrafina Energy, LLC | San Antonio, TX 78280 | Oil & Gas Operator | Jul 2025 |
| 556 | Texas Energy Reserves, Inc | New Braunfels, TX 78130 | Oil & Gas Operator | Jun 1996 |
| 557 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 558 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 559 | Texas Sunset Energy And Ent Inc | Victoria, TX 77904 | Oil Operator | Aug 2003 |
| 560 | Texegy Operating Company LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Dec 2024 |
| 561 | Texron Operating, LLC | Bulverde, TX 78163 | Oil & Gas Operator | Jul 2025 |
| 562 | Thomas Oil & Gas Company | Luling, TX 78648 | Oil & Gas Operator | Aug 2003 |
| 563 | Thunderbird Energy, Inc. | Norman, OK 73069 | Oil & Gas Operator | Jul 2025 |
| 564 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Jul 2025 |
| 565 | Tidemark Petroleum, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2002 |
| 566 | Tiger Resources, L.L.C. | Houston, TX 77070 | Oil & Gas Operator | Feb 2004 |
| 567 | Tomlinson, Thomas K. Inc. | Port Lavaca, TX 77979 | Oil & Gas Operator | Jul 2003 |
| 568 | Totalfinaelf E&P USA Inc | Houston, TX 77024 | Oil & Gas Operator | Jul 2007 |
| 569 | Trailblazer Energy Resources, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Jul 2025 |
| 570 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Jul 2025 |
| 571 | Traton Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Mar 2019 |
| 572 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 573 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 574 | Triangle Three Resources L.L.C. | Dallas, TX 75240 | Oil & Gas Operator | Jul 2025 |
| 575 | Trident Corporation | Woodsboro, TX 78393 | Oil & Gas Operator | Jul 2025 |
| 576 | Triple "S" Resources Inc | Sapulpa, OK 74066 | Oil & Gas Operator | Jun 1995 |
| 577 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Jul 2025 |
| 578 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Jul 2025 |
| 579 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 580 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 581 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Jul 2025 |
| 582 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Jul 2025 |
| 583 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 584 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Jul 2025 |
| 585 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Jul 2025 |
| 586 | Valerius, Inc. & Zine, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Jul 1994 |
| 587 | Valerius, Robert D. Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Aug 2003 |
| 588 | Validus NRG Aquilas Assetco LLC | Denver, CO 80202 | Oil & Gas Operator | Nov 2022 |
| 589 | Valley Gathering Company | Midland, TX 79702 | Oil & Gas Operator | Feb 1997 |
| 590 | Vanguard Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Feb 2021 |
| 591 | Vaquero Operating | FT Stockton, TX 79735 | Oil & Gas Operator | Jul 2025 |
| 592 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 593 | Verdun Oil & Gas LLC | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 594 | Verus Energy, Inc | Houston, TX 77098 | Oil & Gas Operator | Sep 2004 |
| 595 | Victoria Operating, Inc. | Victoria, TX 77903 | Oil & Gas Operator | Jul 2025 |
| 596 | Virtex Operating Company, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2023 |
| 597 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 598 | Wadi Petroleum Inc | Houston, TX 77014 | Oil & Gas Operator | May 2018 |
| 599 | Wagner & Brown, LTD. | Midland, TX 79702 | Oil & Gas Operator | Aug 2014 |
| 600 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Jul 2025 |