| 501 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Feb 2025 |
| 502 | Samurai Operating Co. L.L.C. | Dayton, TX 77535 | Oil & Gas Operator | May 2025 |
| 503 | San Cajo Oil Company | Edmonds, WA 98020 | Oil & Gas Operator | May 2025 |
| 504 | San Patricio Corporation | Dinero, TX 78350 | Oil & Gas Operator | Sep 2003 |
| 505 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 506 | Sanchez-O'Brien Oil & Gas Corp | Houston, TX 77057 | Oil & Gas Operator | May 1998 |
| 507 | Sandel Energy, Inc. | Huntsville, TX 77342 | Oil & Gas Operator | Apr 2004 |
| 508 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | May 2025 |
| 509 | Sandia Operating Corp. | San Antonio, TX 78270 | Oil & Gas Operator | May 2010 |
| 510 | Sandridge Onshore, LLC | Houston, TX 77010 | Oil & Gas Operator | Jun 2014 |
| 511 | Santos USA Corp. | Houston, TX 77042 | Oil & Gas Operator | Dec 2008 |
| 512 | Saxum Oil & Gas, LLC | Beeville, TX 78104 | Oil & Gas Operator | May 2025 |
| 513 | Se USA Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2009 |
| 514 | Sea Eagle Ford, LLC | Denver, CO 80265 | Oil & Gas Operator | Jun 2022 |
| 515 | Seagull Operating Co., Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jan 2025 |
| 516 | Secondary Oil Corp., Inc. | Austin, TX 78750 | Oil Operator | Apr 1999 |
| 517 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 518 | Sheridan Energy,Inc. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 519 | Sheridan Production Company, LLC | Houston, TX 77056 | Oil & Gas Operator | Feb 2025 |
| 520 | Sierra Exploration Company | San Antonio, TX 78209 | Oil & Gas Operator | Mar 2008 |
| 521 | Sierra Resources, LLC | Houston, TX 77219 | Oil & Gas Operator | Aug 2021 |
| 522 | Silverbow Resources Oper, LLC | Houston, TX 77002 | Oil & Gas Operator | May 2025 |
| 523 | Simray GP, LLC | Richardson, TX 75080 | Oil & Gas Operator | Dec 2015 |
| 524 | Simray Oil & Gas, Inc. | Richardson, TX 75080 | Oil & Gas Operator | Sep 2003 |
| 525 | Simray Operating Corp. | Richardson, TX 75080 | Oil & Gas Operator | Mar 2009 |
| 526 | Skidmore Exploration, Inc. | Dallas, TX 75219 | Oil & Gas Operator | Jul 1997 |
| 527 | SM Operating Company LLC | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 528 | Smith Petroleum Company | Spring, TX 77389 | Oil & Gas Operator | May 2025 |
| 529 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | May 2025 |
| 530 | South Texas Operating Company | San Antonio, TX 78217 | Oil & Gas Operator | May 2025 |
| 531 | South Texas SWD, Inc. | Beeville, TX 78104 | Oil & Gas Operator | Aug 2003 |
| 532 | Southern Resource Company | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Mar 2022 |
| 533 | Southern Royalty Inc. | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Feb 1997 |
| 534 | Southland Royalty Company | Houston, TX 77210 | Oil & Gas Operator | Sep 2011 |
| 535 | Southwest Gathering Company | Alice, TX 78332 | Oil & Gas Operator | May 2025 |
| 536 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 537 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 538 | Stallion Oil Company | Lafayette, LA 70505 | Oil & Gas Operator | Jun 2004 |
| 539 | Staples, James W. Prod. Co. | Tuleta, TX 78162 | Oil & Gas Operator | May 2025 |
| 540 | Star Production, Inc. | Dallas, TX 75360 | Oil & Gas Operator | May 2025 |
| 541 | Starco Exploration, Inc. | Dallas, TX 75360 | Oil & Gas Operator | May 2025 |
| 542 | Statoil Texas Onshore Prop LLC | Austin, TX 78730 | Oil & Gas Operator | Dec 2018 |
| 543 | Sterling Engine Service, Inc. | Alice, TX 78333 | Oil & Gas Operator | May 2025 |
| 544 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | May 2025 |
| 545 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 546 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 547 | Suemaur Expl. & Prod., LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Jun 2024 |
| 548 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 549 | Sun Exploration, Inc. | Alice, TX 78332 | Oil & Gas Operator | May 2025 |
| 550 | Sundown Energy LP | Dallas, TX 75248 | Oil & Gas Operator | May 2025 |
| 551 | Sure Flow Oil & Gas, Inc. | Victoria, TX 77902 | Oil & Gas Operator | May 2025 |
| 552 | Sutton Producing Corp. | San Antonio, TX 78270 | Oil & Gas Operator | May 2025 |
| 553 | SV Energy Company, LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Mar 2017 |
| 554 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 555 | Syj Oil & Gas, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | May 2025 |
| 556 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 557 | Talbott, Stan C. | Midland, TX 79701 | Oil & Gas Operator | Feb 2005 |
| 558 | Talisman Energy USA Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | May 2016 |
| 559 | Tallgrass Energy, L.L.C. | Tulsa, OK 74136 | Oil & Gas Operator | May 2025 |
| 560 | Tana Oil And Gas Corporation | Irving, TX 75062 | Oil & Gas Operator | Mar 2000 |
| 561 | Tanos Production, Inc. | Houston, TX 77077 | Oil & Gas Operator | Aug 2003 |
| 562 | Tare Resources, LLC | Corpus Chrsti, TX 78426 | Oil & Gas Operator | May 2025 |
| 563 | Targa Midstream Services LLC | Houston, TX 77002 | Oil Operator | Mar 2023 |
| 564 | TC Oil And Gas, LLC | Denton, TX 76205 | Oil Operator | May 2025 |
| 565 | Teal Operating, LLC | Dallas, TX 75225 | Oil & Gas Operator | Oct 2021 |
| 566 | Tejones Operating Corporation | San Antonio, TX 78217 | Oil & Gas Operator | May 2025 |
| 567 | Terrafina Energy, LLC | San Antonio, TX 78280 | Oil & Gas Operator | May 2025 |
| 568 | Tesoro E&P Company, L.P. | San Antonio, TX 78216 | Oil & Gas Operator | Jan 2000 |
| 569 | Teton Petroleum Corporation | Kerrville, TX 78028 | Oil & Gas Operator | May 2025 |
| 570 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | May 2025 |
| 571 | Texas Crude, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 1995 |
| 572 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | May 2025 |
| 573 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | May 2025 |
| 574 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 575 | Texas Land & Petro Co., LLC | Carrollton, TX 75010 | Oil & Gas Operator | May 2025 |
| 576 | Texas Secondary Oil Corporation | Devine, TX 78016 | Oil & Gas Operator | May 2025 |
| 577 | Texas Southern Petroleum Corp. | Corpus Chrsti, TX 78410 | Oil & Gas Operator | May 2025 |
| 578 | Texas Western Energy Corporation | Portland, TX 78374 | Oil & Gas Operator | Nov 2002 |
| 579 | Texas, Les & Co. | Austin, TX 78746 | Oil & Gas Operator | May 2025 |
| 580 | Thomas Oil & Gas Company | Luling, TX 78648 | Oil & Gas Operator | Aug 2003 |
| 581 | Three C Exploration, LLC | Hebbronville, TX 78361 | Oil & Gas Operator | May 2025 |
| 582 | Thunder Oil & Gas, LLC | Ardmore, OK 73402 | Oil & Gas Operator | Feb 2025 |
| 583 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | May 2025 |
| 584 | Tidewater Minerals Corporation | Orange Grove, TX 78372 | Oil & Gas Operator | May 2025 |
| 585 | Torch Energy Services, Inc. | Houston, TX 77010 | Oil & Gas Operator | Sep 2011 |
| 586 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 587 | Tradition Resources Oper, LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2017 |
| 588 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 589 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | May 2025 |
| 590 | Trident Corporation | Woodsboro, TX 78393 | Oil & Gas Operator | May 2025 |
| 591 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 592 | Triple L Oil Company | Corpus Chrsti, TX 78469 | Oil & Gas Operator | Jan 1998 |
| 593 | Tschoepe, Arthur J. | Leakey, TX 78873 | Oil & Gas Operator | Jun 2001 |
| 594 | TT Operating, LLC | Kilgore, TX 75663 | Oil & Gas Operator | May 2025 |
| 595 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 596 | Turner, M. O. | San Antonio, TX 78278 | Oil & Gas Operator | Apr 2003 |
| 597 | Tuthill & Barbee | Amarillo, TX 79101 | Oil & Gas Operator | Nov 1994 |
| 598 | TX Petroleum Company | Corpus Chrsti, TX 78412 | Oil & Gas Operator | Apr 1996 |
| 599 | U.S. Enercorp, LLC | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2004 |
| 600 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |