| 501 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 502 | Shidler, Mark L., Inc. | Houston, TX 77055 | Oil & Gas Operator | Apr 2024 |
| 503 | Shiner Exploration, LLC | Houston, TX 77091 | Oil & Gas Operator | Apr 2024 |
| 504 | Shoreham Oil & Gas Company, Inc. | Katy, TX 77492 | Oil & Gas Operator | Apr 2024 |
| 505 | Shoreline Southeast LLC | Lafayette, LA 70508 | Oil & Gas Operator | Jun 2017 |
| 506 | Silverbow Resources Oper, LLC | Houston, TX 77024 | Oil & Gas Operator | Apr 2024 |
| 507 | Slant Operating, LLC | Lafayette, LA 70503 | Oil & Gas Operator | Apr 2024 |
| 508 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Apr 2024 |
| 509 | SN Operating, LLC | Houston, TX 77002 | Oil & Gas Operator | May 2023 |
| 510 | Sonat Exploration Co. | Houston, TX 77251 | Oil & Gas Operator | Dec 2021 |
| 511 | South Leeville, LLC | Houston, TX 77069 | Oil & Gas Operator | Oct 2022 |
| 512 | Southern G Holdings, LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2007 |
| 513 | Southern Mineral Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2001 |
| 514 | Southern Union Exploration Co. | Austin, TX 78701 | Oil & Gas Operator | Feb 2002 |
| 515 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Apr 2024 |
| 516 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | Jan 2024 |
| 517 | Stewardship Resources | Roanoke, TX 76262 | Oil & Gas Operator | Jun 2022 |
| 518 | Stone & Webster Oil Company, Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 1995 |
| 519 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Apr 2024 |
| 520 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Apr 2024 |
| 521 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2024 |
| 522 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 523 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 524 | Sulphur River Exploration, Inc. | Dallas, TX 75244 | Oil & Gas Operator | Apr 2024 |
| 525 | Suncoast Technical Services Inc | Dallas, TX 75251 | Oil & Gas Operator | Apr 2024 |
| 526 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 527 | Swift Energy Operating, LLC | Houston, TX 77079 | Oil & Gas Operator | Jun 2017 |
| 528 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 529 | T & G Oil, Inc. | White Oak, TX 75693 | Oil & Gas Operator | Dec 2010 |
| 530 | T & T Production Co. | Victoria, TX 77902 | Oil & Gas Operator | Feb 1995 |
| 531 | T-C Oil Company, LLC | Refugio, TX 78377 | Oil & Gas Operator | Apr 2024 |
| 532 | T.D. Operating Company, Inc. | New Braunfels, TX 78130 | Oil & Gas Operator | Nov 1999 |
| 533 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 534 | Tamarack Petroleum Company, Inc. | Midland, TX 79701 | Oil & Gas Operator | Apr 2024 |
| 535 | TC Oil And Gas, LLC | Denton, TX 76205 | Oil Operator | Apr 2024 |
| 536 | TDC Engineering, Inc. | Abilene, TX 79604 | Oil & Gas Operator | Apr 2024 |
| 537 | TDX Energy, LLC | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2023 |
| 538 | Teal Operating, LLC | Dallas, TX 75225 | Oil & Gas Operator | Oct 2021 |
| 539 | Tend Oil Inc. | Tyler, TX 75703 | Oil & Gas Operator | Jul 1995 |
| 540 | Tensas Delta Explo. Co., LLC | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2011 |
| 541 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 542 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Apr 2024 |
| 543 | Texakoma E & P, LLC | Plano, TX 75024 | Oil & Gas Operator | Apr 2024 |
| 544 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | Apr 2024 |
| 545 | Texas Crude Energy, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 2012 |
| 546 | Texas Gulf Gas Corporation | Fayetteville, TX 78940 | Oil & Gas Operator | Jun 2005 |
| 547 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Apr 2024 |
| 548 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 549 | Texas Onshore Energy, Inc. | Austin, TX 78704 | Oil & Gas Operator | Apr 2024 |
| 550 | Texcal Energy (GP) LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2016 |
| 551 | Texron Operating, LLC | Bulverde, TX 78163 | Oil & Gas Operator | Apr 2024 |
| 552 | Tgo Operating, LLC | Midland, TX 79705 | Oil & Gas Operator | Dec 2008 |
| 553 | Thorp Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2014 |
| 554 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Apr 2024 |
| 555 | TMR Exploration, Inc. | Bossier City, LA 71171 | Oil & Gas Operator | Apr 2024 |
| 556 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 557 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 558 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Apr 2024 |
| 559 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 560 | Tri-Union Development Corp. | Houston, TX 77002 | Oil & Gas Operator | Apr 2024 |
| 561 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 562 | Triangle Development Co | Mahtomedi, MN 55115 | Gas Operator | Feb 1982 |
| 563 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 564 | Trio Consulting & Management,LLC | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2024 |
| 565 | Trio Operating Company, Inc. | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2006 |
| 566 | Trio Production Company, LLC | Stephens, AR 71764 | Oil Operator | Feb 2024 |
| 567 | Triple J Investments Inc | Longview, TX 75606 | Oil & Gas Operator | Feb 2023 |
| 568 | Triton Oil & Gas Corp. | Houston, TX 77002 | Oil & Gas Operator | Nov 2014 |
| 569 | Tsar Energy, LLC | Dallas, TX 75205 | Oil & Gas Operator | Apr 2024 |
| 570 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2024 |
| 571 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 572 | Unicorn Energy, Inc. | Elgin, TX 78621 | Oil & Gas Operator | Apr 2024 |
| 573 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Apr 2024 |
| 574 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 575 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 576 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Apr 2024 |
| 577 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 578 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 579 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 580 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Apr 2024 |
| 581 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Apr 2024 |
| 582 | Valley Gathering Company | Midland, TX 79702 | Oil & Gas Operator | Feb 1997 |
| 583 | Vaquero Operating | FT Stockton, TX 79735 | Oil & Gas Operator | Apr 2024 |
| 584 | Vermillion Production, Inc. | Pearsall, TX 78061 | Oil & Gas Operator | Apr 2024 |
| 585 | Victoria Operating, Inc. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2024 |
| 586 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Dec 2023 |
| 587 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Apr 2024 |
| 588 | Viper S.W.D., LLC | El Campo, TX 77437 | Oil & Gas Operator | Apr 2024 |
| 589 | Wadi Petroleum Inc | Houston, TX 77014 | Oil & Gas Operator | May 2018 |
| 590 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2024 |
| 591 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 592 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 593 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | Apr 2024 |
| 594 | Wandoo Energy, LLC | The Woodlands, TX 77382 | Oil & Gas Operator | Apr 2024 |
| 595 | Warbonnet Exploration Company | Houston, TX 77056 | Oil & Gas Operator | Apr 2016 |
| 596 | Watco Energy, Inc. | Tyler, TX 75713 | Oil & Gas Operator | Apr 1996 |
| 597 | Weber Energy Corporation | Dallas, TX 75219 | Oil & Gas Operator | Feb 2017 |
| 598 | Weeks Exploration Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 599 | Weiser-Brown Operating Company | Magnolia, AR 71754 | Oil & Gas Operator | Apr 2024 |
| 600 | Wellstar Corporation | Northglenn, CO 80233 | Oil & Gas Operator | Feb 2024 |