| 501 | Seisgen Exploration, Inc | Houston, TX 77024 | Gas Operator | Aug 2005 |
| 502 | Sellers Lease Service, Inc. | Flatonia, TX 78941 | Oil & Gas Operator | Apr 2025 |
| 503 | Sendero Energy Inc. | Dallas, TX 75205 | Oil & Gas Operator | Apr 2025 |
| 504 | Seneca Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Dec 2017 |
| 505 | Sequoia Management, LLC | Houston, TX 77060 | Oil & Gas Operator | Nov 2009 |
| 506 | Sev Texas Operating, LLC | Long Beach, CA 90755 | Oil & Gas Operator | Apr 2025 |
| 507 | Sevenbar Resources, LLC | Hallettsville, TX 77964 | Oil & Gas Operator | Apr 2025 |
| 508 | SFM Holdings, Inc. | Dallas, TX 75240 | Oil & Gas Operator | Jul 1995 |
| 509 | Shale Hunter, LLC | Irving, TX 75039 | Oil & Gas Operator | Jan 2016 |
| 510 | Shana Petroleum Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2002 |
| 511 | Shanghai Energy Corporation | Houston, TX 77027 | Oil & Gas Operator | Apr 2003 |
| 512 | Sharon Hunter Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Sep 2012 |
| 513 | Sharon Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Aug 2010 |
| 514 | Shell Trading Us Company | Houston, TX 77210 | Oil & Gas Operator | Jan 2025 |
| 515 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 516 | Shidler, Mark L., Inc. | Houston, TX 77055 | Oil & Gas Operator | Apr 2025 |
| 517 | Shiner Exploration, LLC | Houston, TX 77091 | Oil & Gas Operator | Apr 2025 |
| 518 | Shoreham Oil & Gas Company, Inc. | Katy, TX 77492 | Oil & Gas Operator | Apr 2025 |
| 519 | Silverbow Resources Oper, LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2025 |
| 520 | Slant Operating, LLC | Lafayette, LA 70503 | Oil & Gas Operator | Apr 2025 |
| 521 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Apr 2025 |
| 522 | SN Operating, LLC | Houston, TX 77002 | Oil & Gas Operator | May 2023 |
| 523 | Sonat Exploration Co. | Houston, TX 77251 | Oil & Gas Operator | Dec 2021 |
| 524 | South Leeville, LLC | Houston, TX 77069 | Oil & Gas Operator | Oct 2022 |
| 525 | Southern G Holdings, LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2007 |
| 526 | Southern Mineral Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2001 |
| 527 | Southern Union Exploration Co. | Austin, TX 78701 | Oil & Gas Operator | Feb 2002 |
| 528 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Apr 2025 |
| 529 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | Feb 2025 |
| 530 | Stewardship Resources | Roanoke, TX 76262 | Oil & Gas Operator | Jun 2022 |
| 531 | Stone & Webster Oil Company, Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 1995 |
| 532 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Apr 2025 |
| 533 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Apr 2025 |
| 534 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2025 |
| 535 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 536 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 537 | Sulphur River Exploration, Inc. | Dallas, TX 75244 | Oil & Gas Operator | Apr 2025 |
| 538 | Suncoast Technical Services Inc | Dallas, TX 75251 | Oil & Gas Operator | Apr 2025 |
| 539 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 540 | Swift Energy Operating, LLC | Houston, TX 77079 | Oil & Gas Operator | Jun 2017 |
| 541 | SWN Production LLC | Spring, TX 77389-4954 | Oil & Gas Operator | Feb 2022 |
| 542 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 543 | T & G Oil, Inc. | White Oak, TX 75693 | Oil & Gas Operator | Dec 2010 |
| 544 | T & T Production Co. | Victoria, TX 77902 | Oil & Gas Operator | Feb 1995 |
| 545 | T-C Oil Company, LLC | Refugio, TX 78377 | Oil & Gas Operator | Apr 2025 |
| 546 | T.D. Operating Company, Inc. | New Braunfels, TX 78130 | Oil & Gas Operator | Nov 1999 |
| 547 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 548 | Tamarack Petroleum Company, Inc. | Midland, TX 79701 | Oil & Gas Operator | Apr 2025 |
| 549 | TC Oil And Gas, LLC | Denton, TX 76205 | Oil Operator | Apr 2025 |
| 550 | TDC Engineering, Inc. | Abilene, TX 79604 | Oil & Gas Operator | Apr 2025 |
| 551 | TDX Energy, LLC | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2024 |
| 552 | Teal Operating, LLC | Dallas, TX 75225 | Oil & Gas Operator | Oct 2021 |
| 553 | Tend Oil Inc. | Tyler, TX 75703 | Oil & Gas Operator | Jul 1995 |
| 554 | Tensas Delta Explo. Co., LLC | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2011 |
| 555 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 556 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Apr 2025 |
| 557 | Texakoma E & P, LLC | Plano, TX 75024 | Oil & Gas Operator | Apr 2025 |
| 558 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | Apr 2025 |
| 559 | Texas Crude Energy, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 2012 |
| 560 | Texas Gulf Gas Corporation | Fayetteville, TX 78940 | Oil & Gas Operator | Jun 2005 |
| 561 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Apr 2025 |
| 562 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 563 | Texas Onshore Energy, Inc. | Austin, TX 78704 | Oil & Gas Operator | Apr 2025 |
| 564 | Texcal Energy (GP) LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2016 |
| 565 | Texron Operating, LLC | Bulverde, TX 78163 | Oil & Gas Operator | Apr 2025 |
| 566 | Tgo Operating, LLC | Midland, TX 79705 | Oil & Gas Operator | Dec 2008 |
| 567 | Thorp Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2014 |
| 568 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Apr 2025 |
| 569 | TMR Exploration, Inc. | Bossier City, LA 71171 | Oil & Gas Operator | Apr 2025 |
| 570 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 571 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 572 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Apr 2025 |
| 573 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 574 | Tri-Union Development Corp. | Houston, TX 77002 | Oil & Gas Operator | Apr 2025 |
| 575 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 576 | Triangle Development Co | Mahtomedi, MN 55115 | Gas Operator | Feb 1982 |
| 577 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 578 | Trio Consulting & Management,LLC | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2025 |
| 579 | Trio Operating Company, Inc. | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2006 |
| 580 | Triple J Investments Inc | Longview, TX 75606 | Oil & Gas Operator | Feb 2023 |
| 581 | Triton Oil & Gas Corp. | Houston, TX 77002 | Oil & Gas Operator | Nov 2014 |
| 582 | Tsar Energy, LLC | Dallas, TX 75205 | Oil & Gas Operator | Apr 2025 |
| 583 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2025 |
| 584 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 585 | Unicorn Energy, Inc. | Elgin, TX 78621 | Oil & Gas Operator | Apr 2025 |
| 586 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Apr 2025 |
| 587 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 588 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 589 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Apr 2025 |
| 590 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 591 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 592 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 593 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Apr 2025 |
| 594 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Apr 2025 |
| 595 | Valley Gathering Company | Midland, TX 79702 | Oil & Gas Operator | Feb 1997 |
| 596 | Vaquero Operating | FT Stockton, TX 79735 | Oil & Gas Operator | Apr 2025 |
| 597 | Vermillion Production, Inc. | Pearsall, TX 78061 | Oil & Gas Operator | Apr 2025 |
| 598 | Victoria Operating, Inc. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2025 |
| 599 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Jan 2025 |
| 600 | Viola Prod., Inc. | Dallas, TX 75251 | Oil & Gas Operator | Apr 2025 |