| 501 | Southwestern Electric Power Co | Dallas, TX 75266 | Oil & Gas Operator | Dec 1989 |
| 502 | Stephens, Glynn | Overton, TX 75684 | Oil & Gas Operator | Oct 2001 |
| 503 | Stetson Petroleum Corp. | Rollins, MT 59931 | Oil & Gas Operator | Jun 2026 |
| 504 | Stoneburner Exploration, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Oct 1997 |
| 505 | Stroud Petroleum, Inc. | Shreveport, LA 71162 | Oil & Gas Operator | Jun 2026 |
| 506 | Sulphur River Exploration, Inc. | Dallas, TX 75244 | Oil & Gas Operator | Jun 2026 |
| 507 | Sun Oil Company | Dallas, TX 75373 | Oil & Gas Operator | Dec 2021 |
| 508 | Sydri Operating, LLC | Dallas, TX 75231 | Oil & Gas Operator | Jun 2026 |
| 509 | T & G Oil, Inc. | White Oak, TX 75693 | Oil & Gas Operator | Dec 2010 |
| 510 | T & J Oil Production, L.L.C. | Lone Grove, OK 73443 | Oil & Gas Operator | Mar 2026 |
| 511 | T M Hopkins Operating Co | Kilgore, TX 75663 | Oil & Gas Operator | Oct 2002 |
| 512 | T. J. Oil And Gas, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Oct 2002 |
| 513 | T.O.I. | Midland, TX 79710 | Oil & Gas Operator | Mar 2001 |
| 514 | Tanos Exploration II, LLC | Tyler, TX 75701 | Oil & Gas Operator | Sep 2023 |
| 515 | Tanos Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Oct 2018 |
| 516 | Tascosa Petroleum Corporation | Amarillo, TX 79105 | Oil & Gas Operator | Jun 2026 |
| 517 | Tate, Larry V. Operating, Inc. | Kilgore, TX 75662 | Oil & Gas Operator | Apr 2002 |
| 518 | Texaco E & P Inc. | Houston, TX 77099 | Oil & Gas Operator | Jun 2026 |
| 519 | Texas Energy Operations, LC | Wichita Falls, TX 76301 | Oil & Gas Operator | Jun 2026 |
| 520 | Texas M.O.R., Inc. | Corsicana, TX 75109 | Oil Operator | Sep 2013 |
| 521 | Texas Royalty Corp. | Austin, TX 78746 | Oil & Gas Operator | Jun 2026 |
| 522 | Texlan Oil Company, Inc. | Tyler, TX 75701 | Oil & Gas Operator | Nov 1994 |
| 523 | Texlan Oil Company, L.C. | Tyler, TX 75711 | Oil & Gas Operator | Aug 2003 |
| 524 | Texstar Petroleum, Inc. | Houston, TX 77002 | Oil & Gas Operator | Nov 2000 |
| 525 | TGNR East Texas II LLC | Houston, TX 77002 | Oil & Gas Operator | Jun 2026 |
| 526 | TGNR East Texas LLC | Houston, TX 77002 | Oil & Gas Operator | Jun 2026 |
| 527 | TGNR Gulf Coast LLC | Houston, TX 77002 | Oil & Gas Operator | Jun 2026 |
| 528 | Three J Energy, Inc. | Seguin, TX 78155 | Oil & Gas Operator | Jun 2026 |
| 529 | Three R Oil Company | Post, TX 79356 | Oil & Gas Operator | Jun 2026 |
| 530 | Three Sisters Petroleum, Inc. | Oil City, LA 71061 | Oil & Gas Operator | Jan 2025 |
| 531 | Titan Rock E&P, LLC | Kilgore, TX 75663 | Oil & Gas Operator | Jan 2024 |
| 532 | Tola Production Company | Dallas, TX 75367 | Oil & Gas Operator | Jun 2026 |
| 533 | Toomey Oil Company Inc | Tulsa, OK 74120 | Oil & Gas Operator | Jan 2026 |
| 534 | Torch Energy Services, Inc. | Houston, TX 77010 | Oil & Gas Operator | Sep 2011 |
| 535 | Tri "M" Oil & Gas | Muenster, TX 76252 | Oil & Gas Operator | Jun 2026 |
| 536 | Tri-Am Operating Company | Frankston, TX 75763 | Oil & Gas Operator | Jun 2026 |
| 537 | Triple "S" Resources Inc | Sapulpa, OK 74066 | Oil & Gas Operator | Jun 1995 |
| 538 | Triple J Investments Inc | Longview, TX 75606 | Oil & Gas Operator | Feb 2023 |
| 539 | Triple M Saltwater Disposal, LP | Kilgore, TX 75663 | Oil Operator | Jun 2026 |
| 540 | Trivium Operating, LLC | Fort Worth, TX 76107 | Oil & Gas Operator | Jun 2026 |
| 541 | Txok Texas Energy Resources,L.P. | Dallas, TX 75251 | Oil & Gas Operator | Apr 2008 |
| 542 | TXX Operating LLC | Shreveport, LA 71133 | Oil & Gas Operator | Jun 2026 |
| 543 | Tyler Oil & Gas Inc. | Tyler, TX 75702 | Oil & Gas Operator | Sep 2004 |
| 544 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Jul 2025 |
| 545 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 546 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 547 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Jun 2026 |
| 548 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 549 | Uplands Resources Inc | Tulsa, OK 74103-4141 | Oil & Gas Operator | Mar 2026 |
| 550 | Ursus Oil And Gas | Tyler, TX 75703 | Oil & Gas Operator | Jun 2026 |
| 551 | Usfg Oil & Gas, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Dec 2005 |
| 552 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Jun 2026 |
| 553 | Van Oil Co Inc | Fort Worth, TX 76116 | Oil Operator | Dec 1997 |
| 554 | Vaquero Gas Company,Incorporated | Houston, TX 77002 | Oil & Gas Operator | Jun 1993 |
| 555 | Vector Energy Corporation | Houston, TX 77060 | Oil & Gas Operator | Jun 2026 |
| 556 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 557 | Verado Energy, Inc. | Allen, TX 75013 | Oil & Gas Operator | Oct 2025 |
| 558 | Vista Oil & Gas, Inc. | The Woodlands, TX 77382 | Oil & Gas Operator | Feb 2000 |
| 559 | Vtex Energy, Inc. | Houston, TX 77057 | Oil & Gas Operator | Jun 2026 |
| 560 | W.H.D., Inc. | Euless, TX 76039 | Oil & Gas Operator | Aug 1998 |
| 561 | Wagner & Brown, LTD. | Midland, TX 79702 | Oil & Gas Operator | Aug 2014 |
| 562 | Walter Exploration Inc | Dallas, TX 75206 | Oil & Gas Operator | May 2009 |
| 563 | Warren American Oil Co | Tulsa, OK 74147 | Oil & Gas Operator | Apr 2026 |
| 564 | Weatherly Oil & Gas, LLC | Dallas, TX 75206 | Oil & Gas Operator | Jun 2026 |
| 565 | West Mountain Operating Co, Inc. | Longview, TX 75604 | Oil & Gas Operator | Feb 2019 |
| 566 | Western Production Company | Fort Worth, TX 76102 | Oil & Gas Operator | Jun 2026 |
| 567 | White Marlin Operating Company, LLC | Houston, TX 77002 | Oil & Gas Operator | Jun 2026 |
| 568 | Whittington, G. R. | Amarillo, TX 79109 | Oil & Gas Operator | Jan 1994 |
| 569 | Whittington, G. R. Estate | Amarillo, TX 79109 | Oil & Gas Operator | Mar 2008 |
| 570 | Wilcox Operating Corporation | Shreveport, LA 71115 | Oil & Gas Operator | Jun 2026 |
| 571 | Williams, Clayton Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | Jun 2026 |
| 572 | Willow Springs Prod. Serv.,LLC | Kilgore, TX 75663 | Oil & Gas Operator | Aug 1997 |
| 573 | Willow Springs Production, Inc. | Longview, TX 75606 | Oil & Gas Operator | Sep 1999 |
| 574 | Wilson Hydrocarbon Inc. | Houston, TX 77066 | Oil & Gas Operator | Jun 2026 |
| 575 | Wilson Resources, Inc. | Longview, TX 75601 | Oil & Gas Operator | Jun 2026 |
| 576 | Wimco | Dallas, TX 75229 | Oil & Gas Operator | Jul 2008 |
| 577 | Woodbine Production Corporation | Kilgore, TX 75663 | Oil & Gas Operator | Jun 2026 |
| 578 | WTR Operating LLC | Kilgore, TX 75663 | Oil & Gas Operator | Jun 2026 |
| 579 | WTXR Operating (Texas), Inc. | Carrollton, TX 75007 | Oil Operator | Jun 2026 |
| 580 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 581 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Jun 2026 |
| 582 | Xtreme Operating Company LLC | Flower Mound, TX 75022 | Oil Operator | Jun 2026 |
| 583 | Young, Clint Inc. | Graham, TX 76450 | Oil & Gas Operator | Jun 2026 |
| 584 | Zivney Energy | White Oak, TX 75693 | Oil & Gas Operator | Jun 2026 |
| 585 | Zoe Oil & Energy, LP | Watauga, TX 76148 | Oil & Gas Operator | Jun 2026 |
| 586 | Zone Energy, LLC | Houston, TX 77251 | Oil & Gas Operator | Jan 2025 |
| 587 | ZTH Operating, LLC | Troup, TX 75789 | Oil & Gas Operator | Jun 2026 |