| 401 | Royal Oil & Gas Corp. | Indiana, PA 15701 | Oil & Gas Operator | Apr 2014 |
| 402 | Royal Production Company, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Mar 2026 |
| 403 | Sabco Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2011 |
| 404 | Sable Energy Corp. | Houston, TX 77057 | Oil & Gas Operator | Nov 1999 |
| 405 | Samedan Oil Corporation | Houston, TX 77067 | Oil & Gas Operator | Dec 2019 |
| 406 | Samis Oil Company, Inc. | Oklahoma City, OK 73156 | Oil & Gas Operator | Sep 2000 |
| 407 | San Patricio Corporation | Dinero, TX 78350 | Oil & Gas Operator | Sep 2003 |
| 408 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | Mar 2026 |
| 409 | Sanchez-O'Brien Oil & Gas Corp | Houston, TX 77057 | Oil & Gas Operator | May 1998 |
| 410 | Sandia Operating Corp. | San Antonio, TX 78270 | Oil & Gas Operator | May 2010 |
| 411 | Santa Fe Energy Oper. Part., LP | Houston, TX 77057 | Oil & Gas Operator | Dec 1994 |
| 412 | Santos USA Corp. | Houston, TX 77042 | Oil & Gas Operator | Dec 2008 |
| 413 | Savage Exploration, Inc. | San Marcos, TX 78666 | Oil & Gas Operator | Mar 2026 |
| 414 | Saxet Energy, LTD. | Houston, TX 77057 | Oil & Gas Operator | Mar 2004 |
| 415 | SBJ Oil & Gas, LLC | Iraan, TX 79744 | Oil & Gas Operator | Mar 2026 |
| 416 | Schmid Properties, Inc. | Hico, TX 76457 | Oil & Gas Operator | Mar 2026 |
| 417 | Seagull Energy E & P Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2015 |
| 418 | Seguro Well Service, Inc. | Gonzales, TX 78629 | Oil & Gas Operator | Mar 2026 |
| 419 | Sharon Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Aug 2010 |
| 420 | Silver Hill Energy Operating, LLC | Dallas, TX 75201 | Oil & Gas Operator | Mar 2026 |
| 421 | Smith Petroleum Company | Spring, TX 77389 | Oil & Gas Operator | Mar 2026 |
| 422 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Mar 2026 |
| 423 | Smyth Oil Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2003 |
| 424 | South Oil, Inc. | Houston, TX 77057 | Oil & Gas Operator | Nov 2018 |
| 425 | Southern Bay Operating, L.L.C. | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 426 | Southern G Holdings, LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2007 |
| 427 | Southwest Gas Systems, Inc. | Spring, TX 77379 | Oil & Gas Operator | Mar 2026 |
| 428 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 429 | Spur Operating Co. | Austin, TX 78701 | Oil & Gas Operator | Mar 2026 |
| 430 | Staples, Tommy Oil Co. | Pettus, TX 78146 | Oil & Gas Operator | Mar 2008 |
| 431 | Statoil Texas Onshore Prop LLC | Austin, TX 78730 | Oil & Gas Operator | Dec 2018 |
| 432 | Strand Energy, Inc. (I) | Houston, TX 77002 | Oil & Gas Operator | Sep 1996 |
| 433 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Mar 2026 |
| 434 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 435 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 436 | Summit Discovery Res II LLC | Houston, TX 77024 | Oil & Gas Operator | Sep 2019 |
| 437 | Sunburst, Inc. | Wheat Ridge, CO 80033 | Oil & Gas Operator | Dec 2025 |
| 438 | Sunwest Operating Company L.L.C. | Englewood, CO 80155 | Oil & Gas Operator | Aug 2002 |
| 439 | Sure Flow Oil & Gas, Inc. | Victoria, TX 77902 | Oil & Gas Operator | Mar 2026 |
| 440 | Talisman Energy USA Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | May 2016 |
| 441 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 442 | Targa Midstream Services LLC | Houston, TX 77002 | Oil Operator | Mar 2023 |
| 443 | TBM Catarina, LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2026 |
| 444 | Teal Operating, LLC | Dallas, TX 75225 | Oil & Gas Operator | Oct 2021 |
| 445 | Texaco E & P Inc. | Houston, TX 77099 | Oil & Gas Operator | Mar 2026 |
| 446 | Texakoma Oil & Gas Corp | Dallas, TX 75240 | Oil & Gas Operator | Sep 2014 |
| 447 | Texas American Resources Company | Austin, TX 78701 | Oil & Gas Operator | Mar 2026 |
| 448 | Texas Crude Energy, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 2012 |
| 449 | Texas Western Energy Corporation | Portland, TX 78374 | Oil & Gas Operator | Nov 2002 |
| 450 | Texoma Oil Tools, Inc. | Wichita Falls, TX 76308 | Oil & Gas Operator | Mar 2026 |
| 451 | Texron Operating, LLC | Bulverde, TX 78163 | Oil & Gas Operator | Mar 2026 |
| 452 | Texstar North America, Inc. | Waynesboro, MS 39367 | Oil & Gas Operator | Aug 1994 |
| 453 | The Quintin Little Company Inc | Ardmore, OK 73401 | Oil & Gas Operator | Jan 2026 |
| 454 | Thompson, Richard W. Inc. | Plano, TX 75024 | Oil & Gas Operator | Mar 2026 |
| 455 | Three J Energy, Inc. | Seguin, TX 78155 | Oil & Gas Operator | Mar 2026 |
| 456 | Thunder Oil & Gas, LLC | Ardmore, OK 73402 | Oil & Gas Operator | Jan 2026 |
| 457 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Mar 2026 |
| 458 | Tidewater Minerals Corporation | Orange Grove, TX 78372 | Oil & Gas Operator | Mar 2026 |
| 459 | Tiza Operating Company | Austin, TX 78716 | Oil & Gas Operator | Jan 2000 |
| 460 | Tradestar Energy, Inc. | Hot Springs, AR 71913 | Oil Operator | Feb 2021 |
| 461 | Trailblazer Oil & Gas LLC | Goliad, TX 77963 | Oil & Gas Operator | Mar 2026 |
| 462 | Trans Texas Minerals Company | Austin, TX 78714 | Oil & Gas Operator | Aug 1999 |
| 463 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Mar 2026 |
| 464 | Traton Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Mar 2019 |
| 465 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Mar 2026 |
| 466 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 467 | Trinity Operating (Usg), LLC | Houston, TX 77002 | Oil & Gas Operator | Mar 2026 |
| 468 | Trinity River Energy Oper, LLC | Houston, TX 77008 | Oil & Gas Operator | May 2018 |
| 469 | Triple "S" Resources Inc | Sapulpa, OK 74066 | Oil & Gas Operator | Jun 1995 |
| 470 | Triple J Investments Inc | Longview, TX 75606 | Oil & Gas Operator | Feb 2023 |
| 471 | Tsoco | Tuleta, TX 78162 | Oil & Gas Operator | Apr 2017 |
| 472 | Turner, M. O. | San Antonio, TX 78278 | Oil & Gas Operator | Apr 2003 |
| 473 | Tuskar (Texas), Inc. | Nichols Hill, OK 73116 | Oil & Gas Operator | Jan 2016 |
| 474 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 475 | Validus NRG Aquilas Assetco LLC | Denver, CO 80202 | Oil & Gas Operator | Nov 2022 |
| 476 | Valley Gathering Company | Midland, TX 79702 | Oil & Gas Operator | Feb 1997 |
| 477 | Vastar Resources Inc | Houston, TX 77253 | Oil & Gas Operator | Sep 2025 |
| 478 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 479 | Verdun Oil & Gas LLC | Houston, TX 77024 | Oil & Gas Operator | Mar 2026 |
| 480 | Viceroy Petroleum GP, LLC | Rockdale, TX 76567 | Oil & Gas Operator | Feb 2010 |
| 481 | Viceroy Petroleum, LP | College Sta, TX 77845 | Oil & Gas Operator | Mar 2026 |
| 482 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Dec 2025 |
| 483 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Mar 2026 |
| 484 | Viper S.W.D., LLC | El Campo, TX 77437 | Oil & Gas Operator | Mar 2026 |
| 485 | Virtex Operating Company, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2023 |
| 486 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 487 | Vondra Energy Corp. | Alvin, TX 77512 | Oil & Gas Operator | Mar 2026 |
| 488 | VSP Operating, LLC | Castle Rock, CO 80108 | Oil Operator | Mar 2026 |
| 489 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2026 |
| 490 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 491 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2026 |
| 492 | Warner Sisters, LLC | Thompsons Sta, TN 37179 | Oil Operator | Mar 2026 |
| 493 | Warwick-Artemis, LLC | Nichols Hill, OK 73116 | Oil & Gas Operator | Mar 2026 |
| 494 | Waters Eng. & Operating, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Sep 2013 |
| 495 | Weeks Exploration Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 496 | Wejco, Inc. | Rising Star, TX 76471 | Oil & Gas Operator | Mar 2026 |
| 497 | Welder Exploration & Prod., Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Dec 2022 |
| 498 | Welderxp LTD. | San Antonio, TX 78212 | Oil & Gas Operator | Mar 2026 |
| 499 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 500 | Westport Oil And Gas Company Inc | Denver, CO 80202 | Oil & Gas Operator | Feb 2002 |