| 401 | Samson Hydrocarbons Company | Tulsa, OK 74103 | Oil & Gas Operator | Nov 2016 |
| 402 | Samson Lone Star LP | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2007 |
| 403 | Samson Lone Star, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Dec 2025 |
| 404 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Oct 2025 |
| 405 | San Patricio Corporation | Dinero, TX 78350 | Oil & Gas Operator | Sep 2003 |
| 406 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | Dec 2025 |
| 407 | Sanchez-O'Brien Oil & Gas Corp | Houston, TX 77057 | Oil & Gas Operator | May 1998 |
| 408 | Sarrita Oil Co., Inc. | Floresville, TX 78114 | Oil & Gas Operator | Jul 2002 |
| 409 | Saxet Energy, LTD. | Houston, TX 77057 | Oil & Gas Operator | Mar 2004 |
| 410 | Scorpion Operating, Inc. | Benavides, TX 78341 | Oil Operator | Dec 2025 |
| 411 | Se USA Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2009 |
| 412 | Senora Resources, Inc. | Dime Box, TX 77853 | Oil & Gas Operator | Dec 2025 |
| 413 | Shana Petroleum Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2002 |
| 414 | Shell Western E&P | Houston, TX 77001 | Oil & Gas Operator | Dec 2025 |
| 415 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 416 | Sheridan Production Company, LLC | Houston, TX 77056 | Oil & Gas Operator | Oct 2025 |
| 417 | Sierra Resources, LLC | Houston, TX 77219 | Oil & Gas Operator | Aug 2021 |
| 418 | Skrivanos Engineering, Inc. | Shreveport, LA 71164 | Oil & Gas Operator | Dec 2011 |
| 419 | Smith Operating And MGMT Co. | Shreveport, LA 71161 | Oil & Gas Operator | Jun 2023 |
| 420 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Dec 2025 |
| 421 | Sonterra Operating, Inc. | Houston, TX 77060 | Oil & Gas Operator | Dec 2025 |
| 422 | South Central Texas Oil & Gas Co | Houston, TX 77060 | Oil & Gas Operator | Dec 2025 |
| 423 | South Texas Limited Partnership | Houston, TX 77060 | Oil & Gas Operator | Feb 1994 |
| 424 | Southern Mineral Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2001 |
| 425 | Southern Resource Company | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Mar 2022 |
| 426 | Southern Tejas Asset Group LLC | McAllen, TX 78501 | Oil & Gas Operator | Dec 2025 |
| 427 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 428 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 429 | Southwest Resources, Inc. | Brenham, TX 77834 | Oil & Gas Operator | Dec 2025 |
| 430 | Speller Oil Corporation | Oklahoma City, OK 73112 | Oil & Gas Operator | Oct 2025 |
| 431 | Spiller Operating Co., Inc. | Round Rock, TX 78665 | Oil & Gas Operator | May 2015 |
| 432 | Spiller, Robert S. | San Antonio, TX 78213 | Oil & Gas Operator | Oct 1995 |
| 433 | Star Of Texas Energy SRVS, Inc. | Austin, TX 78702 | Oil & Gas Operator | Dec 2025 |
| 434 | Starco Exploration, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Dec 2025 |
| 435 | Starr Operating, LLC | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2025 |
| 436 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | Oct 2025 |
| 437 | Stone & Webster Oil Company, Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 1995 |
| 438 | Stonegate Operators, Inc. | Addison, TX 75001 | Oil Operator | Dec 2025 |
| 439 | Strata Operating, Inc. | Corpus Chrsti, TX 78466 | Oil & Gas Operator | Dec 2025 |
| 440 | Stroube Energy Corporation | Dallas, TX 75248 | Oil & Gas Operator | Jan 2012 |
| 441 | Stroud Production LLC | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2024 |
| 442 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 443 | Suemaur Expl. & Prod., LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Jun 2024 |
| 444 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 445 | Sure Flow Oil & Gas Company | Victoria, TX 77902 | Oil & Gas Operator | Mar 2008 |
| 446 | Sure Flow Oil & Gas, Inc. | Victoria, TX 77902 | Oil & Gas Operator | Dec 2025 |
| 447 | Tag Operating Company, Inc. | Houston, TX 77092 | Oil & Gas Operator | Dec 2025 |
| 448 | Tam2 Squared Operating, LLC | Rockwall, TX 75032 | Oil & Gas Operator | Dec 2025 |
| 449 | Tasca Exploration Company | Houston, TX 77257 | Oil & Gas Operator | Jun 2002 |
| 450 | Tejones Operating Corporation | San Antonio, TX 78217 | Oil & Gas Operator | Dec 2025 |
| 451 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 452 | Tesoro E&P Company, L.P. | San Antonio, TX 78216 | Oil & Gas Operator | Jan 2000 |
| 453 | Tesoro Expl. & Prod. Company | San Antonio, TX 78216 | Gas Operator | Sep 2010 |
| 454 | Texaco E & P Inc. | Houston, TX 77099 | Oil & Gas Operator | Dec 2025 |
| 455 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | Dec 2025 |
| 456 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Dec 2025 |
| 457 | Texas Independent Explor., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 458 | Texas Valley Oil & Gas, LLC | Hidalgo, TX 78557 | Oil Operator | Dec 2025 |
| 459 | Texas Western Energy Corporation | Portland, TX 78374 | Oil & Gas Operator | Nov 2002 |
| 460 | Texas, Les & Co. | Brenham, TX 77833 | Oil & Gas Operator | Dec 2025 |
| 461 | Tharp Operating Company | Houston, TX 77070 | Oil & Gas Operator | Nov 2014 |
| 462 | Thorp Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2014 |
| 463 | Three C Exploration, LLC | Hebbronville, TX 78361 | Oil & Gas Operator | Dec 2025 |
| 464 | Three-C Oil And Gas | Hebbronville, TX 78361 | Oil & Gas Operator | Dec 2025 |
| 465 | Thresher Energy, Inc. | Houston, TX 77060 | Oil & Gas Operator | Dec 2025 |
| 466 | Tidelands Oil Corporation | Crystal City, TX 78839 | Oil & Gas Operator | Aug 2003 |
| 467 | Tiza Energy, Inc. | Austin, TX 78715 | Oil & Gas Operator | Dec 2025 |
| 468 | TNR Petroleum, Inc. | Austin, TX 78747 | Oil & Gas Operator | Sep 1999 |
| 469 | TNT Petroleum Company, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Feb 1996 |
| 470 | Toma Oil & Gas, Inc. | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Oct 1997 |
| 471 | Total E&P USA, Inc. | Houston, TX 77210 | Oil & Gas Operator | May 2025 |
| 472 | Totalfinaelf E&P USA Inc | Houston, TX 77024 | Oil & Gas Operator | Jul 2007 |
| 473 | Touchstone Resources USA, Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2006 |
| 474 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Dec 2025 |
| 475 | Transpacific Energy, LLC | Katy, TX 77450 | Oil & Gas Operator | Dec 2025 |
| 476 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 477 | Trap Rock Oil Company | Cambridge, MA 02138 | Oil & Gas Operator | Nov 2005 |
| 478 | Trap Rock Oil, LTD. | Houston, TX 77005 | Oil & Gas Operator | Dec 2025 |
| 479 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Dec 2025 |
| 480 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 481 | Triad O&G, LLC | Dallas, TX 75225 | Oil & Gas Operator | Dec 2025 |
| 482 | Trinity River Energy Oper, LLC | Houston, TX 77008 | Oil & Gas Operator | May 2018 |
| 483 | True Oil Company | Casper, WY 82602 | Oil & Gas Operator | Aug 2003 |
| 484 | Txco Resources Inc. | San Antonio, TX 78280 | Oil & Gas Operator | Dec 2025 |
| 485 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 486 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 487 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 488 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 489 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 490 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Dec 2025 |
| 491 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Dec 2025 |
| 492 | V/J Oil Company | Yancey, TX 78886 | Oil & Gas Operator | Oct 2015 |
| 493 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Dec 2025 |
| 494 | Valley Petrochemicals, LLC | Pharr, TX 78577 | Oil Operator | Dec 2025 |
| 495 | Valor Energy, LLC | Dallas, TX 75205 | Oil & Gas Operator | May 2023 |
| 496 | Vantage Operating, LLC | San Antonio, TX 78230 | Oil & Gas Operator | Dec 2025 |
| 497 | Varas Energy Operating Company, LLC | Houston, TX 77005 | Oil & Gas Operator | Dec 2025 |
| 498 | Vastar Resources Inc | Houston, TX 77253 | Oil & Gas Operator | Jun 2025 |
| 499 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Dec 2025 |
| 500 | Vision Oil And Gas LLC | Laredo, TX 78041 | Oil & Gas Operator | Dec 2025 |