| 401 | Rock Energy Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 402 | Rocker A Operating Company | Post, TX 79356 | Oil & Gas Operator | Aug 2022 |
| 403 | Rodessa Operating Company | Corpus Chrsti, TX 78426 | Oil & Gas Operator | May 2025 |
| 404 | Roma Oil And Gas, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | May 2025 |
| 405 | Rosetta Resources Operating LP | San Antonio, TX 78216 | Oil & Gas Operator | May 2025 |
| 406 | Ross Production Co. | Shreveport, LA 71101 | Oil & Gas Operator | Mar 2000 |
| 407 | Royal Oil & Gas Corp. | Indiana, PA 15701 | Oil & Gas Operator | Apr 2014 |
| 408 | Rusk Energy Operating LLC | Houston, TX 77040 | Oil & Gas Operator | May 2025 |
| 409 | S & S Operating Company, Inc. | Winnie, TX 77665 | Oil & Gas Operator | May 2025 |
| 410 | Samson Exploration LLC | Tulsa, OK 74101 | Oil & Gas Operator | Mar 2025 |
| 411 | Samson Hydrocarbons Company | Tulsa, OK 74103 | Oil & Gas Operator | Nov 2016 |
| 412 | Samson Lone Star LP | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2007 |
| 413 | Samson Lone Star, LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2025 |
| 414 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Feb 2025 |
| 415 | Sandalwood Oil & Gas, Inc. | Houston, TX 77057 | Oil & Gas Operator | May 2025 |
| 416 | Sandel Energy, Inc. | Huntsville, TX 77342 | Oil & Gas Operator | Apr 2004 |
| 417 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | May 2025 |
| 418 | Sandridge Exploration And Production LLC | Oklahoma City, OK 73104 | Oil & Gas Operator | May 2025 |
| 419 | Sanhall Corporation | Huntsville, TX 77340 | Oil & Gas Operator | Oct 1993 |
| 420 | Santa Fe Energy Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 421 | Santos USA Corp. | Houston, TX 77042 | Oil & Gas Operator | Dec 2008 |
| 422 | Scana Petroleum Resources Inc | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 423 | Scoggins Oil & Gas Co. | Seabrook, TX 77586 | Oil & Gas Operator | Jun 2000 |
| 424 | Seagull Operating Co., Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jan 2025 |
| 425 | Sedona Oil & Gas Corporation | Austin, TX 78746 | Oil & Gas Operator | May 2025 |
| 426 | Seguro Well Service, Inc. | Gonzales, TX 78629 | Oil & Gas Operator | May 2025 |
| 427 | Seismic Investment Group, Inc. | Houston, TX 77055 | Oil & Gas Operator | Jun 2008 |
| 428 | Sellers Lease Service, Inc. | Flatonia, TX 78941 | Oil & Gas Operator | May 2025 |
| 429 | Seneca Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Dec 2017 |
| 430 | Shana Petroleum Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2002 |
| 431 | Shanghai Energy Corporation | Houston, TX 77027 | Oil & Gas Operator | Apr 2003 |
| 432 | Sharon Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Aug 2010 |
| 433 | Shell Western E&P | Houston, TX 77001 | Oil & Gas Operator | May 2025 |
| 434 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 435 | Shepperd, William M. | Houston, TX 77279 | Oil & Gas Operator | Sep 2012 |
| 436 | Sheridan Energy,Inc. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 437 | Shiner Exploration, LLC | Houston, TX 77091 | Oil & Gas Operator | May 2025 |
| 438 | Sien Operating Company, LLC | San Antonio, TX 78209 | Oil Operator | May 2023 |
| 439 | Silver Star Operating Co., LLC | Nada, TX 77460 | Gas Operator | May 2025 |
| 440 | Slawson Exploration Company Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | May 2025 |
| 441 | Southern Union Exploration Co. | Austin, TX 78701 | Oil & Gas Operator | Feb 2002 |
| 442 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 443 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | May 2025 |
| 444 | Stanotex, LLC | Katy, TX 77494 | Oil & Gas Operator | May 2025 |
| 445 | Stanton Mineral Development Inc | Austin, TX 78759 | Oil & Gas Operator | May 2025 |
| 446 | Stephens, Autry C. | Midland, TX 79701 | Oil & Gas Operator | Mar 2023 |
| 447 | Stone & Webster Oil Company, Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 1995 |
| 448 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | May 2025 |
| 449 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 450 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 451 | Sundown Energy LP | Dallas, TX 75248 | Oil & Gas Operator | May 2025 |
| 452 | Sunray Operating Company LLC | Sugar Land, TX 77498 | Oil & Gas Operator | May 2025 |
| 453 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 454 | Sydri Operating, LLC | Dallas, TX 75231 | Oil & Gas Operator | May 2025 |
| 455 | Tag Operating Company, Inc. | Houston, TX 77092 | Oil & Gas Operator | May 2025 |
| 456 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 457 | Tamarack Petroleum Company, Inc. | Midland, TX 79701 | Oil & Gas Operator | May 2025 |
| 458 | Teamco Operating LLC | Houston, TX 77042 | Oil & Gas Operator | Oct 2002 |
| 459 | Tejones Operating Corporation | San Antonio, TX 78217 | Oil & Gas Operator | May 2025 |
| 460 | Tensas Delta Explo. Co., LLC | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2011 |
| 461 | Terrafina Energy, LLC | San Antonio, TX 78280 | Oil & Gas Operator | May 2025 |
| 462 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | May 2025 |
| 463 | Texas Gulf Gas Corporation | Fayetteville, TX 78940 | Oil & Gas Operator | Jun 2005 |
| 464 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | May 2025 |
| 465 | Texas Sunset Energy And Ent Inc | Victoria, TX 77904 | Oil Operator | Aug 2003 |
| 466 | Texlan Oil Company, Inc. | Tyler, TX 75701 | Oil & Gas Operator | Nov 1994 |
| 467 | Thunderbird Energy, Inc. | Norman, OK 73069 | Oil & Gas Operator | May 2025 |
| 468 | TMR Exploration, Inc. | Bossier City, LA 71171 | Oil & Gas Operator | May 2025 |
| 469 | Toklan Oil And Gas Corporation | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2025 |
| 470 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 471 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 472 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 473 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | May 2025 |
| 474 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 475 | Triangle Development Co | Mahtomedi, MN 55115 | Gas Operator | Feb 1982 |
| 476 | Trinity River Energy Oper, LLC | Houston, TX 77008 | Oil & Gas Operator | May 2018 |
| 477 | Triple L Oil Company | Corpus Chrsti, TX 78469 | Oil & Gas Operator | Jan 1998 |
| 478 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 479 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 480 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 481 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | May 2025 |
| 482 | Us Petro LP | Amarillo, TX 79106 | Oil & Gas Operator | Apr 2020 |
| 483 | Vantage Operating, LLC | San Antonio, TX 78230 | Oil & Gas Operator | May 2025 |
| 484 | Vaquero Operating | FT Stockton, TX 79735 | Oil & Gas Operator | May 2025 |
| 485 | Verus Energy, Inc | Houston, TX 77098 | Oil & Gas Operator | Sep 2004 |
| 486 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Feb 2025 |
| 487 | Vintage Petroleum, LLC | Houston, TX 77210 | Oil & Gas Operator | Dec 2019 |
| 488 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | May 2025 |
| 489 | Viper S.W.D., LLC | El Campo, TX 77437 | Oil & Gas Operator | May 2025 |
| 490 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 491 | Vista Resources, Inc. (A) | Midland, TX 79701 | Oil & Gas Operator | Feb 2000 |
| 492 | Vistatex Energy LLC | Houston, TX 77057 | Oil & Gas Operator | Mar 2025 |
| 493 | VT VIstatex Energy LLC | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 494 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | May 2025 |
| 495 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 496 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 497 | Walter Exploration Company | Dallas, TX 75206 | Oil & Gas Operator | May 2025 |
| 498 | Walter Exploration Inc | Dallas, TX 75206 | Oil & Gas Operator | May 2009 |
| 499 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | May 2025 |
| 500 | Wandoo Energy, LLC | The Woodlands, TX 77382 | Oil & Gas Operator | May 2025 |