| 401 | Rio Grande Drilling Company | San Antonio, TX 78212 | Oil & Gas Operator | Dec 1999 |
| 402 | Ritchie, H. G. Jr. | Taft, TX 78390 | Oil & Gas Operator | May 2025 |
| 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 | Ross Gas And Oil, LTD. Co. | Dripping SPGS, TX 78620 | Oil & Gas Operator | May 2025 |
| 406 | Royal Oil & Gas Corp. | Indiana, PA 15701 | Oil & Gas Operator | Apr 2014 |
| 407 | Royal Production Company, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | May 2025 |
| 408 | Royko Oil Company | Horseshoe Bay, TX 78657 | Oil & Gas Operator | May 2025 |
| 409 | S & J Operating Company | Wichita Falls, TX 76301 | Oil & Gas Operator | Mar 2015 |
| 410 | Sabco Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2011 |
| 411 | Sabco Operating Company, LLC | Houston, TX 77056 | Oil & Gas Operator | Jun 2018 |
| 412 | Salida Exploration, LLC | Abilene, TX 79603 | Oil & Gas Operator | May 2025 |
| 413 | Salvador Oil, LLC | Dallas, TX 75201 | Oil & Gas Operator | May 2025 |
| 414 | Samson Hydrocarbons Company | Tulsa, OK 74103 | Oil & Gas Operator | Nov 2016 |
| 415 | Samson Lone Star LP | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2007 |
| 416 | Samson Lone Star, LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2025 |
| 417 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Feb 2025 |
| 418 | Samurai Operating Co. L.L.C. | Dayton, TX 77535 | Oil & Gas Operator | May 2025 |
| 419 | San Patricio Corporation | Dinero, TX 78350 | Oil & Gas Operator | Sep 2003 |
| 420 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 421 | Sanchez-O'Brien Oil & Gas Corp | Houston, TX 77057 | Oil & Gas Operator | May 1998 |
| 422 | Sandalwood Exploration, L.P. | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 423 | Sandalwood Oil & Gas, Inc. | Houston, TX 77057 | Oil & Gas Operator | May 2025 |
| 424 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | May 2025 |
| 425 | Sandia Energy Corporation-NM | Holdenville, OK 74848 | Oil & Gas Operator | Aug 2003 |
| 426 | Santos USA Corp. | Houston, TX 77042 | Oil & Gas Operator | Dec 2008 |
| 427 | Sarita Energy Resources, LTD. | Houston, TX 77277 | Oil & Gas Operator | May 2025 |
| 428 | Savage Exploration, Inc. | San Marcos, TX 78666 | Oil & Gas Operator | May 2025 |
| 429 | Saxet Energy, LTD. | Houston, TX 77057 | Oil & Gas Operator | Mar 2004 |
| 430 | Scana Petroleum Resources Inc | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 431 | Scully Energy Corporation | Salado, TX 76571 | Oil & Gas Operator | Mar 2012 |
| 432 | Seagull Operating Co., Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jan 2025 |
| 433 | Serra Energy, Inc. | Hailey, ID 83333 | Oil & Gas Operator | May 2011 |
| 434 | SFM Holdings, Inc. | Dallas, TX 75240 | Oil & Gas Operator | Jul 1995 |
| 435 | Shell Western E&P | Houston, TX 77001 | Oil & Gas Operator | May 2025 |
| 436 | Sierra Exploration Company | San Antonio, TX 78209 | Oil & Gas Operator | Mar 2008 |
| 437 | Silver Fox Oil & Gas LLC | Hebbronville, TX 78361 | Oil & Gas Operator | May 2025 |
| 438 | Silver Pines Energy Corp. | Houston, TX 77005 | Oil & Gas Operator | Feb 2025 |
| 439 | Sisters Operating Company | Victoria, TX 77904 | Oil & Gas Operator | Nov 2010 |
| 440 | Slawson Exploration Company Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | May 2025 |
| 441 | Smith Petroleum Company | Spring, TX 77389 | Oil & Gas Operator | May 2025 |
| 442 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | May 2025 |
| 443 | South Central Texas Oil & Gas Co | Houston, TX 77060 | Oil & Gas Operator | May 2025 |
| 444 | Southcoast Production Inc | Houston, TX 77010 | Oil & Gas Operator | May 2025 |
| 445 | Southern Bay Operating, L.L.C. | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 446 | Southern Resource Company | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Mar 2022 |
| 447 | Southern Royalty Inc. | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Feb 1997 |
| 448 | Southwest Gathering Company | Alice, TX 78332 | Oil & Gas Operator | May 2025 |
| 449 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 450 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 451 | Spiller, Robert S. | San Antonio, TX 78213 | Oil & Gas Operator | Oct 1995 |
| 452 | Spur Operating Co. | Austin, TX 78701 | Oil & Gas Operator | May 2025 |
| 453 | SSC, Inc. | Lubbock, TX 79408 | Oil & Gas Operator | May 2025 |
| 454 | Star Production, Inc. | Dallas, TX 75360 | Oil & Gas Operator | May 2025 |
| 455 | Starco Exploration, Inc. | Dallas, TX 75360 | Oil & Gas Operator | May 2025 |
| 456 | Statia Enterprises, Inc | Irving, TX 75014 | Oil & Gas Operator | May 2025 |
| 457 | Stephens & Johnson Operating Co. | Wichita Falls, TX 76307 | Oil & Gas Operator | May 2025 |
| 458 | Stinger Oil & Gas Inc. | Sherman Oaks, CA 91403 | Oil & Gas Operator | Oct 2013 |
| 459 | Stone & Webster Oil Company, Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 1995 |
| 460 | Stonegate Operators, Inc. | Addison, TX 75001 | Oil Operator | May 2025 |
| 461 | Stout Consulting Services, Inc. | Alice, TX 78333 | Oil & Gas Operator | May 1999 |
| 462 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 463 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 464 | Suemaur Expl. & Prod., LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Jun 2024 |
| 465 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 466 | Sulphur River Exploration, Inc. | Dallas, TX 75244 | Oil & Gas Operator | May 2025 |
| 467 | Sun Exploration, Inc. | Alice, TX 78332 | Oil & Gas Operator | May 2025 |
| 468 | Sutton Producing Corp. | San Antonio, TX 78270 | Oil & Gas Operator | May 2025 |
| 469 | Swope Corp. | Austin, TX 78735 | Oil & Gas Operator | May 2025 |
| 470 | Sydri Operating, LLC | Dallas, TX 75231 | Oil & Gas Operator | May 2025 |
| 471 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 472 | Synergy Production Company | Houston, TX 77024 | Oil & Gas Operator | Jan 1996 |
| 473 | T-C Oil Company, LLC | Refugio, TX 78377 | Oil & Gas Operator | May 2025 |
| 474 | T.O.I. | Midland, TX 79710 | Oil & Gas Operator | Mar 2001 |
| 475 | Taft Investment Co., Inc. | Taft, TX 78390 | Oil Operator | May 2025 |
| 476 | Tare Resources, LLC | Corpus Chrsti, TX 78426 | Oil & Gas Operator | May 2025 |
| 477 | Targa Midstream Services LLC | Houston, TX 77002 | Oil Operator | Mar 2023 |
| 478 | Tasca Exploration Company | Houston, TX 77257 | Oil & Gas Operator | Jun 2002 |
| 479 | TBC Petroleum | Cuero, TX 77954 | Oil & Gas Operator | Sep 2023 |
| 480 | Teamco Operating LLC | Houston, TX 77042 | Oil & Gas Operator | Oct 2002 |
| 481 | Tejones Operating Corporation | San Antonio, TX 78217 | Oil & Gas Operator | May 2025 |
| 482 | Tema Oil And Gas Company | Houston, TX 77084 | Oil & Gas Operator | May 2025 |
| 483 | Tema Oil And Gas, LLC | Houston, TX 77040 | Oil & Gas Operator | Apr 2000 |
| 484 | Tennessee Gas Pipeline Company, LLC | Houston, TX 77252 | Oil Operator | Dec 2024 |
| 485 | Texacal, Inc. | Newport Beach, CA 92660 | Oil & Gas Operator | May 2025 |
| 486 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | May 2025 |
| 487 | Texas Crude, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 1995 |
| 488 | Texas Onshore Energy, Inc. | Austin, TX 78704 | Oil & Gas Operator | May 2025 |
| 489 | Texas Southern Petroleum Corp. | Corpus Chrsti, TX 78410 | Oil & Gas Operator | May 2025 |
| 490 | Texas Western Energy Corporation | Portland, TX 78374 | Oil & Gas Operator | Nov 2002 |
| 491 | Texas, Les & Co. | Austin, TX 78746 | Oil & Gas Operator | May 2025 |
| 492 | TGX Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2004 |
| 493 | Thunder Oil & Gas, LLC | Ardmore, OK 73402 | Oil & Gas Operator | Feb 2025 |
| 494 | Thunderbird Energy, Inc. | Norman, OK 73069 | Oil & Gas Operator | May 2025 |
| 495 | Tierra Mineral Development, L.C. | Dallas, TX 75244 | Oil & Gas Operator | Oct 1994 |
| 496 | Tipperary Oil & Gas Corp | Denver, CO 80202 | Oil & Gas Operator | May 2014 |
| 497 | Tiza Energy, Inc. | Austin, TX 78715 | Oil & Gas Operator | May 2025 |
| 498 | TNT Petroleum Company, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Feb 1996 |
| 499 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 500 | Total E&P USA, Inc. | Houston, TX 77210 | Oil & Gas Operator | Nov 2011 |