| 501 | Southern Union Exploration Co. | Austin, TX 78701 | Oil & Gas Operator | Feb 2002 |
| 502 | Southland Royalty Company | Houston, TX 77210 | Oil & Gas Operator | Sep 2011 |
| 503 | Southwest Royalties, Inc. | Midland, TX 79710 | Oil & Gas Operator | Feb 2026 |
| 504 | Southwestern Energy Prod Co | Houston, TX 77032 | Oil & Gas Operator | Jun 2015 |
| 505 | Spartan Oil Corporation | Abilene, TX 79601 | Oil & Gas Operator | Aug 2003 |
| 506 | Special JHR Corp | Bridgeville, PA 15017 | Oil & Gas Operator | Feb 2026 |
| 507 | Spence Energy Company | Dallas, TX 75360 | Oil & Gas Operator | Feb 2026 |
| 508 | Spenergy Corp. | Midland, TX 79701 | Oil & Gas Operator | Dec 1999 |
| 509 | Spheric Petroleum Inc. | Baltimore, MD 21208 | Oil & Gas Operator | Nov 2006 |
| 510 | Spiller Operating Co., Inc. | Round Rock, TX 78665 | Oil & Gas Operator | May 2015 |
| 511 | SRG Oil Corporation | Abilene, TX 79604 | Oil & Gas Operator | Apr 1994 |
| 512 | St. Clair Energy Corporation | Tulsa, OK 74153 | Oil & Gas Operator | Mar 2008 |
| 513 | Staghorn Resources, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2015 |
| 514 | Staley Oil Company | Wichita Falls, TX 76308 | Oil & Gas Operator | Jan 2000 |
| 515 | Star Production, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Feb 2026 |
| 516 | Startex Energy, Inc. | Abilene, TX 79608 | Oil & Gas Operator | Feb 2026 |
| 517 | Stonebriar Oil LLC | Frisco, TX 75034 | Oil & Gas Operator | Feb 2026 |
| 518 | Stovall Operating Co. | Graham, TX 76450 | Oil & Gas Operator | Feb 2026 |
| 519 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 520 | Sun-Key Oil Co., Inc. | Dublin, TX 76446 | Oil & Gas Operator | Feb 2026 |
| 521 | Sundance Consulting Corp. | Abilene, TX 79605 | Oil & Gas Operator | Feb 2026 |
| 522 | Sundial Resources, Inc. | Graham, TX 76450 | Oil & Gas Operator | Feb 2026 |
| 523 | Susanna Corporation | Breckenridge, TX 76424 | Oil & Gas Operator | Feb 2026 |
| 524 | Sutton Oil Co. | San Antonio, TX 78254 | Oil & Gas Operator | Feb 2026 |
| 525 | Swaringin, Howard Operating | Maryneal, TX 79535 | Oil & Gas Operator | May 2003 |
| 526 | Sweet Crude Operating LLC | Brenham, TX 77834 | Oil & Gas Operator | Feb 2026 |
| 527 | Sweetwater Drilling Co., Inc. | Fort Worth, TX 76116 | Oil & Gas Operator | Feb 2026 |
| 528 | T-N-T Engineering, Inc. | Fort Worth, TX 76107 | Oil & Gas Operator | Feb 2026 |
| 529 | Tahoe Exploration Inc. | Abilene, TX 79608 | Oil & Gas Operator | Mar 2016 |
| 530 | Talon Production, Inc. | Wichita Falls, TX 76301 | Oil & Gas Operator | Feb 2026 |
| 531 | Taurus Exploration U.S.A., Inc. | Midland, TX 79705 | Oil & Gas Operator | Nov 1998 |
| 532 | Taylor, Ben J. Inc. | Fort Worth, TX 76185 | Oil & Gas Operator | Feb 2022 |
| 533 | Taylor-McIlhenny Oper. Co., Inc. | Lewisville, TX 75029 | Oil & Gas Operator | Jan 1996 |
| 534 | TCS Petroleum Co., LLC | Abilene, TX 79608 | Oil & Gas Operator | Feb 2026 |
| 535 | TDC Engineering, Inc. | Abilene, TX 79604 | Oil & Gas Operator | Feb 2026 |
| 536 | Telesis Operating Co. | Fort Worth, TX 76116 | Oil & Gas Operator | Feb 2026 |
| 537 | Tema Oil And Gas Company | Houston, TX 77084 | Oil & Gas Operator | Feb 2026 |
| 538 | Tema Oil And Gas, LLC | Houston, TX 77040 | Oil & Gas Operator | Apr 2000 |
| 539 | Texaco E & P Inc. | Houston, TX 77099 | Oil & Gas Operator | Feb 2026 |
| 540 | Texaco Exploration & Prod | Midland, TX 79702 | Oil & Gas Operator | Aug 2002 |
| 541 | Texakoma E & P, LLC | Plano, TX 75024 | Oil & Gas Operator | Feb 2026 |
| 542 | Texakoma Oil & Gas Corp | Dallas, TX 75240 | Oil & Gas Operator | Sep 2014 |
| 543 | Texas Crude Operator, Inc. | Houston, TX 77098 | Oil & Gas Operator | Aug 2017 |
| 544 | Texas United Geoproduction, Inc. | Abilene, TX 79606 | Oil & Gas Operator | Feb 2026 |
| 545 | Texland Petroleum Inc. | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2003 |
| 546 | Texona Petroleum Corporation | Houston, TX 77084 | Oil & Gas Operator | Aug 2003 |
| 547 | Texstar North America, Inc. | Waynesboro, MS 39367 | Oil & Gas Operator | Aug 1994 |
| 548 | Texzona Oil & Gas, Inc. | Abilene, TX 79608 | Oil & Gas Operator | Dec 1997 |
| 549 | Three Rivers Operating Co LLC | Austin, TX 78735 | Oil & Gas Operator | Mar 2017 |
| 550 | Tidmore, Ann | Albany, TX 76430 | Oil & Gas Operator | Feb 2026 |
| 551 | Titan Energy, Inc. | Austin, TX 78703 | Oil & Gas Operator | Feb 2026 |
| 552 | Tola Production Company | Dallas, TX 75367 | Oil & Gas Operator | Feb 2026 |
| 553 | Toreador Exploration & Prod Inc | Dallas, TX 75240 | Oil & Gas Operator | Feb 2008 |
| 554 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Feb 2026 |
| 555 | Trey Exploration, Inc. | San Angelo, TX 76901 | Oil & Gas Operator | Dec 2020 |
| 556 | Tri-Tex Exploration LTD | Abilene, TX 79608 | Oil Operator | Apr 2019 |
| 557 | Triangle P Development Corp. | Bronte, TX 76933 | Oil & Gas Operator | Feb 2026 |
| 558 | Trilogy Operating, Inc. | Midland, TX 79708 | Oil & Gas Operator | Feb 2026 |
| 559 | Triple T Resources, LP | Dallas, TX 75205 | Oil & Gas Operator | Sep 2025 |
| 560 | Tripower Resources, Inc. | Ardmore, OK 73402 | Oil & Gas Operator | Mar 2020 |
| 561 | Triton Operating LLC | Wichita Falls, TX 76310 | Oil & Gas Operator | Feb 2026 |
| 562 | Tucker Drilling Company, Inc. | San Angelo, TX 76903 | Oil & Gas Operator | Jul 1996 |
| 563 | Tuthill & Barbee | Amarillo, TX 79101 | Oil & Gas Operator | Nov 1994 |
| 564 | U S Energy Corp. Of Amer. Inc. | Cisco, TX 76437 | Oil & Gas Operator | Feb 2026 |
| 565 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | Feb 2026 |
| 566 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 567 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Feb 2026 |
| 568 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Feb 2026 |
| 569 | V-F Petroleum Inc. | Midland, TX 79702 | Oil & Gas Operator | Feb 2026 |
| 570 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Feb 2026 |
| 571 | Van Operating, LTD. | Albany, TX 76430 | Oil & Gas Operator | Feb 2026 |
| 572 | Vanco Oil & Gas Corp. | Abilene, TX 79604 | Oil & Gas Operator | Feb 2026 |
| 573 | Vanguard Production Company | Lubbock, TX 79410 | Oil & Gas Operator | Feb 2026 |
| 574 | Vaughn Petroleum, Inc. | Dallas, TX 75219 | Oil & Gas Operator | May 2004 |
| 575 | Veneto Exploration, LLC | Richardson, TX 75083 | Oil & Gas Operator | Feb 2026 |
| 576 | Ventex Operating Corp. | Addison, TX 75001 | Oil & Gas Operator | Feb 2026 |
| 577 | Viathon Hydrocarbons, Inc. | Dallas, TX 75205 | Oil & Gas Operator | Oct 2020 |
| 578 | Viejo Services, LLC | Boyd, TX 76023 | Oil & Gas Operator | Feb 2026 |
| 579 | Vision Minerals, LLC | Midland, TX 79701 | Oil & Gas Operator | Feb 2026 |
| 580 | Vista Resources, Inc. (A) | Midland, TX 79701 | Oil & Gas Operator | Feb 2000 |
| 581 | VX Operating, LLC | Abilene, TX 79605 | Oil & Gas Operator | Feb 2026 |
| 582 | W & W Production, LLC | Wichita Falls, TX 76308 | Oil Operator | Feb 2026 |
| 583 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 584 | Walbet, Inc. | Monahans, TX 79756 | Oil & Gas Operator | Feb 2026 |
| 585 | Walsh & Watts Inc | Aledo, TX 76008 | Oil & Gas Operator | Feb 2026 |
| 586 | Walsh Resources, Inc. | Tyler, TX 75713 | Oil & Gas Operator | Feb 2026 |
| 587 | Walter Exploration Company | Dallas, TX 75206 | Oil & Gas Operator | Feb 2026 |
| 588 | Walter Exploration Inc | Dallas, TX 75206 | Oil & Gas Operator | May 2009 |
| 589 | Walton Producing Company | Breckenridge, TX 76424 | Oil & Gas Operator | Jul 2005 |
| 590 | Walton, W. W. | Breckenridge, TX 76424 | Oil & Gas Operator | Sep 1994 |
| 591 | Watco Energy, Inc. | Tyler, TX 75713 | Oil & Gas Operator | Apr 1996 |
| 592 | Wes-Tex Drilling Company | Abilene, TX 79604 | Oil & Gas Operator | Jan 2000 |
| 593 | West Inland Energy, Inc. | Fort Worth, TX 76179 | Oil & Gas Operator | Feb 2026 |
| 594 | Western Sky Oil & Gas | Abilene, TX 79604 | Oil & Gas Operator | Aug 2003 |
| 595 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 596 | Westoil LLC | Austin, TX 78747 | Oil & Gas Operator | Feb 2026 |
| 597 | Weststar Oil & Gas Inc | Edmond, OK 73013 | Oil & Gas Operator | Dec 2025 |
| 598 | Westwin Energy I, LP | Midland, TX 79701 | Oil & Gas Operator | Aug 2003 |
| 599 | Westwood Energy, Inc. | Abilene, TX 79608 | Oil & Gas Operator | May 2013 |
| 600 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |