| 401 | The Cornell Corporation | Fort Worth, TX 76109 | Oil & Gas Operator | Sep 1993 |
| 402 | Thomas Operating LTD. Co. | Dallas, TX 75220 | Oil & Gas Operator | Mar 2025 |
| 403 | Thomas, B. K. | Plano, TX 75093 | Oil & Gas Operator | Jan 2008 |
| 404 | Thor Operating Company | Tyler, TX 75710 | Oil & Gas Operator | Dec 1995 |
| 405 | Thunder Oil & Gas, LLC | Ardmore, OK 73402 | Oil & Gas Operator | Dec 2024 |
| 406 | TK Drilling Corp. | Tulsa, OK 74133 | Oil & Gas Operator | Dec 2024 |
| 407 | Tracy Production | Lindale, TX 75771 | Oil & Gas Operator | Mar 2025 |
| 408 | Trans-Tex Operating LLC | Dallas, TX 75367 | Oil & Gas Operator | Mar 2025 |
| 409 | Tri-State Exploration & Prod Inc | Marshall, TX 75671 | Oil & Gas Operator | Aug 2003 |
| 410 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 411 | Triple J Investments Inc | Longview, TX 75606 | Oil & Gas Operator | Feb 2023 |
| 412 | Tritex Production Co. | Iowa Park, TX 76367 | Oil & Gas Operator | Jan 2013 |
| 413 | Triton Oil & Gas Corp. | Houston, TX 77002 | Oil & Gas Operator | Nov 2014 |
| 414 | Trivium Operating, LLC | Fort Worth, TX 76107 | Oil & Gas Operator | Mar 2025 |
| 415 | Tyler Oil & Gas Inc. | Tyler, TX 75702 | Oil & Gas Operator | Sep 2004 |
| 416 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 417 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 418 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 419 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Mar 2025 |
| 420 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 421 | Upstream Properties, LLC | Southlake, TX 76092 | Oil & Gas Operator | Mar 2025 |
| 422 | Ursus Oil And Gas | Tyler, TX 75703 | Oil & Gas Operator | Mar 2025 |
| 423 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Mar 2025 |
| 424 | Vastar Resources Inc | Houston, TX 77253 | Oil & Gas Operator | Nov 2024 |
| 425 | Vess Oil Corporation | Dallas, TX 75201 | Oil & Gas Operator | Mar 2025 |
| 426 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Dec 2024 |
| 427 | Wagner & Brown, LTD. | Midland, TX 79702 | Oil & Gas Operator | Aug 2014 |
| 428 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 429 | Weatherly Oil & Gas, LLC | Dallas, TX 75206 | Oil & Gas Operator | Mar 2025 |
| 430 | Weathers Exploration, Inc. | Tyler, TX 75702 | Oil & Gas Operator | Mar 2025 |
| 431 | Weeks Exploration Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 432 | Wenexco, Inc. | Streetman, TX 75859 | Oil & Gas Operator | Mar 2025 |
| 433 | West Inland Energy, Inc. | N Richlnd HLS, TX 76182 | Oil & Gas Operator | Mar 2025 |
| 434 | West Mountain Operating Co, Inc. | Longview, TX 75604 | Oil & Gas Operator | Feb 2019 |
| 435 | Western Chief Oil & Gas Company | Graham, TX 76450 | Oil & Gas Operator | Jul 2009 |
| 436 | Weststar Oil & Gas Inc | Edmond, OK 73013 | Oil & Gas Operator | Jan 2025 |
| 437 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Mar 2025 |
| 438 | Wilco Properties, Inc. | Dallas, TX 75205 | Oil & Gas Operator | Jan 2004 |
| 439 | Wilcox Operating Corporation | Shreveport, LA 71115 | Oil & Gas Operator | Mar 2025 |
| 440 | Will-Drill Production Co., Inc. | Shreveport, LA 71105 | Oil & Gas Operator | Mar 2025 |
| 441 | Williams Petroleum Company, Inc. | Burkburnett, TX 76354 | Oil & Gas Operator | Mar 2025 |
| 442 | Wilson - Owens Production Co. | Longview, TX 75601 | Oil & Gas Operator | Nov 1998 |
| 443 | Wilson Hydrocarbon Inc. | Houston, TX 77066 | Oil & Gas Operator | Mar 2025 |
| 444 | Wilson Resources, Inc. | Longview, TX 75601 | Oil & Gas Operator | Mar 2025 |
| 445 | Wing Corporation | Houston, TX 77002 | Oil & Gas Operator | Jun 2000 |
| 446 | Winwell, L.L.C. | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2007 |
| 447 | Wisenbaker Production Company | Tyler, TX 75702 | Oil & Gas Operator | Oct 2011 |
| 448 | WJW Operating Co.,LLC | Austin, TX 78738 | Oil & Gas Operator | May 2002 |
| 449 | Woodbine Production Corporation | Kilgore, TX 75663 | Oil & Gas Operator | Mar 2025 |
| 450 | WSF, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jun 2013 |
| 451 | WTXR Operating (Texas), Inc. | Carrollton, TX 75007 | Oil Operator | Mar 2025 |
| 452 | Wynn-Crosby Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2005 |
| 453 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Mar 2025 |
| 454 | Zadeck Energy Group | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2011 |
| 455 | Zapata-Fender, L. L. C. | Tyler, TX 75710 | Oil & Gas Operator | Apr 2001 |