| 401 | Tundra Operating LLC | Spring, TX 77386 | Oil Operator | May 2017 |
| 402 | Txco Resources Inc. | San Antonio, TX 78280 | Oil & Gas Operator | May 2026 |
| 403 | Tyl Oil | Canon City, CO 81212 | Gas Operator | May 1994 |
| 404 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Jul 2025 |
| 405 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 406 | U.S.A. Plugging Company | Pearsall, TX 78061 | Oil & Gas Operator | May 2026 |
| 407 | Uhc Petroleum Corporation | Rocksprings, TX 78880 | Oil & Gas Operator | May 2026 |
| 408 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 409 | Unitex Oil & Gas, L.L.C. | Midland, TX 79701 | Oil & Gas Operator | May 2026 |
| 410 | Unoco, Inc. | Kerrville, TX 78029 | Oil & Gas Operator | Jan 1999 |
| 411 | V/J Oil Company | Yancey, TX 78886 | Oil & Gas Operator | Oct 2015 |
| 412 | Vac-U-Lift Production Co.,Inc. | Lake Forest, CA 92630 | Oil & Gas Operator | May 2026 |
| 413 | Venus Oil Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2002 |
| 414 | Verdun Oil & Gas LLC | Houston, TX 77024 | Oil & Gas Operator | May 2026 |
| 415 | Verdun Oil Ef II LLC | Houston, TX 77024 | Oil & Gas Operator | May 2026 |
| 416 | Vermillion Production, Inc. | Pearsall, TX 78061 | Oil & Gas Operator | May 2026 |
| 417 | Virtex Operating Company, Inc. | Corpus Christ, TX 78401 | Oil & Gas Operator | Oct 2023 |
| 418 | Virtex Petroleum Company, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2008 |
| 419 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 420 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | May 2026 |
| 421 | WCS Oil & Gas Corporation | Dallas, TX 75209 | Oil & Gas Operator | Aug 2021 |
| 422 | West Bay Exploration Company | Muenster, TX 76252 | Oil & Gas Operator | Feb 2026 |
| 423 | Western Field Exploration, Inc. | Dilley, TX 78017 | Oil & Gas Operator | May 2026 |
| 424 | White Marlin Operating Company, LLC | Houston, TX 77002 | Oil & Gas Operator | May 2026 |
| 425 | Whittier Operating Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2007 |
| 426 | Wilbanks, Bruce A. | Midland, TX 79701 | Oil & Gas Operator | Aug 1996 |
| 427 | Williamson Operating Co. | Uvalde, TX 78801 | Oil & Gas Operator | May 2026 |
| 428 | Wilmoth Interests, Inc. | Marion Center, PA 15759 | Oil & Gas Operator | Dec 2025 |
| 429 | Wilson, Don H., Inc. | Elkhart, TX 75839 | Oil & Gas Operator | May 2019 |
| 430 | Windsor Exploration Company | Dallas, TX 75204 | Oil & Gas Operator | Jan 1994 |
| 431 | Wineland Oil - LLC | Hays, KS 67601 | Oil Operator | Dec 2025 |
| 432 | Winn Exploration Co., Inc. | Corpus Christ, TX 78401 | Oil & Gas Operator | May 2026 |
| 433 | Wolverine Exploration Company | Houston, TX 77002 | Oil & Gas Operator | May 2019 |
| 434 | Yarborough, W. B. | Midland, TX 79701 | Oil & Gas Operator | Nov 1995 |