| 501 | Trio Operating Company, Inc. | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2006 |
| 502 | Triple "N" Services, Inc. | Midland, TX 79702 | Oil & Gas Operator | Sep 2026 |
| 503 | Triton Oil & Gas Corp. | Houston, TX 77002 | Oil & Gas Operator | Nov 2014 |
| 504 | Tumbleweed Energy Limited | Midland, TX 79704 | Oil & Gas Operator | Dec 2022 |
| 505 | U. S. Energy Development Corporation | Fort Worth, TX 76164 | Oil & Gas Operator | Sep 2026 |
| 506 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | Sep 2026 |
| 507 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 508 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 509 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 510 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Sep 2026 |
| 511 | V-F Petroleum Inc. | Midland, TX 79702 | Oil & Gas Operator | Sep 2026 |
| 512 | Vanguard Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Jan 2021 |
| 513 | Vanguard Permian, LLC | Houston, TX 77057 | Oil & Gas Operator | Nov 2018 |
| 514 | Verdad Oil & Gas Corporation | Dallas, TX 75235 | Oil & Gas Operator | May 2026 |
| 515 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Sep 2026 |
| 516 | Vista Petroleum Corp | Houston, TX 77277 | Oil & Gas Operator | Dec 1996 |
| 517 | Vista Resources, Inc. (A) | Midland, TX 79701 | Oil & Gas Operator | Feb 2000 |
| 518 | Vital Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | Sep 2026 |
| 519 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 520 | Walter Exploration Inc | Dallas, TX 75206 | Oil & Gas Operator | May 2009 |
| 521 | Walton Properties LTD. | Midland, TX 79702 | Oil & Gas Operator | Feb 2004 |
| 522 | Warrior Exploration LLC | Sapulpa, OK 74067-1912 | Oil & Gas Operator | Mar 2026 |
| 523 | Watusi Energy LLC | Midland, TX 79710 | Oil & Gas Operator | Sep 2026 |
| 524 | Wes-Tex Drilling Company | Abilene, TX 79604 | Oil & Gas Operator | Jan 2000 |
| 525 | West Texas Oil And Gas Oper.,Inc | Houston, TX 77046 | Oil & Gas Operator | Jul 2024 |
| 526 | Westerly Exploration, Inc. | Houston, TX 77256 | Oil & Gas Operator | Sep 2026 |
| 527 | Western Reserves Oil Co Inc | Midland, TX 79705 | Oil & Gas Operator | Oct 2020 |
| 528 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 529 | Williams, Clayton Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | Sep 2026 |
| 530 | Willow Bend Oil LLC | Dallas, TX 75206 | Oil & Gas Operator | Sep 2026 |
| 531 | Willow Creek Resources, Inc. | Midland, TX 79702 | Oil & Gas Operator | Feb 2009 |
| 532 | Winchester Operating, Inc. | Bryan, TX 77808 | Oil & Gas Operator | Aug 2001 |
| 533 | Wind River Energy, Inc. | Midland, TX 79710 | Oil & Gas Operator | Sep 2026 |
| 534 | Wind River Resources Inc | Tulsa, OK 74136-6381 | Oil & Gas Operator | Jun 2010 |
| 535 | Winn Operating, LLC | Kilgore, TX 75663 | Oil & Gas Operator | Sep 2026 |
| 536 | Wiseman, B. W., Jr. | Midland, TX 79702 | Oil & Gas Operator | Dec 2002 |
| 537 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2023 |
| 538 | Wood, McShane & Thams | Midland, TX 79702 | Oil & Gas Operator | Oct 1995 |
| 539 | Woodbine Petroleum, Inc. | Dallas, TX 75204 | Oil & Gas Operator | Aug 2003 |
| 540 | World Producers, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Nov 1994 |
| 541 | Wynne Petroleum Co. | Fort Worth, TX 76116 | Oil & Gas Operator | Nov 1997 |
| 542 | Xeric Oil & Gas Company | Midland, TX 79702 | Oil & Gas Operator | Jul 1997 |
| 543 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 544 | Xog Operating LLC | Midland, TX 79702 | Oil & Gas Operator | Sep 2026 |
| 545 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Sep 2026 |
| 546 | Yates, Harvey E. Company | Roswell, NM 88201 | Oil & Gas Operator | Dec 2002 |
| 547 | Young, Marshall R., Oil Co. | Fort Worth, TX 76107 | Oil & Gas Operator | Mar 2011 |
| 548 | Yukon Exploration Operating, LLC | Dallas, TX 75219 | Oil & Gas Operator | Sep 2026 |