| 401 | Trace Operators, Inc. | | Oil & Gas Operator | Nov 2024 |
| 402 | Traillour Oil Co. | | Oil & Gas Operator | Mar 1990 |
| 403 | Tribal Oil Company | | Oil & Gas Operator | Dec 1981 |
| 404 | Triumph Energy Inc | Lafayette, LA 70505 | Oil & Gas Operator | Nov 2015 |
| 405 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 406 | U S Exploraton Liq Trust | | Oil & Gas Operator | Oct 1994 |
| 407 | U S Liquids Of La., L.P. | | Oil Operator | Apr 2014 |
| 408 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 409 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 410 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 411 | Union Expl. Partners, LTD. | | Oil & Gas Operator | Aug 1990 |
| 412 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 413 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 414 | Union Texas Petroleum Corp | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 415 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Dec 2025 |
| 416 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |
| 417 | United World Energy Corporation | | Oil & Gas Operator | Dec 2024 |
| 418 | Unocal Exploration Corporation | Houston, TX 77001 | Oil & Gas Operator | May 1992 |
| 419 | Us Liquids Of La, LTD | | Oil Operator | Jul 2002 |
| 420 | Verado Energy, Inc. | Allen, TX 75013 | Oil & Gas Operator | Oct 2025 |
| 421 | Vermilion Bay Land Co. | | Oil & Gas Operator | Dec 1994 |
| 422 | Vermilion Exploration, Inc. | | Oil & Gas Operator | Dec 1982 |
| 423 | Vernon E. Faulconer, Inc. | Tyler, TX 75711 | Oil & Gas Operator | Dec 2024 |
| 424 | Victory Financial Group, Inc. | | Oil & Gas Operator | Sep 2002 |
| 425 | Vinbar Oil & Gas, LLC | | Oil & Gas Operator | Jan 2018 |
| 426 | W. B. McCarter, Jr., Inc. | | Oil & Gas Operator | Dec 1995 |
| 427 | W. L. Estis | | Oil & Gas Operator | Dec 1999 |
| 428 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Dec 2025 |
| 429 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 430 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 431 | Watson Energy, L.L.C. | | Oil & Gas Operator | Jun 2005 |
| 432 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 433 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Dec 2025 |
| 434 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Jan 2025 |
| 435 | Whitton Company, Inc. | | Oil & Gas Operator | Jul 2020 |
| 436 | Will Haristy, Jr. | | Oil & Gas Operator | Nov 2024 |
| 437 | William Lagnion | | Oil & Gas Operator | Aug 1998 |
| 438 | Williams Exploration Company | | Oil & Gas Operator | Dec 1986 |
| 439 | Williams-Cody, Inc. | Houston, TX 77060 | Oil & Gas Operator | May 1994 |
| 440 | Windsor Gas Corporation | | Oil & Gas Operator | Aug 1989 |
| 441 | Wle, Inc. | | Oil & Gas Operator | Feb 2012 |
| 442 | WM B Hill Production Co | | Oil Operator | Jun 1991 |
| 443 | WM. H. Kenny Consultants, LTD. | | Oil & Gas Operator | Nov 1991 |
| 444 | WM. T. Burton Industries, Inc. | | Oil & Gas Operator | Apr 1988 |
| 445 | WM. Zuhone, Jr. | | Oil & Gas Operator | Aug 1988 |
| 446 | Woodlawn Energy Dev., L.L.C. | | Oil & Gas Operator | Aug 2006 |
| 447 | Woolf & Magee, Inc. | | Oil & Gas Operator | Oct 1991 |
| 448 | WRT Energy Corporation | Oklahoma City, OK 73118 | Oil & Gas Operator | May 1998 |
| 449 | Yuma E & P Company, Inc. | Houston, TX 77027 | Oil & Gas Operator | Dec 2025 |
| 450 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | Dec 2025 |
| 451 | Zadeck Energy Group, Inc. | | Oil & Gas Operator | Dec 2011 |
| 452 | Zenergy Inc | Tulsa, OK 74136 | Oil & Gas Operator | Nov 2025 |
| 453 | Zero Mass Mining, LLC | | Oil Operator | Jan 2025 |
| 454 | Zinke & Trumbo, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2007 |