| 401 | Union Seaboard Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 402 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Mar 2025 |
| 403 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 404 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 405 | Upstream Exploration LLC | Metairie, LA 70002 | Oil & Gas Operator | Jan 2020 |
| 406 | Vanya Oil & Gas, Inc. | Hardin, TX 77561 | Oil & Gas Operator | Mar 2025 |
| 407 | Ventex Operating Corp. | Addison, TX 75001 | Oil & Gas Operator | Mar 2025 |
| 408 | Venture 9 | Sourlake, TX 77659 | Oil & Gas Operator | Aug 2003 |
| 409 | Votaw Production Company LLC | Houston, TX 77007 | Oil Operator | Mar 2025 |
| 410 | Wagner & Brown, LTD. | Midland, TX 79702 | Oil & Gas Operator | Aug 2014 |
| 411 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2025 |
| 412 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 413 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 414 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | Mar 2025 |
| 415 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 416 | Wapiti Operating, LLC | Houston, TX 77043 | Oil & Gas Operator | Mar 2025 |
| 417 | Westco Oil Company | Ozona, TX 76943 | Oil & Gas Operator | Mar 2025 |
| 418 | Western Energy Group, LLC | Leander, TX 78641 | Oil & Gas Operator | Mar 2025 |
| 419 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 420 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 421 | WFMMS, Inc. | Batson, TX 77519 | Oil & Gas Operator | Mar 2025 |
| 422 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Mar 2025 |
| 423 | Whitehead Resources, LTD. | Buna, TX 77612 | Oil & Gas Operator | Mar 2025 |
| 424 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 425 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Aug 2024 |
| 426 | Wilco Properties, Inc. | Dallas, TX 75205 | Oil & Gas Operator | Jan 2004 |
| 427 | Xplor Energy Operating Co. | Houston, TX 77079 | Oil & Gas Operator | Jan 2012 |
| 428 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Mar 2025 |
| 429 | Yust, C. F. & R. L. | Batson, TX 77519 | Oil & Gas Operator | Sep 2002 |
| 430 | Zachry Exploration, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | Mar 2025 |
| 431 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | Mar 2025 |
| 432 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |
| 433 | Zarvona Energy LLC | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 434 | Zinn Petroleum Co. | Houston, TX 77024 | Oil & Gas Operator | Nov 2021 |