| 401 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 402 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 403 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | Dec 2025 |
| 404 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 405 | Wapiti Operating, LLC | Houston, TX 77043 | Oil & Gas Operator | Dec 2025 |
| 406 | Well-Co Solutions, LLC | Batson, TX 77519 | Oil Operator | Dec 2025 |
| 407 | Westco Oil Company | Ozona, TX 76943 | Oil & Gas Operator | Dec 2025 |
| 408 | Western Energy Group, LLC | Leander, TX 78641 | Oil & Gas Operator | Dec 2025 |
| 409 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 410 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 411 | WFMMS, Inc. | Batson, TX 77519 | Oil & Gas Operator | Dec 2025 |
| 412 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Dec 2025 |
| 413 | Whitehead Resources, LTD. | Buna, TX 77612 | Oil & Gas Operator | Dec 2025 |
| 414 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 415 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Jan 2025 |
| 416 | Xplor Energy Operating Co. | Houston, TX 77079 | Oil & Gas Operator | Jan 2012 |
| 417 | Yust, C. F. & R. L. | Batson, TX 77519 | Oil & Gas Operator | Sep 2002 |
| 418 | Zachry Exploration, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | Dec 2025 |
| 419 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | Dec 2025 |
| 420 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |
| 421 | Zarvona Energy LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 422 | Zinn Petroleum Co. | Houston, TX 77024 | Oil & Gas Operator | Nov 2021 |