| 601 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2025 |
| 602 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 603 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 604 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | Mar 2025 |
| 605 | Wandoo Energy, LLC | The Woodlands, TX 77382 | Oil & Gas Operator | Mar 2025 |
| 606 | Warbonnet Exploration Company | Houston, TX 77056 | Oil & Gas Operator | Apr 2016 |
| 607 | Watco Energy, Inc. | Tyler, TX 75713 | Oil & Gas Operator | Apr 1996 |
| 608 | Weber Energy Corporation | Dallas, TX 75219 | Oil & Gas Operator | Feb 2017 |
| 609 | Weeks Exploration Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 610 | Weiser-Brown Operating Company | Magnolia, AR 71754 | Oil & Gas Operator | Mar 2025 |
| 611 | Wellstar Corporation | Northglenn, CO 80233 | Oil & Gas Operator | Jan 2025 |
| 612 | Western Energy Group, LLC | Leander, TX 78641 | Oil & Gas Operator | Mar 2025 |
| 613 | Westhall Associates, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Aug 1997 |
| 614 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 615 | White Marlin Operating Company, LLC | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 616 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Mar 2025 |
| 617 | Whitehead Prod. Co., Inc. | Humble, TX 77338 | Oil & Gas Operator | Dec 2024 |
| 618 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 619 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Aug 2024 |
| 620 | Wilcox Operating Corporation | Shreveport, LA 71115 | Oil & Gas Operator | Mar 2025 |
| 621 | Willstar Energy GP, LLC | Houston, TX 77279 | Oil & Gas Operator | Sep 2013 |
| 622 | Wilson, Charles B., Jr., Inc. | Houston, TX 77027 | Oil & Gas Operator | Apr 2000 |
| 623 | Winn Exploration Co., Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Mar 2025 |
| 624 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2018 |
| 625 | WJC, Inc. | Post, TX 79356 | Oil & Gas Operator | Mar 2025 |
| 626 | Wofford, C. J. | El Campo, TX 77437 | Oil & Gas Operator | Mar 2025 |
| 627 | Wynn-Crosby Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2005 |
| 628 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Mar 2025 |
| 629 | Young, John H., Inc. | Houston, TX 77027 | Oil & Gas Operator | Mar 2025 |
| 630 | Yuma Petroleum Company | Houston, TX 77027 | Oil & Gas Operator | Aug 2002 |
| 631 | Zachry Exploration, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | Mar 2025 |
| 632 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | Mar 2025 |
| 633 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |
| 634 | Zaza Energy, LLC | Houston, TX 77010 | Oil & Gas Operator | Mar 2025 |
| 635 | Zilkha Energy Company | Houston, TX 77046 | Oil & Gas Operator | Oct 2002 |
| 636 | Zinn Petroleum Co. | Houston, TX 77024 | Oil & Gas Operator | Nov 2021 |