| 601 | Westar Energy, Inc. | Midland, TX 79705 | Oil & Gas Operator | Mar 2008 |
| 602 | Western Reserves Oil Co Inc | Midland, TX 79705 | Oil & Gas Operator | Oct 2020 |
| 603 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 604 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 605 | Westport Oil And Gas Company Inc | Denver, CO 80202 | Oil & Gas Operator | Feb 2002 |
| 606 | White Wing Petroleum Inc. | Midland, TX 79702 | Oil & Gas Operator | Jul 2012 |
| 607 | White'S Industrial Engine'S | Houston, TX 77070 | Oil & Gas Operator | Feb 2026 |
| 608 | Wigington, James Robert | Ackerly, TX 79713 | Oil & Gas Operator | Aug 2003 |
| 609 | Wilbanks Reserve Corporation | Denver, CO 80203 | Oil & Gas Operator | Feb 2026 |
| 610 | Wilbanks, Bruce A. | Midland, TX 79701 | Oil & Gas Operator | Aug 1996 |
| 611 | Wilbanks, Bruce A. Company | Midland, TX 79702 | Oil & Gas Operator | Feb 2026 |
| 612 | Wilco Properties, Inc. | Dallas, TX 75205 | Oil & Gas Operator | Jan 2004 |
| 613 | Williams, Clayton Energy, Inc. | Houston, TX 77070 | Oil & Gas Operator | Feb 2026 |
| 614 | Williamson, J. C. | Midland, TX 79701 | Oil & Gas Operator | Jan 2001 |
| 615 | Wilson, WM. B. Exploration Inc. | Midland, TX 79701 | Oil & Gas Operator | Jan 1996 |
| 616 | Winchester Production Company | Shreveport, LA 71129 | Oil & Gas Operator | Nov 2008 |
| 617 | Wind River Resources Inc | Tulsa, OK 74136-6381 | Oil & Gas Operator | Jun 2010 |
| 618 | Wing Corporation | Houston, TX 77002 | Oil & Gas Operator | Jun 2000 |
| 619 | Winn Operating, LLC | Kilgore, TX 75663 | Oil & Gas Operator | Feb 2026 |
| 620 | WJC, Inc. | Post, TX 79356 | Oil & Gas Operator | Feb 2026 |
| 621 | WTG Exploration | Midland, TX 79705 | Oil & Gas Operator | Feb 2026 |
| 622 | Wynn-Crosby Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2005 |
| 623 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 624 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Feb 2026 |
| 625 | Yarborough Oil & Gas L.P. | Midland, TX 79701 | Oil & Gas Operator | Oct 2000 |
| 626 | Yates Oil & Gas Company | Midland, TX 79702 | Oil & Gas Operator | Mar 2008 |