| 601 | Winchester Oil & Gas LLC | Katy, TX 77449 | Oil Operator | May 2025 |
| 602 | Winchester Production Company | Shreveport, LA 71129 | Oil & Gas Operator | Nov 2008 |
| 603 | Window Operating Co., The | Coleman, TX 76834 | Oil & Gas Operator | May 2025 |
| 604 | Winfield Operating Company | Dallas, TX 75214 | Oil & Gas Operator | May 2025 |
| 605 | Wise Exploration | Perrin, TX 76486 | Oil & Gas Operator | May 2025 |
| 606 | Wise Production Company | Bowie, TX 76230 | Oil & Gas Operator | May 2025 |
| 607 | Wise Supply Company | Bowie, TX 76230 | Oil & Gas Operator | May 2025 |
| 608 | Wise Well Service | Bowie, TX 76230 | Oil & Gas Operator | Jul 2017 |
| 609 | Wolfson Oil Co. | Dallas, TX 75230 | Oil & Gas Operator | Sep 1999 |
| 610 | Wolsey Oil Inc. | Bowie, TX 76230 | Oil & Gas Operator | Oct 2013 |
| 611 | Wolsey Well Service, Inc. | Windthorst, TX 76389 | Oil & Gas Operator | Jul 2006 |
| 612 | Wolsey Well Service, L.P. | Bowie, TX 76230 | Oil & Gas Operator | Jun 2014 |
| 613 | Woodbine Petroleum, Inc. | Dallas, TX 75204 | Oil & Gas Operator | Aug 2003 |
| 614 | Wooley Petroleum | Alvord, TX 76225 | Oil & Gas Operator | Oct 1994 |
| 615 | WPX Energy Gulf Coast, LP | Benbrook, TX 76126 | Oil & Gas Operator | May 2012 |
| 616 | WT Fitts Operating | Bowie, TX 76230 | Oil & Gas Operator | May 2025 |
| 617 | Xplore Operating, LLC | Arlington, TX 76001 | Oil & Gas Operator | May 2025 |
| 618 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | May 2025 |
| 619 | Xyz Oil, Inc. | Muenster, TX 76252 | Oil & Gas Operator | May 2025 |
| 620 | Yellow Rose Oil & Gas Operating | Cisco, TX 76437 | Oil & Gas Operator | Jan 1996 |
| 621 | Zapata-Fender, L. L. C. | Tyler, TX 75710 | Oil & Gas Operator | Apr 2001 |
| 622 | Zavala Independent Gas, Inc. | San Antonio, TX 78217 | Oil & Gas Operator | Oct 2007 |