| 601 | Western American Resources LLC | Denver, CO 80202 | Oil & Gas Operator | Jun 2024 |
| 602 | Western Gas Resources Inc | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 603 | Western Interior Energy Inc. | Denver, CO 80202 | Oil & Gas Operator | Dec 2016 |
| 604 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 605 | Wexpro Company | Rock Springs, WY 82902-0458 | Oil & Gas Operator | May 2026 |
| 606 | Wheless Drilling Company | | Oil & Gas Operator | Dec 1989 |
| 607 | White Rock Oil & Gas, LLC | Plano, TX 75024 | Oil & Gas Operator | Jul 2026 |
| 608 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Jul 2026 |
| 609 | Wichita River Oil Corporation | Englewood, CO 80111 | Oil & Gas Operator | Apr 2009 |
| 610 | Wildfire Partners Inc | Ardmore, OK 73402 | Oil & Gas Operator | Dec 2009 |
| 611 | Williams Exploration Company | | Oil & Gas Operator | Dec 1986 |
| 612 | Williams Ted H | | Oil & Gas Operator | Dec 2008 |
| 613 | Winco Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 1997 |
| 614 | Windsor Energy Group LLC | Oklahoma City, OK 73118 | Oil & Gas Operator | Aug 2021 |
| 615 | Winter Ridge Energy LLC | Denver, CO 80202 | Oil & Gas Operator | Sep 2011 |
| 616 | WLP Oil Inc | Gillette, WY 82717 | Oil & Gas Operator | Dec 2018 |
| 617 | Wold Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2022 |
| 618 | Wold Oil & Gas | | Oil & Gas Operator | Oct 1996 |
| 619 | Wold Oil Properties Inc | Denver, CO 80203 | Oil & Gas Operator | Feb 2018 |
| 620 | Wolf Energy Company | | Oil & Gas Operator | Dec 1985 |
| 621 | Wolverine Operations LLC | Buffalo, WY 82834 | Gas Operator | Oct 2008 |
| 622 | Wood River Oil & Refining Co | | Oil & Gas Operator | Dec 1998 |
| 623 | Woods Petroleum Corporation | Oklahoma City, OK 73112 | Oil & Gas Operator | Mar 2015 |
| 624 | WPX Energy Rocky Mountain LLC | Tulsa, OK 74101 | Oil & Gas Operator | May 2026 |
| 625 | WRC Energy LLC | Tulsa, OK 74135 | Oil & Gas Operator | May 2026 |
| 626 | Wulf Oil Co | | Oil & Gas Operator | Dec 1984 |
| 627 | Wy Basin Operating LLC | Dallas, TX 75206 | Oil & Gas Operator | May 2026 |
| 628 | Wyatt Petroleum Corporation | Evergreen, CO 80437 | Gas Operator | Jul 2002 |
| 629 | Wyoil Corp | Buffalo, WY 82834 | Oil Operator | Aug 2025 |
| 630 | Wyoming Resources Corporation | Rapid City, SD 57702 | Oil & Gas Operator | Oct 2018 |
| 631 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 632 | Xog Operating LLC | Midland, TX 79702 | Oil & Gas Operator | Jul 2026 |
| 633 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Jul 2026 |
| 634 | Yates Drilling Company | Artesia, NM 88210 | Oil & Gas Operator | Dec 2021 |
| 635 | Z & S Construction Co Inc | Kimball, NE 69145 | Oil & Gas Operator | Feb 2026 |
| 636 | Zerbst James E | | Oil & Gas Operator | Apr 2007 |