| 601 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 602 | Union Texas Petroleum | Houston, TX 77252 | Oil & Gas Operator | Oct 1991 |
| 603 | United Natural Resources Corp | | Oil Operator | Jan 1986 |
| 604 | United Petroleum Corporation | Edgwater, CO 80214 | Oil & Gas Operator | May 1996 |
| 605 | Updike Resources Inc | Newcastle, WY 82701 | Oil & Gas Operator | Jun 1998 |
| 606 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Sep 2026 |
| 607 | USA Exploration & Production LLC | Mills, WY 82644 | Oil & Gas Operator | Sep 2012 |
| 608 | Valero Producing Company | | Oil Operator | Sep 1987 |
| 609 | Valkyrie Operating LLC | Denver, CO 80202 | Oil & Gas Operator | Jul 2026 |
| 610 | Van Norman Pipe And Supply | | Oil & Gas Operator | Mar 2010 |
| 611 | Vast Oil Inc | Fullerton, CA 92832 | Oil & Gas Operator | Mar 2024 |
| 612 | Vecta Oil & Gas LTD | Dallas, TX 75235 | Oil & Gas Operator | Jun 2026 |
| 613 | Vermilion Energy USA LLC | | Oil & Gas Operator | Jul 2025 |
| 614 | Vicorp Energy Inc | Denver, CO 80202-4927 | Oil & Gas Operator | Mar 2001 |
| 615 | Viking Resources Corp | Deerfield, OH 44411-0160 | Oil & Gas Operator | Dec 2007 |
| 616 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Jun 2026 |
| 617 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Sep 2026 |
| 618 | Wacker Oil Inc. | Houston, TX 77002 | Oil & Gas Operator | Aug 1996 |
| 619 | Waggoner-Baldridge Energy | | Oil Operator | Jun 1988 |
| 620 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 621 | Wallway M J | Casper, WY 82601 | Oil & Gas Operator | Jan 1993 |
| 622 | Warren E & P Inc | Dallas, TX 75240 | Oil & Gas Operator | Jul 2026 |
| 623 | Warren Enterprises Inc | Gillette, WY 82718 | Oil Operator | Dec 2022 |
| 624 | Washakie Energies Company | Worland, WY 82401 | Oil & Gas Operator | Dec 2019 |
| 625 | Washington Energy Exploration | | Oil & Gas Operator | Dec 1997 |
| 626 | Wave Petroleum Operating LLC | Denver, CO 80202 | Oil & Gas Operator | Jul 2026 |
| 627 | Weaver Oil Inc | | Oil & Gas Operator | Oct 2011 |
| 628 | Wellstar Corporation | Northglenn, CO 80233 | Oil & Gas Operator | Jul 2026 |
| 629 | Wem Joint Venture | Gillette, WY 82716 | Oil & Gas Operator | Sep 2015 |
| 630 | Wesco Operating Inc | Casper, WY 82602 | Oil & Gas Operator | Jul 2026 |
| 631 | Wessely Energy Corporation | | Oil & Gas Operator | Feb 1989 |
| 632 | West Gas Inc | | Oil & Gas Operator | Dec 2017 |
| 633 | Westburne Petroleum Inc | | Oil Operator | Jun 1990 |
| 634 | Westech Energy Corporation | Denver, CO 80237 | Oil & Gas Operator | Mar 2011 |
| 635 | Western American Resources LLC | Denver, CO 80202 | Oil & Gas Operator | Jun 2024 |
| 636 | Western Gas Resources Inc | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 637 | Western Interior Energy Inc. | Denver, CO 80202 | Oil & Gas Operator | Dec 2016 |
| 638 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 639 | Wexpro Company | Rock Springs, WY 82902-0458 | Oil & Gas Operator | Jun 2026 |
| 640 | Wheless Drilling Company | | Oil & Gas Operator | Dec 1989 |
| 641 | White Rock Oil & Gas, LLC | Plano, TX 75024 | Oil & Gas Operator | Sep 2026 |
| 642 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2026 |
| 643 | Wichita River Oil Corporation | Englewood, CO 80111 | Oil & Gas Operator | Apr 2009 |
| 644 | Wildfire Partners Inc | Ardmore, OK 73402 | Oil & Gas Operator | Dec 2009 |
| 645 | Williams Exploration Company | | Oil & Gas Operator | Dec 1986 |
| 646 | Williams Ted H | | Oil & Gas Operator | Dec 2008 |
| 647 | Winco Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 1997 |
| 648 | Windsor Energy Group LLC | Oklahoma City, OK 73118 | Oil & Gas Operator | Aug 2021 |
| 649 | Winter Ridge Energy LLC | Denver, CO 80202 | Oil & Gas Operator | Sep 2011 |
| 650 | WLP Oil Inc | Gillette, WY 82717 | Oil & Gas Operator | Dec 2018 |
| 651 | Wold Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2022 |
| 652 | Wold Oil & Gas | | Oil & Gas Operator | Oct 1996 |
| 653 | Wold Oil Properties Inc | Denver, CO 80203 | Oil & Gas Operator | Feb 2018 |
| 654 | Wolf Energy Company | | Oil & Gas Operator | Dec 1985 |
| 655 | Wolverine Operations LLC | Buffalo, WY 82834 | Gas Operator | Oct 2008 |
| 656 | Wood River Oil & Refining Co | | Oil & Gas Operator | Dec 1998 |
| 657 | Woods Petroleum Corporation | Oklahoma City, OK 73112 | Oil & Gas Operator | Mar 2015 |
| 658 | WPX Energy Rocky Mountain LLC | Tulsa, OK 74101 | Oil & Gas Operator | May 2026 |
| 659 | WRC Energy LLC | Tulsa, OK 74135 | Oil & Gas Operator | Jul 2026 |
| 660 | Wulf Oil Co | | Oil & Gas Operator | Dec 1984 |
| 661 | Wy Basin Operating LLC | Dallas, TX 75206 | Oil & Gas Operator | Jun 2026 |
| 662 | Wyatt Petroleum Corporation | Evergreen, CO 80437 | Gas Operator | Jul 2002 |
| 663 | Wyoil Corp | Buffalo, WY 82834 | Oil Operator | Aug 2025 |
| 664 | Wyoming Resources Corporation | Rapid City, SD 57702 | Oil & Gas Operator | Oct 2018 |
| 665 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 666 | Xog Operating LLC | Midland, TX 79702 | Oil & Gas Operator | Sep 2026 |
| 667 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Sep 2026 |