| 501 | South Pass Petroleum Inc | Casper, WY 82601 | Oil & Gas Operator | May 2026 |
| 502 | Southland Royalty Company | Houston, TX 77210 | Oil & Gas Operator | Sep 2011 |
| 503 | Southwestern Energy Prod Co | Houston, TX 77032 | Oil & Gas Operator | Jun 2015 |
| 504 | Southwestern Production Corporation | Lakewood, CO 80228 | Oil & Gas Operator | May 2026 |
| 505 | Spirit Energy Inc | Edmond, OK 73034 | Oil & Gas Operator | Apr 1999 |
| 506 | St. Mary Operating Company | Denver, CO 80203 | Oil & Gas Operator | Mar 2019 |
| 507 | Stag Oil Producers Inc | Midland, TX 79701 | Oil & Gas Operator | Jan 1998 |
| 508 | Star Resources LLC | Englewood, CO 80155-5185 | Oil & Gas Operator | Dec 2013 |
| 509 | States Exploration Inc | | Oil Operator | Jul 1985 |
| 510 | Statex Petroleum Inc | Dallas, TX 75229 | Oil & Gas Operator | Dec 2000 |
| 511 | Steamboat Oil And Gas LLC | Gillette, WY 82717 | Oil Operator | Jun 2026 |
| 512 | Stellar Oil Company | Arvada, CO 80006 | Oil & Gas Operator | Dec 1998 |
| 513 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | May 2026 |
| 514 | Sterling Energy Corporation | Denver, CO 80202 | Oil & Gas Operator | Sep 1995 |
| 515 | Stewart Petroleum Corporation | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Dec 2023 |
| 516 | Stone & Wolf LLC | Sheridan, WY 82801 | Oil & Gas Operator | Dec 2006 |
| 517 | Stone Petroleum Corporation | | Oil & Gas Operator | Dec 1996 |
| 518 | Storm Cat Energy USA Operating Corp | Denver, CO 80202 | Gas Operator | Jun 2017 |
| 519 | Stovall Oil Company | Casper, WY 82602 | Oil & Gas Operator | Aug 1998 |
| 520 | Stroud Petroleum, Inc. | Shreveport, LA 71162 | Oil & Gas Operator | Jul 2026 |
| 521 | Summit Gas Resources Inc | Sheridan, WY 82801 | Gas Operator | Dec 2023 |
| 522 | Suncor Energy Natural Gas America Inc | Greenwood VIllage, CO 80111 | Gas Operator | Feb 2010 |
| 523 | Sundance Oil Exploration Co | | Oil Operator | Mar 1986 |
| 524 | Sunshine Valley Petroleum | Casper, WY 82605 | Oil & Gas Operator | May 2026 |
| 525 | Swenco-Western Inc | Houston, TX 77060 | Oil & Gas Operator | Jan 1997 |
| 526 | Swepi LP | Houston, TX 77079 | Oil & Gas Operator | Jul 2020 |
| 527 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 528 | T2 Operating Corporation | Denver, CO 80202 | Oil & Gas Operator | May 2026 |
| 529 | Taqa USA, Inc. | Centennial, CO 80111 | Oil & Gas Operator | Jul 2020 |
| 530 | Tbi Exploration Inc | Englewood, CO 801556525 | Oil & Gas Operator | Jun 2011 |
| 531 | Team Operating, L.L.C. | Pinehurst, TX 77362 | Oil & Gas Operator | Jul 2026 |
| 532 | Temagami Oil & Gas LTD | | Oil & Gas Operator | May 2007 |
| 533 | Tenneco Oil Company | Oklahoma City, OK 73125 | Oil & Gas Operator | Dec 2025 |
| 534 | Territory Resources LLC | Stillwater, OK 74074-1869 | Oil & Gas Operator | Jun 2026 |
| 535 | Terry Production Co | Stroud, OK 74079-0475 | Oil & Gas Operator | Aug 2008 |
| 536 | Texaco Exploration & Prod | Midland, TX 79702 | Oil & Gas Operator | Aug 2002 |
| 537 | Texakota | | Oil & Gas Operator | Mar 1995 |
| 538 | Texas General Petroleum Corp | | Oil & Gas Operator | Aug 1984 |
| 539 | Texas Oil & Gas Corporation | Dallas, TX 75201 | Oil & Gas Operator | Feb 2001 |
| 540 | The Termo Company | Long Beach, CA 90801 | Oil & Gas Operator | May 2026 |
| 541 | Thomas Operating Company Inc | Greeley, CO 80634 | Oil & Gas Operator | Aug 2008 |
| 542 | Three Forks Resources, LLC | Wheat Ridge, CO 80033 | Oil & Gas Operator | Jul 2026 |
| 543 | Timberline Energy Inc | Franklin, PA 16323-0269 | Oil & Gas Operator | Dec 2025 |
| 544 | Timberline Production Company LLC | Casper, WY 82601 | Oil & Gas Operator | Oct 2020 |
| 545 | Tindall Operating Company | Englewood, CO 80112 | Oil & Gas Operator | Jan 2025 |
| 546 | Titan Exploration LLC | Denver, CO 80202 | Oil & Gas Operator | Jan 2026 |
| 547 | Tonka Oil & Gas Production Inc | Buffalo, WY 82834 | Oil & Gas Operator | Sep 1999 |
| 548 | Torch E & P Company | Houston, TX 77010 | Oil & Gas Operator | Jan 2015 |
| 549 | Torch Oil & Gas Company | Houston, TX 77010 | Oil & Gas Operator | Aug 1997 |
| 550 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 551 | Total Petroleum Inc | Houston, TX 77210 | Oil & Gas Operator | Feb 1998 |
| 552 | TR Operating LLC | Graham, TX 76450 | Oil Operator | Jun 2026 |
| 553 | Transcontinental Oil Corp. | | Oil & Gas Operator | Sep 1985 |
| 554 | Transhorizon Energy Inc | Cheyenne, WY 82003 | Oil & Gas Operator | Jul 2023 |
| 555 | Trend Exploration I LLC | Midland, TX 79701 | Oil & Gas Operator | May 2011 |
| 556 | Tresor Petroleum | | Oil & Gas Operator | Sep 1987 |
| 557 | Triangle J Oil Company | | Oil & Gas Operator | Mar 2007 |
| 558 | Trigg Oil Mining Corporation | | Oil & Gas Operator | Dec 2007 |
| 559 | Triple B Energy Inc | Gillette, WY 82716 | Oil Operator | Dec 1999 |
| 560 | Tripower Resources LLC | Ardmore, OK 73402 | Oil & Gas Operator | Jul 2026 |
| 561 | Tripp Oil Company Inc | Houston, TX 77023 | Oil & Gas Operator | Jan 1992 |
| 562 | Trout Kye Jr | | Oil & Gas Operator | Dec 2010 |
| 563 | True Oil LLC | Casper, WY 82602 | Oil & Gas Operator | May 2026 |
| 564 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 565 | U V Industries | | Oil & Gas Operator | Jan 1993 |
| 566 | Underwood Oil & Gas | Casper, WY 82602 | Oil & Gas Operator | Jun 2026 |
| 567 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 568 | Union Texas Petroleum | Houston, TX 77252 | Oil & Gas Operator | Oct 1991 |
| 569 | United Natural Resources Corp | | Oil Operator | Jan 1986 |
| 570 | United Petroleum Corporation | Edgwater, CO 80214 | Oil & Gas Operator | May 1996 |
| 571 | Updike Resources Inc | Newcastle, WY 82701 | Oil & Gas Operator | Jun 1998 |
| 572 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Jul 2026 |
| 573 | USA Exploration & Production LLC | Mills, WY 82644 | Oil & Gas Operator | Sep 2012 |
| 574 | Valero Producing Company | | Oil Operator | Sep 1987 |
| 575 | Valkyrie Operating LLC | Denver, CO 80202 | Oil & Gas Operator | Jun 2026 |
| 576 | Van Norman Pipe And Supply | | Oil & Gas Operator | Mar 2010 |
| 577 | Vast Oil Inc | Fullerton, CA 92832 | Oil & Gas Operator | Mar 2024 |
| 578 | Vecta Oil & Gas LTD | Dallas, TX 75235 | Oil & Gas Operator | Mar 2026 |
| 579 | Vermilion Energy USA LLC | | Oil & Gas Operator | Jul 2025 |
| 580 | Vicorp Energy Inc | Denver, CO 80202-4927 | Oil & Gas Operator | Mar 2001 |
| 581 | Viking Resources Corp | Deerfield, OH 44411-0160 | Oil & Gas Operator | Dec 2007 |
| 582 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Apr 2026 |
| 583 | Viola Production Inc | Dallas, TX 75251 | Oil & Gas Operator | Jul 2026 |
| 584 | Wacker Oil Inc. | Houston, TX 77002 | Oil & Gas Operator | Aug 1996 |
| 585 | Waggoner-Baldridge Energy | | Oil Operator | Jun 1988 |
| 586 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 587 | Wallway M J | Casper, WY 82601 | Oil & Gas Operator | Jan 1993 |
| 588 | Warren E & P Inc | Dallas, TX 75240 | Oil & Gas Operator | May 2026 |
| 589 | Warren Enterprises Inc | Gillette, WY 82718 | Oil Operator | Dec 2022 |
| 590 | Washakie Energies Company | Worland, WY 82401 | Oil & Gas Operator | Dec 2019 |
| 591 | Washington Energy Exploration | | Oil & Gas Operator | Dec 1997 |
| 592 | Wave Petroleum Operating LLC | Denver, CO 80202 | Oil & Gas Operator | May 2026 |
| 593 | Weaver Oil Inc | | Oil & Gas Operator | Oct 2011 |
| 594 | Wellstar Corporation | Northglenn, CO 80233 | Oil & Gas Operator | May 2026 |
| 595 | Wem Joint Venture | Gillette, WY 82716 | Oil & Gas Operator | Sep 2015 |
| 596 | Wesco Operating Inc | Casper, WY 82602 | Oil & Gas Operator | May 2026 |
| 597 | Wessely Energy Corporation | | Oil & Gas Operator | Feb 1989 |
| 598 | West Gas Inc | | Oil & Gas Operator | Dec 2017 |
| 599 | Westburne Petroleum Inc | | Oil Operator | Jun 1990 |
| 600 | Westech Energy Corporation | Denver, CO 80237 | Oil & Gas Operator | Mar 2011 |