| 501 | Powder River Royalty Inc | | Oil & Gas Operator | Dec 1986 |
| 502 | Powerline Energy Corporation | Arlington, TX 76015 | Oil & Gas Operator | Dec 2025 |
| 503 | PRB Oil & Gas Inc | Denver, CO 80202 | Gas Operator | Jul 2008 |
| 504 | Preferred Pipeline Corp. | Victoria, TX 77902 | Oil & Gas Operator | Oct 2025 |
| 505 | Prenalta Corporation | Terrytown, NY 10591 | Oil & Gas Operator | Jan 1997 |
| 506 | Pride Energy Company An Oklahoma GP | Tulsa, OK 74170 | Oil & Gas Operator | Oct 2025 |
| 507 | Prima Exploration, Inc. | Denver, CO 80206 | Oil & Gas Operator | Oct 2025 |
| 508 | Propel Energy Company | | Oil Operator | Oct 1991 |
| 509 | Prospective Invest & Trad Co LTD | Tulsa, OK 74170 | Oil & Gas Operator | Aug 2005 |
| 510 | Provident Resources LTD | | Oil & Gas Operator | Dec 1986 |
| 511 | Puma Petroleum I | | Oil & Gas Operator | Dec 1988 |
| 512 | Pure Petroleum LLC | Gillette, WY 82717 | Oil & Gas Operator | Aug 2011 |
| 513 | Qep Energy Company | Midland, TX 79701 | Oil & Gas Operator | Oct 2025 |
| 514 | Quest Operating LLC | Sheridan, WY 82801 | Gas Operator | Sep 2008 |
| 515 | Quicksilver Resources Inc | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2018 |
| 516 | Quinoco Petroleum Inc | | Oil & Gas Operator | Dec 1990 |
| 517 | Quintana Petroleum Corporation | Denver, CO 80265 | Oil & Gas Operator | Mar 1998 |
| 518 | Rainbow Oil Company | | Oil & Gas Operator | Aug 1999 |
| 519 | Rainbow Resources, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Aug 2007 |
| 520 | Ranch Oil Company | West Linn, OR 97068 | Oil & Gas Operator | Oct 2025 |
| 521 | Ranger Holdings Co | | Oil & Gas Operator | Jul 1993 |
| 522 | RB Operating Company | Shawnee, OK 74802-1488 | Oil & Gas Operator | Apr 2015 |
| 523 | Reading & Bates Petroleum | | Oil & Gas Operator | Apr 1989 |
| 524 | Red Tiger Oil & Gas LLC | Gillette, WY 82718 | Oil & Gas Operator | Oct 2025 |
| 525 | Redbud E & P, Inc. | Giddings, TX 78942 | Oil & Gas Operator | Dec 2025 |
| 526 | Redstone Resources Inc | Newcastle, WY 82701 | Gas Operator | Dec 2010 |
| 527 | Reef Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Feb 2007 |
| 528 | Reliance Resources Inc | Houston, TX 77007 | Gas Operator | Jun 2012 |
| 529 | Renor Exploration | Englewood, CO 80111 | Oil Operator | Feb 2001 |
| 530 | Reserve Oil & Gas Company | | Oil & Gas Operator | Jul 1981 |
| 531 | Resolute Wyoming Inc | Denver, CO 80203 | Oil & Gas Operator | May 2018 |
| 532 | Resource Enterprises Inc | Salt Lake City, UT 84108 | Gas Operator | Dec 1990 |
| 533 | Resources Investment Corp | Denver, CO 80202 | Oil & Gas Operator | Sep 2018 |
| 534 | Reunion Energy Company | Houston, TX 77056 | Oil & Gas Operator | May 1996 |
| 535 | Richardson Operating Company | Denver, CO 80237 | Oil & Gas Operator | Nov 2025 |
| 536 | Ridge Energy Partners LLC | Casper, WY 82601 | Oil Operator | Dec 2018 |
| 537 | Rim Operating, Inc. | Englewood, CO 80112 | Oil & Gas Operator | Dec 2025 |
| 538 | Rme Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Nov 2016 |
| 539 | Rochelle Oil & Gas | Gillette, WY 82717 | Oil & Gas Operator | Mar 2024 |
| 540 | Rock Creek Resources LLC | Englewood, CO 80112 | Oil & Gas Operator | Dec 2021 |
| 541 | Rock Oil Corporation | Lawrence, KS 66046 | Oil Operator | Oct 2004 |
| 542 | Rockies Resources Holdings LLC | Lakewood, CO 80228 | Oil & Gas Operator | Oct 2025 |
| 543 | Rocky Mountain Gas Inc | Sheridan, WY 82801 | Gas Operator | Nov 2009 |
| 544 | Roemer Oil Company | Denver, CO 80202 | Oil & Gas Operator | Nov 1998 |
| 545 | Roff Operating Company LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 546 | Royal Resources Exploration | | Oil & Gas Operator | Mar 1984 |
| 547 | Ruby Drilling Company Inc | Gillette, WY 82718 | Oil Operator | Oct 2007 |
| 548 | Sabine Corporation | Oklahoma City, OK 73116 | Oil & Gas Operator | Jul 1996 |
| 549 | Sabine Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 550 | Saga Petroleum LLC Of Colorado | Norman, OK 73072 | Oil & Gas Operator | Dec 2025 |
| 551 | Sage Butte PRB Operating, LLC | Denver, CO 80202 | Oil & Gas Operator | Sep 2025 |
| 552 | Samedan Oil Corporation | Houston, TX 77067 | Oil & Gas Operator | Dec 2019 |
| 553 | Samson Oil & Gas USA Inc | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 554 | Samson Resources Company LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2021 |
| 555 | San Marco Petroleum Inc | Denver, CO 80293 | Oil & Gas Operator | Oct 2025 |
| 556 | Sands Oil Company Inc | Billings, MT 59103 | Oil & Gas Operator | Sep 2025 |
| 557 | Santa Rosa Petroleum LLC | Recluse, WY 82725 | Oil & Gas Operator | Oct 2025 |
| 558 | Scana Petroleum Resources Inc | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 559 | Schmid Properties, Inc. | Hico, TX 76457 | Oil & Gas Operator | Dec 2025 |
| 560 | Seagull Energy E & P Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2015 |
| 561 | Seer Operating LLC | Sheridan, WY 82801 | Oil & Gas Operator | Oct 2016 |
| 562 | Seguro Oil & Gas Inc | | Oil Operator | Jul 1992 |
| 563 | Seven Sisters Oil & Gas LLC | Casper, WY 82602 | Oil & Gas Operator | Jan 2022 |
| 564 | Shar Alan Oil Company | | Oil & Gas Operator | Oct 2005 |
| 565 | Sharkey Well Service Inc | | Oil Operator | Dec 2023 |
| 566 | Shenandoah Energy Inc | Denver, CO 80265-1050 | Oil & Gas Operator | Dec 2014 |
| 567 | Sheridan Production Company, LLC | Houston, TX 77056 | Oil & Gas Operator | Oct 2025 |
| 568 | Siegfried R H Inc | Tulsa, OK 74104 | Oil & Gas Operator | Mar 2008 |
| 569 | Simasko Production Co | Denver, CO 80204 | Oil & Gas Operator | Nov 1997 |
| 570 | Six Bar Oil LLC | Pine Haven, WY 82721 | Oil & Gas Operator | Oct 2025 |
| 571 | Skinner Oil & Gas LLC | Gillette, WY 82717 | Oil & Gas Operator | Jan 2024 |
| 572 | Skull Creek A LLC | Douglas, WY 82633 | Oil & Gas Operator | Nov 2025 |
| 573 | Skyline Oil Company | Salt Lake City, UT 84111 | Oil & Gas Operator | Jan 1987 |
| 574 | Slaughter J M Oil Company | Fort Worth, TX 76116 | Oil & Gas Operator | Jan 2001 |
| 575 | Slawson Exploration Company Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | Dec 2025 |
| 576 | SM Energy Company | Midland, TX 79707 | Oil & Gas Operator | Dec 2025 |
| 577 | Smith Conley P Operating Co | Eglewood, CO 80112-3640 | Oil & Gas Operator | Jun 2000 |
| 578 | Smokey Oil Company Inc | Casper, WY 82601 | Oil & Gas Operator | Dec 1996 |
| 579 | Snowy Owl LLC | Gillette, WY 82717 | Oil & Gas Operator | Oct 2025 |
| 580 | Snyder Oil Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 581 | Sonat Exploration Co. | Houston, TX 77251 | Oil & Gas Operator | Dec 2021 |
| 582 | South Coast Oil Corporation | Boulder, CO 80302 | Oil & Gas Operator | Oct 2015 |
| 583 | South Pass Petroleum Inc | Casper, WY 82601 | Oil & Gas Operator | Oct 2025 |
| 584 | Southland Royalty Company | Houston, TX 77210 | Oil & Gas Operator | Sep 2011 |
| 585 | Southwestern Energy Prod Co | Houston, TX 77032 | Oil & Gas Operator | Jun 2015 |
| 586 | Southwestern Production Corporation | Lakewood, CO 80228 | Oil & Gas Operator | Oct 2025 |
| 587 | Spirit Energy Inc | Edmond, OK 73034 | Oil & Gas Operator | Apr 1999 |
| 588 | St. Mary Operating Company | Denver, CO 80203 | Oil & Gas Operator | Mar 2019 |
| 589 | Stag Oil Producers Inc | Midland, TX 79701 | Oil & Gas Operator | Jan 1998 |
| 590 | Star Resources LLC | Englewood, CO 80155-5185 | Oil & Gas Operator | Dec 2013 |
| 591 | States Exploration Inc | | Oil Operator | Jul 1985 |
| 592 | Statex Petroleum Inc | Dallas, TX 75229 | Oil & Gas Operator | Dec 2000 |
| 593 | Steamboat Oil And Gas LLC | Gillette, WY 82717 | Oil Operator | Oct 2025 |
| 594 | Stellar Oil Company | Arvada, CO 80006 | Oil & Gas Operator | Dec 1998 |
| 595 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | Oct 2025 |
| 596 | Sterling Energy Corporation | Denver, CO 80202 | Oil & Gas Operator | Sep 1995 |
| 597 | Stewart Petroleum Corporation | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Dec 2023 |
| 598 | Stone & Wolf LLC | Sheridan, WY 82801 | Oil & Gas Operator | Dec 2006 |
| 599 | Stone Petroleum Corporation | | Oil & Gas Operator | Dec 1996 |
| 600 | Storm Cat Energy USA Operating Corp | Denver, CO 80202 | Gas Operator | Jun 2017 |