| 501 | H & M Oil Producers | Littleton, CO 80160 | Oil & Gas Operator | Apr 2000 |
| 502 | H & R Oil Company | | Oil & Gas Operator | Dec 2000 |
| 503 | H & R Well Services, Inc. | FT Morgan, CO 80701 | Oil & Gas Operator | Apr 2015 |
| 504 | H C M Energy LLC | Billings, MT 59102 | Oil Operator | Jul 2003 |
| 505 | H D Oil Company | Thermopolis, WY 82443 | Oil Operator | Feb 2026 |
| 506 | H G H Oil Company | | Oil Operator | Dec 1990 |
| 507 | H2oil Services LLC | | Oil Operator | Jul 2026 |
| 508 | Hadley/Jackson Energy LLC | Lake Forest, IL 60045 | Oil & Gas Operator | Jul 2026 |
| 509 | Hadson Petroleum Corporation | Oklahoma City, OK 73102 | Oil & Gas Operator | Mar 2015 |
| 510 | Hallador Petroleum LLP | Denver, CO 80264 | Oil & Gas Operator | Feb 2019 |
| 511 | Hallwood Petroleum | Denver, CO 80237 | Oil & Gas Operator | Dec 1997 |
| 512 | Hamon Jake L | Dallas, TX 75201-3902 | Oil & Gas Operator | Nov 1997 |
| 513 | Hanson Operating Company Inc | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2026 |
| 514 | Harpel John P Jr | FT. Collins, CO 80525 | Oil & Gas Operator | May 1998 |
| 515 | Harper Oil Co. | Denver, CO 80217 | Oil & Gas Operator | May 2026 |
| 516 | Harrell Oil Company LLC | Ardmore, OK 73402 | Oil Operator | Jan 2025 |
| 517 | Harvey E Yates Company | Roswell, NM 88202 | Oil & Gas Operator | Feb 2015 |
| 518 | Haug Lawrence | Kimball, NE 69145 | Oil & Gas Operator | Jul 2007 |
| 519 | Havoco Inc | Newcastle, WY 82701 | Oil & Gas Operator | Aug 2005 |
| 520 | Hawks Company | Casper, WY 82602 | Oil & Gas Operator | Apr 2007 |
| 521 | Hawks Industries Inc | Casper, WY 82601 | Oil & Gas Operator | Jun 1993 |
| 522 | Hay Leonard | Rock Springs, WY 82901 | Oil & Gas Operator | Sep 1994 |
| 523 | Headington Oil Company, L.P. | Dallas, TX 75231 | Oil & Gas Operator | Mar 2008 |
| 524 | Heartland Energy Company | Big Horn, WY 82833 | Gas Operator | Jun 2012 |
| 525 | Hedges Spencer | Casper, WY 82604 | Oil Operator | Mar 2024 |
| 526 | Helena Resources Inc | Lakewood, CO 80215 | Oil & Gas Operator | Apr 2026 |
| 527 | Helis Oil & Gas Company LLC Estate | New Orleans, LA 70130 | Oil & Gas Operator | Jul 2022 |
| 528 | Henderson Petroleum Corp | San Angelo, TX 76906 | Oil & Gas Operator | Jul 2013 |
| 529 | Herbaly Petroleum Corp | FT Worth, TX 76102 | Oil & Gas Operator | Feb 2002 |
| 530 | Hershey Oil Corporation | | Oil & Gas Operator | Jul 1992 |
| 531 | Hesperus Energy II LLC | | Oil Operator | Jun 2026 |
| 532 | Hi-Pro Production | Gillette, WY 82717 | Gas Operator | Nov 2003 |
| 533 | High Plains Gas LLC | Gillette, WY 82717 | Gas Operator | Aug 2014 |
| 534 | High River Resources Operating, LLC | Farmington, NM 87401 | Oil & Gas Operator | Jul 2026 |
| 535 | High Summit Oil & Gas Inc | | Oil & Gas Operator | Sep 1987 |
| 536 | Highland Exploration | | Oil Operator | Sep 1979 |
| 537 | Hilcorp Energy Company | Houston, TX 77208 | Oil & Gas Operator | Sep 2026 |
| 538 | Hilliard Oil & Gas, Inc. | New Orleans, LA 70112 | Oil & Gas Operator | May 2001 |
| 539 | HMX Investments, Inc. | Katy, TX 77494 | Oil & Gas Operator | Jun 2026 |
| 540 | HNG Oil Company | | Oil & Gas Operator | Jun 1987 |
| 541 | Hodge T F | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2007 |
| 542 | Hoff Elmer & Mildred | | Oil & Gas Operator | Jan 1991 |
| 543 | Holden Harold B | Billings, MT 59103 | Oil Operator | Jun 1996 |
| 544 | Holly Energy Inc | | Oil Operator | Apr 1983 |
| 545 | Holwell Drilling Company | | Oil Operator | Sep 1992 |
| 546 | Home Petroleum Corp | Victoria, TX 77902 | Oil & Gas Operator | Sep 2026 |
| 547 | Hondo Oil & Gas | Houston, TX 77042 | Oil & Gas Operator | Oct 1995 |
| 548 | Hot Springs Resources LTD | Casper, WY 82601 | Oil Operator | Dec 2014 |
| 549 | Houston Oil And Minerals | | Oil & Gas Operator | Oct 1993 |
| 550 | Howell Petroleum Corporation | Houston, TX 77251 | Oil & Gas Operator | Jun 2026 |
| 551 | HR Energy LLC | Shelby, MT 59474 | Oil & Gas Operator | Jun 2026 |
| 552 | HRM Resources II, LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2026 |
| 553 | HRM Resources III LLC | Denver, CO 80202 | Oil & Gas Operator | Jun 2022 |
| 554 | HRM Resources LLC | Denver, CO 80202 | Oil & Gas Operator | Aug 2015 |
| 555 | Hrubetz Oil Co. | Dallas, TX 75225 | Oil Operator | Sep 1986 |
| 556 | HS Resources, Inc. | Denver, CO 80202 | Oil & Gas Operator | Sep 2002 |
| 557 | Huber J M Corp | Edison, NJ 08837 | Oil & Gas Operator | Sep 2026 |
| 558 | Hudson Group LLC | Casper, WY 82601 | Oil & Gas Operator | Jul 2025 |
| 559 | Hughes Oil Company Inc | Odessa, TX 79765 | Oil & Gas Operator | Feb 2004 |
| 560 | Hugoton Energy Corporation | Oklahoma City, OK 73113 | Oil & Gas Operator | Dec 2019 |
| 561 | Hunt Oil Company | Dallas, TX 75201 | Oil & Gas Operator | Sep 2026 |
| 562 | Hunt Petroleum (Aec), Inc. | Dallas, TX 75201 | Oil & Gas Operator | Nov 2008 |
| 563 | Huntington Energy LLC | Nichols Hill, OK 73116 | Oil & Gas Operator | Sep 2026 |
| 564 | Hurley Oil Company | | Oil Operator | Dec 1988 |
| 565 | Husky Oil Company | Cody, WY 82414 | Oil & Gas Operator | Dec 1984 |
| 566 | Hyco Oil Inc | Newcastle, WY 82701 | Oil & Gas Operator | Dec 2006 |
| 567 | Hydrocarbon Management, Inc. | San Antonio, TX 78216 | Oil & Gas Operator | Dec 1996 |
| 568 | Hyland Oil Corporation | | Oil & Gas Operator | Apr 1990 |
| 569 | Hyperion Oil & Gas LLC | Dallas, TX 75251 | Oil & Gas Operator | Jul 2026 |
| 570 | I C Gas Amcana Inc | Tulsa, OK 74103-3713 | Oil & Gas Operator | Apr 1996 |
| 571 | Ibex Resources Operating LLC | The Woodlands, TX 77380 | Oil & Gas Operator | Jun 2007 |
| 572 | Iks Operating | Upton, WY 82703 | Oil & Gas Operator | Jul 2013 |
| 573 | Impact Energy Operating LLC | Oklahoma City, OK 73172 | Oil & Gas Operator | Jul 2026 |
| 574 | Impact Exploration & Production LLC | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Dec 2025 |
| 575 | Incline Reserves Inc | Topeka, KS BAD ADDR | Oil & Gas Operator | Mar 1994 |
| 576 | Incremental Oil & Gas USA Holdings Inc | Denver, CO 80202 | Oil & Gas Operator | Apr 2021 |
| 577 | Independent Production Company | Greenwood VIllage, CO 80121 | Oil & Gas Operator | May 2003 |
| 578 | Indian Creek Resources Inc | Loveland, CO 80538 | Oil & Gas Operator | Dec 2024 |
| 579 | Industrial Gas Services Inc | Wheat Ridge, CO 80033 | Oil & Gas Operator | Feb 2023 |
| 580 | Inexco Oil Company | Houston, TX 77210 | Oil & Gas Operator | Mar 2013 |
| 581 | Infield Discovery LLC | Madison, MS 39110 | Oil & Gas Operator | Apr 2026 |
| 582 | Infinity Oil & Gas Of Wyoming | Rock Springs, WY 82902 | Oil & Gas Operator | Feb 2009 |
| 583 | Inland Production Company | Vernal, UT 84079 | Oil & Gas Operator | Dec 2004 |
| 584 | Integrated Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 585 | Integrated Petroleum Corporation | Denver, CO 80202 | Oil Operator | Jan 2010 |
| 586 | Integrity Oil & Gas | Golden, CO 80401 | Oil & Gas Operator | May 2011 |
| 587 | Intercoast Oil And Gas Company | Tulsa, OK 74136 | Oil & Gas Operator | Jun 1997 |
| 588 | Intercontinental Petroleum | | Oil Operator | Oct 2012 |
| 589 | Interline Resources Corp | Casper, WY 82601 | Oil & Gas Operator | Oct 2009 |
| 590 | Internorth Inc | Tulsa, OK 74136 | Oil & Gas Operator | Apr 2014 |
| 591 | Intoil, Inc. | Englewood, CO 80155 | Oil & Gas Operator | Dec 2002 |
| 592 | Intrepid Oil & Gas LLC | Denver, CO 80202 | Oil & Gas Operator | Apr 2021 |
| 593 | Intrepid Production Corporation | Denver, CO 80202 | Oil & Gas Operator | Jul 2026 |
| 594 | Investment Equipment LLC | FT Morgan, CO 80701 | Oil & Gas Operator | May 2026 |
| 595 | Ip Petroleum Company, Inc. | Houston, TX 77210 | Oil & Gas Operator | Mar 2008 |
| 596 | Iron Creek Properties Inc | Casper, WY 82604 | Oil & Gas Operator | Sep 2025 |
| 597 | Itr Petroleum Inc | Houston, TX 77002 | Oil & Gas Operator | Apr 1998 |
| 598 | J & J Production LLC | Worland, WY 82401 | Oil Operator | May 2026 |
| 599 | J-Bird Well Service Incorporated | Gillette, WY 82717 | Oil Operator | Jul 2026 |
| 600 | J-W Operating Company | Christoval, TX 76935 | Oil & Gas Operator | Sep 2026 |