| 501 | Harrison Energy | Tippecanoe, OH 44699 | Oil & Gas Operator | Dec 2000 |
| 502 | Harrison Interests, LTD. | Houston, TX 77002 | Oil & Gas Operator | Jun 2025 |
| 503 | Harrison Oil & Gas Inc | Houston, TX 77019 | Oil & Gas Operator | Jan 2025 |
| 504 | Harrison, Dan J III&Bruce F Est | Houston, TX 77002 | Oil & Gas Operator | Jun 2025 |
| 505 | Harrison, Dan J. III&Bruce F. | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 506 | Harrison, Mark V. | Madison, KS 66860 | Oil Operator | Jul 1995 |
| 507 | Harrison, Sam G. Oil, Inc. | Houston, TX 77019 | Oil & Gas Operator | Nov 2019 |
| 508 | Harrison, Thomas D | Park City, UT 84060-7307 | Gas Operator | Dec 1998 |
| 509 | Harrison-Wright Oil Company LLC | Tulsa, OK 74133-7035 | Oil & Gas Operator | Feb 2025 |
| 510 | Harrod Leasing | Edmond, OK 73034 | Oil & Gas Operator | Feb 2025 |
| 511 | Harry Feder | | Oil & Gas Operator | Dec 1999 |
| 512 | Harry L. Neeb | | Oil Operator | May 1985 |
| 513 | Harsh International Inc | | Oil & Gas Operator | Dec 2013 |
| 514 | Hart & McFarland | Vivian, LA 71082 | Oil & Gas Operator | Jun 2025 |
| 515 | Hart David | Chickasha, OK 73018-7756 | Oil & Gas Operator | Mar 2015 |
| 516 | Hart Energies, LLC | Tulsa, OK 74133 | Oil & Gas Operator | Dec 2016 |
| 517 | Hart Energy LLC | | Oil Operator | Dec 2024 |
| 518 | Hart Oil & Gas Inc | Houston, TX 77024 | Oil & Gas Operator | Jan 2017 |
| 519 | Hart Oil, LLC | | Oil Operator | Dec 2014 |
| 520 | Hart Petroleum Services, Inc | Robstown, TX 78380 | Oil & Gas Operator | Jun 2025 |
| 521 | Hart, Nick And Connie | Paola, KS 66071 | Oil Operator | Feb 2025 |
| 522 | Hartco Oil Co. | | Oil Operator | Jan 2025 |
| 523 | Hartel, Inc. | Abilene, TX 79601 | Oil & Gas Operator | Aug 1997 |
| 524 | Harter Energy Inc. | Tulsa, OK 74105 | Oil & Gas Operator | Mar 2025 |
| 525 | Harter Oil Company | | Oil & Gas Operator | Apr 2011 |
| 526 | Harter, Ron | Midland, TX 79702 | Oil & Gas Operator | Jun 2025 |
| 527 | Hartley Natural Resource Development | | Oil & Gas Operator | Mar 2025 |
| 528 | Hartline Tom | Drumright, OK 74030 | Oil Operator | Jan 2025 |
| 529 | Hartman Oil And Gas Company | | Oil Operator | Dec 1998 |
| 530 | Hartman Oil Co., Inc. | Wichita, KS 67206 | Oil & Gas Operator | Feb 2025 |
| 531 | Hartman W L Trus | | Oil Operator | Jun 1992 |
| 532 | Hartoil Corporation | Post, TX 79356 | Oil & Gas Operator | Jun 2025 |
| 533 | Harus Inc | Indiana, PA 15701-9401 | Oil & Gas Operator | Dec 2024 |
| 534 | Harvard Investments, Inc. | | Oil & Gas Operator | Oct 2002 |
| 535 | Harvard Petroleum Company, LLC | Roswell, NM 88202 | Oil & Gas Operator | Jun 2025 |
| 536 | Harvard Petroleum Corporation | Roswell, NM 88201 | Oil & Gas Operator | Dec 2004 |
| 537 | Harvest (Us) Holdings, Inc | Houston, TX 77077 | Oil & Gas Operator | Apr 2011 |
| 538 | Harvest Energy Company | Englewood, CO 80110 | Oil & Gas Operator | Aug 2001 |
| 539 | Harvest Oil & Gas, LLC | | Oil & Gas Operator | Feb 2012 |
| 540 | Harvest Operating Company, Inc. | Cisco, TX 76437 | Oil & Gas Operator | Dec 1997 |
| 541 | Harvest Petroleum Inc. | Frisco, TX 75033 | Oil & Gas Operator | Jun 2025 |
| 542 | Harvest Petroleum Partners, LLC | Midland, TX 79705 | Oil & Gas Operator | Mar 2025 |
| 543 | Harvey A B | Seminole, OK 74868-1724 | Oil Operator | Mar 2015 |
| 544 | Harvey Brothers Oil & Gas | Corpus Chrsti, TX 78408 | Oil & Gas Operator | Jul 2004 |
| 545 | Harvey Broyles | | Oil & Gas Operator | May 2012 |
| 546 | Harvey Broyles & Munoco Co. | | Oil & Gas Operator | Jan 2002 |
| 547 | Harvey Broyles, Et Al | | Gas Operator | Nov 1985 |
| 548 | Harvey E Yates Company | Roswell, NM 88202 | Oil & Gas Operator | Feb 2015 |
| 549 | Harvey, James W. | Wichita Falls, TX 76301 | Oil & Gas Operator | Mar 2008 |
| 550 | Harvey, Mike W. Oil & Gas | Corpus Chrsti, TX 78408 | Oil & Gas Operator | Aug 2003 |
| 551 | Harvey, Robert E., Jr. | Nixon, TX 78140 | Oil & Gas Operator | Oct 2003 |
| 552 | Harvick Oil Co. | Albany, TX 76430 | Oil & Gas Operator | Feb 2009 |
| 553 | Harvick, George R. | Albany, TX 76430 | Oil & Gas Operator | Jun 2025 |
| 554 | Harwell Enterprises | Loveland, CO 80537 | Gas Operator | Nov 2019 |
| 555 | Harwell Enterprises Inc. | Weatherford, TX 76086 | Oil & Gas Operator | Jan 2005 |
| 556 | Harwood Exploration, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Aug 1995 |
| 557 | Harwood Oil & Gas Inc | Greeley, CO 80631-8233 | Oil & Gas Operator | Feb 2025 |
| 558 | Hasada Industrie | | Oil & Gas Operator | Jul 1995 |
| 559 | Haskit, Kendall | Kyle, TX 78640 | Oil & Gas Operator | Jun 2025 |
| 560 | Hassie Hunt Expl. Company | Dallas, TX 75201 | Oil & Gas Operator | Aug 2008 |
| 561 | Hasso Energy LLC | | Oil & Gas Operator | Jan 2025 |
| 562 | Hastings, J. W. Oil Co. | Wichita Falls, TX 76301 | Oil & Gas Operator | Mar 2010 |
| 563 | Hat Creek Cattle Company, A General Partnership | Paola, KS 66071 | Oil Operator | Aug 2016 |
| 564 | Hat Creek Energy LLC | Denver, CO 80209 | Oil & Gas Operator | Jun 2019 |
| 565 | Hat Oil & Gas, Inc. | Slaton, TX 79364 | Oil & Gas Operator | Feb 2002 |
| 566 | Hat Production LLC | Mound City, KS 66056 | Oil Operator | Jan 2025 |
| 567 | Hat-Top Production Co | Duncan, OK 73533 | Oil Operator | Apr 2011 |
| 568 | Hatch, Jeffrey And Chelsea | Bemus Point, NY 14712 | Gas Operator | Dec 2023 |
| 569 | Hatcher, Ray | Burkburnett, TX 76354 | Oil & Gas Operator | Jun 2002 |
| 570 | Hatco Productions LTD | North Augusta, SC 29860 | Oil Operator | Dec 2024 |
| 571 | Hathaway Company | | Oil & Gas Operator | Mar 2025 |
| 572 | Hathaway LLC | | Oil & Gas Operator | Apr 2025 |
| 573 | Hathaway Operators, Inc | | Oil & Gas Operator | Dec 2000 |
| 574 | Hatler Oil Company, Inc. | Graham, TX 76450 | Oil & Gas Operator | Sep 2000 |
| 575 | Haug Lawrence | Kimball, NE 69145 | Oil & Gas Operator | Jul 2007 |
| 576 | Haught Energy Corporation | Smithville, WV 26178-7004 | Oil & Gas Operator | Dec 2021 |
| 577 | Haught Harold | Hominy, OK 74035 | Oil Operator | Feb 2012 |
| 578 | Haught, Glenn L. & Sons | | Oil & Gas Operator | Dec 1997 |
| 579 | Haught, Inc. | Smithville, WV 26178 | Oil & Gas Operator | Nov 2021 |
| 580 | Haul-Pac, Inc. | Hiawatha, KS 66434 | Oil Operator | Dec 2024 |
| 581 | Haussler Farms Inc. | | Oil Operator | Dec 1992 |
| 582 | Haven Oil & Gas | Hutchinson, KS 67504 | Oil & Gas Operator | Mar 2009 |
| 583 | Havenor Operating Co | Roswell, NM 88201 | Oil & Gas Operator | Jun 2018 |
| 584 | Havens Oil Company | Early, TX 76803 | Oil & Gas Operator | Mar 2025 |
| 585 | Haverkamp, Floyd | Muenster, TX 76252 | Oil & Gas Operator | Oct 2001 |
| 586 | Havins Energy | Burkburnett, TX 76354 | Oil & Gas Operator | May 2006 |
| 587 | Havoco Inc | Newcastle, WY 82701 | Oil & Gas Operator | Aug 2005 |
| 588 | Haw Corporation | | Oil Operator | Dec 1979 |
| 589 | Hawk Exploration And Production | Corpus Chrsti, TX 78412 | Oil & Gas Operator | Oct 1995 |
| 590 | Hawk Oil Co. | Luling, TX 78648 | Oil & Gas Operator | Aug 2003 |
| 591 | Hawk Petroleum, L L C | San Diego, TX 78384 | Oil & Gas Operator | Jun 2025 |
| 592 | Hawk Well Service | Borger, TX 79007 | Oil & Gas Operator | Jun 2025 |
| 593 | Hawk, Lisa | Fredonia, NY 14063 | Gas Operator | Dec 2023 |
| 594 | Hawk-Hill Operating Company, LLC | Plano, TX 75093 | Oil & Gas Operator | Jun 2009 |
| 595 | Hawkbend LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Jun 2025 |
| 596 | Hawke Inc | Barbertib, OH 44203 | Oil & Gas Operator | Dec 2024 |
| 597 | Hawkeye Drilling Co. | Waskom, TX 75692 | Oil & Gas Operator | Feb 2023 |
| 598 | Hawkeye Oil | | Oil & Gas Operator | Jun 2007 |
| 599 | Hawkeye Oil & Gas, Inc. | | Gas Operator | Jun 1995 |
| 600 | Hawkeye Transmission Company | Dallas, TX 75244 | Oil & Gas Operator | Jun 2000 |