| 401 | Hardin Productions | Okemah, OK 74859 | Oil & Gas Operator | Dec 2006 |
| 402 | Hardin, W.V. Estate | San Antonio, TX 78258 | Oil & Gas Operator | Apr 2002 |
| 403 | Harding & Shelton Inc | Oklahoma City, OK 73104-2410 | Oil & Gas Operator | Jun 2026 |
| 404 | Harding And Shelton Exploration LLC | Oklahoma City, OK 73101-1557 | Oil & Gas Operator | Mar 2026 |
| 405 | Harding Company | Dallas, TX 75244 | Oil & Gas Operator | Jan 2015 |
| 406 | Harding Exploration, Inc. | Wichita Falls, TX 76308 | Oil & Gas Operator | Dec 2016 |
| 407 | Harding Well Service Co. | Coahoma, TX 79511 | Oil & Gas Operator | Aug 2003 |
| 408 | Hardrock Oil Company | Great Falls, MT 59403 | Gas Operator | Jun 2026 |
| 409 | Hardrock Operating Company, Inc. | Fort Worth, TX 76161 | Oil & Gas Operator | Sep 2026 |
| 410 | Hardrock Resources Inc. | Winters, TX 79567 | Oil & Gas Operator | Sep 2026 |
| 411 | Hardway Prod & Operating, LLC | Abilene, TX 79608 | Oil & Gas Operator | Aug 2016 |
| 412 | Hardwick Oil Company | Sugar Land, TX 77478 | Oil & Gas Operator | Nov 2014 |
| 413 | Hardwick, Ross H. Oil Company | Devine, TX 78016 | Oil & Gas Operator | Sep 2026 |
| 414 | Hardy And Hardy Consulting LLC | | Oil & Gas Operator | Jul 2026 |
| 415 | Hardy Oil & Gas USA Inc. | Houston, TX 77079 | Oil & Gas Operator | Jun 1996 |
| 416 | Hardy Ranch, Inc. | Henderson, TX 75654 | Oil & Gas Operator | Sep 2026 |
| 417 | Hardy Salt Co. | | Oil & Gas Operator | Apr 1986 |
| 418 | Hargraves Daughters | | Oil Operator | Mar 1992 |
| 419 | Hargraves Elston | Ponca City, OK 74604 | Oil & Gas Operator | Jul 2003 |
| 420 | Hargraves Production, LLC | | Oil Operator | Jan 2025 |
| 421 | Hargus Curtis | Macomb, OK 74852-8508 | Oil Operator | May 2017 |
| 422 | Hargus Irrevocable Trust | Tecumseh, OK 74873-0590 | Oil Operator | Apr 2014 |
| 423 | Haring Energy Company | Tuleta, TX 78162 | Oil & Gas Operator | Mar 2003 |
| 424 | Harken Exploration Company | Houston, TX 77079 | Oil & Gas Operator | Mar 2008 |
| 425 | Harken Southwest Corp | Dallas, TX 752612007 | Oil & Gas Operator | Feb 2001 |
| 426 | Harkey Energy Inc. | Odessa, TX 79762 | Oil & Gas Operator | Feb 2020 |
| 427 | Harkins & Co. | | Oil & Gas Operator | Oct 1986 |
| 428 | Harkins And Co., Et Al | | Oil & Gas Operator | Dec 1980 |
| 429 | Harleton Oil & Gas Inc. | Tyler, TX 75710 | Oil & Gas Operator | Sep 2026 |
| 430 | Harley Drilling & Producing LTD | Burbank, OH 44214 | Oil & Gas Operator | Dec 2025 |
| 431 | Harlo Oil Compan | | Oil Operator | Dec 1994 |
| 432 | Harlow Corporation, The | Amarillo, TX 79101 | Oil & Gas Operator | Apr 2014 |
| 433 | Harlow Enterprises LLC | Artesia, NM 88210 | Oil & Gas Operator | Jun 2026 |
| 434 | Harman Operating Company, Inc. | Tyler, TX 75702 | Oil & Gas Operator | Dec 2007 |
| 435 | Harmel And Shawver Oil LLC | Wichita Falls, TX 76310 | Oil Operator | Sep 2026 |
| 436 | Harmon O G LLC | Graysville, OH 45734 | Oil & Gas Operator | Dec 2025 |
| 437 | Harmon, C. E. Oil, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Oct 2019 |
| 438 | Harmonia Petroleum Corporation | Missouri City, TX 77459 | Oil & Gas Operator | May 2017 |
| 439 | Harmons Well Service | Graysville, OH 45734 | Oil & Gas Operator | Dec 2019 |
| 440 | Harmony Drilling Company, Inc. | Denver, CO 80222 | Oil & Gas Operator | Nov 2016 |
| 441 | Harmony Exploration, Inc. | College Sta, TX 77842 | Oil & Gas Operator | Sep 2026 |
| 442 | Harmony Oil & Gas Co Inc | Reno, NV 89509 | Oil Operator | Dec 1994 |
| 443 | Harmony Producing Co Inc | | Oil & Gas Operator | Dec 1995 |
| 444 | Harms Petroleum | | Oil & Gas Operator | May 1991 |
| 445 | Harms, H. Allan Petroleum Co., Inc. | Great Bend, KS 67530 | Oil Operator | Apr 1999 |
| 446 | Harms, Vance N. | Talpa, TX 76882 | Oil & Gas Operator | Mar 2016 |
| 447 | Harnetty Francis Dba Harnetty Oil & Gas | Junction City, OH 43748 | Oil & Gas Operator | Dec 2019 |
| 448 | Harold G Raper Family Trust | Mansfield, TX 76063-1667 | Oil Operator | May 2023 |
| 449 | Harold H. Hollenshead | | Oil & Gas Operator | May 2002 |
| 450 | Harold M Root Foundation | | Oil Operator | Jun 2026 |
| 451 | Harold R Elkin | Punxsutawney, PA 15767-7922 | Oil & Gas Operator | Dec 2016 |
| 452 | Harp Peggy A | Seminole, OK 74868-2284 | Oil & Gas Operator | Mar 2024 |
| 453 | Harp, Stephen J. | Fredonia, NY 14063 | Gas Operator | Dec 2025 |
| 454 | Harpel John P Jr | FT. Collins, CO 80525 | Oil & Gas Operator | May 1998 |
| 455 | Harper Crosby Holdings, LLC | Weston, WV 26452 | Oil & Gas Operator | Dec 2025 |
| 456 | Harper Hefte, Inc. | Corpus Christ, TX 78410 | Oil & Gas Operator | Sep 2026 |
| 457 | Harper Joe Howard Dba J H Field Service | Nowata, OK 74048-9704 | Oil & Gas Operator | Mar 2026 |
| 458 | Harper Oil And Gas, LLC | Pratt, KS 67124 | Oil & Gas Operator | May 2026 |
| 459 | Harper Oil Co. | Denver, CO 80217 | Oil & Gas Operator | May 2026 |
| 460 | Harper Production, LLC | Spearman, TX 79081 | Oil & Gas Operator | Sep 2026 |
| 461 | Harper, Clint | Woodson, TX 76491 | Oil & Gas Operator | Sep 2026 |
| 462 | Harper, Mr. William | Clyde, NY 14433 | Gas Operator | Dec 2025 |
| 463 | Harper, Wayne | Dallas, TX 75206 | Oil & Gas Operator | Mar 2008 |
| 464 | Harper, William E. | Woodson, TX 76491 | Oil & Gas Operator | Jul 2016 |
| 465 | Harrell Oil Company LLC | Ardmore, OK 73402 | Oil Operator | Jan 2025 |
| 466 | Harrell Operating Inc | Graham, TX 76450 | Oil & Gas Operator | Sep 2005 |
| 467 | Harrell Operating, L.L.C. | Graham, TX 76450 | Oil & Gas Operator | Jun 2008 |
| 468 | Harrell Petroleum Inc | Oklahoma City, OK 73102-7201 | Oil & Gas Operator | Oct 2017 |
| 469 | Harrell Verlan W | Oklahoma City, OK 73102-7201 | Oil & Gas Operator | Nov 1999 |
| 470 | Harrell, Charles | Graham, TX 76450 | Oil & Gas Operator | Dec 2000 |
| 471 | Harrier Holdings, LTD. | Burnet, TX 78611 | Oil Operator | Sep 2026 |
| 472 | Harrigan Energy Partners, Inc. | Houston, TX 77058 | Oil & Gas Operator | Sep 2010 |
| 473 | Harrigan Operating, LLC | Houston, TX 77258 | Oil & Gas Operator | Apr 2020 |
| 474 | Harrington Billy B | Depew, OK 74028-3495 | Oil & Gas Operator | May 2006 |
| 475 | Harrington Oil Inc. | | Oil & Gas Operator | Apr 1978 |
| 476 | Harrington Orville | Dewey, OK 74029 | Oil Operator | Jun 2026 |
| 477 | Harrington SR Tommy W | Drumright, OK 74030-5778 | Oil Operator | May 2015 |
| 478 | Harris & Payne-Randel Drilling | | Oil & Gas Operator | Dec 1989 |
| 479 | Harris & Walton | Midland, TX 79702 | Oil & Gas Operator | Feb 2004 |
| 480 | Harris B D | Norman, OK 73071-4802 | Oil & Gas Operator | Apr 2014 |
| 481 | Harris Energy Services, LLC | Dallas, TX 75201 | Oil & Gas Operator | Sep 2026 |
| 482 | Harris Engineering Co | Dallas, TX 75248 | Oil & Gas Operator | Dec 1996 |
| 483 | Harris Mildred C | Tulsa, OK 74120 | Oil & Gas Operator | Jun 2026 |
| 484 | Harris Minerals Corp (The) | Oklahoma City, OK 73162-1045 | Oil & Gas Operator | Feb 2026 |
| 485 | Harris Oil & Gas | | Oil & Gas Operator | Jul 1995 |
| 486 | Harris Oil & Gas Company | Denver, CO 80202 | Oil & Gas Operator | Jun 2016 |
| 487 | Harris Olin | Okmulgee, OK 74447-8508 | Oil Operator | Feb 2012 |
| 488 | Harris, David | Toronto, KS 66777 | Oil Operator | May 2026 |
| 489 | Harris, Jake, Trustee | Wichita Falls, TX 76301 | Oil & Gas Operator | Jun 2001 |
| 490 | Harris, Sam E. | Albany, TX 76430 | Oil & Gas Operator | Aug 2003 |
| 491 | Harris, William H. Jr. | Le Roy, NY 14482 | Gas Operator | Dec 2025 |
| 492 | Harrison & Lee | | Oil Operator | Sep 1996 |
| 493 | Harrison Drilling Co | | Oil & Gas Operator | Mar 1981 |
| 494 | Harrison Energy | Tippecanoe, OH 44699 | Oil & Gas Operator | Dec 2000 |
| 495 | Harrison Interests, LTD. | Houston, TX 77002 | Oil & Gas Operator | Sep 2026 |
| 496 | Harrison Oil & Gas Inc | Houston, TX 77019 | Oil & Gas Operator | Jun 2026 |
| 497 | Harrison, Dan J III&Bruce F Est | Houston, TX 77002 | Oil & Gas Operator | Sep 2026 |
| 498 | Harrison, Dan J. III&Bruce F. | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 499 | Harrison, Mark V. | Madison, KS 66860 | Oil Operator | Jul 1995 |
| 500 | Harrison, Sam G. Oil, Inc. | Houston, TX 77019 | Oil & Gas Operator | Nov 2019 |