| 401 | Medicine Bow Operating Company | Houston, TX 77002 | Oil & Gas Operator | Apr 2014 |
| 402 | Mega Energy LLC | Gillette, WY 82718 | Gas Operator | Oct 2025 |
| 403 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Dec 2025 |
| 404 | Meritage Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2005 |
| 405 | Merrimac Oil & Gas LLC | Houston, TX 77054 | Gas Operator | Dec 2008 |
| 406 | Merrion Oil & Gas Corp | Farmington, NM 87401 | Oil & Gas Operator | Nov 2025 |
| 407 | Methane Productions Inc | Recluse, WY 82725 | Oil & Gas Operator | Apr 2007 |
| 408 | Meyer Douglas P | Longmont, CO 80501 | Oil & Gas Operator | Aug 2006 |
| 409 | Mi3 Energy LLC | | Oil & Gas Operator | Oct 2025 |
| 410 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 411 | Mid-Con Energy Operating, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Nov 2025 |
| 412 | Midgard Energy Company | The Woodlands, TX 77380 | Oil & Gas Operator | Dec 2014 |
| 413 | Minnelusa Oil LLC | Temecula, CA 92589 | Oil Operator | Feb 2002 |
| 414 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 415 | Mitchell M J | | Oil & Gas Operator | Jan 1983 |
| 416 | Mobil Expl & Producing North America Inc | | Oil & Gas Operator | Nov 1986 |
| 417 | Monahan Rex | Sterling, CO 80751 | Oil & Gas Operator | Jun 2002 |
| 418 | Moncrief W A Jr | Fort Worth, TX 76102 | Oil & Gas Operator | Oct 2025 |
| 419 | Monsanto Company | Indianapolis, IN 46280 | Oil & Gas Operator | Jan 2005 |
| 420 | Montex Drilling Company LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Dec 2025 |
| 421 | Montex Exploration | Sugarland, TX 77478 | Oil Operator | Apr 2003 |
| 422 | Mosbacher Production Co. | Casper, WY 82602 | Oil & Gas Operator | Aug 1984 |
| 423 | Mountain Hawk Energy LLC | Athens, TX 75751 | Gas Operator | Jan 2015 |
| 424 | MTG Operating Inc | Ridgeland, MS 39158 | Gas Operator | Apr 2011 |
| 425 | Mull Drilling Company | Wichita, KS 67206 | Oil & Gas Operator | Sep 2025 |
| 426 | Murphy Oil USA, Inc. | New Orleans, LA 70161 | Oil & Gas Operator | Jan 1993 |
| 427 | Murphy Sheldon L & Loretta | Newcastle, WY 82701 | Oil & Gas Operator | Nov 2025 |
| 428 | MWJ Producing Company | Midland, TX 79701 | Oil & Gas Operator | Jul 1998 |
| 429 | Nadel And Gussman Rockies, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2012 |
| 430 | Nance Petroleum Corporation | Billings, MT 59103-7168 | Oil & Gas Operator | Nov 2007 |
| 431 | National Energy Group Inc | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 432 | National Oil Company | Garden City, KS 67846 | Oil & Gas Operator | Jun 2024 |
| 433 | National Pride Operating | Parker, CO 80134 | Oil & Gas Operator | Dec 2017 |
| 434 | Natomas North America Inc | | Oil & Gas Operator | Aug 1993 |
| 435 | Navigation Powder River LLC | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 436 | Neward Corporation | FT. Worth, TX 76102 | Oil & Gas Operator | Dec 1997 |
| 437 | Newport Gas Partners LLC | Gillette, WY 82716 | Oil & Gas Operator | Oct 2025 |
| 438 | Nicolaysen G G Jr | | Oil & Gas Operator | Dec 1995 |
| 439 | Nicor Exploration | | Oil Operator | Jul 1993 |
| 440 | Nicor Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Jun 1993 |
| 441 | Nielson & Associates, Inc | Cody, WY 82414 | Oil & Gas Operator | Feb 2016 |
| 442 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Dec 2025 |
| 443 | Nonsuch Natural Gas Inc | Naples, FL 34108 | Oil & Gas Operator | Nov 2025 |
| 444 | Norcen Energy Inc | | Oil Operator | Dec 1989 |
| 445 | Nordstrand Engineering Inc | Houston, TX 77019 | Oil & Gas Operator | Dec 2025 |
| 446 | North Finn LLC | Casper, WY 82605 | Oil & Gas Operator | Nov 2025 |
| 447 | Northern Production Co | Gillette, WY 82717 | Oil & Gas Operator | Apr 2013 |
| 448 | Northstar Operating Company | Midland, TX 79702 | Oil & Gas Operator | Jun 2024 |
| 449 | Norton Frickey | Lakewood, CO 80215 | Oil & Gas Operator | Dec 2023 |
| 450 | Nova Energy Inc | Casper, WY 82601 | Oil & Gas Operator | Oct 2020 |
| 451 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Dec 2025 |
| 452 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 453 | Oedekoven Amerifields Resources LLC | Sugar Land, TX 77478 | Oil Operator | Aug 2025 |
| 454 | Oedekoven Water & Hot Oil | Recluse, WY 82725 | Oil & Gas Operator | Nov 2025 |
| 455 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | Oct 2025 |
| 456 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Oct 2025 |
| 457 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 458 | Olympic Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Jul 2004 |
| 459 | Opes Production Inc | Buffalo, WY 82834 | Gas Operator | Mar 2015 |
| 460 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 461 | Osborn Heirs Company LTD | San Antonio, TX 78217 | Oil & Gas Operator | Sep 2025 |
| 462 | Outlaw Oil And Gas LLC | Kaw City, OK 74641 | Oil & Gas Operator | Oct 2025 |
| 463 | Oxford Exploration Company | Denver, CO 80237 | Oil & Gas Operator | Aug 1995 |
| 464 | Oxy Petroleum Inc | | Oil & Gas Operator | Jan 1986 |
| 465 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Dec 2025 |
| 466 | P & M Petroleum Management LLC | Denver, CO 80202 | Oil & Gas Operator | Oct 2021 |
| 467 | P & P Producing Inc | Midland, TX 79702 | Oil & Gas Operator | Feb 2015 |
| 468 | P.O.&G. Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Dec 2025 |
| 469 | Pacific Enterprises Oil Co USA | Dallas, TX 75201 | Oil & Gas Operator | Feb 2001 |
| 470 | Palo Petroleum Inc | Dallas, TX 75360 | Oil & Gas Operator | Dec 2025 |
| 471 | Park Robert E | | Oil Operator | May 1983 |
| 472 | Parker & Parsley Producing LP | Midland, TX 79702 | Oil & Gas Operator | Oct 1997 |
| 473 | Pathfinder Energy Inc | Casper, WY 82605 | Oil & Gas Operator | May 2024 |
| 474 | Patrick Petroleum Co. | Jackson, MI 49201 | Oil & Gas Operator | Nov 1993 |
| 475 | Patriot Energy Resources LLC | Golden, CO 80401 | Gas Operator | Aug 2014 |
| 476 | Patriot Production LLC | Southlake, TX 76092 | Oil & Gas Operator | Apr 2023 |
| 477 | Peabody Natural Gas LLC | Gillette, WY 82718 | Oil & Gas Operator | Nov 2025 |
| 478 | Peak Powder River Resources LLC | Durango, CO 81301 | Oil & Gas Operator | Oct 2025 |
| 479 | Pedco Resources Company | Tulsa, OK 74170 | Oil & Gas Operator | Mar 2008 |
| 480 | Pendragon Energy Partners Inc | Midland, TX 79701 | Oil & Gas Operator | Nov 2009 |
| 481 | Pennaco Energy Incorporated | Gillette, WY 82718 | Oil & Gas Operator | Feb 2021 |
| 482 | Pennzoil Company | Midland, TX 79710-0090 | Oil & Gas Operator | Mar 2000 |
| 483 | Petro Search Exploration Corp | | Oil & Gas Operator | May 1993 |
| 484 | Petro-Canada Resources (USA) Inc | Denver, CO 80202-472 | Oil & Gas Operator | Feb 2010 |
| 485 | Petro-Hunt Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2003 |
| 486 | Petro-Hunt, L.L.C. | Dallas, TX 75201 | Oil & Gas Operator | Dec 2025 |
| 487 | Petro-Lewis Corp. | | Oil & Gas Operator | Feb 1994 |
| 488 | Petrocorp Incorporated | Tulsa, OK 74170 | Oil & Gas Operator | Nov 2021 |
| 489 | Petrogulf Corporation | Denver, CO 80202 | Oil & Gas Operator | Dec 2025 |
| 490 | Petroleum Inc | Wichita, KS 67202 | Oil & Gas Operator | Oct 2021 |
| 491 | Petrox Resources Inc | Meeker, CO 81641 | Oil & Gas Operator | Nov 2025 |
| 492 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |
| 493 | Phoenix Resources Co | | Oil & Gas Operator | Jun 1984 |
| 494 | Pine Haven Resources LLC | Boulder, CO 80305 | Oil Operator | Nov 2025 |
| 495 | Pine Ridge Petroleum LLC | Moorcroft, WY 82721 | Oil Operator | Nov 2025 |
| 496 | Pioneer Exploration, LLC | Houston, TX 77090 | Oil & Gas Operator | Nov 2025 |
| 497 | Pioneer Natural Resources USA Inc | Irving, TX 75039 | Oil & Gas Operator | Sep 2025 |
| 498 | Plains Petroleum Operating Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2014 |
| 499 | PML Operating LLC | | Oil Operator | Oct 2025 |
| 500 | Poc-I LLC | Casper, WY 82605 | Oil & Gas Operator | Nov 2025 |