| 301 | Martens & Peck Operating Co | | Gas Operator | Feb 1997 |
| 302 | Martens & Peck Production Co | Denver, CO 80222 | Oil & Gas Operator | Feb 1997 |
| 303 | Matrix Production Company | Sugar Land, TX 77478 | Oil & Gas Operator | May 2026 |
| 304 | Maxim Drilling & Expl Inc | Gillette, WY 82717 | Oil & Gas Operator | May 2026 |
| 305 | Maximus Operating, LTD. | Kilgore, TX 75663 | Oil & Gas Operator | Jul 2026 |
| 306 | Mbi Oil & Gas LLC | Dickinson, ND 58601 | Oil & Gas Operator | May 2026 |
| 307 | McAdams Roux & Associates | Denver, CO 80202 | Oil & Gas Operator | Dec 1999 |
| 308 | McClure Enterprises | Recluse, WY 82725 | Oil & Gas Operator | Dec 2025 |
| 309 | McGuire John C | Gillette, WY 82717 | Oil & Gas Operator | Oct 2005 |
| 310 | McKenzie Production Company | Houston, TX 77063 | Oil & Gas Operator | May 1995 |
| 311 | MCL 1 Oil & Gas Wyoming LLC | Minneapolis, MN 55402 | Oil & Gas Operator | Jul 2018 |
| 312 | McMahon-Bullington LP | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2009 |
| 313 | McMurry Oil LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2004 |
| 314 | McRae & Henry LTD | Golden, CO 80401 | Oil & Gas Operator | May 2022 |
| 315 | MDS Energy Development LLC | | Oil & Gas Operator | May 2026 |
| 316 | Medallion Exploration | Holladay, UT 84117 | Oil & Gas Operator | Dec 2015 |
| 317 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 318 | Medicine Bow Operating Company | Houston, TX 77002 | Oil & Gas Operator | Apr 2014 |
| 319 | Mega Energy LLC | Gillette, WY 82718 | Gas Operator | May 2026 |
| 320 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Jul 2026 |
| 321 | Meritage Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2005 |
| 322 | Merrion Oil & Gas Corp | Farmington, NM 87401 | Oil & Gas Operator | May 2026 |
| 323 | Methane Productions Inc | Recluse, WY 82725 | Oil & Gas Operator | Apr 2007 |
| 324 | Meyer Douglas P | Longmont, CO 80501 | Oil & Gas Operator | Aug 2006 |
| 325 | Mi3 Energy LLC | | Oil & Gas Operator | May 2026 |
| 326 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 327 | Mid-Con Energy Operating, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Jun 2026 |
| 328 | Midgard Energy Company | The Woodlands, TX 77380 | Oil & Gas Operator | Dec 2014 |
| 329 | Minnelusa Oil LLC | Temecula, CA 92589 | Oil Operator | Feb 2002 |
| 330 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 331 | Mitchell M J | | Oil & Gas Operator | Jan 1983 |
| 332 | Mobil Expl & Producing North America Inc | | Oil & Gas Operator | Nov 1986 |
| 333 | Monahan Rex | Sterling, CO 80751 | Oil & Gas Operator | Jun 2002 |
| 334 | Moncrief W A Jr | Fort Worth, TX 76102 | Oil & Gas Operator | May 2026 |
| 335 | Monsanto Company | Indianapolis, IN 46280 | Oil & Gas Operator | Jan 2005 |
| 336 | Montex Drilling Company LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Jul 2026 |
| 337 | Montex Exploration | Sugarland, TX 77478 | Oil Operator | Apr 2003 |
| 338 | Mosbacher Production Co. | Houston, TX 77001 | Oil & Gas Operator | Aug 1984 |
| 339 | Mountain Hawk Energy LLC | Athens, TX 75751 | Gas Operator | Jan 2015 |
| 340 | MTG Operating Inc | Ridgeland, MS 39158 | Gas Operator | Apr 2011 |
| 341 | Mull Drilling Company | Wichita, KS 67206 | Oil & Gas Operator | Apr 2026 |
| 342 | Murphy Oil USA, Inc. | New Orleans, LA 70161 | Oil & Gas Operator | Jan 1993 |
| 343 | Murphy Sheldon L & Loretta | Newcastle, WY 82701 | Oil & Gas Operator | Jun 2026 |
| 344 | MWJ Producing Company | Midland, TX 79701 | Oil & Gas Operator | Jul 1998 |
| 345 | Nadel And Gussman Rockies, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2012 |
| 346 | Nance Petroleum Corporation | Billings, MT 59103-7168 | Oil & Gas Operator | Nov 2007 |
| 347 | National Energy Group Inc | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 348 | National Oil Company | Garden City, KS 67846 | Oil & Gas Operator | Jun 2024 |
| 349 | National Pride Operating | Parker, CO 80134 | Oil & Gas Operator | Dec 2017 |
| 350 | Natomas North America Inc | | Oil & Gas Operator | Aug 1993 |
| 351 | Navigation Powder River LLC | Houston, TX 77024 | Oil & Gas Operator | May 2026 |
| 352 | Neward Corporation | FT. Worth, TX 76102 | Oil & Gas Operator | Dec 1997 |
| 353 | Newport Gas Partners LLC | Gillette, WY 82716 | Oil & Gas Operator | Oct 2025 |
| 354 | Nicolaysen G G Jr | | Oil & Gas Operator | Dec 1995 |
| 355 | Nicor Exploration | | Oil Operator | Jul 1993 |
| 356 | Nicor Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Jun 1993 |
| 357 | Nielson & Associates, Inc | Cody, WY 82414 | Oil & Gas Operator | Feb 2016 |
| 358 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Jul 2026 |
| 359 | Nonsuch Natural Gas Inc | Naples, FL 34108 | Oil & Gas Operator | Jun 2026 |
| 360 | Norcen Energy Inc | | Oil Operator | Dec 1989 |
| 361 | Nordstrand Engineering Inc | Houston, TX 77019 | Oil & Gas Operator | Jul 2026 |
| 362 | North Finn LLC | Casper, WY 82605 | Oil & Gas Operator | Jun 2026 |
| 363 | Northern Production Co | Gillette, WY 82717 | Oil & Gas Operator | Apr 2013 |
| 364 | Northstar Operating Company | Midland, TX 79702 | Oil & Gas Operator | Jun 2024 |
| 365 | Norton Frickey | Lakewood, CO 80215 | Oil & Gas Operator | Dec 2023 |
| 366 | Nova Energy Inc | Casper, WY 82601 | Oil & Gas Operator | Oct 2020 |
| 367 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Jul 2026 |
| 368 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 369 | Oedekoven Amerifields Resources LLC | Sugar Land, TX 77478 | Oil Operator | Apr 2026 |
| 370 | Oedekoven Water & Hot Oil | Recluse, WY 82725 | Oil & Gas Operator | Jun 2026 |
| 371 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | May 2026 |
| 372 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2026 |
| 373 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 374 | Olympic Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Jul 2004 |
| 375 | Opes Production Inc | Buffalo, WY 82834 | Gas Operator | Mar 2015 |
| 376 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 377 | Osborn Heirs Company LTD | San Antonio, TX 78217 | Oil & Gas Operator | Mar 2026 |
| 378 | Oxford Exploration Company | Denver, CO 80237 | Oil & Gas Operator | Aug 1995 |
| 379 | Oxy Petroleum Inc | | Oil & Gas Operator | Jan 1986 |
| 380 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Jul 2026 |
| 381 | P & M Petroleum Management LLC | Denver, CO 80202 | Oil & Gas Operator | Oct 2021 |
| 382 | P & P Producing Inc | Midland, TX 79702 | Oil & Gas Operator | Feb 2015 |
| 383 | P.O.&G. Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Jul 2026 |
| 384 | Pacific Enterprises Oil Co USA | Dallas, TX 75201 | Oil & Gas Operator | Feb 2001 |
| 385 | Palo Petroleum, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Jul 2026 |
| 386 | Park Robert E | | Oil Operator | May 1983 |
| 387 | Parker & Parsley Producing LP | Midland, TX 79702 | Oil & Gas Operator | Oct 1997 |
| 388 | Pathfinder Energy Inc | Casper, WY 82605 | Oil & Gas Operator | May 2024 |
| 389 | Patrick Petroleum Co. | Jackson, MI 49201 | Oil & Gas Operator | Nov 1993 |
| 390 | Patriot Energy Resources LLC | Golden, CO 80401 | Gas Operator | Aug 2014 |
| 391 | Patriot Production LLC | Southlake, TX 76092 | Oil & Gas Operator | Apr 2023 |
| 392 | Peabody Natural Gas LLC | Gillette, WY 82718 | Oil & Gas Operator | Apr 2026 |
| 393 | Peak Powder River Resources LLC | Durango, CO 81301 | Oil & Gas Operator | May 2026 |
| 394 | Pedco Resources Company | Tulsa, OK 74170 | Oil & Gas Operator | Mar 2008 |
| 395 | Pendragon Energy Partners Inc | Midland, TX 79701 | Oil & Gas Operator | Nov 2009 |
| 396 | Pennaco Energy Incorporated | Gillette, WY 82718 | Oil & Gas Operator | Feb 2021 |
| 397 | Pennzoil Company | Midland, TX 79710-0090 | Oil & Gas Operator | Mar 2000 |
| 398 | Petro Search Exploration Corp | | Oil & Gas Operator | May 1993 |
| 399 | Petro-Canada Resources (USA) Inc | Denver, CO 80202-472 | Oil & Gas Operator | Feb 2010 |
| 400 | Petro-Hunt Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2003 |