| 301 | LNG Gathering Company | | Oil Operator | Jul 2024 |
| 302 | Louisiana Crude Oil&Gas Co Inc | | Oil & Gas Operator | Mar 1984 |
| 303 | Louisiana Resources Co | | Oil Operator | May 1992 |
| 304 | Loutex Energy, Inc. | Shrevesport, LA 71101 | Oil & Gas Operator | Apr 1992 |
| 305 | Lucky Lad Energy, LLC | Magnolia, TX 77353 | Oil & Gas Operator | Nov 2024 |
| 306 | Lynal, Inc. | | Oil & Gas Operator | Oct 1988 |
| 307 | Lyons Petroleum Inc.-Dykes | | Oil & Gas Operator | Oct 1988 |
| 308 | Lyons Petroleum, Inc. | | Oil & Gas Operator | Oct 1988 |
| 309 | M & M Investments | | Oil & Gas Operator | May 1990 |
| 310 | M-P Petroleum Inc | McPherson, KS 67460 | Oil & Gas Operator | Jan 2013 |
| 311 | M. F. McCain, Inc. | | Oil & Gas Operator | Jul 1987 |
| 312 | Mack Energy Co. | Duncan, OK 73534 | Oil & Gas Operator | Sep 2024 |
| 313 | Magnum Hunter Resources Corporation | | Oil & Gas Operator | Nov 2019 |
| 314 | Manti Exploration Operating LLC | Corpus Chrsti, TX 78403 | Oil & Gas Operator | Feb 2015 |
| 315 | Manti Operating Company | Covington, LA 70435 | Oil & Gas Operator | Nov 2024 |
| 316 | Mar-Low Corporation | | Oil & Gas Operator | Mar 1992 |
| 317 | Marathon Oil Company | Houston, TX 77024 | Oil & Gas Operator | Sep 2024 |
| 318 | Mariner Energy, Inc. | Houston, TX 77042 | Oil & Gas Operator | Nov 2010 |
| 319 | Marquee Corporation | Houston, TX 77024 | Oil & Gas Operator | Nov 2024 |
| 320 | Marquis Resources, LLC | | Oil & Gas Operator | Jul 2021 |
| 321 | Marsh Engineering, Inc. | | Oil & Gas Operator | Dec 1990 |
| 322 | Masters Resources, L.L.C. | Houston, TX 77079 | Oil & Gas Operator | Dec 2008 |
| 323 | Matzinger & Bell Inc-Carl O&G | | Oil & Gas Operator | Dec 1981 |
| 324 | Matzinger & Bell, Inc. | | Oil & Gas Operator | Dec 1982 |
| 325 | Matzinger Petroleum Co. | | Oil & Gas Operator | Jan 1991 |
| 326 | Maxus Exploration Company | Dallas, TX 75201 | Oil & Gas Operator | Jan 1995 |
| 327 | McAlester Fuel Co | Houston, TX 77042 | Oil & Gas Operator | Jan 2010 |
| 328 | McCormick Operating Company | | Oil & Gas Operator | Mar 1984 |
| 329 | McCormick Operating PRTNSHP | | Oil & Gas Operator | Sep 1985 |
| 330 | McCormick-Ciroco, Inc. | | Oil & Gas Operator | Jan 1984 |
| 331 | McLain J. Forman | | Oil & Gas Operator | Mar 1988 |
| 332 | McMoran Oil & Gas LLC | New Orleans, LA 70160 | Oil & Gas Operator | Oct 2021 |
| 333 | McOr Oil Development, Inc. | | Oil & Gas Operator | Feb 1990 |
| 334 | McRae Exploration, Inc. | | Oil & Gas Operator | Mar 1984 |
| 335 | McRae Oil Corporation | | Oil & Gas Operator | Mar 1984 |
| 336 | MCZ, Inc. | Houston, TX 77026 | Oil & Gas Operator | Sep 1990 |
| 337 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 338 | Meridian Oil Offshore Inc. | | Oil & Gas Operator | Aug 1996 |
| 339 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Nov 2024 |
| 340 | Merrico Resources, Inc. | Ardmore, OK 73402 | Oil & Gas Operator | Mar 2008 |
| 341 | Michel T. Halbouty | | Oil & Gas Operator | Dec 1996 |
| 342 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 343 | Mideast Gas Systems, Inc. | Midland, TX 79702 | Oil & Gas Operator | Dec 2005 |
| 344 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 345 | Mission Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 346 | Mississippi Ventures | | Gas Operator | Feb 1992 |
| 347 | Mobil E&P North America Inc. | | Oil & Gas Operator | Dec 1993 |
| 348 | Mobil Oil E & P Southeast Inc | | Oil & Gas Operator | Sep 2013 |
| 349 | Moore McCormack Energy, Inc. | | Oil & Gas Operator | Jul 1988 |
| 350 | Mosbacher Energy Company | Houston, TX 77002 | Oil & Gas Operator | Nov 2024 |
| 351 | Mullins & Prichard | | Oil & Gas Operator | May 1992 |
| 352 | Murphy Exploration & Prod. Co. | Houston, TX 77094 | Oil & Gas Operator | Jun 2011 |
| 353 | MW Petroleum Corporation | Houston, TX 77056 | Oil & Gas Operator | Mar 2015 |
| 354 | Nasser Oil & Gas, Inc. | The Woodlands, TX 77380 | Oil & Gas Operator | Apr 1998 |
| 355 | Nat. Gas Pipeline Co Of Amer. | | Oil Operator | Dec 2008 |
| 356 | National Exploration Company | | Oil & Gas Operator | Mar 1982 |
| 357 | National Offshore LP | Oklahoma City, OK 73154 | Oil & Gas Operator | Mar 2008 |
| 358 | Natomas-McCormick-Coastal | | Oil & Gas Operator | Feb 1984 |
| 359 | NCX Company, Inc. | | Oil & Gas Operator | Aug 1999 |
| 360 | Nerco Oil & Gas, Inc. | | Oil & Gas Operator | Dec 1996 |
| 361 | Nestor Petroleum Company | | Oil & Gas Operator | Jun 1986 |
| 362 | Neumin Production Company | Point Comfort, TX 77978 | Oil & Gas Operator | Nov 2024 |
| 363 | Newfield Exploration Company | The Woodlands, TX 77380 | Oil & Gas Operator | Jun 2017 |
| 364 | Newhaven Operating Inc | | Oil & Gas Operator | Dec 1998 |
| 365 | Nicco Operating Co. | | Oil & Gas Operator | May 1990 |
| 366 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Nov 2024 |
| 367 | Noex, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Apr 1998 |
| 368 | Nomeco Oil & Gas Co. | Jackson, MI 49204 | Oil & Gas Operator | Dec 1994 |
| 369 | Norcen Explorer, Inc. | Houston, TX 77079 | Oil & Gas Operator | May 1998 |
| 370 | North American Royalties, Inc. | Chattanooga, TN 37408 | Oil & Gas Operator | Oct 2001 |
| 371 | Northern Michigan Expl Co | | Oil & Gas Operator | Jul 1990 |
| 372 | Northstar Offshore Group, LLC | | Oil & Gas Operator | Apr 2020 |
| 373 | Northwest Oil Company | Dallas, TX 75204 | Oil & Gas Operator | Jun 2014 |
| 374 | Nuevo Energy Company | Houston, TX 77002 | Oil & Gas Operator | Dec 2002 |
| 375 | O'Sullivan Oil & Gas Co., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2000 |
| 376 | Occidental Energy Company, Inc. | Houston, TX 77282 | Oil & Gas Operator | Jul 2021 |
| 377 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 378 | Ody Oil Corp. | | Oil & Gas Operator | Oct 1994 |
| 379 | Oil And Gas Futures, Inc. | | Oil & Gas Operator | May 1977 |
| 380 | Oleum Incorporated | | Oil & Gas Operator | Mar 1996 |
| 381 | Oleum Operating Company, L.C. | Longview, TX 75606 | Oil & Gas Operator | Dec 2021 |
| 382 | Oleum Operating La LLC | | Oil & Gas Operator | Nov 2022 |
| 383 | Olipdp II, LLC | Lafayette, LA 70503 | Oil & Gas Operator | Nov 2024 |
| 384 | Opmi Operating Company | Houston, TX 77057 | Oil & Gas Operator | Jun 2008 |
| 385 | Orleans Exploration Co., Inc. | | Oil & Gas Operator | Aug 1990 |
| 386 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 387 | Osr Oil & Gas Corp | Midland, TX 79710 | Oil & Gas Operator | Jun 2024 |
| 388 | Oxtex Inc | | Oil & Gas Operator | Oct 1989 |
| 389 | P & A Well Service | | Oil & Gas Operator | Jan 1994 |
| 390 | P & P Producing Inc | Midland, TX 79702 | Oil & Gas Operator | Feb 2015 |
| 391 | P. B. Operating Company | | Oil & Gas Operator | Feb 1978 |
| 392 | P.C.S.I. | | Oil & Gas Operator | Jun 1987 |
| 393 | Palace Operating Company | Tulsa, OK 74136 | Oil & Gas Operator | Aug 2009 |
| 394 | Pan-Ok Production Company | | Oil & Gas Operator | Jul 2024 |
| 395 | Panaco Production Co | Houston, TX 77002 | Oil & Gas Operator | Dec 1999 |
| 396 | Panaco, Inc. | Oklahoma City, OK 73102 | Oil & Gas Operator | Jul 2024 |
| 397 | Parker & Parsley Development Co. | Midland, TX 79702 | Oil & Gas Operator | May 1995 |
| 398 | Parker & Parsley Petroleum Co. | | Oil & Gas Operator | Dec 1990 |
| 399 | Partners Oil Company | Tulsa, OK 74135 | Oil & Gas Operator | Aug 1995 |
| 400 | Patrick Petroleum Corp. | | Oil & Gas Operator | Oct 1984 |