| 1 | Mack Energy Co. | Duncan, OK 73534 | Oil & Gas Operator | Jul 2025 |
| 2 | Magnum Minerals, Inc. | | Oil & Gas Operator | May 1998 |
| 3 | Manti Exploration Operating LLC | Corpus Chrsti, TX 78403 | Oil & Gas Operator | Feb 2015 |
| 4 | Manti Operating Company | Covington, LA 70435 | Oil & Gas Operator | Oct 2025 |
| 5 | Marion Corporation | | Oil & Gas Operator | Jan 2001 |
| 6 | Maritech Resources, LLC | | Oil & Gas Operator | May 2011 |
| 7 | Mark Producing, Inc. | Houston, TX 77057 | Oil & Gas Operator | Dec 1987 |
| 8 | Marlin Energy Offshore, L.L.C. | | Oil & Gas Operator | Jun 2006 |
| 9 | Marquis Resources, LLC | | Oil & Gas Operator | Jul 2021 |
| 10 | Martin Exploration Co. | | Oil & Gas Operator | Apr 1986 |
| 11 | Masters Resources, L.L.C. | Houston, TX 77079 | Oil & Gas Operator | Dec 2008 |
| 12 | Maxus Exploration Company | Dallas, TX 75201 | Oil & Gas Operator | Jan 1995 |
| 13 | McAlester Fuel Co | Houston, TX 77042 | Oil & Gas Operator | Jan 2010 |
| 14 | McCord-Goodrich Oil Company | | Oil & Gas Operator | Oct 1991 |
| 15 | McCormick Operating Company | | Oil & Gas Operator | Mar 1984 |
| 16 | McCormick Operating PRTNSHP | | Oil & Gas Operator | Sep 1985 |
| 17 | McFarland Energy, Inc. | New Orleans, LA 70160 | Oil & Gas Operator | Dec 2009 |
| 18 | McMoran Exploration Company | | Oil & Gas Operator | May 1985 |
| 19 | McMoran Production Co. | | Oil & Gas Operator | May 1985 |
| 20 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 21 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 22 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 23 | Meridian Oil Offshore Inc. | | Oil & Gas Operator | Aug 1996 |
| 24 | Merritt Operating, Inc. | Mineola, TX 75773 | Oil & Gas Operator | Oct 2025 |
| 25 | Mesa Gulf Coast LLC | | Oil & Gas Operator | Dec 2020 |
| 26 | Micron Minerals Company | | Oil & Gas Operator | Sep 1988 |
| 27 | Mid-America Resources Corporation | | Oil Operator | Jan 2019 |
| 28 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 29 | Mission Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 30 | Mobil E&P N.A.-WM Scully Et Al | | Oil & Gas Operator | Dec 1993 |
| 31 | Mobil E&P North America Inc. | | Oil & Gas Operator | Jan 1994 |
| 32 | Mobil Oil E & P Southeast Inc | | Oil & Gas Operator | Sep 2013 |
| 33 | Mongrue Oil Company, Inc. | | Oil & Gas Operator | Oct 1999 |
| 34 | Monterey Pipeline Co. | | Oil Operator | Aug 1993 |
| 35 | Moon Operating, Inc. | Longview, TX 75601 | Oil & Gas Operator | Mar 2003 |
| 36 | Mosbacher Energy Company | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 37 | Mullins & Prichard | | Oil & Gas Operator | May 1992 |
| 38 | Mustang Energy L C | | Oil & Gas Operator | Jan 2013 |
| 39 | MW Petroleum Corporation | Houston, TX 77056 | Oil & Gas Operator | Mar 2015 |