| 1 | M.J. Bernos, Jr./PKR Oil, Inc. | | Gas Operator | Aug 1990 |
| 2 | Magnolia Production Company LLC | | Oil & Gas Operator | Nov 2024 |
| 3 | Mantle Oil & Gas, LLC | Friendswood, TX 77546 | Oil & Gas Operator | Mar 2025 |
| 4 | Manursing Island Prod. Corp. | | Oil & Gas Operator | Sep 2002 |
| 5 | Marine Properties, Inc. | | Oil & Gas Operator | Feb 1995 |
| 6 | Matzinger Petroleum Co. | | Oil & Gas Operator | Jan 1991 |
| 7 | McAlester Fuel Co | Houston, TX 77042 | Oil & Gas Operator | Jan 2010 |
| 8 | McFarland Energy, Inc. | New Orleans, LA 70160 | Oil & Gas Operator | Dec 2009 |
| 9 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 10 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Mar 2025 |
| 11 | Mertz Energy LLC | Houston, TX 77098 | Oil & Gas Operator | Jan 2025 |
| 12 | Midnight Drilling LLC | | Oil & Gas Operator | Jan 2016 |
| 13 | Midstates Petroleum Company LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2018 |
| 14 | Miss-Lou Operating, LLC | | Oil & Gas Operator | Dec 2024 |
| 15 | Miss-Lou Petroleum LLC | | Oil & Gas Operator | Jun 2011 |
| 16 | Mole Operating Co., Inc. | | Oil & Gas Operator | Oct 1983 |
| 17 | Moon Operating, Inc. | Longview, TX 75601 | Oil & Gas Operator | Mar 2003 |
| 18 | Moore McCormack Energy, Inc. | | Oil & Gas Operator | Jul 1988 |
| 19 | Mountain Front Pipeline Co Inc | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2015 |