| 1 | M.J.O.G., Inc. | Fort Smith, AR 72903 | Oil Operator | Mar 2015 |
| 2 | Marino, Charles B. | Tomball, TX 77377 | Oil & Gas Operator | Oct 2025 |
| 3 | Mark L Shidler Inc | Houston, TX 77055 | Oil & Gas Operator | Jul 2025 |
| 4 | McBee Company, The | Dallas, TX 75219 | Oil & Gas Operator | Dec 1997 |
| 5 | McCauley, F. R. | Houston, TX 77002 | Oil & Gas Operator | Apr 2000 |
| 6 | McDonald Production | Lubbock, TX 79408 | Oil & Gas Operator | Mar 2003 |
| 7 | McDonnold Operating, Inc. | Midland, TX 79701 | Oil & Gas Operator | Oct 2025 |
| 8 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Oct 2025 |
| 9 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 10 | Memorial Production Operating LLC | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 11 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 12 | Meridian Resource & Expl LLC,The | Houston, TX 77094 | Oil & Gas Operator | Nov 2012 |
| 13 | Merritt Operating, Inc. | Mineola, TX 75773 | Oil & Gas Operator | Oct 2025 |
| 14 | Merritt, William Kevin | Dallas, TX 75225 | Oil & Gas Operator | Dec 1994 |
| 15 | Mexco Energy Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2020 |
| 16 | Millennium Exploration Co. LLC | San Antonio, TX 78232 | Oil & Gas Operator | Oct 2025 |
| 17 | Mitchell Energy Company L.P. | Spring, TX 77387 | Oil & Gas Operator | Mar 2008 |
| 18 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 19 | Mojac Energy Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 1997 |
| 20 | Murphy Energy Services, LP | Saratoga, TX 77585 | Oil Operator | Dec 2018 |