| 1 | Maersk Energy Inc. | Houston, TX 77042 | Oil & Gas Operator | Oct 1994 |
| 2 | Magna Oil & Gas Corporation | Irving, TX 75017 | Oil & Gas Operator | Feb 2016 |
| 3 | Magnolia Oil & Gas Operating LLC | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |
| 4 | Magnum Producing & Operating Co. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Jan 2004 |
| 5 | Magnum Producing, LP | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2025 |
| 6 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Aug 2025 |
| 7 | Mariner Energy, Inc. | Houston, TX 77042 | Oil & Gas Operator | Nov 2010 |
| 8 | Marjo Operating Company Inc | Tulsa, OK 741010729 | Oil & Gas Operator | Jun 2025 |
| 9 | MBX Operating LLC | Houston, TX 77007 | Oil & Gas Operator | Oct 2025 |
| 10 | McCarthy Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | Oct 2007 |
| 11 | McGehee, George T. Operating Co. | Houston, TX 77024 | Oil & Gas Operator | Oct 1997 |
| 12 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 13 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 14 | Merritt Operating, Inc. | Mineola, TX 75773 | Oil & Gas Operator | Oct 2025 |
| 15 | Merritt, William Kevin | Dallas, TX 75225 | Oil & Gas Operator | Dec 1994 |
| 16 | Mitchell Energy Company L.P. | Spring, TX 77387 | Oil & Gas Operator | Mar 2008 |
| 17 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 18 | MLC Operating, LP | Houston, TX 77063 | Oil & Gas Operator | Oct 2025 |
| 19 | Mobil Producing TX. & N.M. Inc. | Spring, TX 77389 | Oil & Gas Operator | Oct 2025 |
| 20 | Moncrief W A Jr | Fort Worth, TX 76102 | Oil & Gas Operator | Aug 2025 |