| 1 | M & R Exploration Company | Houston, TX 77074 | Oil & Gas Operator | Aug 2003 |
| 2 | Magnum Producing & Operating Co. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Jan 2004 |
| 3 | Magnum Producing, LP | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2025 |
| 4 | Maralo, Inc. | Midland, TX 79702 | Oil & Gas Operator | Dec 1998 |
| 5 | Mariner Energy, Inc. | Houston, TX 77042 | Oil & Gas Operator | Nov 2010 |
| 6 | Marjo Operating Company Inc | Tulsa, OK 741010729 | Oil & Gas Operator | Jun 2025 |
| 7 | Marmaton Oil Company | Houston, TX 77002 | Oil & Gas Operator | Jul 1998 |
| 8 | Marwell Petroleum, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2006 |
| 9 | Mascot Oil Company | Schulenburg, TX 78956 | Oil & Gas Operator | Oct 2025 |
| 10 | Maxim Energy Corporation | Baytown, TX 77520 | Oil & Gas Operator | Jul 2025 |
| 11 | Maynard Oil Co. | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 12 | McLeod, George L. Inc. | Houston, TX 77079 | Oil & Gas Operator | Sep 2002 |
| 13 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 14 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Oct 2025 |
| 15 | Metano Energy, LP | San Antonio, TX 78216 | Oil & Gas Operator | Aug 2008 |
| 16 | Mexco Energy Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2020 |
| 17 | MGF Oil Corporation | Tulsa, OK 74121 | Oil & Gas Operator | Jun 1998 |
| 18 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 19 | Milestone Operating, Inc. | Montgomery, TX 77316 | Oil & Gas Operator | Oct 2025 |
| 20 | Minyak Producing Company, Inc. | Sabine Pass, TX 77655 | Oil & Gas Operator | Oct 2025 |
| 21 | Miocene Oil & Gas, Inc. | Englewood, CO 80155 | Oil & Gas Operator | Jul 1998 |
| 22 | Miocene Oil & Gas, LTD. | Englewood, CO 80110 | Oil & Gas Operator | Oct 2025 |
| 23 | Mission Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 24 | Mobil Producing TX. & N.M. Inc. | Spring, TX 77389 | Oil & Gas Operator | Oct 2025 |
| 25 | MW Petroleum Corporation | Houston, TX 77056 | Oil & Gas Operator | Mar 2015 |