| 1 | M-V Company | Refugio, TX 78377 | Oil & Gas Operator | Jun 2004 |
| 2 | M. J. G., Inc. | Alice, TX 78333 | Oil & Gas Operator | Jul 2010 |
| 3 | M.R.M. Operating, Inc. | Midland, TX 79707 | Oil & Gas Operator | Aug 2003 |
| 4 | Maggert Energy Corp. | Spring, TX 77387 | Gas Operator | Jun 1998 |
| 5 | Magnum Engineering Company | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2025 |
| 6 | Magnum Producing & Operating Co. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Jan 2004 |
| 7 | Magnum Producing, LP | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2025 |
| 8 | Mantle Oil & Gas, LLC | Friendswood, TX 77546 | Oil & Gas Operator | Oct 2025 |
| 9 | Maran Oil Company | San Antonio, TX 78216 | Oil & Gas Operator | Dec 2020 |
| 10 | Maran Oil Company, LLC | San Antonio, TX 78216 | Oil & Gas Operator | Mar 2022 |
| 11 | Marquee Corporation | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 12 | Marwell Petroleum, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2006 |
| 13 | Maynard Oil Co. | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 14 | McCarter, W. B. Jr. | Houston, TX 77063 | Oil & Gas Operator | Feb 2002 |
| 15 | McDonald & Johnson Resources,LLC | Cypress, TX 77429 | Oil & Gas Operator | Dec 2010 |
| 16 | McLeod, George L. Inc. | Houston, TX 77079 | Oil & Gas Operator | Sep 2002 |
| 17 | Meeker & Company | Fort Worth, TX 76102 | Oil & Gas Operator | Oct 2025 |
| 18 | Mellon Oil Unit | Refugio, TX 78377 | Oil & Gas Operator | Jun 2004 |
| 19 | Merrimac Energy Corp. | Dallas, TX 75206 | Oil & Gas Operator | Aug 1999 |
| 20 | Mesa Chica Corp. | San Antonio, TX 78278 | Oil & Gas Operator | May 2018 |
| 21 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 22 | Millennium Exploration Co. LLC | San Antonio, TX 78232 | Oil & Gas Operator | Oct 2025 |
| 23 | Mission River Systems, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Oct 2025 |
| 24 | Modern Exploration, Inc. | Sherman, TX 75090 | Oil & Gas Operator | Oct 2025 |
| 25 | Momentum Energy Corporation | Austin, TX 78746 | Oil & Gas Operator | Oct 2025 |
| 26 | MPG Petroleum | San Antonio, TX 78217 | Oil & Gas Operator | Aug 2003 |
| 27 | MPG Petroleum, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Oct 2025 |
| 28 | Mueller Engineering Corp. | Corpus Chrsti, TX 78476 | Oil & Gas Operator | Feb 2002 |
| 29 | Mustang Oil & Gas Corporation | Wichita Falls, TX 76308 | Oil & Gas Operator | Jul 2021 |