| 1 | Mapco Oil Company | | Oil & Gas Operator | Jan 1985 |
| 2 | Mar/Reg Investments | Irving, TX 75016 | Oil & Gas Operator | Jul 1999 |
| 3 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Aug 2025 |
| 4 | Martens & Peck Production Co | Denver, CO 80222 | Oil & Gas Operator | Feb 1997 |
| 5 | Martin Exploration | Westminster, CO 80030 | Oil & Gas Operator | Dec 1993 |
| 6 | Matrix Production Company | Sugar Land, TX 77478 | Oil & Gas Operator | Aug 2025 |
| 7 | McCartney Engineering LLC | Wheat Ridge, CO 80033 | Oil & Gas Operator | Aug 2025 |
| 8 | Meerkat Logistics And Operations LLC | Tuscaloosa, AL 35401 | Oil Operator | Jul 2025 |
| 9 | Mels Water Service Inc | Lysite, WY 82642 | Oil Operator | Mar 2013 |
| 10 | Memorial Exploration Company | Saint Louis, MO 63105 | Oil & Gas Operator | Aug 1996 |
| 11 | Memorial Production Operating LLC | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 12 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Oct 2025 |
| 13 | Meritage Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2005 |
| 14 | Merrion Oil & Gas Corp | Farmington, NM 87401 | Oil & Gas Operator | Aug 2025 |
| 15 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 16 | Mobil Expl & Producing North America Inc | | Oil & Gas Operator | Nov 1986 |
| 17 | Moncrief W A Jr | Fort Worth, TX 76102 | Oil & Gas Operator | Aug 2025 |
| 18 | Monsanto Company | Indianapolis, IN 46280 | Oil & Gas Operator | Jan 2005 |
| 19 | Montex Drilling Company LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Oct 2025 |
| 20 | Monument Global Resources Inc | Dallas, TX 75243 | Oil & Gas Operator | Jan 2025 |
| 21 | Morsey Oil & Gas Corporation | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2025 |
| 22 | Mosbacher Production Co. | Houston, TX 77001 | Oil & Gas Operator | Aug 1984 |
| 23 | Mountain Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Jan 2016 |
| 24 | MRD Operating LLC (Delaware) | Houston, TX 77010 | Oil & Gas Operator | Jul 2015 |