| 1 | Machin & Associates, Inc. | Longview, TX 75606 | Oil & Gas Operator | Oct 2025 |
| 2 | Mack Energy Co. | Duncan, OK 73534 | Oil & Gas Operator | Jul 2025 |
| 3 | Maddox Oil & Gas, Inc. | | Oil Operator | Apr 1983 |
| 4 | Magnolia Production Company LLC | | Oil & Gas Operator | Nov 2024 |
| 5 | Magnum Producing & Operating Co. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Jan 2004 |
| 6 | Mar-Low Corporation | | Oil & Gas Operator | Mar 1992 |
| 7 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Aug 2025 |
| 8 | Marine Cont. & Supply Inc. | | Oil & Gas Operator | Nov 1985 |
| 9 | Marlin Exploration, Inc. | | Oil & Gas Operator | Oct 2006 |
| 10 | Marline Petroleum Corporation | | Oil & Gas Operator | Dec 1985 |
| 11 | Marquee Corporation | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 12 | Marsh Engineering, Inc. | | Oil & Gas Operator | Dec 1990 |
| 13 | Martin Exploration Co. | | Oil & Gas Operator | Apr 1986 |
| 14 | Master Well Works, Inc. | | Oil Operator | Dec 2024 |
| 15 | Matzinger Petroleum Co. | | Oil & Gas Operator | Jan 1991 |
| 16 | May Petroleum, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Nov 1998 |
| 17 | Maybrier Brothers | | Oil Operator | Apr 2006 |
| 18 | Maybrier Production, L.L.C. | | Oil Operator | Oct 2022 |
| 19 | McClinton & 4-M Invest Inc | | Oil & Gas Operator | Aug 1992 |
| 20 | McClinton & Mosing | | Oil & Gas Operator | Oct 1977 |
| 21 | McCord Oil Co. And T. Walker | | Oil & Gas Operator | Dec 1985 |
| 22 | McCord-Goodrich Oil Company | | Oil & Gas Operator | Oct 1991 |
| 23 | McCormick Operating Company | | Oil & Gas Operator | Mar 1984 |
| 24 | McCormick Operating PRTNSHP | | Oil & Gas Operator | Sep 1985 |
| 25 | McCulloch Oil Corp.-Ids | | Oil & Gas Operator | Dec 1981 |
| 26 | McFarland Energy, Inc. | New Orleans, LA 70160 | Oil & Gas Operator | Dec 2009 |
| 27 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 28 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Oct 2025 |
| 29 | McIntyre Oil Company | | Oil & Gas Operator | Jan 1992 |
| 30 | McMoran-Transco | | Oil & Gas Operator | Aug 1979 |
| 31 | McOr Oil & Gas Corp | Houston, TX 77002 | Oil & Gas Operator | Oct 2013 |
| 32 | McOr Oil Development, Inc. | | Oil & Gas Operator | Feb 1990 |
| 33 | McRae Exploration, Inc. | | Oil & Gas Operator | Mar 1984 |
| 34 | MCZ, Inc. | Houston, TX 77026 | Oil & Gas Operator | Sep 1990 |
| 35 | Medders Oil Company | Wichita Falls, TX 76308 | Oil & Gas Operator | Oct 2025 |
| 36 | Mesa Operating LTD Partnership | Amarillo, TX 79189 | Oil & Gas Operator | May 1994 |
| 37 | MFP Petroleum LTD. Partnership | Oklahoma City, OK 73142 | Oil & Gas Operator | Nov 2017 |
| 38 | Michael W Mills | | Oil Operator | Jul 2007 |
| 39 | Michel T. Halbouty Energy Co. | | Oil & Gas Operator | Nov 1986 |
| 40 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 41 | Midstates Petroleum Company LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2018 |
| 42 | Midstates Petroleum Corp. | | Oil & Gas Operator | Dec 2008 |
| 43 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 44 | Minden Oil & Gas, Inc. | | Oil & Gas Operator | May 1985 |
| 45 | Miss-Lou Operating LLC | | Oil & Gas Operator | Jul 2025 |
| 46 | Miss-Lou Petroleum LLC | | Oil & Gas Operator | Jun 2011 |
| 47 | Mobil E&P North America Inc. | | Oil & Gas Operator | Jan 1994 |
| 48 | Mobil Oil E & P Southeast Inc | | Oil & Gas Operator | Sep 2013 |
| 49 | Monterey Pipeline Co. | | Oil Operator | Aug 1993 |
| 50 | Moore McCormack Energy, Inc. | | Oil & Gas Operator | Jul 1988 |
| 51 | Mosbacher Energy Company | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 52 | Munday Operating Co., L.L.C. | | Oil & Gas Operator | May 2007 |
| 53 | Murray J. Evans | | Oil Operator | Mar 1985 |