| 1 | M & M Investments | | Oil & Gas Operator | May 1990 |
| 2 | M. P. S. Prod. Co. | Houston, TX 77225 | Oil & Gas Operator | Dec 1996 |
| 3 | Mammoth Service Group, LLC | | Oil & Gas Operator | Aug 2025 |
| 4 | Manti Operating Company | Covington, LA 70435 | Oil & Gas Operator | Dec 2025 |
| 5 | Mar-Low Corporation | | Oil & Gas Operator | Mar 1992 |
| 6 | Marion Corporation | | Oil & Gas Operator | Jan 2001 |
| 7 | Mark L Shidler Inc | Houston, TX 77055 | Oil & Gas Operator | Sep 2025 |
| 8 | Mark Producing Inc | Houston, TX 77057 | Oil & Gas Operator | Dec 1987 |
| 9 | Marlin Exploration, Inc. | | Oil & Gas Operator | Oct 2006 |
| 10 | Marquis Resources, LLC | | Oil & Gas Operator | Jul 2021 |
| 11 | Marshall Prod. & Energy Inc. | | Oil & Gas Operator | Jan 1992 |
| 12 | Maxus Exploration Company | Dallas, TX 75201 | Oil & Gas Operator | Jan 1995 |
| 13 | Mayne & Mertz, Inc. | Midland, TX 79702 | Oil & Gas Operator | Mar 2013 |
| 14 | Mbo, LLC | | Oil Operator | Jan 2025 |
| 15 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 16 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Dec 2025 |
| 17 | McMoran Oil & Gas LLC | New Orleans, LA 70160 | Oil & Gas Operator | Oct 2021 |
| 18 | McMoran-Transco | | Oil & Gas Operator | Aug 1979 |
| 19 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 20 | Medallion Petroleum, Inc. | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2015 |
| 21 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 22 | Medders Oil Company | Wichita Falls, TX 76308 | Oil & Gas Operator | Dec 2025 |
| 23 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 24 | Mesa Operating LTD Partnership | Amarillo, TX 79189 | Oil & Gas Operator | May 1994 |
| 25 | Micron Minerals Company | | Oil & Gas Operator | Sep 1988 |
| 26 | Middle Bay Production Co. Inc. | Houston, TX 77010 | Oil & Gas Operator | Sep 2014 |
| 27 | Miller Oil Field Services, Inc | | Oil Operator | Feb 1990 |
| 28 | Mobil E&P North America Inc. | | Oil & Gas Operator | Jan 1994 |
| 29 | Mobil Oil E & P Southeast Inc | | Oil & Gas Operator | Sep 2013 |
| 30 | Moore Oil & Gas-Marion Corp. | | Oil & Gas Operator | Nov 1986 |
| 31 | MTBB Acquisition Company, LLC | Houston, TX 77002 | Oil & Gas Operator | Aug 2022 |
| 32 | Mullen Exploration Inc | | Oil & Gas Operator | Dec 2002 |
| 33 | MVM Resources Louisiana L.L.C. | | Oil & Gas Operator | Jan 2025 |
| 34 | MW Petroleum Corporation | Houston, TX 77056 | Oil & Gas Operator | Mar 2015 |