| 1 | Magna Oil & Gas Corporation | Irving, TX 75017 | Oil & Gas Operator | Feb 2016 |
| 2 | Magnolia Oil & Gas Operating LLC | Houston, TX 77046 | Oil & Gas Operator | Dec 2024 |
| 3 | Maguire Oil Company | Dallas, TX 75270 | Oil & Gas Operator | Mar 2015 |
| 4 | Marathon Oil Company | Houston, TX 77024 | Oil & Gas Operator | Oct 2024 |
| 5 | Mark IV Energy | San Antonio, TX 78213 | Oil & Gas Operator | Apr 1993 |
| 6 | Martineau Petroleum, Inc. | Dallas, TX 75206 | Oil & Gas Operator | May 2024 |
| 7 | Maverick Prod. Co., Inc. | Houston, TX 77056 | Oil & Gas Operator | Dec 2024 |
| 8 | Maynard Oil Co. | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 9 | McCombs Energy LLC | Houston, TX 77056 | Oil & Gas Operator | Jan 2006 |
| 10 | McDaniel Company, Inc., The | Dallas, TX 75230 | Oil & Gas Operator | Dec 2024 |
| 11 | McDay Energy Corp. | Dallas, TX 75206 | Oil & Gas Operator | Dec 2024 |
| 12 | MCR Operating Group | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2024 |
| 13 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 14 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Dec 2024 |
| 15 | Mexco Energy Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2020 |
| 16 | MGF Oil Corporation | Tulsa, OK 74121 | Oil & Gas Operator | Jun 1998 |
| 17 | Mission River Systems, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Dec 2024 |
| 18 | MJM Oil & Gas, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Aug 2003 |
| 19 | Mobil Producing TX. & N.M. Inc. | Spring, TX 77389 | Oil & Gas Operator | Dec 2024 |
| 20 | Mobile Production Systems, Inc. | Austin, TX 78711 | Oil & Gas Operator | Feb 1995 |
| 21 | Montgomery Petroleum, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Aug 2007 |
| 22 | Murphy Expl. & Prod. Co. - USA | Houston, TX 77024 | Oil & Gas Operator | Dec 2024 |
| 23 | Murphy Exploration & Prod. Co. | Houston, TX 77094 | Oil & Gas Operator | Jun 2011 |
| 24 | Murphy Exploration & Production | Houston, TX 77024 | Oil Operator | Jul 2024 |