| 801 | Mar/Reg Investments | Irving, TX 75016 | Oil & Gas Operator | Jul 1999 |
| 802 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Feb 2026 |
| 803 | Markus Production | Littleton, CO 80123 | Oil & Gas Operator | Jan 2026 |
| 804 | Marlin Oil Company LLC | Gillette, WY 82718 | Oil & Gas Operator | Mar 2023 |
| 805 | Marmik Oil Company | El Dorado, AR 71730 | Oil & Gas Operator | Jan 2015 |
| 806 | Marquis-Allred Eng Inc | | Oil & Gas Operator | Apr 1992 |
| 807 | Marshall & Winston, Inc. | Midland, TX 79710 | Oil & Gas Operator | Feb 2026 |
| 808 | Martens & Peck Operating Co | | Gas Operator | Feb 1997 |
| 809 | Martens & Peck Production Co | Denver, CO 80222 | Oil & Gas Operator | Feb 1997 |
| 810 | Martin Exploration | Westminster, CO 80030 | Oil & Gas Operator | Dec 1993 |
| 811 | Materi Exploration Inc | Upton, WY 82730 | Oil Operator | Nov 2021 |
| 812 | Matrix Production Company | Sugar Land, TX 77478 | Oil & Gas Operator | Feb 2026 |
| 813 | Maxim Drilling & Expl Inc | Gillette, WY 82717 | Oil & Gas Operator | Jan 2026 |
| 814 | Maximus Operating, LTD. | Kilgore, TX 75663 | Oil & Gas Operator | Apr 2026 |
| 815 | Mbi Oil & Gas LLC | Dickinson, ND 58601 | Oil & Gas Operator | Feb 2026 |
| 816 | McAdams Roux & Associates | Denver, CO 80202 | Oil & Gas Operator | Dec 1999 |
| 817 | McCartney Engineering LLC | Wheat Ridge, CO 80033 | Oil & Gas Operator | Feb 2026 |
| 818 | McClure Enterprises | Recluse, WY 82725 | Oil & Gas Operator | Dec 2025 |
| 819 | McCulliss Resource Company Inc | Denver, CO 80202 | Oil & Gas Operator | Jun 1999 |
| 820 | McEna Inc | Tulsa, OK 74135 | Oil & Gas Operator | Jul 2005 |
| 821 | McGuire John C | Gillette, WY 82717 | Oil & Gas Operator | Oct 2005 |
| 822 | McKenzie Production Company | Houston, TX 77063 | Oil & Gas Operator | May 1995 |
| 823 | MCL 1 Oil & Gas Wyoming LLC | Minneapolis, MN 55402 | Oil & Gas Operator | Jul 2018 |
| 824 | MCM Operating LLC | Midland, TX 79702 | Oil & Gas Operator | Mar 2026 |
| 825 | McMahon-Bullington LP | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2009 |
| 826 | McMurry Energy Company | | Oil & Gas Operator | Dec 2001 |
| 827 | McMurry Oil LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2004 |
| 828 | McO Resources Corporation | | Oil & Gas Operator | Feb 1986 |
| 829 | McQueen Ed & Company Inc | Lindsey, OK 73052 | Oil & Gas Operator | Apr 2014 |
| 830 | McRae & Henry LTD | Golden, CO 80401 | Oil & Gas Operator | May 2022 |
| 831 | MDS Energy Development LLC | | Oil & Gas Operator | Feb 2026 |
| 832 | Meadow Deep LLC | | Oil & Gas Operator | Feb 2026 |
| 833 | Medallion Exploration | Holladay, UT 84117 | Oil & Gas Operator | Dec 2015 |
| 834 | Medallion Petroleum, Inc. | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2015 |
| 835 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 836 | Medicine Bow Operating Company | Houston, TX 77002 | Oil & Gas Operator | Apr 2014 |
| 837 | Meerkat Logistics And Operations LLC | Tuscaloosa, AL 35401 | Oil Operator | Jan 2026 |
| 838 | Mega Energy LLC | Gillette, WY 82718 | Gas Operator | Jan 2026 |
| 839 | Mels Water Service Inc | Lysite, WY 82642 | Oil Operator | Mar 2013 |
| 840 | Memorial Exploration Company | Saint Louis, MO 63105 | Oil & Gas Operator | Aug 1996 |
| 841 | Memorial Production Operating LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2026 |
| 842 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Apr 2026 |
| 843 | Merit Productions | | Oil Operator | Sep 1996 |
| 844 | Meritage Energy Company LLC | Denver, CO 80202 | Oil & Gas Operator | May 2013 |
| 845 | Meritage Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2005 |
| 846 | Merrico Resources | | Oil Operator | Mar 1992 |
| 847 | Merrion Oil & Gas Corp | Farmington, NM 87401 | Oil & Gas Operator | Feb 2026 |
| 848 | Methane Productions Inc | Recluse, WY 82725 | Oil & Gas Operator | Apr 2007 |
| 849 | Meyer Douglas P | Longmont, CO 80501 | Oil & Gas Operator | Aug 2006 |
| 850 | Mi3 Energy LLC | | Oil & Gas Operator | Feb 2026 |
| 851 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 852 | Mid Central Production LLC | Evanston, WY 82930 | Oil Operator | Dec 2025 |
| 853 | Mid-Con Energy Operating, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Feb 2026 |
| 854 | Midgard Energy Company | The Woodlands, TX 77380 | Oil & Gas Operator | Dec 2014 |
| 855 | Millennium Oil & Gas LLC | Denver, CO 80203 | Oil & Gas Operator | Oct 2025 |
| 856 | Mineral Resources & Engineering | Aladdin, WY 82710 | Oil Operator | Jul 1991 |
| 857 | Mingo Oil Producers | Salt Lake City, UT 84111 | Oil & Gas Operator | Nov 1987 |
| 858 | Minnelusa Oil LLC | Temecula, CA 92589 | Oil Operator | Feb 2002 |
| 859 | Misahar Investments | Evergreen, CO 80439 | Oil Operator | Dec 1992 |
| 860 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 861 | Mitchell M J | | Oil & Gas Operator | Jan 1983 |
| 862 | MKM Services Inc | | Oil Operator | Mar 2026 |
| 863 | Mobil Expl & Producing North America Inc | | Oil & Gas Operator | Nov 1986 |
| 864 | Moco Oil Inc | | Oil Operator | May 1984 |
| 865 | Mon-Oil Inc | | Oil & Gas Operator | Apr 1996 |
| 866 | Monahan Rex | Sterling, CO 80751 | Oil & Gas Operator | Jun 2002 |
| 867 | Moncrief W A Jr | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 2026 |
| 868 | Monsanto Company | Indianapolis, IN 46280 | Oil & Gas Operator | Jan 2005 |
| 869 | Montana Power Company | Butte, MT 59701 | Oil & Gas Operator | Apr 2002 |
| 870 | Montex Drilling Company LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2026 |
| 871 | Montex Exploration | Sugarland, TX 77478 | Oil Operator | Apr 2003 |
| 872 | Monument Global Resources Inc | Dallas, TX 75243 | Oil & Gas Operator | Jan 2025 |
| 873 | Morgan Energy Corporation | Englewood, CO 80110 | Oil & Gas Operator | Mar 2006 |
| 874 | Morning Star Oil Company | Thermopolis, WY 82443 | Oil Operator | Feb 2025 |
| 875 | Morsey Oil & Gas Corporation | Corpus Christ, TX 78401 | Oil & Gas Operator | Apr 2026 |
| 876 | Mosbacher Production Co. | Houston, TX 77001 | Oil & Gas Operator | Aug 1984 |
| 877 | Moss Properties Inc | | Oil & Gas Operator | Mar 1986 |
| 878 | Mountain Hawk Energy LLC | Athens, TX 75751 | Gas Operator | Jan 2015 |
| 879 | Mountain Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Apr 2013 |
| 880 | Mountain Resource Corporation | Salt Lake City, UT 84124 | Oil & Gas Operator | Dec 1988 |
| 881 | MRD Operating LLC (Delaware) | Houston, TX 77010 | Oil & Gas Operator | Jul 2015 |
| 882 | MTG Operating Inc | Ridgeland, MS 39158 | Gas Operator | Apr 2011 |
| 883 | Mueller Fred W | | Oil & Gas Operator | Dec 1995 |
| 884 | Mull Drilling Company | Wichita, KS 67206 | Oil & Gas Operator | Jan 2026 |
| 885 | Mundell F E | Watertown, SD 57201 | Oil & Gas Operator | Aug 1994 |
| 886 | Murex Petroleum Corporation | Humble, TX 77347 | Oil & Gas Operator | Feb 2026 |
| 887 | Murphy D V | | Oil Operator | Dec 1989 |
| 888 | Murphy Oil USA, Inc. | New Orleans, LA 70161 | Oil & Gas Operator | Jan 1993 |
| 889 | Murphy Sheldon L & Loretta | Newcastle, WY 82701 | Oil & Gas Operator | Jan 2026 |
| 890 | Mustang Oil & Gas Corporation | Wichita Falls, TX 76308 | Oil & Gas Operator | Jul 2021 |
| 891 | Mustang Resources LLC | Houston, TX 77046 | Oil & Gas Operator | Jan 2026 |
| 892 | MWJ Producing Company | Midland, TX 79701 | Oil & Gas Operator | Jul 1998 |
| 893 | Mystique Developments | Denver, CO 80202 | Oil & Gas Operator | Dec 1997 |
| 894 | Nadel And Gussman Rockies, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2012 |
| 895 | Nance Petroleum Corporation | Billings, MT 59103-7168 | Oil & Gas Operator | Nov 2007 |
| 896 | Nanke Energy LLC | Westminster, CO 80234 | Oil & Gas Operator | Oct 2025 |
| 897 | National Energy Group Inc | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 898 | National Fuel Corporation | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Feb 2026 |
| 899 | National Oil Company | Garden City, KS 67846 | Oil & Gas Operator | Jun 2024 |
| 900 | National Pride Operating | Parker, CO 80134 | Oil & Gas Operator | Dec 2017 |