| 901 | Mountain Resource Corporation | Salt Lake City, UT 84124 | Oil & Gas Operator | Dec 1988 |
| 902 | MRD Operating LLC (Delaware) | Houston, TX 77010 | Oil & Gas Operator | Jul 2015 |
| 903 | MTG Operating Inc | Ridgeland, MS 39158 | Gas Operator | Apr 2011 |
| 904 | Mueller Fred W | | Oil & Gas Operator | Dec 1995 |
| 905 | Mull Drilling Company | Wichita, KS 67206 | Oil & Gas Operator | Feb 2026 |
| 906 | Mundell F E | Watertown, SD 57201 | Oil & Gas Operator | Aug 1994 |
| 907 | Murex Petroleum Corporation | Humble, TX 77347 | Oil & Gas Operator | Apr 2026 |
| 908 | Murphy D V | | Oil Operator | Dec 1989 |
| 909 | Murphy Oil USA, Inc. | New Orleans, LA 70161 | Oil & Gas Operator | Jan 1993 |
| 910 | Murphy Sheldon L & Loretta | Newcastle, WY 82701 | Oil & Gas Operator | Apr 2026 |
| 911 | Mustang Oil & Gas Corporation | Wichita Falls, TX 76308 | Oil & Gas Operator | Jul 2021 |
| 912 | Mustang Resources LLC | Houston, TX 77046 | Oil & Gas Operator | Mar 2026 |
| 913 | MWJ Producing Company | Midland, TX 79701 | Oil & Gas Operator | Jul 1998 |
| 914 | Mystique Developments | Denver, CO 80202 | Oil & Gas Operator | Dec 1997 |
| 915 | Nadel And Gussman Rockies, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2012 |
| 916 | Nance Petroleum Corporation | Billings, MT 59103-7168 | Oil & Gas Operator | Nov 2007 |
| 917 | Nanke Energy LLC | Westminster, CO 80234 | Oil & Gas Operator | Oct 2025 |
| 918 | National Energy Group Inc | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 919 | National Fuel Corporation | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Mar 2026 |
| 920 | National Oil Company | Garden City, KS 67846 | Oil & Gas Operator | Jun 2024 |
| 921 | National Pride Operating | Parker, CO 80134 | Oil & Gas Operator | Dec 2017 |
| 922 | National Treasure Mines | San Marina, CA 91118 | Oil Operator | Dec 1998 |
| 923 | Natomas North America Inc | | Oil & Gas Operator | Aug 1993 |
| 924 | Natrona County Holdings LLC | Austin, TX 78701 | Oil & Gas Operator | Nov 2020 |
| 925 | Natural Gas Corp Of California | Vernal, UT 84078 | Oil & Gas Operator | Dec 1989 |
| 926 | Natural Gas Processing Company | Worland, WY 82401 | Oil & Gas Operator | Mar 2026 |
| 927 | Natural Resource Corporation | Rock Springs, WY 82901 | Oil & Gas Operator | Sep 1983 |
| 928 | Nautilus Exploration LLC | Denver, CO 80218 | Oil Operator | Mar 2011 |
| 929 | Navigation Powder River LLC | Houston, TX 77024 | Oil & Gas Operator | Apr 2026 |
| 930 | Nearburg Producing Company | Dallas, TX 75380 | Oil & Gas Operator | Jun 2026 |
| 931 | Nella Company LTD | | Oil Operator | Dec 1986 |
| 932 | Nepeco | Byron, WY 82412 | Oil Operator | Jan 2026 |
| 933 | New Era Oil/Preferred Energy | | Oil & Gas Operator | Sep 1993 |
| 934 | New Era Petroleum Inc | Sheridan, WY 82801 | Oil Operator | Mar 2026 |
| 935 | New Horizon Resources LLC | Houston, TX 77057 | Oil & Gas Operator | Jun 2026 |
| 936 | Neward Corporation | FT. Worth, TX 76102 | Oil & Gas Operator | Dec 1997 |
| 937 | Newcastle Oil & Gas Inc | | Oil Operator | Dec 1988 |
| 938 | Newfield Production Company | The Woodlands, TX 77380-2764 | Oil & Gas Operator | Jul 2022 |
| 939 | Newman Bros Drilling | | Oil & Gas Operator | Apr 2004 |
| 940 | Newport Gas Partners LLC | Gillette, WY 82716 | Oil & Gas Operator | Oct 2025 |
| 941 | Newport Oil Corporation | Clearwater, FL 33755 | Oil & Gas Operator | Jul 2011 |
| 942 | Newton Steve Drilling | Worland, WY 82401 | Oil Operator | Apr 2001 |
| 943 | Newwoods Petroleum LLC | Oklahoma City, OK 73102 | Oil & Gas Operator | Jan 2016 |
| 944 | Nextraction Energy Us Inc | Las Vegas, NV 89169 | Oil & Gas Operator | Feb 2018 |
| 945 | Nicolaysen G G Jr | | Oil & Gas Operator | Dec 1995 |
| 946 | Nicor Exploration | | Oil Operator | Jul 1993 |
| 947 | Nicor Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Jun 1993 |
| 948 | Nielson & Associates, Inc | Cody, WY 82414 | Oil & Gas Operator | Feb 2016 |
| 949 | Nielson Capital Partners LLC | Cody, WY 82414 | Oil & Gas Operator | Dec 2014 |
| 950 | Noarko Resources | | Oil & Gas Operator | Mar 1990 |
| 951 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Jun 2026 |
| 952 | Nonsuch Natural Gas Inc | Naples, FL 34108 | Oil & Gas Operator | Mar 2026 |
| 953 | Nor-Am Exploration | | Oil Operator | Jun 1981 |
| 954 | Norcen Energy Inc | | Oil Operator | Dec 1989 |
| 955 | Nordstrand Engineering Inc | Houston, TX 77019 | Oil & Gas Operator | Jun 2026 |
| 956 | Nortex Gas & Oil Co | Tulsa, OK 74135 | Oil & Gas Operator | Sep 1993 |
| 957 | North Central Oil Corp | Houston, TX 77252 | Oil & Gas Operator | Dec 2005 |
| 958 | North Finn LLC | Casper, WY 82605 | Oil & Gas Operator | Mar 2026 |
| 959 | North Shore Exploration & Prod LLC | Broomfield, CO 80021 | Oil & Gas Operator | Mar 2026 |
| 960 | North Silo Resources LLC | Houston, TX 77055 | Oil & Gas Operator | Apr 2026 |
| 961 | Northern Michigan Expl Co | | Oil & Gas Operator | Jul 1990 |
| 962 | Northern Production Co | Gillette, WY 82717 | Oil & Gas Operator | Apr 2013 |
| 963 | Northern Pump Company | Denver, CO 80202-3130 | Oil & Gas Operator | Feb 2006 |
| 964 | Northstar Operating Company | Midland, TX 79702 | Oil & Gas Operator | Jun 2024 |
| 965 | Northstar Operating Company Of Texas | Midland, TX 79702 | Oil & Gas Operator | Feb 2008 |
| 966 | Northwest Energy LLC | Buffalo, WY 82834 | Gas Operator | Jan 2010 |
| 967 | Northwest Exploration | | Oil & Gas Operator | Dec 1984 |
| 968 | Northwoods Land Inc | Denver, CO 80202 | Oil & Gas Operator | Mar 2026 |
| 969 | Norton Frickey | Lakewood, CO 80215 | Oil & Gas Operator | Dec 2023 |
| 970 | Nova Energy Inc | Casper, WY 82601 | Oil & Gas Operator | Oct 2020 |
| 971 | Nova Petroleum Cororation | | Oil & Gas Operator | Mar 1987 |
| 972 | Nucor Oil & Gas Inc | Riverton, WY 82501 | Oil & Gas Operator | Mar 2026 |
| 973 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Jun 2026 |
| 974 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 975 | Oci LLC | Thermopolis, WY 82443 | Oil Operator | Jan 2024 |
| 976 | Oedekoven Amerifields Resources LLC | Sugar Land, TX 77478 | Oil Operator | Mar 2026 |
| 977 | Oedekoven Water & Hot Oil | Recluse, WY 82725 | Oil & Gas Operator | Apr 2026 |
| 978 | Oil & Gas Acquisition Group Inc | Austin, TX 78716 | Oil & Gas Operator | May 2003 |
| 979 | Oil Mountain Energy Inc | Casper, WY 82609 | Oil Operator | Apr 2026 |
| 980 | Oildigger Resources Fund L LLLP | Billings, MT 59101 | Oil & Gas Operator | Apr 2026 |
| 981 | Oilfield Consultants | | Oil & Gas Operator | Dec 1987 |
| 982 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | Mar 2026 |
| 983 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Feb 2026 |
| 984 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 985 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 986 | Okt Petroleum Company Inc | Oklahoma City, OK 73118-7425 | Oil & Gas Operator | Oct 2013 |
| 987 | Olds Oil Company | Casper, WY 82604 | Oil Operator | Jun 1988 |
| 988 | Olympic Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Jul 2004 |
| 989 | Omimex Petroleum Inc (Co) | Newcastle, WY 82701 | Oil & Gas Operator | May 2001 |
| 990 | Omimex Petroleum Inc (De) | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2020 |
| 991 | Omni Operating Company | Osage, WY 82723 | Oil & Gas Operator | Sep 2001 |
| 992 | Oneida Energy Corporation | Tulsa, OK 74137 | Oil & Gas Operator | Jul 2003 |
| 993 | Open Range Energy LLC | Jones, OK 73049-8744 | Oil & Gas Operator | Dec 2024 |
| 994 | Opes Production Inc | Buffalo, WY 82834 | Gas Operator | Mar 2015 |
| 995 | Orion Energy Partners LP | Denver, CO 80202 | Oil & Gas Operator | Nov 2010 |
| 996 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 997 | Osage Hot Oil Service | Newcastle, WY 82701 | Oil & Gas Operator | Jul 1997 |
| 998 | Osage Operating Company LLC | Seattle, WA 98133 | Oil Operator | May 2006 |
| 999 | Osage Partners LLC | | Oil & Gas Operator | Apr 2026 |
| 1000 | Osborn Heirs Company LTD | San Antonio, TX 78217 | Oil & Gas Operator | Feb 2026 |