| 1901 | Columbia Gas Dev. Corp. | | Oil & Gas Operator | Apr 1996 |
| 1902 | Columbia Gas Development | Houston, TX 77251 | Oil & Gas Operator | Jun 1996 |
| 1903 | Columbia Gas Development Corp. | Houston, TX 77251 | Oil & Gas Operator | Jun 1996 |
| 1904 | Columbia Gas Trans LLC | Charleston, WV 25325-1273 | Gas Operator | Dec 1987 |
| 1905 | Columbia Gas Transmission, LLC | Charleston, WV 25314 | Oil & Gas Operator | Dec 2021 |
| 1906 | Columbia Gulf Transmission Co. | | Oil Operator | Dec 2014 |
| 1907 | Columbia Gulf Transmission Company, LLC | | Oil Operator | Jan 2025 |
| 1908 | Columbia Minerals Corp., Inc. | | Oil & Gas Operator | May 1996 |
| 1909 | Columbia Natural Res Inc | Charleston, WV 25362-0070 | Gas Operator | Dec 2008 |
| 1910 | Columbia Natural Resources, LLC | Charleston, WV 23502 | Oil & Gas Operator | Dec 2021 |
| 1911 | Columbia Oil Company, Inc | Guy, AR 72061 | Oil & Gas Operator | Jan 2025 |
| 1912 | Columbia Petrole | | Oil Operator | Sep 1988 |
| 1913 | Columbia Petroleum Corp. | | Oil & Gas Operator | Jun 1982 |
| 1914 | Columbia Petroleum LLC | Oyster Bay, NY 11771 | Oil & Gas Operator | Feb 2025 |
| 1915 | Columbia Petroleum, LTD. | Farmington, UT 84025 | Oil Operator | Jul 2025 |
| 1916 | Columbia Production Company | Edmond, OK 73083 | Oil & Gas Operator | May 2020 |
| 1917 | Columbian Production Corporation | Topeka, KS 66601 | Oil Operator | Oct 1999 |
| 1918 | Columbian Servic | | Oil & Gas Operator | Nov 1993 |
| 1919 | Columbian Services C | | Oil Operator | Jan 1992 |
| 1920 | Columbian Services Corporation | Topeka, KS 66603 | Gas Operator | Dec 2009 |
| 1921 | Columbine Associates | | Oil & Gas Operator | Jul 2025 |
| 1922 | Columbine Exploration Corp | Englewood, CO 80111 | Oil & Gas Operator | Aug 1998 |
| 1923 | Columbus Energy Corp. | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2008 |
| 1924 | Columbus Energy, LLC | Houston, TX 77046 | Oil & Gas Operator | Sep 2025 |
| 1925 | Columbus III Production LC | | Oil Operator | Oct 2003 |
| 1926 | Columbus Oil And Gas LLC | | Oil Operator | Oct 2020 |
| 1927 | Columbus Oil Company | Seminole, OK 74868 | Oil & Gas Operator | Jul 2025 |
| 1928 | Columbus Oilfield Explor Co | Powell, OH 43065-9315 | Gas Operator | Dec 2004 |
| 1929 | Columbus Oilfield Exploration Company | Columbus, OH 43220 | Oil & Gas Operator | Dec 2013 |
| 1930 | Columbus Production Inc | | Oil & Gas Operator | Mar 2005 |
| 1931 | Comac Well Service, Inc. | Borger, TX 79008 | Oil & Gas Operator | Mar 2008 |
| 1932 | Comal Operating LLC | San Antonio, TX 78217 | Oil & Gas Operator | Sep 2025 |
| 1933 | Comanche Drilling Company | Cut Bank, MT 59427 | Oil & Gas Operator | Jun 2025 |
| 1934 | Comanche Exploration Co LLC | Oklahoma City, OK 73116-7334 | Oil & Gas Operator | Jul 2025 |
| 1935 | Comanche Exploration Company | Oklahoma City, OK 73120-2797 | Oil & Gas Operator | Feb 2007 |
| 1936 | Comanche Oil & Gas Corp | Salt Lake City, UT 84107-3075 | Oil & Gas Operator | May 2005 |
| 1937 | Comanche Oil And Service, LLC | | Oil Operator | May 2025 |
| 1938 | Comanche Operating Co. | Oklahoma City, OK 73120 | Oil & Gas Operator | Aug 2002 |
| 1939 | Comanche Petroleum Corporation | Oklahoma City, OK 73179 | Oil & Gas Operator | Apr 2024 |
| 1940 | Comanche Product | | Oil & Gas Operator | Jan 1992 |
| 1941 | Comanche Production Co | Oklahoma City, OK 73118 | Oil & Gas Operator | Nov 1998 |
| 1942 | Comanche Production, Inc. | Longview, TX 75606 | Oil & Gas Operator | Jan 2006 |
| 1943 | Comanche Resources Company | Oklahoma City, OK 73116 | Oil & Gas Operator | Jul 2025 |
| 1944 | Comanche Well Service Corp. | Plano, TX 75093 | Oil & Gas Operator | Sep 2025 |
| 1945 | Combest A L | Purcell, OK 73080-6829 | Oil & Gas Operator | Aug 2021 |
| 1946 | Combined Oil & Gas | Denver, CO 80202 | Oil & Gas Operator | Feb 1990 |
| 1947 | Combined Resources Corporation | Edmond, OK 73083 | Oil & Gas Operator | Sep 2025 |
| 1948 | Combs Production LLC | Depew, OK 74028-0483 | Oil & Gas Operator | Jun 2025 |
| 1949 | Combs, Steven H | Corydon, KY 42406 | Oil Operator | Dec 2023 |
| 1950 | Comco Of Louisiana, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jun 2000 |
| 1951 | Comdisco Exploration Inc | | Oil Operator | Dec 1990 |
| 1952 | Comdisco Resources Inc | | Oil Operator | Aug 2004 |
| 1953 | Comerica Properties Corp | | Oil Operator | May 1985 |
| 1954 | Comet Energy Services LLC | Traverse City, MI 49686 | Oil & Gas Operator | Oct 2011 |
| 1955 | Comet Oil & Gas, Inc. | Conroe, TX 77305 | Oil & Gas Operator | Sep 2025 |
| 1956 | Comet Oil Company | Velma, OK 73091 | Oil & Gas Operator | May 2005 |
| 1957 | Comet Production | Conroe, TX 77305 | Oil Operator | Sep 2025 |
| 1958 | Comet-Haines Oil Company | Sulphur, OK 73086-0546 | Oil & Gas Operator | Mar 2013 |
| 1959 | Cometra Oil And Gas, Inc. | Fort Worth, TX 76102 | Oil & Gas Operator | Feb 1997 |
| 1960 | Comgas Inc | Hebron, OH 43025-9716 | Oil & Gas Operator | Dec 1988 |
| 1961 | Comm Energy Inc | Weston, WV 26452-2907 | Gas Operator | Dec 2004 |
| 1962 | Command Energy Operating LLC | Tulsa, OK 74119 | Oil & Gas Operator | Jun 2025 |
| 1963 | Commander Oil Company LTD. | | Oil & Gas Operator | Dec 2021 |
| 1964 | Commerce Energy Co | Cleveland, OH 44115 | Oil & Gas Operator | Dec 1987 |
| 1965 | Commerce Energy, Inc. | | Oil & Gas Operator | Dec 1999 |
| 1966 | Commerce Oil & Gas Co | Rocky River, OH 44116 | Oil & Gas Operator | Dec 1996 |
| 1967 | Commercial Energ | | Gas Operator | Oct 1996 |
| 1968 | Commercial Oil - | | Oil Operator | Apr 1994 |
| 1969 | Commercial Oil Company, Inc. | Wichita, KS 67204 | Oil Operator | Jun 2001 |
| 1970 | Commodore Energy Co | Rolling Hills, CA 90274-5265 | Oil & Gas Operator | Dec 2007 |
| 1971 | Common Energy Inc | Douglas, WY 82633 | Oil & Gas Operator | Aug 1995 |
| 1972 | Common Resources L.L.C. | The Woodlands, TX 77380 | Oil & Gas Operator | May 2010 |
| 1973 | Commonwealth Energy, Inc. | Weston, WV 26452-0000 | Oil & Gas Operator | Dec 2021 |
| 1974 | Commonwealth Pet | | Oil & Gas Operator | Nov 1995 |
| 1975 | Commonwealth Resources, LLC | Fort Collins, CO 80524 | Oil Operator | Dec 2008 |
| 1976 | Commonwealth Royalty, LLC | Balmorhea, TX 79718 | Oil Operator | Sep 2025 |
| 1977 | Compadre Drilling & Expl Corp | Ardmore, OK 73402 | Oil & Gas Operator | Mar 2015 |
| 1978 | Compadres, Inc. | | Oil & Gas Operator | Dec 1988 |
| 1979 | Compass Drilling Inc | Enid, OK 73702-5467 | Oil & Gas Operator | Sep 2014 |
| 1980 | Compass Energy Operating, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Sep 2025 |
| 1981 | Compass Energy, Inc. | Shelby, MT 59474 | Gas Operator | Feb 2007 |
| 1982 | Compass Global Resources LLC | | Oil & Gas Operator | Dec 2015 |
| 1983 | Compass Operating, L.L.C. | Midland, TX 79702 | Oil & Gas Operator | Sep 2025 |
| 1984 | Compass Resources | Enid, OK 73702 | Oil & Gas Operator | Dec 2007 |
| 1985 | Complete Energy Services LLC | Gainesville, TX 76240 | Oil Operator | Aug 2022 |
| 1986 | Compostella Oil Company | Midland, TX 79702 | Oil & Gas Operator | Mar 2008 |
| 1987 | Compressor Syste | | Oil Operator | May 1991 |
| 1988 | Compro Services Inc | Williamstown, WV 26187 | Oil & Gas Operator | Dec 1985 |
| 1989 | Comstock Energy, LLC | Wichita Falls, TX 76301 | Oil & Gas Operator | Sep 2025 |
| 1990 | Comstock Offshore, LLC | | Oil & Gas Operator | Nov 2004 |
| 1991 | Comstock Oil & Gas -- La, Inc. | | Oil & Gas Operator | Mar 2005 |
| 1992 | Comstock Oil & Gas, Inc. | Frisco, TX 75034 | Oil & Gas Operator | Dec 2012 |
| 1993 | Comstock Oil & Gas, LLC | Frisco, TX 75034 | Oil & Gas Operator | Sep 2025 |
| 1994 | Comstock Oil & Gas, LP | Frisco, TX 75034 | Oil & Gas Operator | Aug 2019 |
| 1995 | Comstock Oil & Gas--La, LLC | | Oil & Gas Operator | Dec 2024 |
| 1996 | Comyn Natural Gas, Inc. | Fort Worth, TX 76163 | Oil & Gas Operator | Sep 2025 |
| 1997 | Con-Lin Oil Co. | Graham, TX 76450 | Oil & Gas Operator | Nov 2017 |
| 1998 | Conch Oil, Inc. | Wichita, KS 67202 | Oil Operator | Jun 2002 |
| 1999 | Concho Exploration | Midland, TX 79701 | Oil & Gas Operator | Feb 2004 |
| 2000 | Concho Exploration Inc | Oklahoma City, OK 73154 | Oil & Gas Operator | Mar 2015 |