| 1901 | Colonial Hardwoods Inc | Luthersburg, PA 15848-3506 | Gas Operator | Dec 2019 |
| 1902 | Colonial Resources LLC | Edmond, OK 73003-3207 | Oil & Gas Operator | Aug 2019 |
| 1903 | Colorado Bluebonnet Energy Corp. | Englewood, CO 80112 | Oil & Gas Operator | Feb 2001 |
| 1904 | Colorado Crude E | | Oil Operator | Jan 1986 |
| 1905 | Colorado Drilling Company | Grand Junction, CO 81501 | Oil Operator | Jan 1990 |
| 1906 | Colorado Energy Minerals Inc | | Oil Operator | Dec 2010 |
| 1907 | Colorado Gas Compression Inc | Longmont, CO 80501-5868 | Oil & Gas Operator | Aug 2013 |
| 1908 | Colorado Interst | | Gas Operator | Aug 1995 |
| 1909 | Colorado Interstate Gas Co | Colorado Springs, CO 80944 | Oil & Gas Operator | Jul 2004 |
| 1910 | Colorado Interstate Gas Company LLC | Colorado Springs, CO 80944 | Oil & Gas Operator | Feb 2025 |
| 1911 | Colorado Oil & G | | Oil & Gas Operator | Oct 1987 |
| 1912 | Colorado Oil & Gas Corporation | | Oil & Gas Operator | May 2003 |
| 1913 | Colorado Oil Co., Inc. | | Oil & Gas Operator | Dec 1977 |
| 1914 | Colorado Pica Petro Corp | Cortez, CO 81321 | Oil & Gas Operator | Apr 2007 |
| 1915 | Colorado-Swanson Landing Oil & Gas, LLC | Kilgore, TX 75663 | Oil Operator | Apr 2025 |
| 1916 | Colotex Operating, LLC | Aurora, CO 80015 | Oil & Gas Operator | Apr 2025 |
| 1917 | Colpitt Brothers Oil | Collinsville, OK 74021 | Oil & Gas Operator | Apr 2020 |
| 1918 | Colpitt Brothers Operating Co | Collinsville, OK 74021 | Oil & Gas Operator | Jan 2025 |
| 1919 | Colpitt C H Drilling Co LLC | Collinsville, OK 74021-7107 | Oil Operator | Jan 2025 |
| 1920 | Colpitt Chas H Drilling Co | Collinsville, OK 74021-7105 | Oil & Gas Operator | Mar 2012 |
| 1921 | Colt Energy Inc | Iola, KS 66749 | Oil & Gas Operator | Dec 2024 |
| 1922 | Colt Energy Inco | | Oil & Gas Operator | Dec 1996 |
| 1923 | Colt Oil & Gas Co. | Abilene, TX 79601 | Oil Operator | Apr 2004 |
| 1924 | Colt Oil Company | Andrews, TX 79714 | Oil & Gas Operator | Feb 1996 |
| 1925 | Colt Oil Corporation | Smithville, WV 26178 | Oil & Gas Operator | Dec 2021 |
| 1926 | Colt Oil LLC | Sapulpa, OK 74066-1010 | Oil Operator | Jan 2025 |
| 1927 | Colt Operating Corporation | San Antonio, TX 78231 | Oil & Gas Operator | Aug 2003 |
| 1928 | Colt Production Corp. Inc. | | Oil & Gas Operator | Jul 1996 |
| 1929 | Colt Resources Corporation | Billings, MT 59103 | Oil & Gas Operator | Feb 2013 |
| 1930 | Colter Operating Co | Horseshoe Bay, TX 78654 | Oil & Gas Operator | Nov 1997 |
| 1931 | Coltharp, Edward H | | Oil & Gas Operator | Dec 1970 |
| 1932 | Colton Limited Liability Co | | Oil & Gas Operator | Sep 2023 |
| 1933 | Coltrane Charles | | Oil Operator | Dec 1980 |
| 1934 | Columbia Energy Properties, Inc. | Baytown, TX 77521 | Oil & Gas Operator | Jul 2004 |
| 1935 | Columbia Gas Dev. Corp. | | Oil & Gas Operator | Apr 1996 |
| 1936 | Columbia Gas Development | Houston, TX 77251 | Oil & Gas Operator | Jun 1996 |
| 1937 | Columbia Gas Development Corp. | Houston, TX 77251 | Oil & Gas Operator | Jun 1996 |
| 1938 | Columbia Gas Trans LLC | Charleston, WV 25325-1273 | Gas Operator | Dec 1987 |
| 1939 | Columbia Gas Transmission, LLC | Charleston, WV 25314 | Oil & Gas Operator | Dec 2021 |
| 1940 | Columbia Gulf Transmission Co. | | Oil Operator | Dec 2014 |
| 1941 | Columbia Gulf Transmission Company, LLC | | Oil Operator | Jan 2025 |
| 1942 | Columbia Minerals Corp., Inc. | | Oil & Gas Operator | May 1996 |
| 1943 | Columbia Natural Res Inc | Charleston, WV 25362-0070 | Gas Operator | Dec 2008 |
| 1944 | Columbia Natural Resources, LLC | Charleston, WV 23502 | Oil & Gas Operator | Dec 2021 |
| 1945 | Columbia Oil Company, Inc | Guy, AR 72061 | Oil & Gas Operator | Aug 2024 |
| 1946 | Columbia Petrole | | Oil Operator | Sep 1988 |
| 1947 | Columbia Petroleum Corp. | | Oil & Gas Operator | Jun 1982 |
| 1948 | Columbia Petroleum LLC | Brookhaven, MS 39601 | Oil & Gas Operator | Oct 2024 |
| 1949 | Columbia Petroleum, LTD. | Farmington, UT 84025 | Oil Operator | Jan 2025 |
| 1950 | Columbia Production Company | Edmond, OK 73083 | Oil & Gas Operator | May 2020 |
| 1951 | Columbian Production Corporation | Topeka, KS 66601 | Oil Operator | Oct 1999 |
| 1952 | Columbian Servic | | Oil & Gas Operator | Nov 1993 |
| 1953 | Columbian Services C | | Oil Operator | Jan 1992 |
| 1954 | Columbian Services Corporation | Topeka, KS 66603 | Gas Operator | Dec 2009 |
| 1955 | Columbine Associates | | Oil & Gas Operator | Dec 2024 |
| 1956 | Columbine Exploration Corp | Englewood, CO 80111 | Oil & Gas Operator | Aug 1998 |
| 1957 | Columbus Energy Corp. | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2008 |
| 1958 | Columbus Energy, LLC | Houston, TX 77046 | Oil & Gas Operator | Apr 2025 |
| 1959 | Columbus III Production LC | | Oil Operator | Oct 2003 |
| 1960 | Columbus Oil And Gas LLC | | Oil Operator | Oct 2020 |
| 1961 | Columbus Oil Company | Seminole, OK 74868 | Oil & Gas Operator | Feb 2025 |
| 1962 | Columbus Oilfield Explor Co | Powell, OH 43065-9315 | Gas Operator | Dec 2004 |
| 1963 | Columbus Oilfield Exploration Company | Columbus, OH 43220 | Oil & Gas Operator | Dec 2013 |
| 1964 | Columbus Production Inc | | Oil & Gas Operator | Mar 2005 |
| 1965 | Comac Well Service, Inc. | Borger, TX 79008 | Oil & Gas Operator | Mar 2008 |
| 1966 | Comal Operating LLC | San Antonio, TX 78217 | Oil & Gas Operator | Apr 2025 |
| 1967 | Comanche Drilling Company | Cut Bank, MT 59427 | Oil & Gas Operator | Dec 2024 |
| 1968 | Comanche Exploration Co LLC | Oklahoma City, OK 73116-7334 | Oil & Gas Operator | Feb 2025 |
| 1969 | Comanche Exploration Company | Oklahoma City, OK 73120-2797 | Oil & Gas Operator | Feb 2007 |
| 1970 | Comanche Oil & Gas Corp | Salt Lake City, UT 84107-3075 | Oil & Gas Operator | May 2005 |
| 1971 | Comanche Oil & Service LLC | Hominy, OK 73035 | Oil Operator | Jan 2025 |
| 1972 | Comanche Oil And Gas Company | Brownwood, TX 76801 | Oil & Gas Operator | Apr 2025 |
| 1973 | Comanche Operating Co. | Oklahoma City, OK 73120 | Oil & Gas Operator | Aug 2002 |
| 1974 | Comanche Petroleum Corporation | Norman, OK 73072 | Oil & Gas Operator | Apr 2024 |
| 1975 | Comanche Product | | Oil & Gas Operator | Jan 1992 |
| 1976 | Comanche Production Co | Oklahoma City, OK 73118 | Oil & Gas Operator | Nov 1998 |
| 1977 | Comanche Production, Inc. | Longview, TX 75606 | Oil & Gas Operator | Jan 2006 |
| 1978 | Comanche Resources Company | Oklahoma City, OK 73116 | Oil & Gas Operator | Feb 2025 |
| 1979 | Comanche Well Service Corp. | Plano, TX 75093 | Oil & Gas Operator | Apr 2025 |
| 1980 | Combest A L | Purcell, OK 73080-6829 | Oil & Gas Operator | Aug 2021 |
| 1981 | Combined Oil & Gas | Denver, CO 80202 | Oil & Gas Operator | Feb 1990 |
| 1982 | Combined Resources Corporation | Edmond, OK 73083 | Oil & Gas Operator | Apr 2025 |
| 1983 | Combs Production LLC | Depew, OK 74028-0483 | Oil & Gas Operator | Jan 2025 |
| 1984 | Combs, Steven H | Corydon, KY 42406 | Oil Operator | Dec 2023 |
| 1985 | Comco Of Louisiana, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jun 2000 |
| 1986 | Comdisco Exploration Inc | | Oil Operator | Dec 1990 |
| 1987 | Comdisco Resources Inc | | Oil Operator | Aug 2004 |
| 1988 | Comerica Properties Corp | | Oil Operator | May 1985 |
| 1989 | Comet Energy Services LLC | Traverse City, MI 49686 | Oil & Gas Operator | Oct 2011 |
| 1990 | Comet Oil & Gas, Inc. | Conroe, TX 77305 | Oil & Gas Operator | Apr 2025 |
| 1991 | Comet Oil Company | Velma, OK 73091 | Oil & Gas Operator | May 2005 |
| 1992 | Comet Production | Conroe, TX 77305 | Oil Operator | Apr 2025 |
| 1993 | Comet-Haines Oil Company | Sulphur, OK 73086-0546 | Oil & Gas Operator | Mar 2013 |
| 1994 | Cometra Oil And Gas, Inc. | Fort Worth, TX 76102 | Oil & Gas Operator | Feb 1997 |
| 1995 | Comgas Inc | Hebron, OH 43025-9716-9716 | Oil & Gas Operator | Dec 1988 |
| 1996 | Comm Energy Inc | Weston, WV 26452-2907 | Gas Operator | Dec 2004 |
| 1997 | Command Energy Operating LLC | Tulsa, OK 74119 | Oil & Gas Operator | Jan 2025 |
| 1998 | Commander Oil Company LTD. | | Oil & Gas Operator | Dec 2021 |
| 1999 | Commerce Energy Co | Cleveland, OH 44115 | Oil & Gas Operator | Dec 1987 |
| 2000 | Commerce Energy, Inc. | | Oil & Gas Operator | Dec 1999 |