| 1901 | Gryphon Exploration Company | Mandeville, LA 70471 | Oil & Gas Operator | Aug 2009 |
| 1902 | GT Energy | | Oil & Gas Operator | Mar 1993 |
| 1903 | Guaranty Energy Corporation | | Oil & Gas Operator | Aug 1990 |
| 1904 | Guardian Oil Company | | Oil & Gas Operator | Aug 1985 |
| 1905 | Guernsey Petroleum Corporation | Atlanta, GA 30318 | Oil & Gas Operator | Nov 1997 |
| 1906 | Guernsey/Rosbottom | | Oil Operator | Apr 1989 |
| 1907 | Guido & Arnold | | Oil & Gas Operator | Feb 1982 |
| 1908 | Guido Energy Co & Guernsey Pet | | Oil Operator | Aug 1991 |
| 1909 | Gulf Coast Crude O&G Co., Inc. | | Oil & Gas Operator | May 1982 |
| 1910 | Gulf Exploration Company, Inc. | | Oil & Gas Operator | Dec 2024 |
| 1911 | Gulf Oil Corp. | Denver, CO 80201-0599 | Oil & Gas Operator | Dec 2014 |
| 1912 | Gulf Outlet Resources, L.L.C. | | Oil & Gas Operator | Apr 2008 |
| 1913 | Gulf Production Company, Inc. | | Oil & Gas Operator | Dec 2024 |
| 1914 | Gulf South Minerals, Inc. | | Oil Operator | Nov 1993 |
| 1915 | Gulf South Oil & Gas, Inc. | | Oil & Gas Operator | Feb 1990 |
| 1916 | Gulf South Operators, Inc. | New Orleans, LA 70130 | Oil & Gas Operator | Oct 2015 |
| 1917 | Gulf South Pipeline Company, LLC | | Oil & Gas Operator | Jan 2025 |
| 1918 | Gulf South Pipeline Company, LP | Houston, TX 77046 | Oil & Gas Operator | Dec 2020 |
| 1919 | Gulf States Exploration Co. | | Oil & Gas Operator | Dec 1983 |
| 1920 | Gulf States Pipeline Corp. | | Oil & Gas Operator | May 2003 |
| 1921 | Gulf States Production Company | Houston, TX 77027 | Oil & Gas Operator | Aug 1997 |
| 1922 | Gulf Tech Energy LLC | | Oil & Gas Operator | Dec 2002 |
| 1923 | Gulfland Resources, Inc. | | Oil & Gas Operator | Aug 1996 |
| 1924 | Gulfport Energy Corporation | Oklahoma City, OK 73134-5003 | Oil & Gas Operator | Feb 2025 |
| 1925 | Gulfstream Of Louisiana, Inc. | | Oil & Gas Operator | Jan 1996 |
| 1926 | Gulfstream Petroleum Corp. | | Oil & Gas Operator | Feb 2002 |
| 1927 | Gulfstream Resources, Inc. | | Oil & Gas Operator | May 1996 |
| 1928 | Guynes And Backus | | Oil Operator | Nov 1999 |
| 1929 | Gyb-Britlind Oil, LLC | | Oil & Gas Operator | Jun 2016 |
| 1930 | H & B Production | | Oil Operator | Mar 1995 |
| 1931 | H & B Well Service, Inc. | | Oil & Gas Operator | Aug 1993 |
| 1932 | H & H & S Oil Producers | | Oil Operator | Jan 2025 |
| 1933 | H & H Compressors, Inc. | | Oil & Gas Operator | Oct 1997 |
| 1934 | H & H Oil Co. | | Oil & Gas Operator | Jan 2025 |
| 1935 | H & H Oil Co. #1 | | Oil Operator | Jan 2025 |
| 1936 | H & H Oil Producers | | Oil & Gas Operator | Jan 2025 |
| 1937 | H & H Production Company | Muenster, TX 76252 | Oil & Gas Operator | Oct 2005 |
| 1938 | H & S Operating Co., Inc. | Winesburg, OH 44690 | Oil & Gas Operator | Dec 2024 |
| 1939 | H E C I Exploration Company | | Oil & Gas Operator | Dec 1990 |
| 1940 | H H H Oil Company | | Oil Operator | Jan 2025 |
| 1941 | H M Jarred & Walsh-Watts | | Oil & Gas Operator | Sep 1992 |
| 1942 | H&S Production, LLC | | Oil Operator | Nov 2024 |
| 1943 | H. & H. Development Co. | | Gas Operator | Aug 2019 |
| 1944 | H. & N. Operating Co., Inc. | | Oil & Gas Operator | Oct 1997 |
| 1945 | H. A. Harper | | Oil Operator | Dec 1982 |
| 1946 | H. B. McCullough | | Oil Operator | Oct 2004 |
| 1947 | H. D. McCormick | | Oil & Gas Operator | Jun 2016 |
| 1948 | H. E. Sutton | | Oil & Gas Operator | Jan 1990 |
| 1949 | H. G. Oil Operator | | Oil Operator | Mar 2001 |
| 1950 | H. J. Bonner | | Oil & Gas Operator | Aug 1991 |
| 1951 | H. K. Beebe | | Oil Operator | Jan 1990 |
| 1952 | H. L. Brown, Jr. | Midland, TX 79702 | Oil & Gas Operator | May 2001 |
| 1953 | H. L. McKee & J. P. McKee Jr. | | Gas Operator | Mar 2023 |
| 1954 | H. L. Richey | | Oil & Gas Operator | Sep 1995 |
| 1955 | H. Proler-Luffey Gas Corp. | | Gas Operator | Apr 1979 |
| 1956 | H.E. Sutton, Et Al | | Oil & Gas Operator | Jan 1990 |
| 1957 | H.L.Hawkins &H.L.Hawkins, Jr. | | Oil & Gas Operator | Feb 1989 |
| 1958 | Habetz Oilfield Saltwater Ser, Inc | | Oil Operator | Dec 2024 |
| 1959 | Hackberry Production, Inc. | | Oil Operator | Mar 1988 |
| 1960 | Haddox Petroleum Corp | | Gas Operator | Dec 2010 |
| 1961 | Hadson Energy Resources Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 1994 |
| 1962 | Hadson Petroleum (USA), Inc. | | Oil & Gas Operator | Dec 1992 |
| 1963 | Haffaday Oil LLC | | Oil Operator | Jan 2025 |
| 1964 | Hal Oil & Gas Co., Inc. | | Oil & Gas Operator | Apr 1993 |
| 1965 | Haland Operating Company, LLC | | Oil & Gas Operator | Jul 2018 |
| 1966 | Halbouty-Reserve | | Oil & Gas Operator | Sep 1987 |
| 1967 | Halbouty-Reserve-Pel-Tex | | Oil & Gas Operator | May 1985 |
| 1968 | Halcon Louisiana Operating, LP | | Oil & Gas Operator | Sep 2017 |
| 1969 | Halcon Resources Operating, Inc. | Tulsa, OK 74135 | Oil & Gas Operator | Dec 2013 |
| 1970 | Hale Oil | | Oil & Gas Operator | Dec 2024 |
| 1971 | Hale Oil Co. | | Oil & Gas Operator | Jan 2025 |
| 1972 | Hall Engineering, Inc. | | Oil & Gas Operator | Jan 2007 |
| 1973 | Hall-Hargraves, L.L.C. | | Oil & Gas Operator | Dec 2024 |
| 1974 | Hall-Houston Oil Company | Houston, TX 77002 | Oil & Gas Operator | Oct 2002 |
| 1975 | Hallador Petroleum Company | | Oil & Gas Operator | Feb 1992 |
| 1976 | Hallar Enterprises, Inc. | | Oil Operator | Oct 2007 |
| 1977 | Halliburton Operating Company | Plano, TX 75093 | Oil & Gas Operator | May 2025 |
| 1978 | Hallmark Oil And Gas Co., Inc. | | Oil & Gas Operator | Dec 2024 |
| 1979 | Hallwell Gas & Oil Co. | | Oil & Gas Operator | Sep 1985 |
| 1980 | Hallwood Petroleum, Inc. | Midland, TX 79701 | Oil & Gas Operator | Jan 2025 |
| 1981 | Hallwood Petroleum, LLC | Dallas, TX 75219 | Oil & Gas Operator | Jan 2010 |
| 1982 | Hamilton Brothers Oil Co. | Houston, TX 77057 | Oil & Gas Operator | Mar 2015 |
| 1983 | Hamman Oil & Refining Company | Houston, TX 77098 | Oil & Gas Operator | May 2025 |
| 1984 | Hamon Oil Company | | Oil & Gas Operator | Aug 1985 |
| 1985 | Hamon Operating Company | Dallas, TX 75201 | Oil & Gas Operator | Dec 2011 |
| 1986 | Hampton Resources Corporation | Houston, TX 77010 | Oil & Gas Operator | Mar 1996 |
| 1987 | Hanover Management Company | | Oil Operator | Aug 1979 |
| 1988 | Hansen Oil Corporation | Shreveport, LA 71106 | Oil Operator | Apr 2003 |
| 1989 | Hanson Natural Resources Co. | | Oil & Gas Operator | Nov 1991 |
| 1990 | Hanvey Production Co., Inc. | Roanoke, TX 76262 | Oil & Gas Operator | Nov 2012 |
| 1991 | Harbert Energy Corp | Irving, TX 75015-2510 | Oil & Gas Operator | Feb 1993 |
| 1992 | Harbert Energy Corp/Gulf Coast | | Oil & Gas Operator | Dec 1991 |
| 1993 | Harbor Operating, LLC | | Oil & Gas Operator | Dec 1999 |
| 1994 | Harbor Petroleum, LLC | Granbury, TX 76049 | Oil & Gas Operator | May 2025 |
| 1995 | Harcor Exploration Inc. | | Oil Operator | Aug 1989 |
| 1996 | Hardco, Inc. | Cleveland, OH 44115 | Oil & Gas Operator | Dec 1992 |
| 1997 | Hardey Co., The | Shreveport, LA 71107 | Oil & Gas Operator | May 2025 |
| 1998 | Hardey Production Company | | Oil Operator | Dec 1998 |
| 1999 | Hardy Oil & Gas USA Inc. | Houston, TX 77079 | Oil & Gas Operator | Jun 1996 |
| 2000 | Hargraves Daughters | | Oil Operator | Mar 1992 |