| 30901 | Uinta Oil & Gas | Roosevelt, UT 84066 | Oil & Gas Operator | Nov 1997 |
| 30902 | Uinta Wax Operating, LLC | Fort Worth, TX 76107 | Oil & Gas Operator | Jan 2025 |
| 30903 | Uinta-Taylor Fund, LTD | Roosevelt, UT 84066 | Oil & Gas Operator | Nov 2018 |
| 30904 | Uintah Investors LLC | Vernal, UT 84078 | Oil & Gas Operator | Feb 2025 |
| 30905 | Ulatex Oil & Gas Inc. | Nocona, TX 76255 | Oil & Gas Operator | Dec 1998 |
| 30906 | Ullrich Sandy J | Haskell, OK 74436 | Oil Operator | Jan 2025 |
| 30907 | Ullum Oil And Gas Development Corporation, Inc. | Grantsville, WV 26147-0000 | Oil & Gas Operator | Dec 2021 |
| 30908 | Ulrich, William J., Jr. & Connie K. | Elma, NY 14059 | Gas Operator | Dec 2023 |
| 30909 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | Apr 2025 |
| 30910 | Ultra Petroleum (U.S.A.), Inc. | Granbury, TX 76048 | Oil & Gas Operator | Sep 2003 |
| 30911 | Ultra Production Company, LLC | Cedar Bluff, VA 24609 | Gas Operator | Oct 2014 |
| 30912 | Ultra Resources Inc | Houston, TX 77060 | Oil & Gas Operator | Sep 2018 |
| 30913 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 30914 | Ultramar Production Company | | Oil & Gas Operator | Dec 1991 |
| 30915 | Ulysses, City Of | Ulysses, KS 67880 | Gas Operator | Dec 2024 |
| 30916 | Umberham Oil Company Inc | Oklahoma City, OK 73151-4000 | Oil & Gas Operator | Feb 2025 |
| 30917 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 30918 | Umma Resources, LLC | Portland, TX 78374 | Gas Operator | Apr 2025 |
| 30919 | Ummel'S Tank Ser | | Oil Operator | Sep 1994 |
| 30920 | Unbridled Resources, LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2025 |
| 30921 | Unc Texas Incorp | | Gas Operator | May 1987 |
| 30922 | Underground Energy Inc. | | Oil & Gas Operator | Dec 2024 |
| 30923 | Underwood Oil & Gas | Casper, WY 82602 | Oil & Gas Operator | Feb 2025 |
| 30924 | Underwood Oil And Gas LLC | Chandler, OK 74834-1414 | Oil & Gas Operator | Feb 2025 |
| 30925 | Underwood, Donald D. Dba Mustang Oil Co | Salem, WV 26426 | Oil & Gas Operator | Dec 2020 |
| 30926 | Underwood, Jim | Graham, TX 76450 | Oil & Gas Operator | Mar 2018 |
| 30927 | Underwood, Rip C | Amarillo, TX 79101 | Gas Operator | Sep 1963 |
| 30928 | Unger Well Drilling Corp | Dennison, OH 44621 | Oil & Gas Operator | Dec 1999 |
| 30929 | Uni Production Company, Inc. | | Oil & Gas Operator | Apr 1988 |
| 30930 | Unicon Producing Company | Houston, TX 75252 | Gas Operator | Mar 1994 |
| 30931 | Unicorn Drilling Inc | Cody, WY 82414 | Oil Operator | Dec 1998 |
| 30932 | Unicorn Energy, Inc. | Elgin, TX 78621 | Oil & Gas Operator | Apr 2025 |
| 30933 | Unicorn Oil & Gas Co Inc | Dorset, OH 44032 | Oil & Gas Operator | Dec 1993 |
| 30934 | Unifid Oil & Gas Corp. | | Oil & Gas Operator | Mar 1994 |
| 30935 | Unified Oil & Gas Corp. | Snyder, TX 79550 | Oil Operator | Apr 2025 |
| 30936 | Unioil | Denver, CO 80203 | Oil & Gas Operator | Jun 2012 |
| 30937 | Union Camp Corp | Dover, OH 44622 | Oil & Gas Operator | Dec 2002 |
| 30938 | Union City Boro Muni Auth Erie Cnty | Union City, PA 16438-1326 | Gas Operator | Dec 2023 |
| 30939 | Union Crude Company | Baytown, TX 77521 | Oil & Gas Operator | Apr 2018 |
| 30940 | Union Crude Operating Co. | Baytown, TX 77521 | Oil Operator | Aug 2003 |
| 30941 | Union Development Company Inc | | Oil & Gas Operator | Dec 1992 |
| 30942 | Union Diversified, Inc. | | Gas Operator | Dec 2008 |
| 30943 | Union Drilling &Management Inc | | Gas Operator | Feb 1991 |
| 30944 | Union Exploration Partners, LTD. | | Oil & Gas Operator | Aug 1990 |
| 30945 | Union Gas Corp. (Union Gas Co.) | Charleston, WV 25338-0000 | Oil & Gas Operator | Aug 2021 |
| 30946 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Apr 2025 |
| 30947 | Union Oil Co | Danville, OH 43014 | Oil & Gas Operator | Dec 2014 |
| 30948 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 30949 | Union Operating Corp | Lakewoord, CO 80215 | Oil Operator | Dec 2023 |
| 30950 | Union Pacific Austin Chalk Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 30951 | Union Pacific Re | | Oil & Gas Operator | Dec 1996 |
| 30952 | Union Pacific Resour | | Oil & Gas Operator | Apr 2002 |
| 30953 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 30954 | Union Petro Inc | Uniontown, KY 42461 | Oil Operator | Dec 2023 |
| 30955 | Union Petrochemical | | Oil & Gas Operator | Dec 1982 |
| 30956 | Union Producing Co. | | Gas Operator | Dec 1992 |
| 30957 | Union Resources Inc | | Oil & Gas Operator | Dec 1996 |
| 30958 | Union Royalty, Inc. | Midland, TX 79706 | Oil & Gas Operator | Jul 2014 |
| 30959 | Union Seaboard Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 30960 | Union Springs Central School District | Union Springs, NY 13160 | Gas Operator | Dec 2023 |
| 30961 | Union Texas Petroleum | Houston, TX 77252 | Oil & Gas Operator | Oct 1991 |
| 30962 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 30963 | Union Texas Products Corp | Houston, TX 77252 | Oil & Gas Operator | Nov 1994 |
| 30964 | Union Valley Petroleum Corporation | Enid, OK 73701 | Oil & Gas Operator | Feb 2025 |
| 30965 | Unionville Explo | | Oil Operator | Jul 1984 |
| 30966 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Jan 2025 |
| 30967 | Unit Manager, Citronelle Unit | | Oil & Gas Operator | Sep 2001 |
| 30968 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Apr 2025 |
| 30969 | United Company | Lubbock, TX 79408 | Oil & Gas Operator | Jun 1995 |
| 30970 | United Energy & Expl Inc | Ada, OK 74821-2449 | Oil & Gas Operator | Jan 2025 |
| 30971 | United Energy & Exploration LLC | Ada, OK 74821 | Oil & Gas Operator | Jan 2025 |
| 30972 | United Energy Corporation | San Antonio, TX 78209 | Oil & Gas Operator | Apr 2025 |
| 30973 | United Energy Develop Co LTD | Bartlesville, OK 74003 | Oil Operator | Mar 2004 |
| 30974 | United Energy Inc. | Wichita, KS 67230 | Oil & Gas Operator | Dec 2002 |
| 30975 | United Energy Operating, LLC | Edmond, OK 73083 | Oil & Gas Operator | Apr 2025 |
| 30976 | United Energy Partners, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Mar 2008 |
| 30977 | United Energy Trading LLC | Tulsa, OK 74133 | Oil & Gas Operator | Jan 2025 |
| 30978 | United Fuel Gas Co | | Oil & Gas Operator | Dec 2022 |
| 30979 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |
| 30980 | United Investment Group | | Oil Operator | Nov 2004 |
| 30981 | United Meridian | | Oil Operator | Dec 1992 |
| 30982 | United Natural Gas LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2020 |
| 30983 | United Natural Resources Corp | | Oil Operator | Jan 1986 |
| 30984 | United O&G/Atlee Miller | Millersburg, OH 44654 | Oil & Gas Operator | Dec 1985 |
| 30985 | United Oil & Gas | | Oil Operator | Feb 1988 |
| 30986 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 30987 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 30988 | United Oil Corporation | Denver, CO 80202-3813 | Oil & Gas Operator | Jan 2025 |
| 30989 | United Operating Co. | Olney, TX 76374 | Oil & Gas Operator | Aug 2003 |
| 30990 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Apr 2025 |
| 30991 | United Operators, Inc. | | Oil Operator | Sep 1999 |
| 30992 | United Petro Corp | Columbus, OH 43229-1826 | Gas Operator | Dec 1985 |
| 30993 | United Petro LTD. | | Oil & Gas Operator | Dec 2018 |
| 30994 | United Petroleum | | Oil Operator | Mar 1986 |
| 30995 | United Petroleum & Gas, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Apr 2025 |
| 30996 | United Petroleum Corporation | Edgwater, CO 80214 | Oil & Gas Operator | May 1996 |
| 30997 | United Petroleum Technologies | Hondo, TX 78861 | Oil & Gas Operator | Aug 2001 |
| 30998 | United Primary Resources Inc | Milton, WA 98354-9361 | Oil & Gas Operator | Feb 2016 |
| 30999 | United Producers Inc | Broken Arrow, OK 74012-8247 | Oil & Gas Operator | Mar 2020 |
| 31000 | United Producing Co Inc | | Oil & Gas Operator | May 1961 |