| 1 | U R C C | | Oil & Gas Operator | Jun 1991 |
| 2 | U S Exploraton Liq Trust | | Oil & Gas Operator | Oct 1994 |
| 3 | U S Liquids Of La., L.P. | | Oil Operator | Apr 2014 |
| 4 | U. D. Man, Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Apr 2024 |
| 5 | U. O. C., Inc. | | Oil Operator | Jun 2019 |
| 6 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Apr 2024 |
| 7 | U.S. Capital Corp Of Am, Inc. | | Oil & Gas Operator | Aug 1998 |
| 8 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 9 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 10 | Ultramar Production Company | | Oil & Gas Operator | Dec 1991 |
| 11 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 12 | Uni Production Company, Inc. | | Oil & Gas Operator | Apr 1988 |
| 13 | Unifid Oil & Gas Corp. | | Oil & Gas Operator | Mar 1994 |
| 14 | Union Diversified, Inc. | | Gas Operator | Dec 2008 |
| 15 | Union Exploration Partners, LTD. | | Oil & Gas Operator | Aug 1990 |
| 16 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Apr 2024 |
| 17 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 18 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 19 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 20 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Apr 2024 |
| 21 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |
| 22 | United Investment Group | | Oil Operator | Nov 2004 |
| 23 | United Operators, Inc. | | Oil Operator | Sep 1999 |
| 24 | United Petroleum Corporation | Edgwater, CO 80214 | Oil & Gas Operator | May 1996 |
| 25 | United Southern Resources Inc. | | Gas Operator | Nov 2013 |
| 26 | United World Energy Corporation | | Oil & Gas Operator | Jan 2024 |
| 27 | Universal Drilling Co., Inc. | Denver, CO 80203 | Oil & Gas Operator | Sep 2003 |
| 28 | Universal Land | | Oil Operator | Dec 2023 |
| 29 | Universal Oil Co. | | Oil Operator | Nov 2023 |
| 30 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 31 | Universal Producers, Inc. | | Oil Operator | Jun 2001 |
| 32 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 33 | University Field Management LLC | | Oil Operator | Nov 2023 |
| 34 | Unocal Exploration Corporation | Houston, TX 77001 | Oil & Gas Operator | May 1992 |
| 35 | Upstream Exploration LLC | Metairie, LA 70002 | Oil & Gas Operator | Jan 2020 |
| 36 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Apr 2024 |
| 37 | Us Liquids Of La, LTD | | Oil Operator | Jun 2002 |
| 38 | Us Oil & Gas Inc | Marietta, OH 45750 | Oil & Gas Operator | Feb 2024 |