| 1 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Apr 2024 |
| 2 | U.S. Energy Development Corp | Arlington, TX 76011 | Oil & Gas Operator | Apr 2024 |
| 3 | Ultra Petroleum (U.S.A.), Inc. | Granbury, TX 76048 | Oil & Gas Operator | Sep 2003 |
| 4 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 5 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 6 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Apr 2024 |
| 7 | United Energy Corporation | San Antonio, TX 78209 | Oil & Gas Operator | Apr 2024 |
| 8 | United Energy Trading LLC | Tulsa, OK 74133 | Gas Operator | Feb 2015 |
| 9 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 10 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 11 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 12 | Unitex Oil & Gas, L.L.C. | Midland, TX 79701 | Oil & Gas Operator | Apr 2024 |
| 13 | Upp Operating, LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2024 |