| 1 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 2 | Unbridled Resources, LLC | Houston, TX 77002 | Oil & Gas Operator | Nov 2024 |
| 3 | Unicon Producing Company | Houston, TX 75252 | Gas Operator | Mar 1994 |
| 4 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 5 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 6 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Jul 2024 |
| 7 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Nov 2024 |
| 8 | United Energy Operating, LLC | Edmond, OK 73083 | Oil & Gas Operator | Nov 2024 |
| 9 | United Energy Trading LLC | Tulsa, OK 74133 | Gas Operator | Feb 2015 |
| 10 | United Oil Corporation | Denver, CO 80202-3813 | Oil & Gas Operator | Jul 2024 |
| 11 | United Production Company LLC | Edmond, OK 73003 | Oil & Gas Operator | Aug 2024 |
| 12 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Nov 2024 |