| 1 | U.S. Energy Development Corp | Arlington, TX 76011 | Oil & Gas Operator | Apr 2024 |
| 2 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 3 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 4 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 5 | Union Texas Products Corp | Houston, TX 77252 | Oil & Gas Operator | Nov 1994 |
| 6 | Union Valley Petroleum Corporation | Enid, OK 73701 | Oil & Gas Operator | Feb 2024 |
| 7 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Dec 2023 |
| 8 | United Oil Corporation | Denver, CO 80202-3813 | Oil & Gas Operator | Jan 2024 |
| 9 | United Production Company LLC | Edmond, OK 73083-5348 | Oil & Gas Operator | Feb 2024 |
| 10 | Uptex Operating, L.P. | Dallas, TX 75201 | Oil & Gas Operator | May 2010 |
| 11 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Apr 2024 |
| 12 | Usedc Okc LLC | | Oil & Gas Operator | May 2018 |