| 1 | U S Drilling Company Inc | Holdenville, OK 74848-0913 | Oil & Gas Operator | Mar 2017 |
| 2 | U. S. Energy Development Corporation | Fort Worth, TX 76164 | Oil & Gas Operator | May 2026 |
| 3 | U.S. Oil Reclaimers, LLC | | Oil Operator | Jun 2023 |
| 4 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 5 | Umberham Oil Company Inc | Oklahoma City, OK 73151-4000 | Oil & Gas Operator | Feb 2026 |
| 6 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 7 | Unbridled Resources, LLC | Oklahoma City, OK 73102 | Oil & Gas Operator | May 2026 |
| 8 | Underwood Oil And Gas LLC | Chandler, OK 74834-1414 | Oil & Gas Operator | Feb 2026 |
| 9 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 10 | Union Texas Petroleum Corp | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 11 | Union Valley Petroleum Corp | Enid, OK 73701 | Oil & Gas Operator | Feb 2026 |
| 12 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Dec 2025 |
| 13 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | May 2026 |
| 14 | United Energy & Expl Inc | Ada, OK 74821-2449 | Oil & Gas Operator | Feb 2026 |
| 15 | United Energy & Exploration LLC | Ada, OK 74821 | Oil & Gas Operator | Feb 2026 |
| 16 | United Energy Develop Co LTD | Bartlesville, OK 74003 | Oil Operator | Mar 2004 |
| 17 | United Energy Operating, LLC | Edmond, OK 73083 | Oil & Gas Operator | May 2026 |
| 18 | United Oil Corporation | Denver, CO 80202-3813 | Oil & Gas Operator | Jan 2026 |
| 19 | United Primary Resources Inc | Milton, WA 98354-9361 | Oil & Gas Operator | Feb 2016 |
| 20 | United Producers Inc | Broken Arrow, OK 74012-8247 | Oil & Gas Operator | Mar 2020 |
| 21 | United Production Company LLC | Edmond, OK 73003 | Oil & Gas Operator | Feb 2026 |
| 22 | United States Gypsum Company | Oakfield, NY 14125 | Oil & Gas Operator | Dec 2024 |
| 23 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | May 2026 |
| 24 | Universal Drilling Company | Denver, CO 80203 | Oil & Gas Operator | Sep 2003 |
| 25 | Universal Exploration Inc | Wadsworth, OH 44281-9460 | Oil & Gas Operator | Feb 2012 |
| 26 | Universal Fuels Company | | Oil & Gas Operator | Oct 1993 |
| 27 | Upland Operating, LLC | Dallas, TX 75226 | Oil & Gas Operator | May 2026 |
| 28 | Upland Production Company | Edmond, OK 73083 | Oil & Gas Operator | May 2026 |
| 29 | Upland Resources, Inc. | Canadian, TX 79014 | Oil & Gas Operator | Dec 2009 |
| 30 | Uplands Resources Inc | Tulsa, OK 74103-4141 | Oil & Gas Operator | Feb 2026 |
| 31 | Uptex Operating, L.P. | Dallas, TX 75201 | Oil & Gas Operator | May 2010 |
| 32 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | May 2026 |
| 33 | Usedc Okc LLC | Getzville, NY 14068-1296 | Oil & Gas Operator | May 2018 |