| Company Name | Company Location | Company Type | Most Recent Production | |
|---|---|---|---|---|
| 1 | U S Exploraton Liq Trust | Oil & Gas Operator | Oct 1994 | |
| 2 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 3 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 4 | Ultramar Production Company | Oil & Gas Operator | Dec 1991 | |
| 5 | Union Exploration Partners, LTD. | Oil & Gas Operator | Aug 1990 | |
| 6 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 7 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 8 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 9 | United Gas Pipe Line Co. | Oil Operator | Aug 1993 | |
| 10 | Unocal Exploration Corporation | Oil & Gas Operator | May 1992 | |
| 11 | Upstream Exploration LLC | Metairie, LA 70002 | Oil & Gas Operator | Jan 2020 |