| 301 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 302 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 303 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Apr 2024 |
| 304 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |
| 305 | Unocal Exploration Corporation | Houston, TX 77001 | Oil & Gas Operator | May 1992 |
| 306 | Upstream Exploration LLC | Metairie, LA 70002 | Oil & Gas Operator | Jan 2020 |
| 307 | Us Oil & Gas Inc | Marietta, OH 45750 | Oil & Gas Operator | Feb 2024 |
| 308 | Vermilion Bay Land Co. | | Oil & Gas Operator | Dec 1994 |
| 309 | Vermilion Resources, Inc. | Houston, TX 77060 | Oil & Gas Operator | Sep 2009 |
| 310 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Jan 2024 |
| 311 | Volvo Petroleum, Inc. | | Oil & Gas Operator | Jul 1984 |
| 312 | Vonco Of Mississippi, Inc. | | Oil Operator | Jan 2024 |
| 313 | W. B. McCarter, Jr., Inc. | | Oil & Gas Operator | Dec 1995 |
| 314 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2024 |
| 315 | Walter T. Lanaux | | Oil & Gas Operator | Nov 1990 |
| 316 | Weaver Exploration Company | | Oil & Gas Operator | Jun 1991 |
| 317 | Will-Drill Production Co., Inc. | Shreveport, LA 71105 | Oil & Gas Operator | Apr 2024 |
| 318 | Williams-Cody, Inc. | Houston, TX 77060 | Oil & Gas Operator | May 1994 |
| 319 | Wle, Inc. | | Oil & Gas Operator | Feb 2012 |
| 320 | Woolf & Magee, Inc. | | Oil & Gas Operator | Oct 1991 |
| 321 | WRT Energy Corporation | Oklahoma City, OK 73118 | Oil & Gas Operator | May 1998 |
| 322 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Apr 2024 |
| 323 | Zilkha Energy Company | Houston, TX 77046 | Oil & Gas Operator | Oct 2002 |