| 401 | The Calvert Company | Oklahoma City, OK 73154-1589 | Oil & Gas Operator | Dec 2021 |
| 402 | The Quintin Little Company Inc | Ardmore, OK 73401 | Oil & Gas Operator | Sep 2025 |
| 403 | Thunderbird Drilling, Inc. | Wichita, KS 67207 | Oil Operator | Oct 2008 |
| 404 | Tide West Oil Company | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2021 |
| 405 | Toklan Oil And Gas Corporation | Tulsa, OK 74136 | Oil & Gas Operator | Aug 2025 |
| 406 | Trans Terra Corp., International | Amarillo, TX 79159 | Oil & Gas Operator | Feb 2009 |
| 407 | Travelers Oil Company | Amarillo, TX 79102 | Oil & Gas Operator | Dec 2025 |
| 408 | Tri-Ex Petroleum, L.P. | Amarillo, TX 79101 | Oil & Gas Operator | Jan 2013 |
| 409 | Tritex Production Co. | Iowa Park, TX 76367 | Oil & Gas Operator | Jan 2013 |
| 410 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 411 | Unbridled Resources, LLC | Oklahoma City, OK 73102 | Oil & Gas Operator | Dec 2025 |
| 412 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 413 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Dec 2025 |
| 414 | United Energy Operating, LLC | Edmond, OK 73083 | Oil & Gas Operator | Dec 2025 |
| 415 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 416 | Upland Resources LLC | Canadian, TX 79014 | Oil & Gas Operator | Dec 2025 |
| 417 | Upland Resources, Inc. | Canadian, TX 79014 | Oil & Gas Operator | Dec 2009 |
| 418 | Vaalco Energy (USA), Inc. | Houston, TX 77042 | Oil & Gas Operator | Dec 2016 |
| 419 | Validus Energy II Midcon LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2025 |
| 420 | Vanguard Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Aug 2019 |
| 421 | Vastar Resources Inc | Houston, TX 77253 | Oil & Gas Operator | Jun 2025 |
| 422 | Vega Energy Company | Nichols Hill, OK 73116 | Oil & Gas Operator | Sep 2015 |
| 423 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Aug 2025 |
| 424 | Wagner & Brown, LTD. | Midland, TX 79702 | Oil & Gas Operator | Aug 2014 |
| 425 | Wainoco Oil & Gas Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2005 |
| 426 | Wallace Oil & Gas Inc | Oklahoma City, OK 73156 | Oil & Gas Operator | Dec 2025 |
| 427 | Washita Oil And Gas, L.L.C. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2015 |
| 428 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 429 | Wilbanks Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | May 2002 |
| 430 | Wildhorse Oil & Gas Corporation | Ardmore, OK 73402 | Oil & Gas Operator | May 2019 |
| 431 | Wildhorse Operating Company | Ardmore, OK 73402 | Oil & Gas Operator | Dec 2025 |
| 432 | Williams Production RMT Company | Denver, CO 80202 | Oil & Gas Operator | Oct 2010 |
| 433 | Wilson Energy LLC | Marietta, OH 45750 | Oil & Gas Operator | Dec 2024 |
| 434 | Winright Resources Operating,LLC | Houston, TX 77007 | Oil & Gas Operator | Dec 2025 |
| 435 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2023 |
| 436 | Wolf Creek Exploration Company | Amarillo, TX 79159 | Oil & Gas Operator | Aug 2000 |
| 437 | Wright Aurora Enterprises, LLC | Canyon Lake, TX 78133 | Oil & Gas Operator | May 2020 |
| 438 | Wright Trucking, Inc. | Weatherford, OK 73096 | Oil & Gas Operator | Feb 2019 |
| 439 | Wynn-Crosby Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2005 |
| 440 | Xeric Oil & Gas Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2014 |
| 441 | Zephyr Lone Star Oper Co.,L.L.C. | Oklahoma City, OK 73118 | Oil & Gas Operator | Dec 2025 |