| 301 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | Mar 2025 |
| 302 | Texas Western Energy Corporation | Portland, TX 78374 | Oil & Gas Operator | Nov 2002 |
| 303 | Texas, Les & Co. | Austin, TX 78746 | Oil & Gas Operator | Mar 2025 |
| 304 | Thorp Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2014 |
| 305 | Tiza Energy, Inc. | Austin, TX 78715 | Oil & Gas Operator | Mar 2025 |
| 306 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Mar 2025 |
| 307 | Trident Corporation | Woodsboro, TX 78393 | Oil & Gas Operator | Mar 2025 |
| 308 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 309 | Tsoco | Tuleta, TX 78162 | Oil & Gas Operator | Apr 2017 |
| 310 | Tuthill & Barbee | Amarillo, TX 79101 | Oil & Gas Operator | Nov 1994 |
| 311 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 312 | Unknown | Houston, TX 77208 | Oil & Gas Operator | Dec 2022 |
| 313 | Valence Operating Company | Kingwood, TX 77339 | Oil & Gas Operator | Mar 2025 |
| 314 | Valerius, Inc. & Zine, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Jul 1994 |
| 315 | Valerius, Robert D. Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Aug 2003 |
| 316 | Ventex Operating Corp. | Addison, TX 75001 | Oil & Gas Operator | Mar 2025 |
| 317 | Viola Prod., Inc. | Dallas, TX 75251 | Oil & Gas Operator | Mar 2025 |
| 318 | Wagner, Duer & Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Jan 1999 |
| 319 | Wallis Energy, Inc. | Austin, TX 78746 | Oil & Gas Operator | Mar 2025 |
| 320 | Whitehall Operating Inc. | Houston, TX 77040 | Oil & Gas Operator | Nov 1994 |
| 321 | Whitson, James A., Jr. | Houston, TX 77063 | Oil & Gas Operator | Nov 2011 |
| 322 | Whittier Operating Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2007 |
| 323 | Wild Cat Operating Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 324 | Wilmoth Interests, Inc. | Marion Center, PA 15759 | Oil & Gas Operator | Dec 2024 |
| 325 | Wiser Oil Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2018 |
| 326 | Wofford, C. J. | El Campo, TX 77437 | Oil & Gas Operator | Mar 2025 |
| 327 | Yordes Energy, LLC | El Campo, TX 77437 | Oil Operator | Mar 2025 |