| 1 | Tesoro Expl. & Prod. Company | San Antonio, TX 78216 | Gas Operator | Sep 2010 |
| 2 | Texas Fuel Company | Galveston, TX 77550 | Oil & Gas Operator | Oct 2025 |
| 3 | Texas Secondary Oil Corporation | Devine, TX 78016 | Oil & Gas Operator | Oct 2025 |
| 4 | Texokan Operating, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Oct 2025 |
| 5 | Thalmann Oil Field Service, Inc. | Carrizo SPGS, TX 78834 | Oil & Gas Operator | Mar 2008 |
| 6 | Thalmann, David Vac Service Inc | Carrizo SPGS, TX 78834 | Oil & Gas Operator | Oct 2025 |
| 7 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Oct 2025 |
| 8 | Tidelands Gas Corporation | Flower Mound, TX 75028 | Oil & Gas Operator | Sep 2000 |
| 9 | Tidelands Oil Corporation | Crystal City, TX 78839 | Oil & Gas Operator | Aug 2003 |
| 10 | Touchstone Resources USA, Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2006 |
| 11 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 12 | Txco Resources Inc. | San Antonio, TX 78280 | Oil & Gas Operator | Oct 2025 |