| 1 | T. K. Stanley, Inc. | | Oil & Gas Operator | Jul 1982 |
| 2 | Taurus Exploration, Inc. | | Oil & Gas Operator | Jul 2025 |
| 3 | TC3 Operating Co. | Dallas, TX 75248 | Oil & Gas Operator | Jul 1996 |
| 4 | Tecton Energy Operating LLC | | Oil Operator | Apr 2009 |
| 5 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 6 | Terra Resources, Inc. | Casper, WY 82601 | Oil & Gas Operator | Jun 1990 |
| 7 | Tesoro Petroleum Corporation | | Oil & Gas Operator | May 1982 |
| 8 | Texaco Inc | Kingfisher, OK 73750 | Oil & Gas Operator | Dec 2017 |
| 9 | Texaco Producing Inc. | Rock Springs, WY 82901 | Oil & Gas Operator | Dec 2000 |
| 10 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Oct 2025 |
| 11 | Tidelands Resources, Inc. | | Gas Operator | Oct 1990 |
| 12 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 13 | Tre'J Exploration, Inc. | | Gas Operator | Dec 1991 |
| 14 | Triangle Operating Co., Inc. | | Gas Operator | Jan 2000 |
| 15 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Oct 2025 |
| 16 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |