| 1 | T.O.I. | Midland, TX 79710 | Oil & Gas Operator | Mar 2001 |
| 2 | Talos Third Coast LLC | | Oil & Gas Operator | Dec 2024 |
| 3 | Tebco Oil & Gas | | Oil & Gas Operator | Sep 1996 |
| 4 | Tee Operating Company | | Oil & Gas Operator | Jun 1989 |
| 5 | Tellus Operating Group, LLC | | Oil & Gas Operator | Jun 2025 |
| 6 | Tenneco Oil Company | Oklahoma City, OK 73125 | Oil & Gas Operator | Jul 2025 |
| 7 | Tesla Resources, Inc. | | Oil & Gas Operator | Aug 1996 |
| 8 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Oct 2025 |
| 9 | Texaco Inc | Kingfisher, OK 73750 | Oil & Gas Operator | Dec 2017 |
| 10 | Texaco Producing Inc. | Rock Springs, WY 82901 | Oil & Gas Operator | Dec 2000 |
| 11 | Texas Crude Exploration, Inc. | Fort Worth, TX 76116 | Oil & Gas Operator | Aug 1992 |
| 12 | Texas Energy & Environmental Inc | Houston, TX 77269 | Oil & Gas Operator | Oct 1998 |
| 13 | Texas Gas Transmission Corp. | | Oil Operator | Aug 2003 |
| 14 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Oct 2025 |
| 15 | Texasgulf Inc. | Newgulf, TX 77462 | Oil & Gas Operator | Jul 1994 |
| 16 | The Ballard & Cordell Corp | | Oil & Gas Operator | Feb 1982 |
| 17 | The Harvest Group, LLC | | Oil & Gas Operator | May 2011 |
| 18 | The Meridian Res. & Exp. LLC | | Oil & Gas Operator | Sep 2010 |
| 19 | The Stone Oil Corporation | | Oil & Gas Operator | May 1985 |
| 20 | TMR Exploration, Inc. | Bossier City, LA 71171 | Oil & Gas Operator | Oct 2025 |
| 21 | Tortuga Operating Company | Houston, TX 77055 | Oil & Gas Operator | Oct 2025 |
| 22 | Total Minatome Corporation | Houston, TX 77210 | Oil & Gas Operator | Dec 1998 |
| 23 | Triumph Energy, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Nov 2015 |
| 24 | Trunkline Gas Company | | Oil Operator | Mar 2008 |
| 25 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Oct 2025 |