| 1 | T & B Resources | | Oil & Gas Operator | Jul 1990 |
| 2 | T. N. T. Inc. | | Oil & Gas Operator | Jan 1987 |
| 3 | Tabco Exploration Inc. | New Orleans, LA 70131 | Oil & Gas Operator | Dec 1998 |
| 4 | Tabco Producing Co. | | Oil & Gas Operator | Jan 1998 |
| 5 | Tadlock Properites | | Oil & Gas Operator | Jan 1994 |
| 6 | Targa Midstream Services LLC | Houston, TX 77002 | Oil Operator | Mar 2023 |
| 7 | Teal Petroleum Co. | | Oil & Gas Operator | Sep 1978 |
| 8 | Tee Operating Company | | Oil & Gas Operator | Jun 1989 |
| 9 | Telico Minerals, L.L.C. | | Oil & Gas Operator | Oct 2019 |
| 10 | Tenneco Oil Company | Oklahoma City, OK 73125 | Oil & Gas Operator | Jul 2025 |
| 11 | Tennessee Gas Pipeline Company | | Oil & Gas Operator | Dec 2011 |
| 12 | Tennessee Gas Pipeline Company, LLC | Houston, TX 77002 | Oil Operator | Dec 2024 |
| 13 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 14 | Terra Resources, Inc. | Casper, WY 82601 | Oil & Gas Operator | Jun 1990 |
| 15 | Terrier Oil Company | | Oil & Gas Operator | Feb 2015 |
| 16 | Texaco Inc | Kingfisher, OK 73750 | Oil & Gas Operator | Dec 2017 |
| 17 | Texas Meridian Res. Expl., Inc. | Houston, TX 77079 | Oil & Gas Operator | Jun 1998 |
| 18 | Texas Pacific Oil Company Inc. | | Oil & Gas Operator | Dec 1980 |
| 19 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Oct 2025 |
| 20 | The Exploration Co. Of La, Inc | | Oil & Gas Operator | Nov 1987 |
| 21 | The Meridian Res. & Exp. LLC | | Oil & Gas Operator | Sep 2010 |
| 22 | The Petroleum Corp Of Delaware | | Oil & Gas Operator | May 1991 |
| 23 | Three S & T Oil Co., Inc. | | Oil & Gas Operator | May 1985 |
| 24 | Three Sisters Investments, LTD | | Oil & Gas Operator | Oct 1989 |
| 25 | Toce Energy, L.L.C. | | Oil & Gas Operator | Dec 2017 |
| 26 | Toce Oil Company | | Oil & Gas Operator | Dec 2014 |
| 27 | Tom West | | Oil & Gas Operator | Nov 1989 |
| 28 | Torrid Energy Company | | Oil & Gas Operator | Jun 1988 |
| 29 | Total Minatome Corporation | Houston, TX 77210 | Oil & Gas Operator | Dec 1998 |
| 30 | Traillour Oil Co. | | Oil & Gas Operator | Mar 1990 |
| 31 | Transcontinental Gas P/L Corp. | | Oil & Gas Operator | Dec 2009 |
| 32 | Transcontinental Gas Pipeline Co LLC | | Oil Operator | Jan 2025 |
| 33 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 34 | Transworld Expl. & Prod., Inc. | | Oil & Gas Operator | Mar 2004 |
| 35 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Oct 2025 |
| 36 | Tri Investment Company | | Oil Operator | Mar 1980 |
| 37 | Tri-Production Company | | Oil Operator | Apr 1994 |
| 38 | Tribal Oil Company | | Oil & Gas Operator | Dec 1981 |
| 39 | Trunkline Gas Company | | Oil Operator | Mar 2008 |
| 40 | Tryvest, Inc. | | Oil & Gas Operator | Sep 1991 |
| 41 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Oct 2025 |
| 42 | Tundra Energy | | Oil Operator | Jan 2025 |
| 43 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 44 | TXP Operating Company | | Oil & Gas Operator | Jul 1992 |