| 1 | T & M Gauging | | Oil Operator | Oct 2006 |
| 2 | Tabco Exploration Inc. | New Orleans, LA 70131 | Oil & Gas Operator | Dec 1998 |
| 3 | Tammany Oil & Gas LLC | | Oil & Gas Operator | Feb 2005 |
| 4 | Targa Midstream Services LLC | Houston, TX 77002 | Oil Operator | Mar 2023 |
| 5 | Tarpon Oil Of Texas | | Oil & Gas Operator | Aug 1994 |
| 6 | Taurus Petr-Fieldcrest Petr | | Oil & Gas Operator | Apr 1989 |
| 7 | Taurus Petroleum | | Oil & Gas Operator | Jul 1987 |
| 8 | Tee Operating Company | | Oil & Gas Operator | Jun 1989 |
| 9 | Tellus Operating Group, LLC | | Oil & Gas Operator | Jun 2025 |
| 10 | Tenneco Inc. | | Oil & Gas Operator | Jun 1989 |
| 11 | Terra Resources, Inc. | Casper, WY 82601 | Oil & Gas Operator | Jun 1990 |
| 12 | Terrier Oil Company | | Oil & Gas Operator | Feb 2015 |
| 13 | Tesla Resources, Inc. | | Oil & Gas Operator | Aug 1996 |
| 14 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Oct 2025 |
| 15 | Texaco Producing Inc. | Rock Springs, WY 82901 | Oil & Gas Operator | Dec 2000 |
| 16 | Texas Crude, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 1995 |
| 17 | Texas Eastern Transm. Corp. | | Oil & Gas Operator | Dec 2002 |
| 18 | Texas Gas Exploration Corp. | | Oil & Gas Operator | Nov 1986 |
| 19 | Texas Gas Transmission Corp. | | Oil Operator | Aug 2003 |
| 20 | Texas Gas Transmission LLC | Owensboro, KY 42301 | Oil & Gas Operator | Dec 2024 |
| 21 | Texas Meridian Operating Co. Inc | Houston, TX 77079 | Oil & Gas Operator | Oct 1993 |
| 22 | Texas Pacific Oil Company Inc. | | Oil & Gas Operator | Dec 1980 |
| 23 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Oct 2025 |
| 24 | Texasgulf Inc. | Newgulf, TX 77462 | Oil & Gas Operator | Jul 1994 |
| 25 | The Bering Company | | Oil Operator | Jul 1979 |
| 26 | The Petroleum Corp Of Delaware | | Oil & Gas Operator | May 1991 |
| 27 | The Southern Louisiana Expl. Company LLC | | Oil & Gas Operator | Nov 2024 |
| 28 | The Stone Oil Corporation | | Oil & Gas Operator | May 1985 |
| 29 | Thrall Texas Oil, LLC | | Oil & Gas Operator | Jan 2025 |
| 30 | Three D Petroleum LLC | | Oil Operator | Dec 2024 |
| 31 | Three S & T Oil Co., Inc. | | Oil & Gas Operator | May 1985 |
| 32 | Tideland Industries, Inc. | | Oil & Gas Operator | Dec 1989 |
| 33 | Tideway Oil Programs, Inc. | | Oil & Gas Operator | Oct 1980 |
| 34 | Tiger Petroleum | | Oil Operator | Sep 2002 |
| 35 | Tigner Walker | | Oil & Gas Operator | Dec 2021 |
| 36 | Tillman J. McIntyre | | Oil Operator | Dec 1987 |
| 37 | Toce Energy, L.L.C. | | Oil & Gas Operator | Dec 2017 |
| 38 | Torch Energy Services, Inc. | Houston, TX 77010 | Oil & Gas Operator | Sep 2011 |
| 39 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 40 | Total Minatome Corporation | Houston, TX 77210 | Oil & Gas Operator | Dec 1998 |
| 41 | Trace Operators, Inc. | | Oil & Gas Operator | Nov 2024 |
| 42 | Trafalgar House Oil & Gas Inc. | Houston, TX 77002-7346 | Oil & Gas Operator | Jan 1992 |
| 43 | Trans Ocean Oil, Inc. | | Oil & Gas Operator | Sep 1980 |
| 44 | Transcontinental Oil Corp. | | Oil & Gas Operator | Sep 1985 |
| 45 | Tri-Union Development Corp. | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 46 | Triad Energy Corp. Of Texas | Houston, TX 77057-2696 | Oil & Gas Operator | Sep 2014 |
| 47 | Trinity Resources, Inc. | Houston, TX 77277 | Oil & Gas Operator | May 2020 |
| 48 | Triumph Energy, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Nov 2015 |
| 49 | Two Bayous, Inc. | | Oil & Gas Operator | Dec 2024 |
| 50 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |