| 1 | T & F Oil Company, LLC | | Oil Operator | Oct 2011 |
| 2 | T, F & B Oil Company, LLC | | Oil Operator | Jan 2013 |
| 3 | Tarpon Oil Of Texas | | Oil & Gas Operator | Aug 1994 |
| 4 | Taurus Petr-Fieldcrest Petr | | Oil & Gas Operator | Apr 1989 |
| 5 | Taylor Energy Co. | | Oil & Gas Operator | May 1991 |
| 6 | Team Operating, L.L.C. | Pinehurst, TX 77362 | Oil & Gas Operator | Jun 2025 |
| 7 | Tee Operating Company | | Oil & Gas Operator | Jun 1989 |
| 8 | Tempest Oil Company, Inc. | | Oil & Gas Operator | Jul 1978 |
| 9 | Templeton Energy Inc | | Oil & Gas Operator | Jul 1987 |
| 10 | Tenneco Ventures Corporation | | Oil & Gas Operator | Feb 1996 |
| 11 | Tennessee Gas Pipeline Company | | Oil & Gas Operator | Dec 2011 |
| 12 | Terra Resources, Inc. | Casper, WY 82601 | Oil & Gas Operator | Jun 1990 |
| 13 | Terrier Oil Company | | Oil & Gas Operator | Feb 2015 |
| 14 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Jun 2025 |
| 15 | Texaco Inc | Kingfisher, OK 73750 | Oil & Gas Operator | Dec 2017 |
| 16 | Texaco Inc & A.C. Glassell Jr | | Oil & Gas Operator | Aug 1980 |
| 17 | Texas Crude, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 1995 |
| 18 | Texas Crude-Wainoco-Hilliard | | Oil & Gas Operator | Jul 1978 |
| 19 | Texas Eastern Transm. Corp. | | Oil & Gas Operator | Dec 2002 |
| 20 | Texas Ind. Exploration, Inc. | | Oil & Gas Operator | Oct 2001 |
| 21 | Texas Meridian Res. Expl., Inc. | Houston, TX 77079 | Oil & Gas Operator | Jun 1998 |
| 22 | Texas Pacific Oil Company Inc. | | Oil & Gas Operator | Dec 1980 |
| 23 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Jun 2025 |
| 24 | TGX Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2004 |
| 25 | Tharp Operating Company | Houston, TX 77070 | Oil & Gas Operator | Nov 2014 |
| 26 | The Ballard & Cordell Corp | | Oil & Gas Operator | Feb 1982 |
| 27 | The Dow Chemical Company | | Oil & Gas Operator | Dec 1997 |
| 28 | The Exploration Co. Of La, Inc | | Oil & Gas Operator | Nov 1987 |
| 29 | The Meridian Res. & Exp. LLC | | Oil & Gas Operator | Sep 2010 |
| 30 | The Meridian Resource & Exp Co | | Oil & Gas Operator | Dec 2000 |
| 31 | The Stone Oil Corporation | | Oil & Gas Operator | May 1985 |
| 32 | The Superior Oil Co - Tesoro | | Oil & Gas Operator | Apr 1986 |
| 33 | The WM G Helis Company, L.L.C. | | Oil & Gas Operator | Nov 2003 |
| 34 | Thomas C. Hoffpauir | | Oil & Gas Operator | Mar 1991 |
| 35 | Thomas C. Hoffpauir, Inc. | | Oil & Gas Operator | Jan 1981 |
| 36 | Thrall Texas Oil, LLC | | Oil & Gas Operator | Jan 2025 |
| 37 | Toce Energy, L.L.C. | | Oil & Gas Operator | Dec 2017 |
| 38 | Todd Oil Corp. Of La. Inc. | | Oil & Gas Operator | Jul 2000 |
| 39 | Tom Brown Inc | Denver, CO 80202 | Oil & Gas Operator | Dec 2004 |
| 40 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 41 | Total Minatome Corporation | Houston, TX 77210 | Oil & Gas Operator | Dec 1998 |
| 42 | Touchstone Properties, Inc. | | Oil Operator | Mar 1988 |
| 43 | Transcontinental Gas P/L Corp. | | Oil & Gas Operator | Dec 2009 |
| 44 | Transcontinental Oil Corp. | | Oil & Gas Operator | Sep 1985 |
| 45 | Transworld Expl. & Prod., Inc. | | Oil & Gas Operator | Mar 2004 |
| 46 | Tri Investment Company | | Oil Operator | Mar 1980 |
| 47 | Tricentrol Resources Inc | Englewood, CO 80111 | Oil & Gas Operator | Jun 1984 |
| 48 | Tripower Resources, Inc. | Ardmore, OK 73402 | Oil & Gas Operator | Mar 2020 |
| 49 | Triumph Energy, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Nov 2015 |
| 50 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 51 | TXP Operating Company | | Oil & Gas Operator | Jul 1992 |