| 1 | Adco Producing Company | | Oil & Gas Operator | Mar 1989 |
| 2 | Adobe Resources Corporation | Midland, TX 79701 | Oil & Gas Operator | Aug 2002 |
| 3 | Alliance Operating Corporation | | Oil & Gas Operator | Jan 1995 |
| 4 | Alpine Expl. Companies, Inc. | | Oil & Gas Operator | Jan 2024 |
| 5 | Amax Oil & Gas Inc | Fort Worth, TX 76107 | Oil & Gas Operator | Nov 2014 |
| 6 | Amax Petroleum Corporation | Houston, TX 77042 | Oil & Gas Operator | Dec 2012 |
| 7 | Amerada Hess Corporation | Houston, TX 77252 | Oil & Gas Operator | Aug 2013 |
| 8 | American Petrofina Co Of Texas | | Oil & Gas Operator | Jun 1985 |
| 9 | Americus Resources, Inc. | | Oil & Gas Operator | Feb 1993 |
| 10 | Aminoil Of Louisiana, Inc. | | Oil & Gas Operator | Dec 1981 |
| 11 | Aminoil USA Inc | | Oil & Gas Operator | Jan 1985 |
| 12 | Amoco Production Co. | Houston, TX 77253 | Oil & Gas Operator | Jun 2015 |
| 13 | Anadarko E&P Company LP | Houston, TX 77251 | Oil & Gas Operator | Aug 2014 |
| 14 | Anadarko Petroleum Corporation | Houston, TX 77251 | Oil & Gas Operator | Jul 2025 |
| 15 | Antara Resources Inc | Houston, TX 77002 | Oil & Gas Operator | Apr 2004 |
| 16 | Apache Corporation | Houston, TX 77042 | Oil & Gas Operator | Oct 2025 |
| 17 | Aran Energy USA Inc. | | Oil & Gas Operator | Apr 1997 |
| 18 | Araxas Exploration, Inc. | The Woodlands, TX 77380 | Oil & Gas Operator | Apr 1998 |
| 19 | Arco O & G Co-Div Atl Rich Co | | Oil & Gas Operator | Feb 1994 |
| 20 | Arkla Exploration Co. | Shreveport, LA 71151 | Oil & Gas Operator | Jan 1993 |
| 21 | Ashlawn Energy, Inc. | | Oil & Gas Operator | Jul 1995 |
| 22 | Atlas Production Services | | Oil & Gas Operator | Feb 1999 |
| 23 | Atp Oil & Gas Corporation | Houston, TX 77027 | Oil & Gas Operator | Jun 2008 |
| 24 | Aviara Energy Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2002 |
| 25 | Aviva America, Inc. | | Oil & Gas Operator | Nov 2013 |