| 1 | Acadian Gas Pipeline System | | Oil Operator | Jan 2025 |
| 2 | Ada Oil Exploration Corp | | Oil & Gas Operator | Jan 1986 |
| 3 | Adams Resources Expl. Corp. | Houston, TX 77001 | Oil & Gas Operator | Apr 2020 |
| 4 | Addison Resources Inc. | | Oil & Gas Operator | Jul 1998 |
| 5 | Alfred C. Glassell, Jr. | | Oil & Gas Operator | Apr 2007 |
| 6 | Alliance Exploration Corp. | | Oil & Gas Operator | Mar 1983 |
| 7 | Alliance Resources (USA), Inc. | | Oil & Gas Operator | Oct 2002 |
| 8 | Alpine Expl. Companies, Inc. | | Oil & Gas Operator | Jan 2024 |
| 9 | Amax Oil & Gas Inc | Fort Worth, TX 76107 | Oil & Gas Operator | Nov 2014 |
| 10 | Amerada Hess Corporation | Houston, TX 77252 | Oil & Gas Operator | Aug 2013 |
| 11 | American Exploration Company | Houston, TX 77010 | Oil & Gas Operator | Jan 2000 |
| 12 | American Exploration Oper. Co. | | Oil & Gas Operator | May 1990 |
| 13 | American Explorer, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Jan 1999 |
| 14 | American Petrofina Co Of Texas | | Oil & Gas Operator | Jun 1985 |
| 15 | Americus Resources, Inc. | | Oil & Gas Operator | Feb 1993 |
| 16 | Aminoil Of Louisiana, Inc. | | Oil & Gas Operator | Dec 1981 |
| 17 | Aminoil USA Inc | | Oil & Gas Operator | Jan 1985 |
| 18 | Amoco Production Co. | Houston, TX 77253 | Oil & Gas Operator | Jun 2015 |
| 19 | Apache Corporation | Houston, TX 77042 | Oil & Gas Operator | Oct 2025 |
| 20 | Araxas Exploration, Inc. | The Woodlands, TX 77380 | Oil & Gas Operator | Apr 1998 |
| 21 | Arco O & G Co-Div Atl Rich Co | | Oil & Gas Operator | Feb 1994 |
| 22 | Aroc (Texas) Inc | Houston, TX 77090 | Oil & Gas Operator | Dec 2014 |
| 23 | Arrowhead Energy Expl, LLC | | Oil & Gas Operator | May 2013 |
| 24 | Arrowhead Enterprises, Inc. | Baton Rouge, LA 70816 | Oil & Gas Operator | Apr 2001 |
| 25 | Ascent Energy, Inc | McKinney, TX 75069 | Oil & Gas Operator | Nov 2008 |
| 26 | Ashlawn Corporation | | Oil & Gas Operator | Dec 2008 |
| 27 | Aspect Energy, LLC | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 28 | Aspen Exploration | | Oil & Gas Operator | Jan 1983 |
| 29 | Atc Realty Eight, Inc. | | Oil & Gas Operator | Nov 1988 |
| 30 | Atinum Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 31 | Azimuth Energy, LLC | Denver, CO 80203 | Oil & Gas Operator | Sep 2006 |
| 32 | Aztec Oil & Gas Company | | Oil & Gas Operator | Mar 1978 |