| 1 | Ada Oil Exploration Corp | | Oil & Gas Operator | Jan 1986 |
| 2 | Adams Resources Expl. Corp. | Houston, TX 77001 | Oil & Gas Operator | Apr 2020 |
| 3 | Adobe Resources Corporation | Midland, TX 79701 | Oil & Gas Operator | Aug 2002 |
| 4 | Aegis Energy, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Sep 1998 |
| 5 | All Oil & Gas Inc. | | Oil & Gas Operator | Jul 1989 |
| 6 | Alpine Expl. Companies, Inc. | | Oil & Gas Operator | Jan 2024 |
| 7 | Amarillo Oil Company | | Oil & Gas Operator | Aug 1980 |
| 8 | Amax Oil & Gas Inc | Fort Worth, TX 76107 | Oil & Gas Operator | Nov 2014 |
| 9 | Ambrit Energy Corporation | Garland, TX 75044 | Oil & Gas Operator | Jun 2003 |
| 10 | Amerada Hess Corporation | Houston, TX 77252 | Oil & Gas Operator | Aug 2013 |
| 11 | American Explorer, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Jan 1999 |
| 12 | Amoco Production Co. | Houston, TX 77253 | Oil & Gas Operator | Jun 2015 |
| 13 | Anderson Producing, Inc. | Houston, TX 77057 | Oil & Gas Operator | Sep 2013 |
| 14 | Annco Pet. Co & Equipment, Inc | | Oil & Gas Operator | Sep 1982 |
| 15 | Anr Pipeline Company | Houston, TX 77002 | Oil & Gas Operator | Jan 2025 |
| 16 | Apache Corporation | Houston, TX 77042 | Oil & Gas Operator | Mar 2025 |
| 17 | Apco Oil Corporation | Oklahoma City, OK 73116 | Oil & Gas Operator | Jun 1993 |
| 18 | Arco O & G Co-Div Atl Rich Co | | Oil & Gas Operator | Feb 1994 |
| 19 | Aroc (Texas) Inc | Houston, TX 77090 | Oil & Gas Operator | Dec 2014 |
| 20 | Aspect Energy, LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2025 |
| 21 | Aspen Exploration | | Oil & Gas Operator | Jan 1983 |
| 22 | Atinum Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 23 | Austral Oil & Exploration, Inc | | Oil & Gas Operator | Jun 2004 |
| 24 | Austral Oil Company Incorporated | Sulphur, LA 70663 | Oil & Gas Operator | Mar 2008 |
| 25 | Azimuth Energy, LLC | Denver, CO 80203 | Oil & Gas Operator | Sep 2006 |