| 1 | Agip Petroleum Co., Inc. | | Oil & Gas Operator | Jan 2003 |
| 2 | Aldine Oil And Gas, LP | Houston, TX 77060 | Oil & Gas Operator | Oct 2025 |
| 3 | Alegre Energy, Inc. | San Antonio, TX 78216 | Oil & Gas Operator | Oct 2025 |
| 4 | Alliance Operating Corporation | | Oil & Gas Operator | Jan 1995 |
| 5 | Alltex Exploration, Inc. | Houston, TX 77056 | Oil & Gas Operator | Oct 2025 |
| 6 | Alpine Energy, Inc. | | Oil & Gas Operator | Dec 1999 |
| 7 | Alpine Expl. Companies, Inc. | | Oil & Gas Operator | Jan 2024 |
| 8 | Amax Petroleum Corporation | Houston, TX 77042 | Oil & Gas Operator | Dec 2012 |
| 9 | Amerada Hess Corporation | Houston, TX 77252 | Oil & Gas Operator | Aug 2013 |
| 10 | American Exploration Company | Houston, TX 77010 | Oil & Gas Operator | Jan 2000 |
| 11 | American Petrofina Co Of Texas | | Oil & Gas Operator | Jun 1985 |
| 12 | American Quasar Petroleum Co. | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2014 |
| 13 | Amoco Production Co. | Houston, TX 77253 | Oil & Gas Operator | Jun 2015 |
| 14 | Anadarko Petroleum Corporation | Houston, TX 77251 | Oil & Gas Operator | Jul 2025 |
| 15 | Anderson Exploration Co., Inc. | | Oil & Gas Operator | Sep 2023 |
| 16 | Anderson Producing, Inc. | Houston, TX 77057 | Oil & Gas Operator | Sep 2013 |
| 17 | Anglo Production Company | | Oil & Gas Operator | Nov 1983 |
| 18 | Anr Pipeline Company | | Oil & Gas Operator | Jan 2025 |
| 19 | Anr Production Company | Houston, TX 77046 | Oil & Gas Operator | Aug 2017 |
| 20 | Apache Corporation | Houston, TX 77042 | Oil & Gas Operator | Oct 2025 |
| 21 | Apache Shelf, Inc. | Houston, TX 77056 | Oil & Gas Operator | Jan 2014 |
| 22 | Apexco-McCormick-Coastal | | Oil & Gas Operator | Dec 1977 |
| 23 | Apollo Energy Operating Co, LP | Lake Charles, LA 70601 | Oil & Gas Operator | Dec 2024 |
| 24 | Apollo Energy Operating, LP | | Oil & Gas Operator | Mar 2011 |
| 25 | Araxas Exploration, Inc. | The Woodlands, TX 77380 | Oil & Gas Operator | Apr 1998 |
| 26 | Arco O & G Co-Div Atl Rich Co | | Oil & Gas Operator | Feb 1994 |
| 27 | Ashland Exploration Inc | Houston, TX 77218 | Oil & Gas Operator | Nov 2000 |
| 28 | Aspect Energy, LLC | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 29 | Atlantic & Gulf Petroleum Co. | Houston, TX 77002 | Gas Operator | Mar 1991 |
| 30 | Auro USA, Inc. | | Oil Operator | Dec 2024 |
| 31 | Auster Oil And Gas, Inc. | | Oil & Gas Operator | Mar 1989 |
| 32 | Austral Oil Company Incorporated | Sulphur, LA 70663 | Oil & Gas Operator | Mar 2008 |
| 33 | Azimuth Energy, LLC | Denver, CO 80203 | Oil & Gas Operator | Sep 2006 |