| 1 | Abraxas Petroleum Corporation | San Antonio, TX 78259 | Oil & Gas Operator | Feb 2026 |
| 2 | Adairco LLC | Fort Collins, CO 80525 | Oil & Gas Operator | Feb 2010 |
| 3 | Advanced Recovery Services Co | Denver, CO 80265 | Oil & Gas Operator | Apr 2007 |
| 4 | Aexco Petroleum Inc | Denver, CO 80202 | Oil & Gas Operator | Nov 2025 |
| 5 | Allen And Crouch | Casper, WY 82602 | Oil & Gas Operator | Mar 2020 |
| 6 | American Eagle Oil | Casper, WY 82605 | Oil & Gas Operator | Dec 2012 |
| 7 | American Exploration Company | Houston, TX 77010 | Oil & Gas Operator | Jan 2000 |
| 8 | Anadarko E&P Onshore LLC | Houston, TX 77046 | Oil & Gas Operator | Feb 2026 |
| 9 | Anadarko Petroleum Corporation | Houston, TX 77251 | Oil & Gas Operator | Nov 2025 |
| 10 | Anchor Bay Corporation | Denver, CO 80202 | Oil & Gas Operator | Jun 2007 |
| 11 | Anderson Management Company | Gillette, WY 82716 | Oil & Gas Operator | May 2016 |
| 12 | Anderson Oil Company | Burkburnett, TX 76354 | Oil & Gas Operator | Dec 2015 |
| 13 | Anr Production Company | Houston, TX 77046 | Oil & Gas Operator | Aug 2017 |
| 14 | Anschutz Corporation | Denver, CO 80202 | Oil & Gas Operator | Sep 2016 |
| 15 | Anschutz Exploration Corporation | Denver, CO 80202 | Oil & Gas Operator | Feb 2026 |
| 16 | Anschutz Oil Company LLC | Denver, CO 80202 | Oil & Gas Operator | Sep 2020 |
| 17 | Ant Hills Production | Lusk, WY 82225 | Oil & Gas Operator | Jul 2025 |
| 18 | Antelope Energy Company LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2024 |
| 19 | Apache Corporation | Houston, TX 77042 | Oil & Gas Operator | Feb 2026 |
| 20 | Arjay Oil Company | Salt Lake City, UT 84110 | Oil & Gas Operator | May 2000 |
| 21 | Ashland Exploration | | Oil & Gas Operator | May 1979 |
| 22 | Atlantic Oil Corporation | Denver, CO 80206 | Oil & Gas Operator | Dec 1982 |
| 23 | Atlantic Richfield Company | Plano, TX 75074 | Oil & Gas Operator | Dec 2016 |
| 24 | Avalon Energy Corporation | | Oil & Gas Operator | Jul 1990 |
| 25 | Aztec Gas And Oil Corporation | Elephant Butte, NM 87935-0370 | Oil & Gas Operator | Mar 2005 |