| 201 | Arkla Exploration Co. | Shreveport, LA 71151 | Oil & Gas Operator | Jan 1993 |
| 202 | Arkla Petroleum LLC | | Oil & Gas Operator | May 2006 |
| 203 | Arlen Corporation | Houston, TX 77077 | Oil & Gas Operator | Mar 2008 |
| 204 | Arlis Scogin | | Oil Operator | Jul 1985 |
| 205 | Arlis Scogin Et Al | | Oil & Gas Operator | Jan 1990 |
| 206 | Arnaudville Company Inc. | | Oil & Gas Operator | Apr 1995 |
| 207 | Arnold & Assoc-D&D-Coquina | | Oil Operator | Oct 1985 |
| 208 | Aroc (Texas) Inc. | Houston, TX 77090 | Oil & Gas Operator | Dec 2014 |
| 209 | Array Operating, LLC | | Oil & Gas Operator | Mar 2017 |
| 210 | Arrowhead Energy Expl, LLC | | Oil & Gas Operator | May 2013 |
| 211 | Arrowhead Enterprises, Inc. | Baton Rouge, LA 70816 | Oil & Gas Operator | Apr 2001 |
| 212 | Art Machin & Associates, Inc. | | Oil & Gas Operator | Jul 1997 |
| 213 | Arthur Arnold | | Oil Operator | Dec 1991 |
| 214 | Artra Resources Corp. | | Oil & Gas Operator | Sep 1990 |
| 215 | Artzberger-Johnson | | Oil & Gas Operator | Mar 1978 |
| 216 | Arxana Oil & Gas Company, LLC | | Oil & Gas Operator | Jun 1998 |
| 217 | Asa Energy Corp | | Oil & Gas Operator | Jun 1984 |
| 218 | Ascent Energy, Inc | McKinney, TX 75069 | Oil & Gas Operator | Nov 2008 |
| 219 | Ascot Oils, Inc. | | Oil & Gas Operator | Jul 1993 |
| 220 | Ash Exploration, Inc. | | Oil & Gas Operator | Apr 2010 |
| 221 | Ashland Exploration Inc | Houston, TX 77218 | Oil & Gas Operator | Nov 2000 |
| 222 | Ashland Oil, Inc | | Oil & Gas Operator | Dec 2023 |
| 223 | Ashlawn Corporation | | Oil & Gas Operator | Dec 2008 |
| 224 | Ashlawn Energy, Inc. | | Oil & Gas Operator | Jul 1995 |
| 225 | Ashton Oil & Gas, Inc. | | Oil Operator | Jun 1990 |
| 226 | Ashuca | | Oil Operator | Feb 1998 |
| 227 | Aspect Energy, LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2025 |
| 228 | Aspect Resources LLC | Denver, CO 80202 | Oil & Gas Operator | May 2002 |
| 229 | Aspen Exploration | | Oil & Gas Operator | Jan 1983 |
| 230 | Aspen Exploration, Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2012 |
| 231 | Aspen Oil & Gas LLC | | Oil Operator | Jul 2014 |
| 232 | Associated Natural Gas, Inc. | | Oil Operator | Apr 1996 |
| 233 | Atasca Resources, Inc. | Houston, TX 77219 | Oil & Gas Operator | Dec 2025 |
| 234 | Atc Realty Eight, Inc. | | Oil & Gas Operator | Nov 1988 |
| 235 | Atinum Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2025 |
| 236 | Atkins Production | | Oil Operator | Dec 2008 |
| 237 | Atlanta Exploration Co. | | Oil & Gas Operator | Oct 2001 |
| 238 | Atlantic & Gulf Petroleum Co. | Houston, TX 77002 | Gas Operator | Mar 1991 |
| 239 | Atlantic Petroleum Co. | | Oil Operator | Mar 2000 |
| 240 | Atlas Oil Exploration, Inc | | Oil & Gas Operator | Dec 1977 |
| 241 | Atlas Production Services | | Oil & Gas Operator | Feb 1999 |
| 242 | Atp Oil & Gas Corporation | Houston, TX 77027 | Oil & Gas Operator | Jun 2008 |
| 243 | Attaway Energy Group, Inc. | | Oil & Gas Operator | Aug 1995 |
| 244 | Auro USA, Inc. | | Oil Operator | Dec 2024 |
| 245 | Auster Oil And Gas, Inc. | | Oil & Gas Operator | Mar 1989 |
| 246 | Auster Oil And Gas, Inc. Et Al | | Oil & Gas Operator | May 2001 |
| 247 | Austin E. Stewart | | Oil & Gas Operator | Feb 1979 |
| 248 | Austral Oil & Exploration, Inc | | Oil & Gas Operator | Jun 2004 |
| 249 | Austral Oil Company Incorporated | Sulphur, LA 70663 | Oil & Gas Operator | Mar 2008 |
| 250 | Australis TMS Inc. | | Oil & Gas Operator | Sep 2025 |
| 251 | Autry C. Stephens | Midland, TX 79701 | Oil & Gas Operator | Dec 2001 |
| 252 | Avanti Exploration La, LLC | | Oil & Gas Operator | Nov 2024 |
| 253 | Aviara Energy Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2002 |
| 254 | Aviva America, Inc. | | Oil & Gas Operator | Nov 2013 |
| 255 | Ax Operating, L.L.C. | | Oil & Gas Operator | Jul 2018 |
| 256 | Axiom Tep, LLC | | Oil & Gas Operator | May 2015 |
| 257 | Axis Onshore, LLC | | Oil & Gas Operator | Apr 2008 |
| 258 | Axis Onshore, LP | | Oil & Gas Operator | Dec 2010 |
| 259 | Azimuth Energy, LLC | Denver, CO 80203 | Oil & Gas Operator | Sep 2006 |
| 260 | Aztec Oil & Gas Company | | Oil & Gas Operator | Mar 1978 |
| 261 | Aztec Production Company | | Oil & Gas Operator | Jan 1996 |
| 262 | Aztec-Solatex | | Gas Operator | Aug 1978 |
| 263 | Azul Operating, LLC | | Gas Operator | Dec 2024 |