| 101 | Cimarex Energy Co | Midland, TX 79706 | Oil & Gas Operator | Apr 2025 |
| 102 | Cisco Expro LLC | Park City, UT 84098-5178 | Oil & Gas Operator | Nov 2009 |
| 103 | Citation Oil & Gas Corp. | Houston, TX 77269 | Oil & Gas Operator | Apr 2025 |
| 104 | Cities Serv Oil & Gas Corp | Oklahoma City, OK 73112 | Oil & Gas Operator | Sep 1964 |
| 105 | Clayton Investment | Farmington, NM 87401 | Oil & Gas Operator | Jun 1995 |
| 106 | Cline Oil And Gas Company | Santa Fe, NM 87501 | Oil & Gas Operator | Sep 1994 |
| 107 | Clinton Oil Co | Wichita, KS 67202 | Oil & Gas Operator | Apr 1980 |
| 108 | CNG Producing | New Orleans, LA 70112-6000 | Oil & Gas Operator | Jun 2000 |
| 109 | Coastal Oil & Gas Corporation | Houston, TX 77252 | Oil & Gas Operator | Dec 2009 |
| 110 | Coastal Plains Energy Inc | Oklahoma City, OK 73112 | Oil & Gas Operator | Apr 2025 |
| 111 | Cobra Oil & Gas Corporation | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2025 |
| 112 | Cochrane Resources Inc | Roosevelt, UT 84066 | Oil & Gas Operator | Feb 2025 |
| 113 | Cockrell Oil Corporation | Houston, TX 77002-7348 | Oil & Gas Operator | Feb 2001 |
| 114 | Colorado Drilling Company | Grand Junction, CO 81501 | Oil Operator | Jan 1990 |
| 115 | Colorado Pica Petro Corp | Cortez, CO 81321 | Oil & Gas Operator | Apr 2007 |
| 116 | Colt Resources Corporation | Billings, MT 59103 | Oil & Gas Operator | Feb 2013 |
| 117 | Coltharp, Edward H | | Oil & Gas Operator | Dec 1970 |
| 118 | Columbia Gas Development | Houston, TX 77251 | Oil & Gas Operator | Jun 1996 |
| 119 | Columbus Energy Corp. | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2008 |
| 120 | Comanche Oil & Gas Corp | Salt Lake City, UT 84107-3075 | Oil & Gas Operator | May 2005 |
| 121 | Conoco Inc. | Houston, TX 77252 | Oil & Gas Operator | Mar 2015 |
| 122 | ConocoPhillips Company | Midland, TX 79701 | Oil & Gas Operator | Apr 2025 |
| 123 | Consolidated Oil & Gas Inc | Wichita, KS 67202 | Oil & Gas Operator | Dec 2012 |
| 124 | Continental Oil Co. | Durango, CO 81301 | Oil & Gas Operator | Dec 1983 |
| 125 | Coors Energy | Golden, CO 80402-0467 | Oil & Gas Operator | Sep 1992 |
| 126 | Cordillera Corporation | Denver, CO 80237 | Oil & Gas Operator | Feb 1996 |
| 127 | Coseka Resources USA LTD | Denver, CO 80202-1602 | Oil & Gas Operator | Jun 1988 |
| 128 | Costilla Energy Inc | Midland, TX 79702 | Oil & Gas Operator | Mar 2008 |
| 129 | Costilla Petroleum Corporation | Midland, TX 79702 | Oil & Gas Operator | Mar 2015 |
| 130 | Cotton Petroleum Corp/Apc | Denver, CO 80203-4549 | Oil & Gas Operator | Nov 1990 |
| 131 | Crain & Griffith DRL Co | | Oil Operator | Jun 1963 |
| 132 | Credo Petroleum Corporation | Denver, CO 80202 | Oil & Gas Operator | Jan 2013 |
| 133 | Crescent Point Energy Us Corp | Denver, CO 80202 | Oil & Gas Operator | Apr 2024 |
| 134 | Cross Creek Corporation | Duncan, OK 73534 | Oil & Gas Operator | Mar 1999 |
| 135 | Crownquest Operating, LLC | Midland, TX 79710 | Oil & Gas Operator | Apr 2025 |
| 136 | Crystal Carbon Company | | Gas Operator | Dec 1930 |
| 137 | CSX Oil & Gas Corporation | Houston, TX 77210-4326 | Oil & Gas Operator | Mar 1993 |
| 138 | D & D Oil Company | Dayton, TX 77535 | Oil & Gas Operator | Apr 2025 |
| 139 | D & J Oil Co | Kermit, TX 79745 | Oil & Gas Operator | Apr 2025 |
| 140 | D J Simmons, Inc | Farmington, NM 87499 | Oil & Gas Operator | Apr 2020 |
| 141 | Dalen Resources Oil & Gas | Dallas, TX 75206-3922 | Oil & Gas Operator | Jan 1996 |
| 142 | Daniels Petroleum Co | Denver, CO 80202 | Oil & Gas Operator | Mar 2003 |
| 143 | Davis Oil Company | Pawhuska, OK 74056 | Oil & Gas Operator | Jun 2018 |
| 144 | De Kalb Agric Assn Inc | Vernal, UT | Oil & Gas Operator | Jun 1965 |
| 145 | Del-Rio Resources Inc | Vernal, UT 84079 | Oil & Gas Operator | Jan 2018 |
| 146 | Delhi-Taylor Oil Corp | | Oil & Gas Operator | Dec 1974 |
| 147 | Delhi-Trading LLC | Durango, CO 81301 | Oil & Gas Operator | Feb 2025 |
| 148 | Delta Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2024 |
| 149 | Devon Energy Operating Corp | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2013 |
| 150 | Devon Energy Production Company LP | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2025 |
| 151 | Diamond Shamrock Corp | Amarillo, TX 79105 | Oil & Gas Operator | Jan 1987 |
| 152 | Diamond Shamrock Expl | Dallas, TX 75201 | Oil & Gas Operator | May 1987 |
| 153 | Dirty Devil LP | Eenglewood, CO 80111 | Oil & Gas Operator | Apr 1989 |
| 154 | Discovery Natural Resources LLC | Denver, CO 80202 | Oil & Gas Operator | Apr 2025 |
| 155 | Diversified Energy LLC | Parker, CO 80138 | Oil & Gas Operator | Jan 2025 |
| 156 | DKM Resources, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Sep 2011 |
| 157 | Dominion Exploration & Production Inc | Houston, TX 77060 | Oil & Gas Operator | Apr 2015 |
| 158 | Dominion Ok TX E & P Inc | Oklahoma City, OK 73134 | Oil & Gas Operator | Nov 2018 |
| 159 | Dougherty, H W | Petaluma, CA 94954 | Gas Operator | Oct 2019 |
| 160 | Dugan Production Corp | Farmington, NM 87499 | Oil & Gas Operator | Feb 2025 |
| 161 | Duncan Energy Companyuncan Energy Company | Denver, CO 80210 | Oil & Gas Operator | Jun 1995 |
| 162 | Duncan Oil Inc | Denver, CO 80210 | Oil & Gas Operator | Jun 2016 |
| 163 | Duncan, Raymond T | Denver, CO 80210 | Oil & Gas Operator | Feb 1996 |
| 164 | Dyco Petroleum Corporation | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2015 |
| 165 | Edward Mike Davis | Las Vegas, NV 89107 | Oil & Gas Operator | Feb 2003 |
| 166 | Edwards Energy Corporation | Midland, TX 79702 | Oil & Gas Operator | Apr 2025 |
| 167 | El Paso E&P Company, L.P. | Houston, TX 77002 | Oil & Gas Operator | Mar 2013 |
| 168 | El Paso Natural Gas Company | El Paso, TX 79978 | Oil & Gas Operator | Apr 2013 |
| 169 | El Paso Production Oil & Gas Co. | Houston, TX 77252 | Oil & Gas Operator | Apr 2025 |
| 170 | Elk Operating Services, LLC | Denver, CO 80203 | Oil & Gas Operator | Feb 2025 |
| 171 | Elk Production LLC | Denver, CO 80202 | Oil & Gas Operator | Aug 2011 |
| 172 | Elk Production Uintah LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2014 |
| 173 | Elk Resources, LLC | Denver, CO 80202 | Oil & Gas Operator | Apr 2011 |
| 174 | Elkhorn Exploration Co | Willis, TX 77378-8827 | Oil & Gas Operator | Jan 2025 |
| 175 | Elliott Inc | Roswell, NM 88201 | Oil & Gas Operator | Apr 1962 |
| 176 | Elm Ridge Exploration Company | Dallas, TX 75243-9362 | Oil & Gas Operator | Jan 2019 |
| 177 | Elm Ridge Resources Inc | Dallas, TX 75243 | Oil & Gas Operator | Nov 2005 |
| 178 | Emery Resource Holdings LLC | Scottsdale, AZ 85260 | Gas Operator | Mar 2025 |
| 179 | Encana Oil & Gas (USA) Inc. | Denver, CO 80202 | Oil & Gas Operator | Oct 2020 |
| 180 | Enduring Resources, LLC | Greenwood VLG, CO 80111 | Oil & Gas Operator | Feb 2025 |
| 181 | Energetics Inc | Englewood, CO 80155 | Oil & Gas Operator | Aug 1985 |
| 182 | Energy Reserves Group | Houston, TX 770563020 | Oil & Gas Operator | Apr 1996 |
| 183 | Enerplus Resources USA Corporation | Denver, CO 80202 | Oil & Gas Operator | Feb 2025 |
| 184 | Enerquest Operating, LLC | Oklahoma City, OK 73114 | Oil & Gas Operator | Apr 2025 |
| 185 | Enervest Operating LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2025 |
| 186 | Enogex Exploration Corp | Oklahoma City, OK 73124-0300 | Oil & Gas Operator | Jun 2000 |
| 187 | Enron Oil & Gas Company | Houston, TX 77210 | Oil & Gas Operator | Dec 1999 |
| 188 | Enserch Exploration Inc | Dallas, TX 75206 | Oil & Gas Operator | Apr 2015 |
| 189 | Enstar Corporation | Houston, TX 77252 | Oil & Gas Operator | Apr 1988 |
| 190 | EOG Resources, Inc. | Midland, TX 79702 | Oil & Gas Operator | Apr 2025 |
| 191 | EP Energy E&P Company, LP | Houston, TX 77210 | Oil & Gas Operator | May 2022 |
| 192 | EP Operating Company LP | Midland, TX 79705-5510 | Oil & Gas Operator | Mar 1993 |
| 193 | Eps Resources Corp | Englewood, CO 80111 | Oil & Gas Operator | Dec 2009 |
| 194 | Equitable Resources Energy | Houston, TX 77056-2742 | Oil & Gas Operator | Sep 1997 |
| 195 | Equity Oil Company | Salt Lake City, UT 84110-095 | Oil & Gas Operator | Aug 2004 |
| 196 | Erg Operating Company Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 2006 |
| 197 | Evergreen Energy, Inc | Houston, TX 77098 | Oil & Gas Operator | Apr 2025 |
| 198 | Evergreen Operating Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2019 |
| 199 | Evertson Oil Company Inc | Kimball, NE 69145 | Oil & Gas Operator | Sep 2001 |
| 200 | Exit Inc | | Oil Operator | Dec 1983 |