| 301 | Cody Energy, Inc. | Houston, TX 77077 | Oil & Gas Operator | May 2025 |
| 302 | Cohort Energy Company | Centennial, CO 80112 | Oil & Gas Operator | Feb 2007 |
| 303 | Coleman Oil & Gas Inc | Farmington, NM 87499 | Oil & Gas Operator | Jan 2023 |
| 304 | Colorado Oil & Gas Corporation | | Oil & Gas Operator | May 2003 |
| 305 | Colt Resources Corporation | Billings, MT 59103 | Oil & Gas Operator | Feb 2013 |
| 306 | Coltrane Charles | | Oil Operator | Dec 1980 |
| 307 | Columbine Exploration Corp | Englewood, CO 80111 | Oil & Gas Operator | Aug 1998 |
| 308 | Columbus Energy Corp. | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2008 |
| 309 | Columbus Production Inc | | Oil & Gas Operator | Mar 2005 |
| 310 | Comanche Oil & Gas Corp | Salt Lake City, UT 84107-3075 | Oil & Gas Operator | May 2005 |
| 311 | Combined Oil & Gas | Denver, CO 80202 | Oil & Gas Operator | Feb 1990 |
| 312 | Comdisco Exploration Inc | | Oil Operator | Dec 1990 |
| 313 | Comet Energy Services LLC | Traverse City, MI 49686 | Oil & Gas Operator | Oct 2011 |
| 314 | Common Energy Inc | Douglas, WY 82633 | Oil & Gas Operator | Aug 1995 |
| 315 | Condor Exploration LLC | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Sep 2009 |
| 316 | Conoco Inc. | Houston, TX 77252 | Oil & Gas Operator | Mar 2015 |
| 317 | ConocoPhillips Company | Midland, TX 79701 | Oil & Gas Operator | Jul 2025 |
| 318 | Conquest Exploration | Houston, TX 77068 | Oil & Gas Operator | May 1991 |
| 319 | Consolidated Oil & Gas Inc | Wichita, KS 67202 | Oil & Gas Operator | Dec 2012 |
| 320 | Contango Resources LLC | Andrews, TX 79714 | Oil & Gas Operator | Jul 2025 |
| 321 | Contango Rocky Mountain Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2020 |
| 322 | Continental Industries LC | Casper, WY 82602 | Oil & Gas Operator | Feb 2008 |
| 323 | Continental Operating Co. | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 324 | Continental Production Co LLC | Greenwood VIllage, CO 80155 | Oil & Gas Operator | Aug 2012 |
| 325 | Continental Resources, Inc. | Oklahoma City, OK 73126 | Oil & Gas Operator | Jul 2025 |
| 326 | Convest Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Sep 2014 |
| 327 | Cook D L | Holliday, TX 76366 | Oil & Gas Operator | Dec 2008 |
| 328 | Coquina Oil Corporation | Houston, TX 77227 | Oil & Gas Operator | Mar 2015 |
| 329 | Coral Production Corporation | Denver, CO 80201 | Oil & Gas Operator | Apr 2025 |
| 330 | Cordero Mining Co | Gillette, WY 82717 | Oil Operator | Nov 2009 |
| 331 | Cordero Oil And Gas LLC | Gillette, WY 82716 | Oil Operator | Nov 2021 |
| 332 | Cordillera Corporation | Denver, CO 80237 | Oil & Gas Operator | Feb 1996 |
| 333 | Cork Petroleum Corporation | Thermopolis, WY 82443 | Oil & Gas Operator | Apr 2012 |
| 334 | Cornerstone Natural Resources LLC | Denver, CO 80234 | Oil & Gas Operator | May 2025 |
| 335 | Coronado Oil Company | Denver, CO 80202 | Oil & Gas Operator | Dec 2019 |
| 336 | Corrida Oil Inc | Denver, CO 80217 | Oil & Gas Operator | Jun 1990 |
| 337 | Costilla Energy Inc | Midland, TX 79702 | Oil & Gas Operator | Mar 2008 |
| 338 | Cotton Petroleum Corporation | Tulsa, OK 74102 | Oil & Gas Operator | Jan 2005 |
| 339 | Cottonwood Oil Inc | Worland, WY 82401 | Oil & Gas Operator | Jun 1988 |
| 340 | Cowan Oil Company | | Oil Operator | Sep 1990 |
| 341 | Cowboy Clean Fuels LLC | Laramie, WY 82072 | Gas Operator | Apr 2025 |
| 342 | Cox Edwin L & Berry R | | Oil & Gas Operator | Oct 1987 |
| 343 | Cox Kendall Jay | Recluse, WY 28775 | Oil & Gas Operator | Aug 2016 |
| 344 | CR Energy | | Oil & Gas Operator | Dec 1992 |
| 345 | Cramer Oil Company | Denver, CO 80202 | Oil Operator | Aug 2012 |
| 346 | Crawley Petroleum Corporation | Oklahoma City, OK 73102 | Oil & Gas Operator | Jul 2025 |
| 347 | Creek Oil Company | Colorado Springs, CO 80906 | Oil & Gas Operator | Aug 2001 |
| 348 | Crest Resources Inc | Tulsa, OK 74103 | Oil & Gas Operator | Jul 2025 |
| 349 | Crowheart Energy LLC | Baggs, WY 82321 | Oil & Gas Operator | May 2025 |
| 350 | Crown Central Petroleum Corp | Richmond, TX 77469 | Oil & Gas Operator | Dec 1999 |
| 351 | Crown Energy Partners LLC | Englewood, CO 80112 | Oil & Gas Operator | Sep 2013 |
| 352 | Crown Oil & Gas Co Inc | Labarge, WY 83123 | Oil & Gas Operator | Jan 2023 |
| 353 | Crystal Exploration & Production Company | Shreveport, LA 71120 | Oil & Gas Operator | Feb 1995 |
| 354 | Crystal Oil Company | Shreveport, LA 71120 | Oil & Gas Operator | Jul 1995 |
| 355 | Cumberland Operating LLC | Cody, WY 82414 | Oil & Gas Operator | May 2025 |
| 356 | Czar Resources Inc | Houston, TX 77060 | Oil & Gas Operator | Oct 1992 |
| 357 | D & B Oil Company | Graham, TX 76450 | Oil & Gas Operator | Jul 2025 |
| 358 | D & J Oil Company | Kermit, TX 79745 | Oil & Gas Operator | Jul 2025 |
| 359 | D K Cook Heirs LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2011 |
| 360 | D90 Energy, LLC | Houston, TX 77024 | Oil & Gas Operator | Jul 2025 |
| 361 | Dahill Murray P | Casper, WY 82601 | Oil & Gas Operator | Jun 2007 |
| 362 | Dalen Resources Oil & Gas Co. | Dallas, TX 75206 | Oil & Gas Operator | Jun 2010 |
| 363 | Damson Oil Corporation | Houston, TX 77210 | Oil & Gas Operator | Mar 2005 |
| 364 | Darrah John Jay Jr | Wichita, KS 67201 | Oil & Gas Operator | Apr 2025 |
| 365 | Daube Company The | Ardmore, OK 73401 | Oil & Gas Operator | May 2025 |
| 366 | Davey Corporation | Golden, CO 80401 | Oil & Gas Operator | Jun 2025 |
| 367 | Davis & Tharel | | Oil & Gas Operator | Dec 1988 |
| 368 | Davis Bobby J | Upton, WY 82730 | Oil & Gas Operator | Oct 1989 |
| 369 | Davis Exploration | | Oil Operator | Dec 2007 |
| 370 | Davis Oil Company | Denver, CO 80202 | Oil & Gas Operator | Jun 1988 |
| 371 | Davis Petroleum Corp. | Houston, TX 77027 | Oil & Gas Operator | Jul 2025 |
| 372 | Dawson Resources Inc | Franktown, CO 80116 | Oil & Gas Operator | Mar 2015 |
| 373 | DCD Inc | Gillette, WY 82716 | Oil & Gas Operator | Aug 2003 |
| 374 | Debord Oil Producers | Lincoln, NE 68503 | Oil Operator | Dec 1998 |
| 375 | Deca Energy Corporation | | Oil & Gas Operator | Aug 1986 |
| 376 | Decalta International Corp | Denver, CO 80202 | Oil & Gas Operator | Mar 2015 |
| 377 | Degaugh Well Service Inc | | Oil Operator | Jul 1989 |
| 378 | Dekalb Energy Company | Oklahoma City, OK 73134 | Oil & Gas Operator | Oct 1996 |
| 379 | Delta Exploration Company Inc | Denver, CO 80202 | Oil & Gas Operator | Jul 2025 |
| 380 | Denbury Onshore, LLC | Plano, TX 75024 | Oil & Gas Operator | Jul 2025 |
| 381 | Department Of Energy | Casper, WY 82601 | Oil & Gas Operator | Jan 2015 |
| 382 | Deuel Arch W | | Oil & Gas Operator | Aug 1995 |
| 383 | Devon Energy Operating Corp | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2013 |
| 384 | Devon Energy Production Company LP | Oklahoma City, OK 73102 | Oil & Gas Operator | Jul 2025 |
| 385 | Devon SFS Operating Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | Mar 2008 |
| 386 | Diamond B Industries Inc | Belle Fourche, SD 57717 | Oil & Gas Operator | Apr 2010 |
| 387 | Diamond Oil & Gas LLC | Casper, WY 82604 | Oil & Gas Operator | May 2025 |
| 388 | Diamondback Oil Partners LLP | Arvada, CO 80004 | Oil & Gas Operator | Dec 2016 |
| 389 | Diasu Oil & Gas Co., Inc. | Houston, TX 77002 | Oil & Gas Operator | Mar 2016 |
| 390 | Dietrich Resources Corporation | | Oil & Gas Operator | Jun 2007 |
| 391 | Discovery Oil LTD | Los Angeles, CA 90067 | Oil & Gas Operator | Jan 1993 |
| 392 | DJ Resources Inc | Bowie, TX 76230 | Oil & Gas Operator | Nov 2017 |
| 393 | DKM Resources, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Sep 2011 |
| 394 | DNR Oil And Gas, Inc. | Englewood, CO 80155 | Oil & Gas Operator | Jun 2025 |
| 395 | Dol Resources Inc | Rowlett, TX 75088 | Oil & Gas Operator | Jun 2025 |
| 396 | Dolezal George Jr | Littleton, CO 80163 | Oil & Gas Operator | Sep 2006 |
| 397 | Dome Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2016 |
| 398 | Dominion Exploration & Production Inc | Houston, TX 77060 | Oil & Gas Operator | Apr 2015 |
| 399 | Dominion Oklahoma Texas Expl & Prod Inc | Oklahoma City, OK 73134 | Oil & Gas Operator | Aug 2013 |
| 400 | Duer Wagner & Company | Fort Worth, TX 76102 | Oil & Gas Operator | Dec 1998 |