| 401 | Dominion Oklahoma Texas Expl & Prod Inc | Oklahoma City, OK 73134 | Oil & Gas Operator | Aug 2013 |
| 402 | Duer Wagner & Company | Fort Worth, TX 76102 | Oil & Gas Operator | Dec 1998 |
| 403 | Dugan Production Corp | Farmington, NM 87499 | Oil & Gas Operator | Dec 2025 |
| 404 | Duncan Energy Company | Denver, CO 80202 | Oil & Gas Operator | Mar 2008 |
| 405 | Duncan Oil Inc | Denver, CO 80210 | Oil & Gas Operator | Jun 2016 |
| 406 | Dyco Petroleum Corporation | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2015 |
| 407 | Dyer J G | | Oil & Gas Operator | May 1985 |
| 408 | F & J Oil LLC | Newcastle, WY 82701 | Oil & Gas Operator | Oct 2015 |
| 409 | Fairways Offshore Expl Inc | Houston, TX 77040 | Oil & Gas Operator | Mar 2016 |
| 410 | Falcon Creek Resources, Inc. | Tulsa, OK 74137 | Oil & Gas Operator | Apr 2001 |
| 411 | Family Tree Corporation | Lakewood, CO 80228 | Oil & Gas Operator | Feb 2013 |
| 412 | Fancher Oil LLC | Greenwood, CO 80111 | Oil & Gas Operator | Nov 2006 |
| 413 | Farleigh Oil Properties | Casper, WY 82601 | Gas Operator | Sep 1999 |
| 414 | Farnsworth & Kaiser Oil Company | Newcastle, WY 82701 | Oil & Gas Operator | Sep 2012 |
| 415 | Faulconer, Vernon E., Inc. | Tyler, TX 75711 | Oil & Gas Operator | Dec 2025 |
| 416 | FDF Resources | Newcastle, WY 82701 | Oil & Gas Operator | Dec 2025 |
| 417 | FDL Operating, LLC | Judson, TX 75660 | Oil & Gas Operator | Feb 2026 |
| 418 | Federated Oil & Gas Properties | Traverse City, MI 49685 | Gas Operator | Mar 2014 |
| 419 | Felmont Oil Corporation | Walnut Creek, CA 94596-3568 | Oil & Gas Operator | Feb 1990 |
| 420 | Ferguson & Bosworth | | Oil & Gas Operator | May 2007 |
| 421 | Ferguson Bob | Casper, WY 82605 | Oil Operator | May 2004 |
| 422 | Ferguson Energy Inc | Evanston, WY 82930 | Oil & Gas Operator | Dec 2025 |
| 423 | Ferguson Oil Company Inc | | Oil & Gas Operator | Apr 1994 |
| 424 | Ferreira Oil Properties LLC | Carefree, AZ 85377 | Oil Operator | Apr 2014 |
| 425 | Fidelity Exploration & Production Company | Denver, CO 80203 | Oil & Gas Operator | Jan 2026 |
| 426 | Fina Oil And Chemical Company | Dallas, TX 75221 | Oil & Gas Operator | May 2019 |
| 427 | Finaly Resources LLC | Sunset Beach, CA 90742 | Oil & Gas Operator | Feb 2026 |
| 428 | Finley Resources Inc | Fort Worth, TX 76113 | Oil & Gas Operator | Feb 2026 |
| 429 | First Energy Corporation | | Oil & Gas Operator | Jun 1993 |
| 430 | First Energy Properties | Houston, TX 77060 | Oil & Gas Operator | Dec 1986 |
| 431 | First Sourcenergy Wyoming Inc | Gillette, WY 82718 | Gas Operator | Jul 2003 |
| 432 | Five States Operating Company LLC | Dallas, TX 75206 | Oil & Gas Operator | Dec 2025 |
| 433 | Flag-Redfern Oil Company | Oklahoma City, OK 73125 | Oil & Gas Operator | Jul 2002 |
| 434 | Flahive Oil & Gas LLC | Golden, CO 80401 | Oil Operator | Oct 1995 |
| 435 | Florida Gas Exploration Co | | Oil & Gas Operator | Feb 1985 |
| 436 | Flow Production Company | Midland, TX 79708 | Oil & Gas Operator | Mar 2005 |
| 437 | Flying J Oil & Gas Inc | North Salt Lake, UT 84054 | Oil & Gas Operator | Dec 2009 |
| 438 | FMC Corporation | Green River, WY 82935 | Oil & Gas Operator | Dec 2008 |
| 439 | Forcenergy Inc | Miami, FL 33129 | Oil & Gas Operator | Mar 2015 |
| 440 | Forcenergy Onshore Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2012 |
| 441 | Foree R L | Dallas, TX 75225 | Oil & Gas Operator | Aug 2001 |
| 442 | Foreland Resources LLC | Lakewood, CO 80228 | Oil & Gas Operator | Oct 2025 |
| 443 | Forest Oil Permian Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 444 | Forestar Petroleum Corporation | Denver, CO 80202 | Oil & Gas Operator | May 2017 |
| 445 | Fossil Creek Resources LLC | Arlington, TX 76011-5597 | Oil & Gas Operator | Mar 2015 |
| 446 | Fossil Energy Inc | Austin, TX 78746 | Oil & Gas Operator | Feb 2026 |
| 447 | Foundation Energy Managment LLC | Addison, TX 74119 | Oil & Gas Operator | Nov 2025 |
| 448 | Four-A Energy LLC | Cody, WY 82414 | Oil Operator | Jan 2026 |
| 449 | Frank Louis L | Kingsville, TX 78364 | Oil & Gas Operator | Aug 2003 |
| 450 | Fremont Energy Corporation | Oklahoma City, OK 73112 | Oil & Gas Operator | Dec 2004 |
| 451 | Frickey Investment MGT Co LLC | Lakewood, CO 80215 | Oil & Gas Operator | Dec 2025 |
| 452 | Fruehauf LLC | Gaylord, MI 49735 | Oil Operator | Feb 2005 |
| 453 | Fuel Exploration Inc | Denver, CO 80295 | Oil & Gas Operator | Jan 1992 |
| 454 | Fuel Resources Development Co | Denver, CO 80202 | Oil & Gas Operator | Feb 1994 |
| 455 | G & H Production Company LLC | Denver, CO 80202 | Oil Operator | Jan 2008 |
| 456 | G & H Resources LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2009 |
| 457 | Galaxy Oil Company | Wichita Falls, TX 76307 | Oil & Gas Operator | Mar 2015 |
| 458 | Gallagher Drilling Inc | Evansville, IN 47730 | Oil Operator | Dec 2020 |
| 459 | Gallagher T P | Boulder, CO 80303 | Oil Operator | Apr 2019 |
| 460 | Gary-Williams Production Company | Denver, CO 80202 | Oil & Gas Operator | May 2000 |
| 461 | Gas Ventures LLC | Thermopolis, WY 82443 | Oil & Gas Operator | Oct 2020 |
| 462 | Gasamat Oil Corp Of Colorado | Boulder, CO 80303 | Oil Operator | Dec 2025 |
| 463 | Gasco Inc | | Oil & Gas Operator | Jun 1998 |
| 464 | Gasco Production Company | Denver, CO 80237 | Oil & Gas Operator | Dec 2015 |
| 465 | General American Oil Co Of Texas | | Oil & Gas Operator | Mar 1983 |
| 466 | General Atlantic Resources Inc | Denver, CO 80202 | Oil & Gas Operator | Jan 2022 |
| 467 | General Crude Oil Co | Houston, TX 77005 | Oil & Gas Operator | Dec 1979 |
| 468 | General Oil Company, Inc. | Wichita, KS 67213 | Oil & Gas Operator | Feb 2026 |
| 469 | Genesis Production Company | | Oil & Gas Operator | May 1991 |
| 470 | Genesis St Operating LLC | Kansas City, MO 64108 | Oil & Gas Operator | Feb 2026 |
| 471 | Geodyne Operating Company | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2015 |
| 472 | Germany Operating Company | Houston, TX 77090 | Oil & Gas Operator | Sep 2011 |
| 473 | Getty Oil Company | Hays, KS 67601 | Oil & Gas Operator | Mar 2015 |
| 474 | Gibbs William | | Oil Operator | Feb 2000 |
| 475 | Gibson J W | | Oil & Gas Operator | Sep 1999 |
| 476 | Gilmore Oil & Gas | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 477 | Girouard Richard L | | Oil Operator | May 1985 |
| 478 | GKM Inc | | Oil & Gas Operator | Mar 1990 |
| 479 | Glenmar Company | Monterey, CO 93940 | Oil Operator | Oct 1998 |
| 480 | GLG Energy LP | Austin, TX 78701 | Oil & Gas Operator | Jun 1994 |
| 481 | GMT Energy Corporation | Houston, TX 77042 | Oil & Gas Operator | Feb 2005 |
| 482 | GMT Exploration Company LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2025 |
| 483 | Golden Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Jan 2010 |
| 484 | Golden Eye Resources LLC | Greenwood VLG, CO 80121 | Oil Operator | Mar 2014 |
| 485 | Goldmark Engineering Inc | Casper, WY 82602 | Oil & Gas Operator | Oct 2004 |
| 486 | Goodstein Fred | Casper, WY 82602 | Oil & Gas Operator | Mar 1984 |
| 487 | Gorman Construction LLC | Gillette, WY 82716 | Oil Operator | Nov 2025 |
| 488 | Gould Joseph B | Las Vegas, NV 89101 | Oil & Gas Operator | Apr 2001 |
| 489 | Gpo Operations LLC | Labarge, WY 83123 | Oil & Gas Operator | Dec 2025 |
| 490 | Grace Petroleum Corp. | Tulsa, OK 74103 | Oil & Gas Operator | Oct 1997 |
| 491 | Graham Royalty LTD | Covington, LA 70434 | Oil & Gas Operator | Jul 2007 |
| 492 | Granite Creek Energy LLC | Cody, WY 82414 | Oil & Gas Operator | Dec 2025 |
| 493 | Grayhorse Operating Inc | Tulsa, OK 74103-4438 | Oil & Gas Operator | Nov 2025 |
| 494 | Grayling Resources LTD | Lakewood, CO 80235 | Oil & Gas Operator | Jul 2020 |
| 495 | Grayson Mill Operating LLC | Houston, TX 77024 | Oil & Gas Operator | Aug 2025 |
| 496 | GRB Resources | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2004 |
| 497 | Great Northern Drilling Company | Billings, MT 59103 | Oil & Gas Operator | Jun 2016 |
| 498 | Great Northern Gas Company | Denver, CO 80293-0602 | Oil & Gas Operator | Jun 2016 |
| 499 | Great Western Drilling Company | Midland, TX 79701 | Oil & Gas Operator | Feb 2026 |
| 500 | Great Western Oil Company | | Oil & Gas Operator | Dec 1984 |