| 301 | Hondo Oil & Gas | Houston, TX 77042 | Oil & Gas Operator | Oct 1995 |
| 302 | Houston Oil And Minerals | | Oil & Gas Operator | Oct 1993 |
| 303 | Hovivian Gregory E | La Crescenta, CA 91214 | Gas Operator | Dec 1999 |
| 304 | Howell Petroleum Corporation | Houston, TX 77251 | Oil & Gas Operator | Oct 2015 |
| 305 | HRM Resources II, LLC | Denver, CO 80202 | Oil & Gas Operator | Jan 2022 |
| 306 | HRM Resources LLC | Denver, CO 80202 | Oil & Gas Operator | Aug 2015 |
| 307 | Hrubetz Oil Co. | Dallas, TX 75225 | Oil Operator | Sep 1986 |
| 308 | Huber J M Corp | Edison, NJ 08837 | Oil & Gas Operator | Apr 2025 |
| 309 | Hudson Group LLC | Casper, WY 82601 | Oil & Gas Operator | Feb 2025 |
| 310 | Hugoton Energy Corporation | Oklahoma City, OK 73113 | Oil & Gas Operator | Dec 2019 |
| 311 | Hunt Oil Company | Dallas, TX 75201 | Oil & Gas Operator | Apr 2025 |
| 312 | Hydrocarbon Management, Inc. | San Antonio, TX 78216 | Oil & Gas Operator | Dec 1996 |
| 313 | Impact Energy Operating LLC | Oklahoma City, OK 73172 | Oil & Gas Operator | Feb 2025 |
| 314 | Independent Production Company | Greenwood VIllage, CO 80121 | Oil & Gas Operator | May 2003 |
| 315 | Inexco Oil Company | Houston, TX 77210 | Oil & Gas Operator | Mar 2013 |
| 316 | Integrity Oil & Gas | Golden, CO 80401 | Oil & Gas Operator | May 2011 |
| 317 | Intoil, Inc. | Englewood, CO 80155 | Oil & Gas Operator | Dec 2002 |
| 318 | Investment Equipment LLC | FT Morgan, CO 80701 | Oil & Gas Operator | Jan 2025 |
| 319 | Ip Petroleum Company, Inc. | Houston, TX 77210 | Oil & Gas Operator | Mar 2008 |
| 320 | Itr Petroleum Inc | Houston, TX 77002 | Oil & Gas Operator | Apr 1998 |
| 321 | J & J Production LLC | Worland, WY 82401 | Oil Operator | Jan 2025 |
| 322 | Jade Resources Inc | Englewood, CO 80112 | Oil Operator | Jul 1998 |
| 323 | Jay Management Company LLC | Houston, TX 77057 | Oil & Gas Operator | Apr 2025 |
| 324 | Jenex Petroleum Corporation | The Woodlands, TX 77380 | Oil & Gas Operator | Apr 2025 |
| 325 | Jims Water Service Inc | Gillette, WY 82717 | Oil & Gas Operator | Oct 2016 |
| 326 | JM Cox Resources LP | Midland, TX 79702 | Oil & Gas Operator | Apr 2019 |
| 327 | JN Exploration & Prod | Billings, MT 59103-0159 | Oil & Gas Operator | Apr 2001 |
| 328 | Joemar Wyoming Operating LLC | | Oil & Gas Operator | Feb 2025 |
| 329 | Juniper Petroleum Corporation | | Oil & Gas Operator | Aug 1983 |
| 330 | Justice Oil & Gas LLC | Gillette, WY 82716 | Oil & Gas Operator | Feb 2025 |
| 331 | Jva Operating Company | Midland, TX 79710 | Oil & Gas Operator | Oct 2021 |
| 332 | K & W Oil Company | MT Carmel, IL 62830 | Oil & Gas Operator | May 2013 |
| 333 | Kaiser Energy Inc | Denver, CO 80202 | Oil & Gas Operator | Dec 1990 |
| 334 | Kaiser-Francis Oil Company | Tulsa, OK 74121 | Oil & Gas Operator | Apr 2025 |
| 335 | Kauffman K P Company Inc | Denver, CO 80202 | Oil & Gas Operator | Mar 1996 |
| 336 | KCS Medallion Resources, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Nov 2018 |
| 337 | Keas Production Company LLC | Estes Park, CO 80517 | Oil Operator | Jan 2025 |
| 338 | Keith Walker O & G Co LLC | | Oil Operator | Jan 2025 |
| 339 | Kelly Operating Company | | Oil & Gas Operator | Oct 1991 |
| 340 | Kem Ventures, LP | Katy, TX 77450 | Oil & Gas Operator | Jan 2025 |
| 341 | Kenai Oil & Gas Inc | | Oil & Gas Operator | Jun 1987 |
| 342 | Kennedy & Mitchell | Woodward, OK 73802 | Oil & Gas Operator | Dec 1988 |
| 343 | Kennedy George C | Upton, WY 82730 | Oil & Gas Operator | Oct 2018 |
| 344 | Kennedy Oil | Gillette, WY 82716 | Oil & Gas Operator | Feb 2025 |
| 345 | Kerr-McGee Corporation | Dallas, TX 75380 | Oil & Gas Operator | Jan 2025 |
| 346 | Kestrel Energy Inc | Lakewood, CO 80401 | Oil & Gas Operator | Jan 2008 |
| 347 | Kirkwood W C | Casper, WY 82602 | Oil & Gas Operator | May 2005 |
| 348 | Kissack Resources. LLC | | Oil & Gas Operator | Feb 2025 |
| 349 | Kissack Water & Oil Service Inc | Rozet, WY 82727 | Oil & Gas Operator | Feb 2025 |
| 350 | Kissinger Petroleum Corp | | Oil & Gas Operator | Nov 1983 |
| 351 | Klabzuba Oil & Gas Inc | Denver, CO 80202 | Oil & Gas Operator | Aug 2012 |
| 352 | L & J Operating Inc | Gillette, WY 82718 | Oil & Gas Operator | Aug 2016 |
| 353 | L & R Drilling Company | Belle Fourche, SD 57717 | Oil & Gas Operator | Dec 1999 |
| 354 | L B Industries Inc | Englewood, CO 80112 | Oil & Gas Operator | Jun 2003 |
| 355 | Ladd & Lukowicz | | Oil & Gas Operator | May 1983 |
| 356 | Laguna Petroleum Company | Casper, WY 82601 | Oil & Gas Operator | Dec 1982 |
| 357 | Lance Oil & Gas Company Inc | Kirtland, NM 87417 | Oil & Gas Operator | Mar 2013 |
| 358 | Langley Energy | Euless, TX 76040 | Gas Operator | Jan 2016 |
| 359 | Lario Oil & Gas Company | Odessa, TX 79762 | Oil & Gas Operator | Apr 2025 |
| 360 | Lasmo Energy Corporation | Tulsa, OK 74136 | Oil & Gas Operator | Jan 2024 |
| 361 | Lear Petroleum Exploration | | Oil & Gas Operator | Jul 2013 |
| 362 | Leclair-Westwood Inc | | Oil & Gas Operator | Mar 1982 |
| 363 | Legacy Reserves Operating LP | Denver, CO 80201 | Oil & Gas Operator | Apr 2025 |
| 364 | Levinson Partners Corporation | Denver, CO 80202 | Oil & Gas Operator | Jul 1995 |
| 365 | Liberty Resources Management Co LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2025 |
| 366 | Loil Oil LLC | Golden, CO 80402 | Oil & Gas Operator | Feb 2025 |
| 367 | Long Trust The | Kilgore, TX 75663 | Oil & Gas Operator | Aug 2008 |
| 368 | Loral Operating LLC | Sheridan, WY 82801 | Gas Operator | Apr 2011 |
| 369 | Louisiana Land & Exploration Co. | Houston, TX 77210 | Oil & Gas Operator | Sep 2013 |
| 370 | Low D J | Littleton, CO 80127 | Oil Operator | Dec 1999 |
| 371 | Lowry Exploration Inc | Tulsa, OK 74119 | Oil & Gas Operator | Jan 2025 |
| 372 | Luff Exploration | Denver, CO 80203 | Oil & Gas Operator | Dec 2006 |
| 373 | M & K Oil Company LLC | Gillette, WY 82716 | Oil & Gas Operator | Feb 2025 |
| 374 | Mack Energy Corporation | Artesia, NM 88211 | Oil & Gas Operator | Feb 2025 |
| 375 | Main Energy, Inc. | Houston, TX 77079 | Oil & Gas Operator | May 2009 |
| 376 | Majestic Petroleum Operations Inc | Story, WY 82842 | Gas Operator | Mar 2007 |
| 377 | Mallon Oil Company | Denver, CO 80202 | Oil & Gas Operator | Jun 2005 |
| 378 | Manx Oil Corporation | Casper, WY 82601 | Oil & Gas Operator | Jun 2010 |
| 379 | Marathon Oil Company | Houston, TX 77024 | Oil & Gas Operator | Feb 2025 |
| 380 | Marlin Oil Company LLC | Gillette, WY 82718 | Oil & Gas Operator | Mar 2023 |
| 381 | Marmik Oil Company | El Dorado, AR 71730 | Oil & Gas Operator | Jan 2015 |
| 382 | Martens & Peck Operating Co | | Gas Operator | Feb 1997 |
| 383 | Martens & Peck Production Co | Denver, CO 80222 | Oil & Gas Operator | Feb 1997 |
| 384 | Matrix Production Company | Sugar Land, TX 77478 | Oil & Gas Operator | Jan 2025 |
| 385 | Maxim Drilling & Expl Inc | Gillette, WY 82717 | Oil & Gas Operator | Feb 2025 |
| 386 | Maximus Operating, LTD. | Kilgore, TX 75663 | Oil & Gas Operator | Apr 2025 |
| 387 | Mbi Oil & Gas LLC | Dickinson, ND 58601 | Oil & Gas Operator | Feb 2025 |
| 388 | McAdams Roux & Associates | Denver, CO 80202 | Oil & Gas Operator | Dec 1999 |
| 389 | McClure Enterprises | Recluse, WY 82725 | Oil & Gas Operator | Jan 2025 |
| 390 | McGuire John C | Gillette, WY 82717 | Oil & Gas Operator | Oct 2005 |
| 391 | McKenzie Production Company | Houston, TX 77063 | Oil & Gas Operator | May 1995 |
| 392 | MCL 1 Oil & Gas Wyoming LLC | Minneapolis, MN 55402 | Oil & Gas Operator | Jul 2018 |
| 393 | McMahon-Bullington LP | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2009 |
| 394 | McMurry Oil LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2004 |
| 395 | McRae & Henry LTD | Golden, CO 80401 | Oil & Gas Operator | May 2022 |
| 396 | MDS Energy Development LLC | | Oil & Gas Operator | Feb 2025 |
| 397 | Medallion Exploration | Holladay, UT 84117 | Oil & Gas Operator | Dec 2015 |
| 398 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 399 | Medicine Bow Operating Company | Houston, TX 77002 | Oil & Gas Operator | Apr 2014 |
| 400 | Mega Energy LLC | Gillette, WY 82718 | Gas Operator | Feb 2025 |