| 301 | Northstar Gas Company, Inc. | | Oil & Gas Operator | Jan 2016 |
| 302 | Northwestern Corporation | Butte, MT 59701 | Oil & Gas Operator | Mar 2026 |
| 303 | Northwestern Energy, LLC | Butte, MT 59701 | Oil & Gas Operator | Dec 2004 |
| 304 | NRC Development, LLC | | Gas Operator | Nov 2002 |
| 305 | Oasis Petroleum North America LLC | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 306 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 307 | Ocean Energy Resources Inc. | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 308 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2026 |
| 309 | Olympic Exploration & Production Co | Norman, OK 73072 | Oil Operator | May 2003 |
| 310 | Omimex Canada, LTD. | Fort Worth, TX 76120-3608 | Oil & Gas Operator | Feb 2026 |
| 311 | Omimex Petroleum Inc | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2022 |
| 312 | Orion Energy Partners LP | Denver, CO 80202 | Oil & Gas Operator | Nov 2010 |
| 313 | Outlook Petroleum Corp. | Midland, TX 79702 | Oil & Gas Operator | Jan 2001 |
| 314 | Panther Creek Resources, LLC | Denver, CO 80202 | Oil & Gas Operator | May 2012 |
| 315 | Panther Energy Company, LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2022 |
| 316 | Parsell, R. W. | Whitlash, MT 59545 | Oil & Gas Operator | Jan 2026 |
| 317 | Parsell, RF Partnership | Bellevue, WA 98004 | Oil Operator | Jan 2026 |
| 318 | Pennzoil Exploration & Production Co. | Carthage, TX 75633 | Oil & Gas Operator | Mar 2008 |
| 319 | Petro Productions,Petrotec Production,Inc Dba | Wichita, KS 67202 | Oil Operator | Aug 1993 |
| 320 | Petro-Hunt Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2003 |
| 321 | Petro-Hunt, L.L.C. | Dallas, TX 75201 | Oil & Gas Operator | Apr 2026 |
| 322 | Petroleum Engineering & Management Corp. | Casper, WY 82609 | Oil & Gas Operator | Jul 2018 |
| 323 | Petroleum Inc | Wichita, KS 67202 | Oil & Gas Operator | Oct 2021 |
| 324 | Petrox Petroleum Company | Great Falls, MT 59403-0989 | Oil Operator | Feb 2026 |
| 325 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |
| 326 | Phoenix Energy, Inc. | Oilmont, MT 59466 | Oil & Gas Operator | Dec 2025 |
| 327 | Phoenix Operating LLC | Denver, CO 80237 | Oil & Gas Operator | Feb 2026 |
| 328 | Phoenix Production Company | Cody, WY 82414-3607 | Oil & Gas Operator | Oct 2023 |
| 329 | Pinnacle Energy Group, LLC | Gillette, WY 82717 | Oil & Gas Operator | Nov 2017 |
| 330 | Pinnacle Gas Resources, Inc. | Sheridan, WY 82801 | Gas Operator | Mar 2011 |
| 331 | Pintail Petroleum Inc. | Wichita, KS 67202 | Oil & Gas Operator | Jun 2010 |
| 332 | Pintail Petroleum, LTD. | Wichita, KS 67202 | Oil & Gas Operator | Apr 2021 |
| 333 | Pittencrieff America Inc | Abilene, TX 79608 | Oil & Gas Operator | Feb 2003 |
| 334 | Plains Petroleum Operating Co | Denver, CO 80202 | Oil & Gas Operator | Dec 2014 |
| 335 | Pondera Partners Limited Partnership | Oroville, WA 98844 | Oil Operator | Sep 2023 |
| 336 | Potlatch Oil & Refining Co | Shelby, MT 59474 | Oil & Gas Operator | Jan 2026 |
| 337 | Prairie Dog Exploration, LLC | Calgary, Alberta, T2P 0J9 | Gas Operator | Jun 2009 |
| 338 | Presco Inc | The Woodlands, TX 77380 | Oil & Gas Operator | Oct 2020 |
| 339 | Pride Energy Company | Tulsa, OK 74170 | Oil & Gas Operator | Apr 2026 |
| 340 | Prima Exploration, Inc. | Denver, CO 80206 | Oil & Gas Operator | Feb 2026 |
| 341 | Primewest Petroleum Inc. | Centennial, CO 80111 | Oil & Gas Operator | Jan 2009 |
| 342 | Prospective Investment & Trading Co., LTD. | Tulsa, OK 74170-2320 | Oil & Gas Operator | Apr 2014 |
| 343 | Provident Energy Of Montana, LLC | Cut Bank, MT 59427 | Oil Operator | Jan 2026 |
| 344 | Quest Petroleum Corporation | Reno, NV 89570 | Oil Operator | Apr 1998 |
| 345 | Quicksilver Resources Inc | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2018 |
| 346 | R & A Oil, Inc. | Billings, MT 59105 | Oil & Gas Operator | Dec 2025 |
| 347 | R & B Energy, LLC | Shelby, MT 59474 | Oil Operator | Dec 2025 |
| 348 | R & J Production, Inc. | Laurel, MT 59044 | Oil Operator | Mar 2006 |
| 349 | R & N Associates,Etal Glen Neubert, Agent | Dallas, TX 75244-5100 | Oil Operator | Sep 2005 |
| 350 | R.C.S. Oil, Inc. | Conrad, MT 59425 | Oil Operator | Dec 2025 |
| 351 | R3 Operating Corporation | Denver, CO 80222 | Oil & Gas Operator | Apr 2026 |
| 352 | Ramhorn Energy, LLC | Green River, WY 82935 | Oil & Gas Operator | Jan 2026 |
| 353 | Ranch Oil Company | West Linn, OR 97068 | Oil & Gas Operator | Mar 2026 |
| 354 | Ranck Oil Company | Cut Bank, MT 59427 | Oil & Gas Operator | Feb 2026 |
| 355 | Rankin, Paul | Bridgeville, PA 15017 | Oil & Gas Operator | Jun 2016 |
| 356 | Redstone Gas Partners LLC | Denver, CO 80202 | Gas Operator | Mar 2001 |
| 357 | Remuda Energy Development LLC | Billings, MT 59104 | Oil & Gas Operator | Feb 2026 |
| 358 | Reserve Operating Corp. | Houston, TX 77040 | Oil & Gas Operator | Apr 2026 |
| 359 | Retamco Operating Inc | Red Lodge, MT 59068 | Oil & Gas Operator | Jan 2026 |
| 360 | Richardson Operating Company | Denver, CO 80237 | Oil & Gas Operator | Feb 2026 |
| 361 | Ridge Oil & Gas, LLC | Plano, TX 75024 | Oil & Gas Operator | Feb 2026 |
| 362 | Rim Operating, Inc. | Englewood, CO 80112 | Oil & Gas Operator | Apr 2026 |
| 363 | Rimrock Colony | Sunburst, MT 59482 | Gas Operator | Dec 2025 |
| 364 | Rimrock Oil Company | Kalispell, MT 59901 | Oil & Gas Operator | Dec 2023 |
| 365 | Rincon Oil & Gas LLC | Arvada, CO 80005 | Gas Operator | Jun 2022 |
| 366 | Ritchie Exploration, Inc. | Wichita, KS 67278 | Oil & Gas Operator | Dec 2025 |
| 367 | Ritter, Laber & Associates, Inc. | Williston, ND 58802 | Oil & Gas Operator | Aug 2025 |
| 368 | Rme Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Nov 2016 |
| 369 | Robert Hawkins Inc | Kevin, MT 59454 | Oil & Gas Operator | Feb 2026 |
| 370 | Robinson Oil Company, LLC | Billings, MT 59103 | Gas Operator | Dec 2015 |
| 371 | Rock Creek Oil, Inc. | Dallas, TX 75225 | Oil & Gas Operator | Nov 2019 |
| 372 | Roland Oil And Gas | Cut Bank, MT 59427 | Oil Operator | Feb 2023 |
| 373 | Rosetta Resources Operating LP | San Antonio, TX 78216 | Oil & Gas Operator | Apr 2026 |
| 374 | S & L Energy, Inc.C/O John D. Lawrence, Jr. | Fishtail, MT 59028 | Oil Operator | Oct 2025 |
| 375 | S & W Petroleum Consultants, Inc. | Broomfield, CO 80020 | Gas Operator | Feb 2004 |
| 376 | Saco, Town Of | Saco, MT 59261 | Gas Operator | Jan 2026 |
| 377 | Saga Petroleum, LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2018 |
| 378 | Sage Creek Colony | Chester, MT 59522 | Gas Operator | Feb 2026 |
| 379 | Sagebrush Operating LLC | Denver, CO 80203 | Oil & Gas Operator | Aug 2025 |
| 380 | Samedan Oil Corporation | Houston, TX 77067 | Oil & Gas Operator | Dec 2019 |
| 381 | Samson Oil & Gas USA Inc | Denver, CO 80202 | Oil & Gas Operator | Feb 2026 |
| 382 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2026 |
| 383 | Sands Oil Company Inc | Billings, MT 59103 | Oil & Gas Operator | Feb 2026 |
| 384 | Sannes, Ronald M. Or Margaret Ann | Billings, MT 59103 | Oil & Gas Operator | Oct 2017 |
| 385 | Sauby, Warren | Kevin, MT 59454 | Oil Operator | Feb 2009 |
| 386 | Scout Energy Management LLC | Dallas, TX 75240 | Oil & Gas Operator | Apr 2026 |
| 387 | Sdoco, LLC | Highlands Ranch, CO 80129 | Oil Operator | Dec 2025 |
| 388 | Seagull Energy E & P Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2015 |
| 389 | Seymour, James & Lorraine | Cut Bank, MT 59427 | Oil Operator | Jul 2022 |
| 390 | Shadco | Worland, WY 82401 | Oil & Gas Operator | Aug 2025 |
| 391 | Shakespeare Oil Co Inc | Salem, IL 62881 | Oil & Gas Operator | Jan 2026 |
| 392 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 393 | Sinclair Oil & Gas Company | Salt Lake Cty, UT 84130 | Oil & Gas Operator | Apr 2026 |
| 394 | Slawson Exploration Company Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2026 |
| 395 | Slohcin, Inc. | Shelby, MT 59474 | Oil Operator | Feb 2026 |
| 396 | Slow Poke Production-George L. Dobson Dba | Cut Bank, MT 59427 | Gas Operator | Dec 2025 |
| 397 | SM Energy Company | Midland, TX 79707 | Oil & Gas Operator | Apr 2026 |
| 398 | Smith, Loren E. And Foster, Chas. P. | Broomfield, CO 80020 | Oil Operator | Feb 2026 |
| 399 | Soap Creek Associates, Inc. | Broomfield, CO 80020-2995 | Oil Operator | Feb 2026 |
| 400 | Solomon Exploration Inc. | Havre, MT 59501 | Gas Operator | Dec 2025 |