| 30301 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |
| 30302 | United Investment Group | | Oil Operator | Nov 2004 |
| 30303 | United Meridian | | Oil Operator | Dec 1992 |
| 30304 | United Natural Gas LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2020 |
| 30305 | United Natural Resources Corp | | Oil Operator | Jan 1986 |
| 30306 | United O&G/Atlee Miller | Millersburg, OH 44654 | Oil & Gas Operator | Dec 1985 |
| 30307 | United Oil & Gas | | Oil Operator | Feb 1988 |
| 30308 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 30309 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 30310 | United Oil Corporation | Denver, CO 80202-3813 | Oil & Gas Operator | Jul 2025 |
| 30311 | United Operating Company | Olney, TX 76374 | Oil & Gas Operator | Aug 2003 |
| 30312 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Nov 2025 |
| 30313 | United Operators, Inc. | | Oil Operator | Sep 1999 |
| 30314 | United Petro LTD. | | Oil & Gas Operator | Dec 2018 |
| 30315 | United Petroleum | | Oil Operator | Mar 1986 |
| 30316 | United Petroleum & Gas, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Nov 2025 |
| 30317 | United Petroleum Corporation | Edgwater, CO 80214 | Oil & Gas Operator | May 1996 |
| 30318 | United Petroleum Technologies | Hondo, TX 78861 | Oil & Gas Operator | Aug 2001 |
| 30319 | United Primary Resources Inc | Milton, WA 98354-9361 | Oil & Gas Operator | Feb 2016 |
| 30320 | United Producers Inc | Broken Arrow, OK 74012-8247 | Oil & Gas Operator | Mar 2020 |
| 30321 | United Producing Co Inc | | Oil & Gas Operator | May 1961 |
| 30322 | United Production Company LLC | Edmond, OK 73003 | Oil & Gas Operator | Aug 2025 |
| 30323 | United Reserve G | | Oil Operator | Aug 1987 |
| 30324 | United Resources Corp | Olean, NY 14760 | Oil & Gas Operator | Dec 2020 |
| 30325 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 30326 | United Resources LP A Texas LMTD PRNTSHP | Austin, TX 78746 | Oil & Gas Operator | Sep 2003 |
| 30327 | United Security Associates Inc | | Oil & Gas Operator | Dec 2020 |
| 30328 | United Southern Resources Inc. | | Gas Operator | Nov 2013 |
| 30329 | United States Energy Corp. | Longview, TX 75601 | Oil & Gas Operator | Mar 2025 |
| 30330 | United States Exploration, Inc. | Denver, CO 80802 | Oil & Gas Operator | Apr 2007 |
| 30331 | United States Gypsum Company | Oakfield, NY 14125 | Oil & Gas Operator | Dec 2024 |
| 30332 | United Texas Oil LLC | Houston, TX 77027 | Oil & Gas Operator | Nov 2025 |
| 30333 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Nov 2025 |
| 30334 | United Utilities Corporation | Conroe, TX 77301 | Oil & Gas Operator | Oct 1998 |
| 30335 | United Well Completion, Inc | Corbin, KY 40701 | Oil & Gas Operator | Dec 2023 |
| 30336 | United World Energy Corporation | | Oil & Gas Operator | Dec 2024 |
| 30337 | United World Energy, Inc. | Aurora, CO 80040 | Oil & Gas Operator | Nov 2025 |
| 30338 | Unitex Oil & Gas, L.L.C. | Midland, TX 79701 | Oil & Gas Operator | Nov 2025 |
| 30339 | Unity Petroleum | Howard, OH 43028 | Oil & Gas Operator | Dec 2021 |
| 30340 | Universal Cyclops Specialty Steel Div | Pittsburgh, PA 15228-2702 | Gas Operator | Dec 1985 |
| 30341 | Universal Drilling Company | Denver, CO 80203 | Oil & Gas Operator | Sep 2003 |
| 30342 | Universal Exploration Inc | Wadsworth, OH 44281-9460 | Oil & Gas Operator | Feb 2012 |
| 30343 | Universal Fuels Company | | Oil & Gas Operator | Oct 1993 |
| 30344 | Universal Geopower LLC | Houston, TX 77057 | Oil & Gas Operator | May 2016 |
| 30345 | Universal Land | | Oil Operator | Dec 2024 |
| 30346 | Universal Oil Co. | | Oil Operator | Jan 2025 |
| 30347 | Universal Operating, Inc | Evansville, IN 47715 | Oil & Gas Operator | Dec 2023 |
| 30348 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 30349 | Universal Producers, Inc. | | Oil Operator | Jun 2001 |
| 30350 | Universal Resour | | Oil & Gas Operator | Dec 1996 |
| 30351 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 30352 | Universal Resources Holdings Inc | Dunkirk, NY 14048 | Oil & Gas Operator | Dec 2024 |
| 30353 | University Field Management LLC | | Oil Operator | Nov 2024 |
| 30354 | Unknown | Houston, TX 77208 | Oil & Gas Operator | Dec 2023 |
| 30355 | Unknown Owner | Columbus, OH 43229 | Oil & Gas Operator | Dec 2008 |
| 30356 | Unocal Explor. Corp. | | Oil & Gas Operator | Nov 1990 |
| 30357 | Unocal Exploration Corporation | Houston, TX 77001 | Oil & Gas Operator | May 1992 |
| 30358 | Unoco, Inc. | Kerrville, TX 78029 | Oil & Gas Operator | Jan 1999 |
| 30359 | Unoso Operating Company L.L.C. | Georgetown, TX 78633 | Oil & Gas Operator | Nov 2025 |
| 30360 | Unrein Oil Co | | Oil Operator | Jun 2025 |
| 30361 | Unruh, Elmer | Galva, KS 67443 | Oil & Gas Operator | Aug 1998 |
| 30362 | Unruh, Mark D. | Peru, KS 67360 | Oil Operator | Sep 2011 |
| 30363 | Unswept Oil Company | Corsicana, TX 75151 | Oil & Gas Operator | Jan 2018 |
| 30364 | Untamed Resources, LLC | Spearman, TX 79081 | Gas Operator | Nov 2025 |
| 30365 | Untener Bishop Kenneth (Diocese Of Saginaw) | | Oil Operator | Dec 2024 |
| 30366 | Uosi Operating, Inc. | Lovelady, TX 75851 | Oil & Gas Operator | Nov 2025 |
| 30367 | Upco | Mineral Wells, TX 76068 | Gas Operator | Sep 2001 |
| 30368 | Upcurve Energy, LLC | Houston, TX 77024 | Oil & Gas Operator | Nov 2025 |
| 30369 | Upda Operators, Inc. | Jacksboro, TX 76458 | Oil & Gas Operator | Dec 2009 |
| 30370 | Updike Resources Inc | Newcastle, WY 82701 | Oil & Gas Operator | Jun 1998 |
| 30371 | Upham Oil & Gas Company | Mineral Wells, TX 76068 | Oil & Gas Operator | Nov 2025 |
| 30372 | Upham, Chester R., Jr. | Mineral Wells, TX 76067 | Oil & Gas Operator | Aug 2001 |
| 30373 | Uphill Consulting LLC | Pearland, TX 77584 | Oil & Gas Operator | Nov 2025 |
| 30374 | Upland Exploration, LLC | Boerne, TX 78006 | Oil & Gas Operator | Jul 2024 |
| 30375 | Upland Operating, LLC | Dallas, TX 75226 | Oil & Gas Operator | Nov 2025 |
| 30376 | Upland Production Company | Edmond, OK 73083 | Oil & Gas Operator | Nov 2025 |
| 30377 | Upland Resources | | Oil Operator | Jul 1983 |
| 30378 | Upland Resources LLC | Canadian, TX 79014 | Oil & Gas Operator | Nov 2025 |
| 30379 | Upland Resources, Inc. | Canadian, TX 79014 | Oil & Gas Operator | Dec 2009 |
| 30380 | Uplands Resources Inc | Tulsa, OK 74103-4141 | Oil & Gas Operator | Jun 2025 |
| 30381 | Uplift Production Company, Inc. | Shamrock, TX 79079 | Oil & Gas Operator | Feb 1999 |
| 30382 | Upp Operating, LLC | Houston, TX 77002 | Oil & Gas Operator | Nov 2025 |
| 30383 | Upstream Exploration LLC | Metairie, LA 70002 | Oil & Gas Operator | Jan 2020 |
| 30384 | Upstream Properties, LLC | Southlake, TX 76092 | Oil & Gas Operator | Nov 2025 |
| 30385 | Upstream Resource Partners, LLC | Elkhart, TX 75839 | Oil Operator | Nov 2025 |
| 30386 | Uptex Operating Inc. | Dallas, TX 75201 | Oil & Gas Operator | May 2011 |
| 30387 | Uptex Operating, L.P. | Dallas, TX 75201 | Oil & Gas Operator | May 2010 |
| 30388 | Upton Resources U.S.A. Inc. | | Oil & Gas Operator | Oct 2013 |
| 30389 | Uranus, Inc. | Kansas City, MO 64112 | Oil Operator | Jan 2000 |
| 30390 | Urban Oil & Gas Group, LLC | Plano, TX 75074 | Oil & Gas Operator | Nov 2025 |
| 30391 | Urban, C A & Tersell L W | | Gas Operator | Aug 1937 |
| 30392 | Urroz Oil & Gas LLC | Evanston, WY 82931 | Oil & Gas Operator | Jun 2020 |
| 30393 | Ursa Major (Crow Og), LLC | Billings, MT 59101 | Gas Operator | Aug 2017 |
| 30394 | Ursa Operating Company LLC | Denver, CO 80265 | Oil & Gas Operator | Feb 2014 |
| 30395 | Ursus Oil And Gas | Tyler, TX 75703 | Oil & Gas Operator | Nov 2025 |
| 30396 | Us Ecology Winnie, LLC | Winnie, TX 77665 | Oil Operator | Nov 2025 |
| 30397 | Us Energy Corp. | Houston, TX 77057 | Oil & Gas Operator | Dec 2021 |
| 30398 | Us Energy Dev Corp | Getzville, NY 14068-1558 | Oil & Gas Operator | Dec 2021 |
| 30399 | Us Energy Exploration Corp | Rural Valley, PA 16249 | Oil & Gas Operator | May 2025 |
| 30400 | Us Energy Holdings, LLC | Richardson, TX 75080 | Oil & Gas Operator | Nov 2025 |