| 30001 | Union Royalty, Inc. | Midland, TX 79706 | Oil & Gas Operator | Jul 2014 |
| 30002 | Union Seaboard Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 30003 | Union Springs Central School District | Union Springs, NY 13160 | Gas Operator | Dec 2025 |
| 30004 | Union Texas Petroleum | Houston, TX 77252 | Oil & Gas Operator | Oct 1991 |
| 30005 | Union Texas Petroleum Corp | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 30006 | Union Valley Petroleum Corp | Enid, OK 73701 | Oil & Gas Operator | May 2026 |
| 30007 | Unionville Explo | | Oil Operator | Jul 1984 |
| 30008 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Mar 2026 |
| 30009 | Unit Manager, Citronelle Unit | | Oil & Gas Operator | Sep 2001 |
| 30010 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Jul 2026 |
| 30011 | United Company | Lubbock, TX 79408 | Oil & Gas Operator | Jun 1995 |
| 30012 | United Energy & Expl Inc | Ada, OK 74821-2449 | Oil & Gas Operator | Apr 2026 |
| 30013 | United Energy & Exploration LLC | Ada, OK 74821 | Oil & Gas Operator | May 2026 |
| 30014 | United Energy Corporation | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2026 |
| 30015 | United Energy Develop Co LTD | Bartlesville, OK 74003 | Oil Operator | Mar 2004 |
| 30016 | United Energy Operating, LLC | Edmond, OK 73083 | Oil & Gas Operator | Jul 2026 |
| 30017 | United Energy Partners, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Mar 2008 |
| 30018 | United Energy, Inc. | Wichita, KS 67230 | Oil & Gas Operator | Dec 2002 |
| 30019 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |
| 30020 | United Investment Group | | Oil Operator | Nov 2004 |
| 30021 | United Meridian | | Oil Operator | Dec 1992 |
| 30022 | United Natural Gas LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2020 |
| 30023 | United Natural Resources Corp | | Oil Operator | Jan 1986 |
| 30024 | United O&G/Atlee Miller | Millersburg, OH 44654 | Oil & Gas Operator | Dec 1985 |
| 30025 | United Oil & Gas | | Oil Operator | Feb 1988 |
| 30026 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 30027 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 30028 | United Oil & Shale LLC | Woodward, OK 73801 | Oil & Gas Operator | Jul 2026 |
| 30029 | United Oil Corporation | Denver, CO 80202-3813 | Oil & Gas Operator | Apr 2026 |
| 30030 | United Operating Company | Olney, TX 76374 | Oil & Gas Operator | Aug 2003 |
| 30031 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Jul 2026 |
| 30032 | United Operators, Inc. | | Oil Operator | Sep 1999 |
| 30033 | United Petro LTD. | | Oil & Gas Operator | Dec 2018 |
| 30034 | United Petroleum | | Oil Operator | Mar 1986 |
| 30035 | United Petroleum & Gas, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Jul 2026 |
| 30036 | United Petroleum Corporation | Edgwater, CO 80214 | Oil & Gas Operator | May 1996 |
| 30037 | United Petroleum Technologies | Hondo, TX 78861 | Oil & Gas Operator | Aug 2001 |
| 30038 | United Primary Resources Inc | Milton, WA 98354-9361 | Oil & Gas Operator | Feb 2016 |
| 30039 | United Producers Inc | Broken Arrow, OK 74012-8247 | Oil & Gas Operator | Mar 2020 |
| 30040 | United Producing Co Inc | | Oil & Gas Operator | May 1961 |
| 30041 | United Production Company LLC | Edmond, OK 73003 | Oil & Gas Operator | May 2026 |
| 30042 | United Reserve G | | Oil Operator | Aug 1987 |
| 30043 | United Resources Corp | Olean, NY 14760 | Oil & Gas Operator | Dec 2024 |
| 30044 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 30045 | United Resources LP A Texas LMTD PRNTSHP | Austin, TX 78746 | Oil & Gas Operator | Sep 2003 |
| 30046 | United Security Associates Inc | | Oil & Gas Operator | Dec 2020 |
| 30047 | United Southern Resources Inc. | | Gas Operator | Nov 2013 |
| 30048 | United States Energy Corp. | Longview, TX 75601 | Oil & Gas Operator | Sep 2025 |
| 30049 | United States Exploration, Inc. | Denver, CO 80802 | Oil & Gas Operator | Apr 2007 |
| 30050 | United States Gypsum Company | Oakfield, NY 14125 | Oil & Gas Operator | Dec 2025 |
| 30051 | United Texas Oil LLC | Houston, TX 77027 | Oil & Gas Operator | Jul 2026 |
| 30052 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Jul 2026 |
| 30053 | United Utilities Corporation | Conroe, TX 77301 | Oil & Gas Operator | Oct 1998 |
| 30054 | United Well Completion, Inc | Corbin, KY 40701 | Oil & Gas Operator | Dec 2024 |
| 30055 | United World Energy Corporation | | Oil & Gas Operator | Dec 2024 |
| 30056 | United World Energy, Inc. | Aurora, CO 80040 | Oil & Gas Operator | Jul 2026 |
| 30057 | Unitex Oil & Gas, L.L.C. | Midland, TX 79701 | Oil & Gas Operator | Jul 2026 |
| 30058 | Unity Petroleum | Howard, OH 43028 | Oil & Gas Operator | Dec 2021 |
| 30059 | Universal Cyclops Specialty Steel Div | Pittsburgh, PA 15228-2702 | Gas Operator | Dec 1985 |
| 30060 | Universal Drilling Company | Denver, CO 80203 | Oil & Gas Operator | Sep 2003 |
| 30061 | Universal Exploration Inc | Wadsworth, OH 44281-9460 | Oil & Gas Operator | Feb 2012 |
| 30062 | Universal Fuels Company | | Oil & Gas Operator | Oct 1993 |
| 30063 | Universal Geopower LLC | Houston, TX 77057 | Oil & Gas Operator | May 2016 |
| 30064 | Universal Land | | Oil Operator | Dec 2024 |
| 30065 | Universal Oil Co. | | Oil Operator | Jan 2025 |
| 30066 | Universal Operating, Inc | Evansville, IN 47715 | Oil & Gas Operator | Dec 2024 |
| 30067 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 30068 | Universal Producers, Inc. | | Oil Operator | Jun 2001 |
| 30069 | Universal Resour | | Oil & Gas Operator | Dec 1996 |
| 30070 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 30071 | Universal Resources Holdings Inc | Dunkirk, NY 14048 | Oil & Gas Operator | Dec 2025 |
| 30072 | University Field Management LLC | | Oil Operator | Nov 2024 |
| 30073 | Unknown | Houston, TX 77208 | Oil & Gas Operator | Dec 2024 |
| 30074 | Unknown Owner | Columbus, OH 43229 | Oil & Gas Operator | Dec 2008 |
| 30075 | Unocal Explor. Corp. | | Oil & Gas Operator | Nov 1990 |
| 30076 | Unocal Exploration Corporation | Houston, TX 77001 | Oil & Gas Operator | May 1992 |
| 30077 | Unoco, Inc. | Kerrville, TX 78029 | Oil & Gas Operator | Jan 1999 |
| 30078 | Unoso Operating Company L.L.C. | Georgetown, TX 78633 | Oil & Gas Operator | Jul 2026 |
| 30079 | Unrein Oil Co | | Oil Operator | Mar 2026 |
| 30080 | Unruh, Elmer | Galva, KS 67443 | Oil & Gas Operator | Aug 1998 |
| 30081 | Unruh, Mark D. | Peru, KS 67360 | Oil Operator | Sep 2011 |
| 30082 | Unswept Oil Company | Corsicana, TX 75151 | Oil & Gas Operator | Jan 2018 |
| 30083 | Untamed Resources, LLC | Spearman, TX 79081 | Gas Operator | Jul 2026 |
| 30084 | Untener Bishop Kenneth (Diocese Of Saginaw) | | Oil Operator | Dec 2025 |
| 30085 | Uosi Operating, Inc. | Lovelady, TX 75851 | Oil & Gas Operator | Jul 2026 |
| 30086 | Upco | Mineral Wells, TX 76068 | Gas Operator | Sep 2001 |
| 30087 | Upcurve Energy, LLC | Houston, TX 77024 | Oil & Gas Operator | Jul 2026 |
| 30088 | Upda Operators, Inc. | Jacksboro, TX 76458 | Oil & Gas Operator | Dec 2009 |
| 30089 | Updike Resources Inc | Newcastle, WY 82701 | Oil & Gas Operator | Jun 1998 |
| 30090 | Upham Oil & Gas Company | Mineral Wells, TX 76068 | Oil & Gas Operator | Jul 2026 |
| 30091 | Upham, Chester R., Jr. | Mineral Wells, TX 76067 | Oil & Gas Operator | Aug 2001 |
| 30092 | Uphill Consulting LLC | Pearland, TX 77584 | Oil & Gas Operator | Jul 2026 |
| 30093 | Upland Exploration, LLC | Boerne, TX 78006 | Oil & Gas Operator | Jul 2024 |
| 30094 | Upland Operating, LLC | Dallas, TX 75226 | Oil & Gas Operator | Jul 2026 |
| 30095 | Upland Production Company | Edmond, OK 73083 | Oil & Gas Operator | Jul 2026 |
| 30096 | Upland Resources | | Oil Operator | Jul 1983 |
| 30097 | Upland Resources LLC | Canadian, TX 79014 | Oil & Gas Operator | Jul 2026 |
| 30098 | Upland Resources, Inc. | Canadian, TX 79014 | Oil & Gas Operator | Dec 2009 |
| 30099 | Uplands Resources Inc | Tulsa, OK 74103-4141 | Oil & Gas Operator | Apr 2026 |
| 30100 | Uplift Production Company, Inc. | Shamrock, TX 79079 | Oil & Gas Operator | Feb 1999 |