| 30201 | U V Industries | | Oil & Gas Operator | Jan 1993 |
| 30202 | U-N-I Exploratio | | Oil & Gas Operator | Dec 1990 |
| 30203 | U-N-I Exploration & Development, Inc. | Yates Center, KS 66783 | Oil & Gas Operator | Jan 2003 |
| 30204 | U. D. Man, Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Nov 2025 |
| 30205 | U. O. C., Inc. | | Oil Operator | Jun 2019 |
| 30206 | U. S. Energy Development Corporation | Fort Worth, TX 76164 | Oil & Gas Operator | Nov 2025 |
| 30207 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Jul 2025 |
| 30208 | U.S. Capital Corp Of Am, Inc. | | Oil & Gas Operator | Aug 1998 |
| 30209 | U.S. Enercorp, LLC | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2004 |
| 30210 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 30211 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 30212 | U.S. Oil Reclaimers, LLC | | Oil Operator | Jun 2023 |
| 30213 | U.S. Sovereign Oil And Gas, Inc. | Dallas, TX 75355 | Oil & Gas Operator | Nov 2025 |
| 30214 | U.S. Steel Mining Co., Inc. | | Gas Operator | Jan 2000 |
| 30215 | U.S. Steel Mining Co., LLC | | Gas Operator | Oct 2002 |
| 30216 | U.S.A. Plugging Company | Pearsall, TX 78061 | Oil & Gas Operator | Nov 2025 |
| 30217 | U1 Ranch Oil | Houston, TX 77269 | Oil & Gas Operator | Nov 2025 |
| 30218 | Uae Investco 1 (Estill), LLC | Ravenna, KY 40472 | Oil Operator | Dec 2022 |
| 30219 | Uae Investco 2 (Lee), LLC | Ravenna, KY 40472 | Oil Operator | Dec 2021 |
| 30220 | Ubetco, Inc. | Rockdale, TX 76567 | Oil & Gas Operator | Nov 2025 |
| 30221 | Uebelhor, Theodore | | Oil Operator | Dec 2023 |
| 30222 | Uehlin LLC | Oberlin, KS 67749 | Oil Operator | Dec 2024 |
| 30223 | Uhc New Mexico Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2007 |
| 30224 | Uhc Petroleum Corporation | Rocksprings, TX 78880 | Oil & Gas Operator | Nov 2025 |
| 30225 | Uhl Oil Co., Inc. | Bradford, PA 16701 | Oil & Gas Operator | Dec 2024 |
| 30226 | Uhls, Jimmie J. | Sedan, KS 67361 | Oil Operator | Sep 2019 |
| 30227 | Uinta Oil & Gas | Roosevelt, UT 84066 | Oil & Gas Operator | Nov 1997 |
| 30228 | Uinta Wax Operating, LLC | Fort Worth, TX 76107 | Oil & Gas Operator | Aug 2025 |
| 30229 | Uintah Investors LLC | Vernal, UT 84078 | Oil & Gas Operator | Aug 2025 |
| 30230 | Ulatex Oil & Gas Inc. | Nocona, TX 76255 | Oil & Gas Operator | Dec 1998 |
| 30231 | Ullrich Sandy J | Haskell, OK 74436 | Oil Operator | Jul 2025 |
| 30232 | Ullum Oil And Gas Development Corporation, Inc. | Grantsville, WV 26147-0000 | Oil & Gas Operator | Dec 2021 |
| 30233 | Ulrich, William J., Jr. & Connie K. | Elma, NY 14059 | Gas Operator | Dec 2024 |
| 30234 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | Nov 2025 |
| 30235 | Ultra Petroleum (U.S.A.), Inc. | Granbury, TX 76048 | Oil & Gas Operator | Sep 2003 |
| 30236 | Ultra Production Company, LLC | Cedar Bluff, VA 24609 | Gas Operator | Oct 2014 |
| 30237 | Ultra Resources Inc | Houston, TX 77060 | Oil & Gas Operator | Sep 2018 |
| 30238 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 30239 | Ultramar Production Company | | Oil & Gas Operator | Dec 1991 |
| 30240 | Ulysses, City Of | Ulysses, KS 67880 | Gas Operator | Jun 2025 |
| 30241 | Umad LLC | | Oil & Gas Operator | Feb 2010 |
| 30242 | Umberham Oil Company Inc | Oklahoma City, OK 73151-4000 | Oil & Gas Operator | Aug 2025 |
| 30243 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 30244 | Umma Resources, LLC | Portland, TX 78374 | Gas Operator | Nov 2025 |
| 30245 | Ummel'S Tank Ser | | Oil Operator | Sep 1994 |
| 30246 | Unbridled Resources, LLC | Oklahoma City, OK 73102 | Oil & Gas Operator | Nov 2025 |
| 30247 | Unc Texas Incorp | | Gas Operator | May 1987 |
| 30248 | Underground Energy Inc. | | Oil & Gas Operator | Aug 2025 |
| 30249 | Underwood Oil & Gas | Casper, WY 82602 | Oil & Gas Operator | Sep 2025 |
| 30250 | Underwood Oil And Gas LLC | Chandler, OK 74834-1414 | Oil & Gas Operator | Aug 2025 |
| 30251 | Underwood, Donald D. Dba Mustang Oil Co | Salem, WV 26426 | Oil & Gas Operator | Dec 2020 |
| 30252 | Underwood, Jim | Graham, TX 76450 | Oil & Gas Operator | Mar 2018 |
| 30253 | Underwood, Rip C | Amarillo, TX 79101 | Gas Operator | Sep 1963 |
| 30254 | Unger Well Drilling Corp | Dennison, OH 44621 | Oil & Gas Operator | Dec 1999 |
| 30255 | Uni Production Company, Inc. | | Oil & Gas Operator | Apr 1988 |
| 30256 | Unicon Producing Company | Houston, TX 75252 | Gas Operator | Mar 1994 |
| 30257 | Unicorn Drilling Inc | Cody, WY 82414 | Oil Operator | Dec 1998 |
| 30258 | Unicorn Energy, Inc. | Elgin, TX 78621 | Oil & Gas Operator | Nov 2025 |
| 30259 | Unicorn Oil & Gas Co Inc | Dorset, OH 44032 | Oil & Gas Operator | Dec 1993 |
| 30260 | Unifid Oil & Gas Corp. | | Oil & Gas Operator | Mar 1994 |
| 30261 | Unified Oil & Gas Corp. | Snyder, TX 79550 | Oil Operator | Nov 2025 |
| 30262 | Unioil | Denver, CO 80203 | Oil & Gas Operator | Dec 2010 |
| 30263 | Union Camp Corp | Dover, OH 44622 | Oil & Gas Operator | Dec 2002 |
| 30264 | Union City Boro Muni Auth Erie Cnty | Union City, PA 16438-1326 | Gas Operator | Dec 2024 |
| 30265 | Union Crude Company | Baytown, TX 77521 | Oil & Gas Operator | Apr 2018 |
| 30266 | Union Crude Operating Co. | Baytown, TX 77521 | Oil Operator | Aug 2003 |
| 30267 | Union Development Company Inc | | Oil & Gas Operator | Dec 1992 |
| 30268 | Union Diversified, Inc. | | Gas Operator | Dec 2008 |
| 30269 | Union Drilling &Management Inc | | Gas Operator | Feb 1991 |
| 30270 | Union Expl. Partners, LTD. | | Oil & Gas Operator | Aug 1990 |
| 30271 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Nov 2025 |
| 30272 | Union Oil Co | Danville, OH 43014 | Oil & Gas Operator | Dec 2014 |
| 30273 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 30274 | Union Operating Corp | Lakewoord, CO 80215 | Oil Operator | Dec 2023 |
| 30275 | Union Pacific Austin Chalk Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 30276 | Union Pacific Re | | Oil & Gas Operator | Dec 1996 |
| 30277 | Union Pacific Resour | | Oil & Gas Operator | Apr 2002 |
| 30278 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 30279 | Union Petro Inc | Uniontown, KY 42461 | Oil Operator | Dec 2023 |
| 30280 | Union Petrochemical | | Oil & Gas Operator | Dec 1982 |
| 30281 | Union Producing Co. | | Gas Operator | Dec 1992 |
| 30282 | Union Royalty, Inc. | Midland, TX 79706 | Oil & Gas Operator | Jul 2014 |
| 30283 | Union Seaboard Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 30284 | Union Springs Central School District | Union Springs, NY 13160 | Gas Operator | Dec 2024 |
| 30285 | Union Texas Petroleum | Houston, TX 77252 | Oil & Gas Operator | Oct 1991 |
| 30286 | Union Texas Petroleum Corp | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 30287 | Union Valley Petroleum Corp | Enid, OK 73701 | Oil & Gas Operator | Aug 2025 |
| 30288 | Unionville Explo | | Oil Operator | Jul 1984 |
| 30289 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Apr 2025 |
| 30290 | Unit Manager, Citronelle Unit | | Oil & Gas Operator | Sep 2001 |
| 30291 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Nov 2025 |
| 30292 | United Company | Lubbock, TX 79408 | Oil & Gas Operator | Jun 1995 |
| 30293 | United Energy & Expl Inc | Ada, OK 74821-2449 | Oil & Gas Operator | Jun 2025 |
| 30294 | United Energy & Exploration LLC | Ada, OK 74821 | Oil & Gas Operator | Jun 2025 |
| 30295 | United Energy Corporation | San Antonio, TX 78209 | Oil & Gas Operator | Nov 2025 |
| 30296 | United Energy Develop Co LTD | Bartlesville, OK 74003 | Oil Operator | Mar 2004 |
| 30297 | United Energy Operating, LLC | Edmond, OK 73083 | Oil & Gas Operator | Nov 2025 |
| 30298 | United Energy Partners, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Mar 2008 |
| 30299 | United Energy, Inc. | Wichita, KS 67230 | Oil & Gas Operator | Dec 2002 |
| 30300 | United Fuel Gas Co | | Oil & Gas Operator | Dec 2022 |