| 30501 | Tyson Olan | Hobart, OK 73651-6413 | Oil & Gas Operator | Apr 2015 |
| 30502 | Tytan Operating Company LLC | Edmond, OK 73083-3794 | Oil & Gas Operator | May 2016 |
| 30503 | U Bee Tea Production LLC | Culbertson, MT 59218 | Oil & Gas Operator | Mar 2025 |
| 30504 | U R C C | | Oil & Gas Operator | Jun 1991 |
| 30505 | U S Department Of Energy | | Oil & Gas Operator | Apr 1999 |
| 30506 | U S Drilling Company Inc | Holdenville, OK 74848-0913 | Oil & Gas Operator | Mar 2017 |
| 30507 | U S Energy Corp. Of Amer. Inc. | Ranger, TX 76470 | Oil & Gas Operator | May 2025 |
| 30508 | U S Exploraton Liq Trust | | Oil & Gas Operator | Oct 1994 |
| 30509 | U S Liquids Of La., L.P. | | Oil Operator | Apr 2014 |
| 30510 | U V Industries | | Oil & Gas Operator | Jan 1993 |
| 30511 | U-N-I Exploratio | | Oil & Gas Operator | Dec 1990 |
| 30512 | U-N-I Exploration & Development, Inc. | Yates Center, KS 66783 | Oil & Gas Operator | Jan 2003 |
| 30513 | U. D. Man, Inc. | San Antonio, TX 78212 | Oil & Gas Operator | May 2025 |
| 30514 | U. O. C., Inc. | | Oil Operator | Jun 2019 |
| 30515 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | May 2025 |
| 30516 | U.S. Capital Corp Of Am, Inc. | | Oil & Gas Operator | Aug 1998 |
| 30517 | U.S. Enercorp, LLC | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2004 |
| 30518 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 30519 | U.S. Energy Development Corp | Fort Worth, TX 76164 | Oil & Gas Operator | May 2025 |
| 30520 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 30521 | U.S. Oil Reclaimers, LLC | | Oil Operator | Jun 2023 |
| 30522 | U.S. Sovereign Oil And Gas, Inc. | Dallas, TX 75355 | Oil & Gas Operator | May 2025 |
| 30523 | U.S. Steel Mining Co., Inc. | | Gas Operator | Jan 2000 |
| 30524 | U.S. Steel Mining Co., LLC | | Gas Operator | Oct 2002 |
| 30525 | U.S.A. Plugging Company | Pearsall, TX 78061 | Oil & Gas Operator | May 2025 |
| 30526 | U1 Ranch Oil | Houston, TX 77269 | Oil & Gas Operator | May 2025 |
| 30527 | Uae Investco 1 (Estill), LLC | Ravenna, KY 40472 | Oil Operator | Dec 2022 |
| 30528 | Uae Investco 2 (Lee), LLC | Ravenna, KY 40472 | Oil Operator | Dec 2021 |
| 30529 | Ubetco, Inc. | Rockdale, TX 76567 | Oil & Gas Operator | May 2025 |
| 30530 | Uebelhor, Theodore | | Oil Operator | Dec 2023 |
| 30531 | Uehlin LLC | Oberlin, KS 67749 | Oil Operator | Dec 2024 |
| 30532 | Uhc New Mexico Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2007 |
| 30533 | Uhc Petroleum Corporation | Rocksprings, TX 78880 | Oil & Gas Operator | May 2025 |
| 30534 | Uhl Oil Co., Inc. | Bradford, PA 16701 | Oil & Gas Operator | Dec 2023 |
| 30535 | Uhl, Robert | Bradford, PA 16701 | Oil & Gas Operator | Dec 2023 |
| 30536 | Uhls, Jimmie J. | Sedan, KS 67361 | Oil Operator | Sep 2019 |
| 30537 | Uinta Oil & Gas | Roosevelt, UT 84066 | Oil & Gas Operator | Nov 1997 |
| 30538 | Uinta Wax Operating, LLC | Fort Worth, TX 76107 | Oil & Gas Operator | Mar 2025 |
| 30539 | Uinta-Taylor Fund, LTD | Roosevelt, UT 84066 | Oil & Gas Operator | Nov 2018 |
| 30540 | Uintah Investors LLC | Vernal, UT 84078 | Oil & Gas Operator | Mar 2025 |
| 30541 | Ulatex Oil & Gas Inc. | Nocona, TX 76255 | Oil & Gas Operator | Dec 1998 |
| 30542 | Ullum Oil And Gas Development Corporation, Inc. | Grantsville, WV 26147-0000 | Oil & Gas Operator | Dec 2021 |
| 30543 | Ulrich, William J., Jr. & Connie K. | Elma, NY 14059 | Gas Operator | Dec 2023 |
| 30544 | Ultra Oil & Gas, Inc. | Centerton, AR 72719 | Oil & Gas Operator | May 2025 |
| 30545 | Ultra Petroleum (U.S.A.), Inc. | Granbury, TX 76048 | Oil & Gas Operator | Sep 2003 |
| 30546 | Ultra Production Company, LLC | Cedar Bluff, VA 24609 | Gas Operator | Oct 2014 |
| 30547 | Ultra Resources Inc | Houston, TX 77060 | Oil & Gas Operator | Sep 2018 |
| 30548 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 30549 | Ultramar Production Company | | Oil & Gas Operator | Dec 1991 |
| 30550 | Ulysses, City Of | Ulysses, KS 67880 | Gas Operator | Jan 2025 |
| 30551 | Umberham Oil Company Inc | Oklahoma City, OK 73151-4000 | Oil & Gas Operator | Mar 2025 |
| 30552 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 30553 | Umma Resources, LLC | Portland, TX 78374 | Gas Operator | May 2025 |
| 30554 | Ummel'S Tank Ser | | Oil Operator | Sep 1994 |
| 30555 | Unbridled Resources, LLC | Houston, TX 77002 | Oil & Gas Operator | May 2025 |
| 30556 | Unc Texas Incorp | | Gas Operator | May 1987 |
| 30557 | Underground Energy Inc. | | Oil & Gas Operator | Feb 2025 |
| 30558 | Underwood Oil & Gas | Casper, WY 82602 | Oil & Gas Operator | Apr 2025 |
| 30559 | Underwood Oil And Gas LLC | Chandler, OK 74834-1414 | Oil & Gas Operator | Mar 2025 |
| 30560 | Underwood, Donald D. Dba Mustang Oil Co | Salem, WV 26426 | Oil & Gas Operator | Dec 2020 |
| 30561 | Underwood, Jim | Graham, TX 76450 | Oil & Gas Operator | Mar 2018 |
| 30562 | Underwood, Rip C | Amarillo, TX 79101 | Gas Operator | Sep 1963 |
| 30563 | Unger Well Drilling Corp | Dennison, OH 44621 | Oil & Gas Operator | Dec 1999 |
| 30564 | Uni Production Company, Inc. | | Oil & Gas Operator | Apr 1988 |
| 30565 | Unicon Producing Company | Houston, TX 75252 | Gas Operator | Mar 1994 |
| 30566 | Unicorn Drilling Inc | Cody, WY 82414 | Oil Operator | Dec 1998 |
| 30567 | Unicorn Energy, Inc. | Elgin, TX 78621 | Oil & Gas Operator | May 2025 |
| 30568 | Unicorn Oil & Gas Co Inc | Dorset, OH 44032 | Oil & Gas Operator | Dec 1993 |
| 30569 | Unifid Oil & Gas Corp. | | Oil & Gas Operator | Mar 1994 |
| 30570 | Unified Oil & Gas Corp. | Snyder, TX 79550 | Oil Operator | May 2025 |
| 30571 | Unioil | Denver, CO 80203 | Oil & Gas Operator | Jun 2012 |
| 30572 | Union Camp Corp | Dover, OH 44622 | Oil & Gas Operator | Dec 2002 |
| 30573 | Union City Boro Muni Auth Erie Cnty | Union City, PA 16438-1326 | Gas Operator | Dec 2023 |
| 30574 | Union Crude Company | Baytown, TX 77521 | Oil & Gas Operator | Apr 2018 |
| 30575 | Union Crude Operating Co. | Baytown, TX 77521 | Oil Operator | Aug 2003 |
| 30576 | Union Development Company Inc | | Oil & Gas Operator | Dec 1992 |
| 30577 | Union Diversified, Inc. | | Gas Operator | Dec 2008 |
| 30578 | Union Drilling &Management Inc | | Gas Operator | Feb 1991 |
| 30579 | Union Exploration Partners, LTD. | | Oil & Gas Operator | Aug 1990 |
| 30580 | Union Gas Corp. (Union Gas Co.) | Charleston, WV 25338-0000 | Oil & Gas Operator | Aug 2021 |
| 30581 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | May 2025 |
| 30582 | Union Oil Co | Danville, OH 43014 | Oil & Gas Operator | Dec 2014 |
| 30583 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 30584 | Union Operating Corp | Lakewoord, CO 80215 | Oil Operator | Dec 2023 |
| 30585 | Union Pacific Austin Chalk Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 30586 | Union Pacific Re | | Oil & Gas Operator | Dec 1996 |
| 30587 | Union Pacific Resour | | Oil & Gas Operator | Apr 2002 |
| 30588 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 30589 | Union Petro Inc | Uniontown, KY 42461 | Oil Operator | Dec 2023 |
| 30590 | Union Petrochemical | | Oil & Gas Operator | Dec 1982 |
| 30591 | Union Producing Co. | | Gas Operator | Dec 1992 |
| 30592 | Union Royalty, Inc. | Midland, TX 79706 | Oil & Gas Operator | Jul 2014 |
| 30593 | Union Seaboard Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 30594 | Union Springs Central School District | Union Springs, NY 13160 | Gas Operator | Dec 2023 |
| 30595 | Union Texas Petroleum | Houston, TX 77252 | Oil & Gas Operator | Oct 1991 |
| 30596 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 30597 | Union Valley Petroleum Corporation | Enid, OK 73701 | Oil & Gas Operator | Mar 2025 |
| 30598 | Unionville Explo | | Oil Operator | Jul 1984 |
| 30599 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Feb 2025 |
| 30600 | Unit Manager, Citronelle Unit | | Oil & Gas Operator | Sep 2001 |