| 30501 | Union Camp Corp | Dover, OH 44622 | Oil & Gas Operator | Dec 2002 |
| 30502 | Union City Boro Muni Auth Erie Cnty | Union City, PA 16438-1326 | Gas Operator | Dec 2023 |
| 30503 | Union Crude Company | Baytown, TX 77521 | Oil & Gas Operator | Apr 2018 |
| 30504 | Union Crude Operating Co. | Baytown, TX 77521 | Oil Operator | Aug 2003 |
| 30505 | Union Development Company Inc | | Oil & Gas Operator | Dec 1992 |
| 30506 | Union Diversified, Inc. | | Gas Operator | Dec 2008 |
| 30507 | Union Drilling &Management Inc | | Gas Operator | Feb 1991 |
| 30508 | Union Exploration Partners, LTD. | | Oil & Gas Operator | Aug 1990 |
| 30509 | Union Gas Corp. (Union Gas Co.) | Charleston, WV 25338-0000 | Oil & Gas Operator | Aug 2021 |
| 30510 | Union Gas Operating Company | Houston, TX 77014 | Oil & Gas Operator | Jun 2025 |
| 30511 | Union Oil Co | Danville, OH 43014 | Oil & Gas Operator | Dec 2014 |
| 30512 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 30513 | Union Operating Corp | Lakewoord, CO 80215 | Oil Operator | Dec 2023 |
| 30514 | Union Pacific Austin Chalk Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 30515 | Union Pacific Re | | Oil & Gas Operator | Dec 1996 |
| 30516 | Union Pacific Resour | | Oil & Gas Operator | Apr 2002 |
| 30517 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 30518 | Union Petro Inc | Uniontown, KY 42461 | Oil Operator | Dec 2023 |
| 30519 | Union Petrochemical | | Oil & Gas Operator | Dec 1982 |
| 30520 | Union Producing Co. | | Gas Operator | Dec 1992 |
| 30521 | Union Royalty, Inc. | Midland, TX 79706 | Oil & Gas Operator | Jul 2014 |
| 30522 | Union Seaboard Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 30523 | Union Springs Central School District | Union Springs, NY 13160 | Gas Operator | Dec 2023 |
| 30524 | Union Texas Petroleum | Houston, TX 77252 | Oil & Gas Operator | Oct 1991 |
| 30525 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 30526 | Union Valley Petroleum Corporation | Enid, OK 73701 | Oil & Gas Operator | Apr 2025 |
| 30527 | Unionville Explo | | Oil Operator | Jul 1984 |
| 30528 | Unit Drilling & Exploration Co | Tulsa, OK 74132-5300 | Oil & Gas Operator | Mar 2025 |
| 30529 | Unit Manager, Citronelle Unit | | Oil & Gas Operator | Sep 2001 |
| 30530 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Jun 2025 |
| 30531 | United Company | Lubbock, TX 79408 | Oil & Gas Operator | Jun 1995 |
| 30532 | United Energy & Expl Inc | Ada, OK 74821-2449 | Oil & Gas Operator | Mar 2025 |
| 30533 | United Energy & Exploration LLC | Ada, OK 74821 | Oil & Gas Operator | Mar 2025 |
| 30534 | United Energy Corporation | San Antonio, TX 78209 | Oil & Gas Operator | Jun 2025 |
| 30535 | United Energy Develop Co LTD | Bartlesville, OK 74003 | Oil Operator | Mar 2004 |
| 30536 | United Energy Inc. | Wichita, KS 67230 | Oil & Gas Operator | Dec 2002 |
| 30537 | United Energy Operating, LLC | Edmond, OK 73083 | Oil & Gas Operator | Jun 2025 |
| 30538 | United Energy Partners, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Mar 2008 |
| 30539 | United Fuel Gas Co | | Oil & Gas Operator | Dec 2022 |
| 30540 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |
| 30541 | United Investment Group | | Oil Operator | Nov 2004 |
| 30542 | United Meridian | | Oil Operator | Dec 1992 |
| 30543 | United Natural Gas LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2020 |
| 30544 | United Natural Resources Corp | | Oil Operator | Jan 1986 |
| 30545 | United O&G/Atlee Miller | Millersburg, OH 44654 | Oil & Gas Operator | Dec 1985 |
| 30546 | United Oil & Gas | | Oil Operator | Feb 1988 |
| 30547 | United Oil & Minerals L. P. | Austin, TX 78746 | Oil & Gas Operator | Jun 2003 |
| 30548 | United Oil & Minerals, Inc. | Austin, TX 78746 | Oil & Gas Operator | Jan 2001 |
| 30549 | United Oil Corporation | Denver, CO 80202-3813 | Oil & Gas Operator | Mar 2025 |
| 30550 | United Operating Company | Olney, TX 76374 | Oil & Gas Operator | Aug 2003 |
| 30551 | United Operating, LLC *** | Midland, TX 79710 | Oil & Gas Operator | Jun 2025 |
| 30552 | United Operators, Inc. | | Oil Operator | Sep 1999 |
| 30553 | United Petro LTD. | | Oil & Gas Operator | Dec 2018 |
| 30554 | United Petroleum | | Oil Operator | Mar 1986 |
| 30555 | United Petroleum & Gas, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Jun 2025 |
| 30556 | United Petroleum Corporation | Edgwater, CO 80214 | Oil & Gas Operator | May 1996 |
| 30557 | United Petroleum Technologies | Hondo, TX 78861 | Oil & Gas Operator | Aug 2001 |
| 30558 | United Primary Resources Inc | Milton, WA 98354-9361 | Oil & Gas Operator | Feb 2016 |
| 30559 | United Producers Inc | Broken Arrow, OK 74012-8247 | Oil & Gas Operator | Mar 2020 |
| 30560 | United Producing Co Inc | | Oil & Gas Operator | May 1961 |
| 30561 | United Production Company LLC | Edmond, OK 73003 | Oil & Gas Operator | Apr 2025 |
| 30562 | United Reserve G | | Oil Operator | Aug 1987 |
| 30563 | United Resources Corp | Olean, NY 14760 | Oil & Gas Operator | Dec 2020 |
| 30564 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 30565 | United Resources LP A Texas LMTD PRNTSHP | Austin, TX 78746 | Oil & Gas Operator | Sep 2003 |
| 30566 | United Security Associates Inc | | Oil & Gas Operator | Dec 2020 |
| 30567 | United Southern Resources Inc. | | Gas Operator | Nov 2013 |
| 30568 | United States Exploration, Inc. | Denver, CO 80802 | Oil & Gas Operator | Jun 2009 |
| 30569 | United States Gypsum Co | Oakfield, NY 14125 | Oil & Gas Operator | Dec 2023 |
| 30570 | United Texas Oil LLC | Houston, TX 77027 | Oil & Gas Operator | Jun 2025 |
| 30571 | United Texas Petroleum Inc. | McKinney, TX 75070 | Oil & Gas Operator | Jun 2025 |
| 30572 | United Utilities Corporation | Conroe, TX 77301 | Oil & Gas Operator | Oct 1998 |
| 30573 | United Well Completion, Inc | Corbin, KY 40701 | Oil & Gas Operator | Dec 2023 |
| 30574 | United World Energy Corporation | | Oil & Gas Operator | Dec 2024 |
| 30575 | United World Energy, Inc. | Aurora, CO 80040 | Oil & Gas Operator | Jun 2025 |
| 30576 | Unitex Oil & Gas, L.L.C. | Midland, TX 79701 | Oil & Gas Operator | Jun 2025 |
| 30577 | Unity Petroleum | Howard, OH 43028 | Oil & Gas Operator | Dec 2021 |
| 30578 | Universal Cyclops Specialty Steel Div | Pittsburgh, PA 15228-2702 | Gas Operator | Dec 1985 |
| 30579 | Universal Drilling Co., Inc. | Denver, CO 80203 | Oil & Gas Operator | Sep 2003 |
| 30580 | Universal Exploration Inc | Wadsworth, OH 44281-9460-9460 | Oil & Gas Operator | Feb 2012 |
| 30581 | Universal Fuels Company | | Oil & Gas Operator | Oct 1993 |
| 30582 | Universal Geopower LLC | Houston, TX 77057 | Oil & Gas Operator | May 2016 |
| 30583 | Universal Land | | Oil Operator | Dec 2024 |
| 30584 | Universal Oil Co. | | Oil Operator | Jan 2025 |
| 30585 | Universal Operating, Inc | Evansville, IN 47715 | Oil & Gas Operator | Dec 2023 |
| 30586 | Universal Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Sep 2002 |
| 30587 | Universal Producers, Inc. | | Oil Operator | Jun 2001 |
| 30588 | Universal Resour | | Oil & Gas Operator | Dec 1996 |
| 30589 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 30590 | Universal Resources Holdings Inc | Dunkirk, NY 14048 | Oil & Gas Operator | Dec 2023 |
| 30591 | University Field Management LLC | | Oil Operator | Nov 2024 |
| 30592 | Unknown | Houston, TX 77208 | Oil & Gas Operator | Dec 2023 |
| 30593 | Unknown Owner | Columbus, OH 43229 | Oil & Gas Operator | Dec 2008 |
| 30594 | Unocal Explor. Corp. | | Oil & Gas Operator | Nov 1990 |
| 30595 | Unocal Exploration Corporation | | Oil & Gas Operator | May 1992 |
| 30596 | Unoso Operating Company L.L.C. | Georgetown, TX 78633 | Oil & Gas Operator | Jun 2025 |
| 30597 | Unrein Oil Co | | Oil Operator | Feb 2025 |
| 30598 | Unruh, Elmer | Galva, KS 67443 | Oil & Gas Operator | Aug 1998 |
| 30599 | Unruh, Mark D. | Peru, KS 67360 | Oil Operator | Sep 2011 |
| 30600 | Unswept Oil Company | Corsicana, TX 75151 | Oil & Gas Operator | Jan 2018 |