| 20501 | O. B. Beck | | Oil Operator | Feb 1991 |
| 20502 | O. B. Mobley | | Oil & Gas Operator | Jul 1989 |
| 20503 | O. B. Mobley, Et Al | | Oil Operator | Jul 1989 |
| 20504 | O. B. Whatley | | Oil Operator | Jul 1993 |
| 20505 | O. D. Maybrier | | Oil Operator | Dec 2011 |
| 20506 | O. F. H., Inc. | | Oil Operator | May 1990 |
| 20507 | O. G., Inc. | | Oil & Gas Operator | Nov 1992 |
| 20508 | O. H. B. Inc. | San Angelo, TX 76902 | Oil & Gas Operator | Sep 2019 |
| 20509 | O. H. M. Operating | Pampa, TX 79065 | Oil & Gas Operator | Sep 2024 |
| 20510 | O. O. Cummings | | Gas Operator | Jan 1999 |
| 20511 | O.B. Whatley Oil Company, Inc. | | Oil Operator | Feb 2013 |
| 20512 | O.B., Keith & Owen B. Whatley | | Oil Operator | Jul 1989 |
| 20513 | O.G.O. Refining | Luling, TX 78648 | Oil & Gas Operator | Jun 2013 |
| 20514 | O.G.P. Operating, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Sep 2024 |
| 20515 | O.I.L. Energy, Inc. | | Oil & Gas Operator | Dec 1984 |
| 20516 | O.T. Oil | Kilgore, TX 75663 | Oil Operator | Sep 2024 |
| 20517 | Oahe Oil Company | Texline, TX 79087 | Oil & Gas Operator | May 2004 |
| 20518 | Oak Dale Drilling Co | Logan, OH 43138-1851-1851 | Oil & Gas Operator | Dec 2015 |
| 20519 | Oak Energy, LLC | Houston, TX 77027 | Oil & Gas Operator | Sep 2024 |
| 20520 | Oak Grove Resources, LLC | | Gas Operator | May 2024 |
| 20521 | Oak Hill Petroleum Corporation | Oklahoma City, OK 73116-5627 | Oil & Gas Operator | Jun 2024 |
| 20522 | Oak Hills Drilling & Oper., LLC | Holdenville, OK 74848 | Oil & Gas Operator | May 2013 |
| 20523 | Oak Hills Energy Inc | Holdenville, OK 74848-0470 | Oil & Gas Operator | Sep 2014 |
| 20524 | Oak Prairie Operations, LLC | The Woodlands, TX 77381 | Oil & Gas Operator | Sep 2024 |
| 20525 | Oak Resources Inc | Tulsa, OK 74153 | Oil & Gas Operator | Aug 2013 |
| 20526 | Oak Ridge LLC | Wellsville, KS 66092 | Oil Operator | Dec 2019 |
| 20527 | Oak Tree Natural Res LLC | Oklahoma City, OK 73120-5065 | Oil & Gas Operator | Mar 2015 |
| 20528 | Oak Valley Operating, LLC | The Woodlands, TX 77380 | Oil & Gas Operator | Jun 2015 |
| 20529 | Oak Valley SWD LLC | Enid, OK 73703-4637 | Oil Operator | Aug 2022 |
| 20530 | Oakes Gas Co Inc | Kane, PA 16735-3905 | Gas Operator | Dec 2023 |
| 20531 | Oakfield Energy LLC | | Oil Operator | Jun 2019 |
| 20532 | Oakland Corporation | | Oil & Gas Operator | Dec 1981 |
| 20533 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Sep 2024 |
| 20534 | Oakley Oil & Gas, L.L.C. | | Oil & Gas Operator | Mar 2012 |
| 20535 | Oakmont CC | Oakmont, PA 15139-1135 | Gas Operator | Dec 2023 |
| 20536 | Oakmont Oil And Gas | Graham, TX 76450 | Oil Operator | Sep 2024 |
| 20537 | Oakridge Energy, Inc. | Wichita Falls, TX 76302 | Oil & Gas Operator | Sep 2024 |
| 20538 | Oakridge Oil And Gas, LP | Jacksboro, TX 76458 | Oil & Gas Operator | Sep 2024 |
| 20539 | Oaks Petroleum I | | Oil Operator | Jul 1987 |
| 20540 | Oaktree Oil Company | Albany, TX 76430 | Oil & Gas Operator | Sep 2024 |
| 20541 | Oakwood Resources, Inc. | Dallas, TX 75374 | Oil & Gas Operator | May 1998 |
| 20542 | Oasis Energy Resources LLC | Norman, OK 73072-9668 | Oil & Gas Operator | Jun 2024 |
| 20543 | Oasis Operating, Inc. | Lubbock, TX 79404 | Oil & Gas Operator | Nov 2020 |
| 20544 | Oasis Petroleum North America LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2024 |
| 20545 | Oasis Petroleum Permian LLC | Houston, TX 77002 | Oil & Gas Operator | Sep 2024 |
| 20546 | Oasis Production Co., Inc. | | Oil & Gas Operator | Jun 1988 |
| 20547 | Oast, Thomas H. | Greenville, NC 27835 | Oil Operator | Nov 1985 |
| 20548 | Oates, John Co., Inc. | Stinnett, TX 79083 | Oil & Gas Operator | Sep 2024 |
| 20549 | Obax Oil And Gas LLC | Saint Louis, MO 63131 | Oil Operator | Sep 2024 |
| 20550 | Obele Oil Corporation | Sedona, AZ 86336-5745 | Oil & Gas Operator | May 2017 |
| 20551 | Obele Operating Company LLC | Sedona, AZ 86336-5745 | Oil & Gas Operator | Jun 2024 |
| 20552 | Oberlander Leslie A Jake | Covington, OK 73730 | Oil Operator | Jun 2007 |
| 20553 | Obermeyer, C R | | Oil Operator | Dec 2022 |
| 20554 | Obermiller Clarence Trust | Creston, OH 44217 | Oil & Gas Operator | Dec 1987 |
| 20555 | Obermiller Paul J | Creston, OH 44217 | Oil & Gas Operator | Dec 2014 |
| 20556 | Oblaen Resources LLC | Wallis, TX 77485 | Oil & Gas Operator | Sep 2024 |
| 20557 | Obsidian Energy, LLC | McKinney, TX 75071 | Oil & Gas Operator | Jun 2024 |
| 20558 | Occ Operating Co. | | Oil & Gas Operator | Apr 2019 |
| 20559 | Occidental Energy Company, Inc. | Houston, TX 77282 | Oil & Gas Operator | Jul 2021 |
| 20560 | Occidental Energy Marketing, Inc. | Houston, TX 77227 | Gas Operator | Sep 2015 |
| 20561 | Occidental Energy MKT Inc | Houston, TX 77001 | Oil & Gas Operator | Jan 2011 |
| 20562 | Occidental Of Elk Hills Inc. | | Oil & Gas Operator | Dec 2014 |
| 20563 | Occidental Permian LTD. | Houston, TX 77046 | Oil & Gas Operator | Sep 2024 |
| 20564 | Occidental Petroleum Corporation | | Oil & Gas Operator | Dec 2021 |
| 20565 | Occidental W TX Overthrust, Inc. | Houston, TX 77210 | Oil & Gas Operator | Dec 2021 |
| 20566 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 20567 | Ocean Energy Inc Ndba Devon Louisiana Corp | | Oil & Gas Operator | Jul 2001 |
| 20568 | Ocean Energy Resources Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2024 |
| 20569 | Ocfiw Oil Company, Inc. | Hartington, NE 68739 | Oil & Gas Operator | Dec 2009 |
| 20570 | Ochiltree Oil Company | Edmond, OK 73034 | Oil & Gas Operator | Apr 2020 |
| 20571 | Oci LLC | Thermopolis, WY 82443 | Oil Operator | Jan 2024 |
| 20572 | Octagon Resources Corporation | | Oil Operator | Mar 2005 |
| 20573 | Octagon Resources LLC | Norman, OK 73071-1295 | Oil & Gas Operator | May 2015 |
| 20574 | Octane Energy Operating, LLC | Midland, TX 79701 | Oil & Gas Operator | Sep 2024 |
| 20575 | Odebralski, Michael & Connie | Fredonia, NY 14063 | Gas Operator | Dec 2023 |
| 20576 | Odegard Energy, Inc. | Houston, TX 77024 | Oil & Gas Operator | Jul 2020 |
| 20577 | Odegard Resources/Omni Exp | Columbus, OH 43207 | Oil & Gas Operator | Sep 1986 |
| 20578 | Odell Larry | Oologah, OK 74053 | Oil Operator | Apr 2011 |
| 20579 | Oden, Robin H., Inc. | Midland, TX 79702 | Oil & Gas Operator | Apr 1994 |
| 20580 | Odessa Exploration, Inc. | Midland, TX 79702 | Oil & Gas Operator | Sep 2024 |
| 20581 | Odessa Oil Investment Co., Inc. | Odessa, TX 79762 | Oil & Gas Operator | Nov 2016 |
| 20582 | Odom, Claude | | Oil Operator | Jul 1983 |
| 20583 | Odom, R. H. | Snyder, TX 79550 | Oil & Gas Operator | Jun 1996 |
| 20584 | Odom, Ralph R. | | Oil & Gas Operator | Aug 1993 |
| 20585 | Odum Oil & Gas Co. | Harper, TX 78631 | Oil & Gas Operator | Sep 2024 |
| 20586 | Ody Oil Corp. | | Oil & Gas Operator | Oct 1994 |
| 20587 | Odyssey Operating Company | | Oil & Gas Operator | Sep 2020 |
| 20588 | Odyssey Petroleum Company | Houston, TX 77010 | Oil & Gas Operator | Apr 1995 |
| 20589 | Odyssey Petroleum Corp. | | Oil & Gas Operator | Jun 2011 |
| 20590 | Oedekoven Amerifields Resources LLC | Sugar Land, TX 77478 | Oil Operator | Jun 2024 |
| 20591 | Oedekoven Water & Hot Oil | Recluse, WY 82725 | Oil & Gas Operator | Aug 2024 |
| 20592 | Oeth DRLG Co | | Oil Operator | Dec 2018 |
| 20593 | Oex-1 LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Mar 2024 |
| 20594 | Oexco, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2015 |
| 20595 | Off Broadway Mineral Rights LLC | | Oil & Gas Operator | Jun 2024 |
| 20596 | Offield Lease Operations LLC | Wilson, OK 73463 | Oil & Gas Operator | May 2023 |
| 20597 | Offset Oil & Gas | Big Spring, TX 79720 | Oil & Gas Operator | Aug 2003 |
| 20598 | Offshore Group, Inc. The | Houston, TX 77024 | Oil & Gas Operator | Sep 2024 |
| 20599 | Offshore Oil & Gas Inc | Houston, TX 77063 | Oil & Gas Operator | Sep 1994 |
| 20600 | Offshore Shelf LLC | | Oil & Gas Operator | Dec 2007 |