| 21501 | Oklahoma Prod & Exp Co | Broken Arrow, OK 74012 | Oil & Gas Operator | May 2013 |
| 21502 | Oklahoma RB Operating Company | Midland, TX 79701 | Oil & Gas Operator | Jan 1998 |
| 21503 | Oklahoma Rig & Salvage, Inc. | Oklahoma City, OK 73114 | Oil & Gas Operator | Mar 2015 |
| 21504 | Oklahoma Sterling Oil & Gas Corp | Tulsa, OK 74170 | Oil & Gas Operator | Jun 1997 |
| 21505 | Oklahoma SWD Systems Inc | Odessa, TX 79762-8132 | Oil & Gas Operator | Jan 2025 |
| 21506 | Oklahoma Tank Service Inc | Oklahoma City, OK 73143 | Oil Operator | Aug 1997 |
| 21507 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Feb 2025 |
| 21508 | Oklaoleum Oil And Gas Inc | Bristow, OK 74010-0057 | Oil Operator | Jan 2016 |
| 21509 | Oklatex Energy, Inc. | Beaumont, TX 77702 | Oil Operator | Apr 2025 |
| 21510 | Okmar Oil Compan | | Oil & Gas Operator | Feb 1995 |
| 21511 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 21512 | Okreek Oil Company | Weatherford, TX 76086 | Oil & Gas Operator | Apr 2025 |
| 21513 | Okt Petroleum Company Inc | Oklahoma City, OK 73118-7425 | Oil & Gas Operator | Oct 2013 |
| 21514 | Okt Resources, LLC | Edmond, OK 73013 | Oil & Gas Operator | Apr 2025 |
| 21515 | Oktex Operating LLC | Edmond, OK 73013-1961 | Oil & Gas Operator | May 2020 |
| 21516 | Oky Investments, Inc. | Edmond, OK 73013 | Oil & Gas Operator | Sep 2021 |
| 21517 | Ol' Boys Operations LLC | Pampa, TX 79065 | Oil & Gas Operator | Apr 2025 |
| 21518 | Ol' Oily LLC | | Oil Operator | Dec 2024 |
| 21519 | Old Acres Farm, Inc. | Perry, NY 14530 | Gas Operator | Dec 2023 |
| 21520 | Old Cedron, L.L.C. | Lubbock, TX 79410 | Oil & Gas Operator | May 2004 |
| 21521 | Old Chief Oil, LLC | New Braunfels, TX 78132 | Oil Operator | Apr 2025 |
| 21522 | Old Dominion Oil Corporation | Oklahoma City, OK 73107 | Oil & Gas Operator | Apr 2009 |
| 21523 | Old Field Associates | | Oil & Gas Operator | Dec 2024 |
| 21524 | Old MTN Gas Co Inc | Pleasantville, PA 16341-0329 | Oil & Gas Operator | Dec 2020 |
| 21525 | Old Pine Energy Corporation | Austin, TX 78755 | Oil Operator | Apr 2025 |
| 21526 | Old South Oil LLC | Marietta, OH 45750 | Oil & Gas Operator | Dec 2023 |
| 21527 | Old Timers Oil | Saratoga, TX 77585 | Oil & Gas Operator | Nov 2014 |
| 21528 | Old Timers Oil Company, LLC | Saratoga, TX 77585 | Oil Operator | Aug 2022 |
| 21529 | Old Timers Oil No. 2 Incorporated | Saratoga, TX 77585 | Oil Operator | Apr 2025 |
| 21530 | Old Union Operating Company | Austin, TX 78716 | Oil & Gas Operator | Apr 2025 |
| 21531 | Olde Chautauqua Farms | Portland, NY 14769 | Gas Operator | Dec 2023 |
| 21532 | Older Than Dirt LLC | Palo Pinto, TX 76484 | Oil & Gas Operator | Apr 2025 |
| 21533 | Oldfield Acquisition LP | Austin, TX 78733 | Oil & Gas Operator | Sep 1996 |
| 21534 | Oldfield Operating Corporation | | Oil Operator | Dec 2013 |
| 21535 | Olds Oil Company | Casper, WY 82604 | Oil Operator | Jun 1988 |
| 21536 | Ole Chaparral On Possum Kingdom | Wichita Falls, TX 76307 | Oil & Gas Operator | Dec 1997 |
| 21537 | Ole Crow Operating | Wichita Falls, TX 76308 | Oil Operator | Jan 2025 |
| 21538 | Ole Miss Oil & Gas Inc | New Bremen, OH 45689 | Oil & Gas Operator | Dec 1985 |
| 21539 | Ole, Inc. | Graham, TX 76450 | Oil & Gas Operator | Aug 2003 |
| 21540 | Oleksandr Antonyuk | | Oil & Gas Operator | Dec 2018 |
| 21541 | Oleum Energy LLC | Georgetown, TX 78628 | Oil & Gas Operator | Feb 2025 |
| 21542 | Oleum Exploration, LLC | Brodheadsvill, PA 18322 | Oil & Gas Operator | Mar 2023 |
| 21543 | Oleum Incorporat | | Gas Operator | Dec 1990 |
| 21544 | Oleum Incorporated | | Oil & Gas Operator | Mar 1996 |
| 21545 | Oleum Operating Company, L.C. | Longview, TX 75606 | Oil & Gas Operator | Dec 2021 |
| 21546 | Oleum Operating La LLC | | Oil & Gas Operator | Nov 2022 |
| 21547 | Oleum Partners, LLC | Frisco, TX 75034 | Oil & Gas Operator | Apr 2025 |
| 21548 | Olia Oil & Gas Services LLC | Cedar Park, TX 78630-2049 | Oil & Gas Operator | Aug 2022 |
| 21549 | Oliditt Corporation | | Gas Operator | Mar 2022 |
| 21550 | Oliditt Production Inc. | | Gas Operator | Sep 1998 |
| 21551 | Olifant Energy LLC | Tulsa, OK 74119 | Oil & Gas Operator | Jun 2019 |
| 21552 | Olipdp II, LLC | Lafayette, LA 70503 | Oil & Gas Operator | Apr 2025 |
| 21553 | Oliphant Gertrud | Holdenville, OK 74848-0849 | Oil Operator | Aug 2013 |
| 21554 | Oliphant Operating LTD LLC | Tulsa, OK 74159-4529 | Oil Operator | Jan 2025 |
| 21555 | Olive Oil & Gas | Ellensboro, WV 26346 | Oil & Gas Operator | Dec 2021 |
| 21556 | Olive Oil & Gas Inc | Jennings, OK 74038 | Oil & Gas Operator | Nov 2024 |
| 21557 | Oliver Oil & Gas | Midland, TX 79702 | Oil & Gas Operator | Apr 2025 |
| 21558 | Olmos Partners, Inc. | Boerne, TX 78006 | Oil & Gas Operator | Apr 2025 |
| 21559 | Olney Oil LLC | Boerne, TX 78006 | Oil Operator | Apr 2025 |
| 21560 | Olney Properties, Inc. | Wichita Falls, TX 76307 | Oil & Gas Operator | Sep 2003 |
| 21561 | Olsan Brothers, Inc. | Dallas, TX 75251 | Oil & Gas Operator | Apr 1994 |
| 21562 | Olsen Energy Inc. | Boerne, TX 78006 | Oil & Gas Operator | Apr 2025 |
| 21563 | Olson D Producti | | Oil Operator | Jul 1994 |
| 21564 | Olson, S. A. | Kenedy, TX 78119 | Oil & Gas Operator | Aug 1994 |
| 21565 | Olson-Anderson Lease | | Oil Operator | Mar 2018 |
| 21566 | Oltex Production | Idalou, TX 79329 | Oil & Gas Operator | Apr 2025 |
| 21567 | Olympia Oil Inc | Edmond, OK 73083-7088 | Oil & Gas Operator | Jul 2020 |
| 21568 | Olympic Exploration & Production Co | Norman, OK 73072 | Oil Operator | May 2003 |
| 21569 | Olympic Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Jul 2004 |
| 21570 | Olympic Natural Gas Company | | Oil & Gas Operator | Oct 1990 |
| 21571 | Olympic Oil & Gas Co., Inc. | | Oil Operator | Apr 1991 |
| 21572 | Olympic Oil, Inc. | Hutchinson, KS 67502 | Oil & Gas Operator | Dec 2024 |
| 21573 | Olympic Petroleu | | Oil & Gas Operator | Jul 1993 |
| 21574 | Olympic Petroleum Company | Tulsa, OK 74114 | Oil & Gas Operator | Jun 1998 |
| 21575 | Olympic Production Company | | Oil & Gas Operator | Jul 1994 |
| 21576 | Olympic Resources Co | Wooster, OH 44691 | Oil & Gas Operator | Dec 2000 |
| 21577 | Olympus Energy, LLC | Canonsburg, PA 15317 | Gas Operator | Feb 2025 |
| 21578 | Olympus Prop Inc | Franklin Park, IL 60131-1418 | Oil & Gas Operator | Dec 1997 |
| 21579 | Omac Oil & Gas Co | Newark, OH 43055 | Oil & Gas Operator | Dec 1990 |
| 21580 | Omar Operating Company | Midland, TX 79702 | Oil & Gas Operator | Sep 2013 |
| 21581 | Omber Petroleum & Energy Corp. | New Braunfels, TX 78131 | Oil & Gas Operator | Apr 2025 |
| 21582 | Omeara Bros. | | Oil & Gas Operator | Oct 1982 |
| 21583 | Omega Alpha Resources, LLC | Dallas, TX 75219 | Oil Operator | Apr 2025 |
| 21584 | Omega Energy Corp. | Graham, TX 76450 | Oil & Gas Operator | Apr 2025 |
| 21585 | Omega Energy Incorporated | | Oil & Gas Operator | May 1998 |
| 21586 | Omega Energy, LLC | Corpus Chrsti, TX 78418 | Oil & Gas Operator | Apr 2025 |
| 21587 | Omega Enterprise | | Oil Operator | Sep 1990 |
| 21588 | Omega Oil Corp | Lafayette, IN 47903 | Oil & Gas Operator | Dec 1987 |
| 21589 | Omega Operating, Inc. | Odessa, TX 79769 | Oil & Gas Operator | Mar 2001 |
| 21590 | Omega Resources Inc | | Oil & Gas Operator | Nov 1998 |
| 21591 | Omimex Canada, LTD. | Fort Worth, TX 76120-3608 | Oil & Gas Operator | Feb 2025 |
| 21592 | Omimex Energy, Inc. | Fort Worth, TX 76120 | Oil & Gas Operator | Dec 2024 |
| 21593 | Omimex International Corporation | Fort Worth, TX 76103-2300 | Oil & Gas Operator | Jan 2025 |
| 21594 | Omimex Petroleum Inc | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2022 |
| 21595 | Omimex Petroleum Inc (Co) | Newcastle, WY 82701 | Oil & Gas Operator | May 2001 |
| 21596 | Omimex Petroleum Inc (De) | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2020 |
| 21597 | Omni E & P, Inc. | San Antonio, TX 78229 | Oil Operator | Apr 2010 |
| 21598 | Omni Oil & Gas, Inc. | San Antonio, TX 78229 | Oil & Gas Operator | Oct 2017 |
| 21599 | Omni Operating Company | Osage, WY 82723 | Oil & Gas Operator | Sep 2001 |
| 21600 | Omni Operating Company(A) | Dallas, TX 75370 | Oil & Gas Operator | Apr 2025 |