| 601 | Outlaw Well Service LLC | Hays, KS 67601 | Oil Operator | Mar 2025 |
| 602 | Outline Oil Company LLC | Beeville, TX 78104 | Oil Operator | Jul 2025 |
| 603 | Outline Oil Corp. | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2025 |
| 604 | Outlook Petroleum Corp. | Midland, TX 79702 | Oil & Gas Operator | Jan 2001 |
| 605 | Outman, Joshua J. | Andover, NY 14806 | Oil & Gas Operator | Dec 2024 |
| 606 | Output Acquisition Corp. | | Oil & Gas Operator | Jul 2010 |
| 607 | Output Exploration LLC | | Oil & Gas Operator | Dec 2006 |
| 608 | Ouut Investing LLC | Mineral Wells, TX 76068 | Oil Operator | Mar 2020 |
| 609 | Ovaco Energy Inc. | | Oil & Gas Operator | Nov 2009 |
| 610 | Ovation Energy II, LP | Houston, TX 77279 | Oil & Gas Operator | Jun 2011 |
| 611 | Ovation Energy, LP | N Richlnd HLS, TX 76180 | Oil & Gas Operator | Sep 2004 |
| 612 | Overfield, Lee R | Waverly, KY 42462 | Oil Operator | Dec 2016 |
| 613 | Overflow Energy Stack LLC | Booker, TX 79005 | Oil Operator | Sep 2022 |
| 614 | Overflow Energy, LLC | Perryton, TX 79070 | Oil & Gas Operator | Jul 2025 |
| 615 | Overland Exploration Company | | Oil Operator | Jan 2025 |
| 616 | Overland Investments Inc | Coweta, OK 74429 | Oil & Gas Operator | Apr 2025 |
| 617 | Overland Operating Company, LLC | Abilene, TX 79601 | Oil Operator | Jul 2025 |
| 618 | Overland Resources LLC | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Jul 2019 |
| 619 | Overly Operating Co. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2013 |
| 620 | Overstreet, Jamie L | Hondo, TX 78861 | Oil & Gas Operator | Jul 2025 |
| 621 | Overton Park Oil & Gas LP | Fort Worth, TX 76109 | Oil & Gas Operator | Jul 2025 |
| 622 | Ovintiv Mid-Continent Inc. | The Woodlands, TX 77380-2764 | Oil & Gas Operator | May 2025 |
| 623 | Ovintiv USA Inc. | Denver, CO 80202 | Oil & Gas Operator | Jul 2025 |
| 624 | Owco Production Co., Inc. | | Oil Operator | Aug 1997 |
| 625 | Owen Production Co | | Oil Operator | May 2001 |
| 626 | Owen'S Pumping Service | | Oil Operator | Mar 2025 |
| 627 | Owen, Matthew | Hamilton, KS 66853 | Oil Operator | Sep 2016 |
| 628 | Owens James W | Tulsa, OK 74114-1425 | Oil & Gas Operator | Oct 2022 |
| 629 | Owens Oil | | Oil Operator | Dec 2000 |
| 630 | Owens Oil Company | Iowa Park, TX 76367 | Oil & Gas Operator | Sep 2008 |
| 631 | Owens Oil Company, LLC | Yates Center, KS 66783 | Oil Operator | Mar 2025 |
| 632 | Owens Pet Inc | Midland, TX 79702 | Oil & Gas Operator | Aug 1995 |
| 633 | Owens Petroleum | | Oil Operator | May 2006 |
| 634 | Owens Petroleum LLC | Yates Center, KS 66783 | Oil & Gas Operator | Mar 2025 |
| 635 | Owens Petroleum, Inc. | Midland, TX 79702 | Oil & Gas Operator | Aug 1995 |
| 636 | Owi Operating Co. LC | Ottawa, KS 66067 | Oil & Gas Operator | Dec 2009 |
| 637 | Owl Creek Operating Co., Inc. | Denver, CO 80206 | Oil & Gas Operator | Jul 2025 |
| 638 | Owl Creek Production Co., Inc. | Houston, TX 77027 | Oil & Gas Operator | Apr 2006 |
| 639 | Owl Creek Production Co., LLC | Denver, CO 80265 | Oil & Gas Operator | Jan 2006 |
| 640 | Owl Operating Ventures L.L.C. | Midland, TX 79708 | Oil & Gas Operator | Dec 2022 |
| 641 | Owl Ops II LLC | Midland, TX 79701 | Oil & Gas Operator | Jul 2025 |
| 642 | Owl Ops LLC | Midland, TX 79701 | Oil & Gas Operator | Jul 2025 |
| 643 | Own Resources Operating LLC | The Woodlands, TX 77381 | Oil & Gas Operator | May 2025 |
| 644 | Ows Acquisition Co LLC | Louisville, OH 44641 | Oil & Gas Operator | Dec 2024 |
| 645 | Ows Energy LLC | Carlton, PA 16311-1605 | Oil & Gas Operator | May 2025 |
| 646 | Ows Energy, Inc. | Montgomery, TX 77356 | Oil & Gas Operator | Jul 2025 |
| 647 | Oxbow EP LLC | Mathis, TX 78368 | Oil Operator | Jul 2025 |
| 648 | Oxbow Oil Company,A Kansas General Partnership | Grenola, KS 67346 | Oil Operator | Apr 2015 |
| 649 | Oxbow Petroleum, LLC | Midland, TX 79703 | Oil & Gas Operator | May 2025 |
| 650 | Oxbow Properties Inc | Centennial, CO 80122-1422 | Oil & Gas Operator | Jan 2025 |
| 651 | Oxco, LLC | | Oil & Gas Operator | Feb 2015 |
| 652 | Oxenergy Incorporated | Flower Mound, TX 75022 | Oil & Gas Operator | Jul 2025 |
| 653 | Oxford Explorati | | Oil & Gas Operator | Mar 1993 |
| 654 | Oxford Exploration | | Oil Operator | Apr 1988 |
| 655 | Oxford Exploration Company | Denver, CO 80237 | Oil & Gas Operator | Aug 1995 |
| 656 | Oxford Oil | Zanesville, OH 43702 | Oil & Gas Operator | Dec 2012 |
| 657 | Oxford Oil Co. | Rockdale, TX 76567 | Oil & Gas Operator | Aug 2004 |
| 658 | Oxford Oil Inc | Cleveland, OK 74020 | Oil & Gas Operator | Feb 1997 |
| 659 | Oxley Energy LLC | Houston, TX 77042 | Gas Operator | Apr 2025 |
| 660 | Oxley John C | Tulsa, OK 74103 | Oil & Gas Operator | Sep 1996 |
| 661 | Oxley Petroleum | Tulsa, OK 74119-3609 | Oil & Gas Operator | Jan 2020 |
| 662 | Oxley Petroleum Co | Oklahoma City, OK 73118-1044 | Oil & Gas Operator | Sep 2017 |
| 663 | Oxson Co. | Uvalde, TX 78802 | Gas Operator | Jul 2025 |
| 664 | Oxtex Inc | | Oil & Gas Operator | Oct 1989 |
| 665 | Oxxn | Weatherford, TX 76086 | Oil & Gas Operator | Oct 2023 |
| 666 | Oxy Little Knife, LLC | | Oil & Gas Operator | Jan 2016 |
| 667 | Oxy Petroleum Inc | | Oil & Gas Operator | Jan 1986 |
| 668 | Oxy USA | | Oil Operator | Apr 1992 |
| 669 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Jul 2025 |
| 670 | Oxy USA WTP Limited Partnership | Houston, TX 772104294 | Oil & Gas Operator | May 2025 |
| 671 | Oxy USA WTP LP | Houston, TX 77046 | Oil & Gas Operator | Jul 2025 |
| 672 | Oxyrock Operating, LLC | Houston, TX 77046 | Oil & Gas Operator | Jul 2025 |
| 673 | Oz Gas Corporation | Austin, TX 78746 | Gas Operator | Jul 2025 |
| 674 | Oz Gas LTD | Tidioute, PA 16351-2648 | Oil & Gas Operator | Dec 2016 |
| 675 | Ozark Enterprise | | Oil Operator | Nov 1990 |
| 676 | Ozark Exploration, Inc. | Dallas, TX 75205 | Oil & Gas Operator | Jul 2025 |
| 677 | Ozark Oil Corporation | Springfield, MO 65804 | Oil & Gas Operator | Oct 1992 |
| 678 | Ozark Production Company, Inc. | | Oil & Gas Operator | Jan 2025 |
| 679 | Oztx Oil & Gas, L.L.C. | Ozona, TX 76943 | Oil & Gas Operator | Jul 2025 |
| 680 | Ozzo Corporation, The | Bedford, TX 76021 | Oil Operator | Jul 2025 |