| 601 | O'Brien-Sill | | Oil & Gas Operator | May 2025 |
| 602 | O'Donnell Oil LLC | | Oil & Gas Operator | Apr 2025 |
| 603 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Jul 2025 |
| 604 | Occidental Of Elk Hills Inc. | | Oil & Gas Operator | Dec 2014 |
| 605 | Occidental Petroleum Corporation | | Oil & Gas Operator | Dec 2021 |
| 606 | Off Broadway Mineral Rights LLC | | Oil & Gas Operator | Oct 2024 |
| 607 | Ogle Petroleum Inc. | | Oil & Gas Operator | Dec 1989 |
| 608 | Oil Operators Inc. | | Oil & Gas Operator | Nov 2024 |
| 609 | Oil Production Management Inc | Squaw Valley, CA 93675-9725 | Oil & Gas Operator | Dec 2002 |
| 610 | Oil Securities Inc. | | Gas Operator | Dec 2003 |
| 611 | Oil Well Management Co. | | Oil & Gas Operator | Dec 1989 |
| 612 | Ojai Oil Company | Camarillo, CA 93012 | Oil & Gas Operator | Apr 2025 |
| 613 | Old Field Associates | | Oil & Gas Operator | May 2025 |
| 614 | Oleksandr Antonyuk | | Oil & Gas Operator | Dec 2018 |
| 615 | Omimex Petroleum Inc | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2022 |
| 616 | Optima Conservation Resources Exploration LLC | | Oil & Gas Operator | Apr 2025 |
| 617 | Oro Negro Inc. | | Oil & Gas Operator | Dec 2004 |
| 618 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 619 | Output Exploration LLC | | Oil & Gas Operator | Dec 2006 |
| 620 | Oxy Petroleum Inc | | Oil & Gas Operator | Jan 1986 |
| 621 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Jul 2025 |
| 622 | P & C Oil Company | Leona, TX 75850 | Oil & Gas Operator | May 2025 |
| 623 | P & M Oil Company | Hays, KS 67601 | Oil & Gas Operator | Apr 2025 |
| 624 | Pace Diversified Corporation | | Oil & Gas Operator | Apr 2025 |
| 625 | Pacific Alliance Medical Center | | Oil Operator | Dec 2007 |
| 626 | Pacific Coast Energy Company LP | | Oil & Gas Operator | May 2025 |
| 627 | Pacific Energy Resources Inc. | | Oil Operator | Apr 2025 |
| 628 | Pacific Energy Resources LTD | | Oil & Gas Operator | Sep 2009 |
| 629 | Pacific Gas And Electric Company | | Gas Operator | May 2025 |
| 630 | Pacific Inland Operating Corporation | | Gas Operator | Dec 1993 |
| 631 | Pacific Palms Petroleum LLC | | Oil & Gas Operator | May 2025 |
| 632 | Pacific Petroleum Technology LLC | | Oil & Gas Operator | Dec 2018 |
| 633 | Padre Oil Co. | | Oil & Gas Operator | Apr 2025 |
| 634 | Pan American Energy Corporation | | Oil & Gas Operator | Dec 1998 |
| 635 | Pan Western Petroleum Co. | | Oil & Gas Operator | Dec 1993 |
| 636 | Pancanadian Petroleum Company | | Oil & Gas Operator | Oct 1989 |
| 637 | Panoche Vallecitos Oil Co. | | Oil & Gas Operator | Apr 2025 |
| 638 | Paris Valley Petroleum | | Oil Operator | Dec 2004 |
| 639 | Parlay Oil Company | | Oil Operator | Dec 2002 |
| 640 | Patriot Resources LLC | | Oil & Gas Operator | May 2025 |
| 641 | Paul Graham Drilling & Service Co. | | Oil & Gas Operator | Dec 2011 |
| 642 | Paul M. Woodward | | Oil Operator | Apr 2025 |
| 643 | Peak Operator LLC | | Oil & Gas Operator | Apr 2025 |
| 644 | Peninsula Open Space Trust | | Oil & Gas Operator | Dec 2008 |
| 645 | Penn Inc. | | Oil & Gas Operator | Dec 2004 |
| 646 | Pennant Petroleum Corporation | | Oil Operator | Dec 2002 |
| 647 | Pentarch Petroleum | | Oil Operator | May 2025 |
| 648 | Peoco LLC | | Gas Operator | Apr 2025 |
| 649 | Petaluma Oil & Gas | | Oil & Gas Operator | Dec 1999 |
| 650 | Petersen Production Company LLC | | Oil & Gas Operator | Dec 2019 |
| 651 | Petro Capital Resources LLC | | Oil & Gas Operator | Apr 2025 |
| 652 | Petro Nova | | Oil Operator | Dec 2000 |
| 653 | Petro Resources, Inc. | Fulton, TX 78358 | Oil & Gas Operator | Jul 2025 |
| 654 | Petro-Lewis Corp. | | Oil & Gas Operator | Feb 1994 |
| 655 | Petro-Lud Inc. | | Oil & Gas Operator | May 2025 |
| 656 | Petrogulf Corporation | Denver, CO 80202 | Oil & Gas Operator | Jul 2025 |
| 657 | Petrojen Production Company Inc | Bakersfield, CA 93311 | Oil Operator | Apr 2025 |
| 658 | Petrominerals Corp. | | Oil & Gas Operator | Dec 2003 |
| 659 | Petroprize | | Oil & Gas Operator | May 2025 |
| 660 | Petropro Energy Partners, L.P. | Houston, TX 77024 | Oil & Gas Operator | Jan 2013 |
| 661 | Petrowest | | Oil & Gas Operator | Dec 2001 |
| 662 | Philip H. McAlmond | | Oil Operator | Dec 2002 |
| 663 | Philip R. McPharlin | | Oil & Gas Operator | Dec 1995 |
| 664 | Phillip & Phyllis Pace-Trustee | | Oil & Gas Operator | Dec 2007 |
| 665 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |
| 666 | Pier Oil Company Inc. | | Oil Operator | Apr 2025 |
| 667 | Pine Meadows Ranch Incorporated | | Oil & Gas Operator | Dec 2001 |
| 668 | Pioneer Exploration, LLC | Houston, TX 77090 | Oil & Gas Operator | May 2025 |
| 669 | Plegel Oil Company Inc. | | Oil & Gas Operator | May 2025 |
| 670 | Polaris Production Inc. | | Oil & Gas Operator | Feb 2021 |
| 671 | Pool California Energy Services Inc. | | Oil Operator | Dec 2009 |
| 672 | Portals Woodward Joint Venture | | Oil Operator | Dec 2000 |
| 673 | Porter Sesnon Et Al | | Oil & Gas Operator | Dec 1978 |
| 674 | Poso Creek Energy LLC | | Oil & Gas Operator | Dec 2009 |
| 675 | Power Run Oil LLC | | Oil & Gas Operator | Apr 2025 |
| 676 | Powerdrive Energy Services Company LLC | | Oil & Gas Operator | May 2025 |
| 677 | Prado Petroleum Co. | | Oil & Gas Operator | Dec 1996 |
| 678 | Pre Resources LLC | | Oil & Gas Operator | Apr 2025 |
| 679 | Premier Pumping Unit Services Inc. | | Oil & Gas Operator | May 2025 |
| 680 | Preuitt Production Service | | Oil Operator | Apr 2025 |
| 681 | Princeton Natural Gas LLC | | Gas Operator | Apr 2025 |
| 682 | Production Specialties Company | | Oil & Gas Operator | Dec 2003 |
| 683 | Protho Energy Service LLC | | Oil & Gas Operator | May 2025 |
| 684 | PS126 Investments LLC | | Oil & Gas Operator | Apr 2025 |
| 685 | Pueblo Oil & Gas Inc. | | Gas Operator | Dec 2003 |
| 686 | Pyramid Oil Co. | Litchfield PK, AZ 85340 | Oil & Gas Operator | Jan 2018 |
| 687 | Quadren Cryogenic Process LTD. | | Gas Operator | May 2025 |
| 688 | Quintana Petroleum Corporation | Denver, CO 80265 | Oil & Gas Operator | Mar 1998 |
| 689 | R & R Entertainment Inc. | | Oil & Gas Operator | Dec 2011 |
| 690 | R&R Resources LLC | | Oil & Gas Operator | Apr 2025 |
| 691 | R. J. Bellevue | | Oil & Gas Operator | Apr 2025 |
| 692 | R. Scott Price | | Oil & Gas Operator | Dec 1994 |
| 693 | R. W. Henry | | Oil & Gas Operator | Dec 1999 |
| 694 | R. W. Shull | | Oil & Gas Operator | Dec 1986 |
| 695 | Raak-Wilson Properties | | Oil & Gas Operator | Dec 1999 |
| 696 | Randy J. & Deborah R. Allison | | Oil & Gas Operator | Dec 2003 |
| 697 | Rare Petro Exploration LLC | | Oil & Gas Operator | May 2025 |
| 698 | Razar Resources | | Oil & Gas Operator | Dec 2000 |
| 699 | Reabold California LLC | | Oil & Gas Operator | Apr 2025 |
| 700 | Redbank Oil Co. | | Oil Operator | Apr 2025 |