| 501 | Oren Stone | Erick, OK 73645-4542 | Gas Operator | Jun 2022 |
| 502 | Oretta Holdings LLC | Houston, TX 77010 | Oil & Gas Operator | Oct 2025 |
| 503 | Organic Energy Company LLC | | Oil & Gas Operator | Sep 2025 |
| 504 | Origin Prod Co Gonzales Prop LLC | New Braunfels, TX 78132 | Oil & Gas Operator | Oct 2025 |
| 505 | Origin Production Company, Inc. | New Braunfels, TX 78132 | Oil & Gas Operator | Oct 2025 |
| 506 | Origin Production Group LLC | Luling, TX 78648 | Oil Operator | Oct 2025 |
| 507 | Oringderff, Alma Oil Properties | Dallas, TX 75225 | Oil & Gas Operator | Mar 2012 |
| 508 | Oriole Operating LLC | Wichita Falls, TX 76308 | Oil Operator | Oct 2025 |
| 509 | Orion Energen Inc. | Austin, TX 78731 | Oil & Gas Operator | Jul 2023 |
| 510 | Orion Energy Corp | MT Vernon, IL 62864 | Oil & Gas Operator | Dec 1984 |
| 511 | Orion Energy Partners LP | Denver, CO 80202 | Oil & Gas Operator | Nov 2010 |
| 512 | Orion Exploration LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Apr 2015 |
| 513 | Orion Exploration Partners LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Jul 2025 |
| 514 | Orion Oil & Gas Prop | Roswell, NM 88202 | Oil & Gas Operator | Apr 1998 |
| 515 | Orion Oil & Gas Properties | Amarillo, TX 79109 | Gas Operator | Oct 2000 |
| 516 | Orion Oil & Gas, LLC | Houston, TX 77042 | Oil & Gas Operator | Oct 2007 |
| 517 | Orion Oil And Gas Corporation | Houston, TX 77082 | Oil & Gas Operator | Oct 2025 |
| 518 | Orion Petro Corp | MT Vernon, IL 62864 | Oil & Gas Operator | Dec 2016 |
| 519 | Orisol Oil Co. | Houston, TX 77206 | Oil Operator | Jun 2000 |
| 520 | Orla Petco Inc & Hopi Drilling Co | Midland, TX 79702 | Oil Operator | Sep 2004 |
| 521 | Orla Petco, Inc. | Midland, TX 79708 | Oil & Gas Operator | Oct 2025 |
| 522 | Orland Oil & Gas LLC | FT Lauderdale, FL 33305 | Oil Operator | Aug 2024 |
| 523 | Orleans Exploration Co., Inc. | | Oil & Gas Operator | Aug 1990 |
| 524 | Orloski John C | Bartlesville, OK 74006 | Oil & Gas Operator | Jun 2025 |
| 525 | Ormand, Don R. | Midland, TX 79705 | Oil & Gas Operator | Jan 2016 |
| 526 | Oro Negro Inc. | | Oil & Gas Operator | Dec 2004 |
| 527 | Oro Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 528 | Orr Energy LLC | | Oil & Gas Operator | Nov 2012 |
| 529 | Orr Production Company | Austin, TX 78746 | Oil & Gas Operator | Dec 2000 |
| 530 | Orr Robert W Jr | Zanesville, OH 43702-2683 | Oil & Gas Operator | Dec 2023 |
| 531 | Orr, Jr., Donald R. | Batavia, NY 14020 | Gas Operator | Dec 2024 |
| 532 | Orr, Robert M. | Monahans, TX 79756 | Oil & Gas Operator | Oct 1998 |
| 533 | Orsburn, Wade Inc. | Gainesville, TX 76240 | Oil & Gas Operator | Nov 2002 |
| 534 | Orson Leasing & Supply | Rockdale, TX 76567 | Oil & Gas Operator | Dec 2006 |
| 535 | Orth Oil Company, Inc. | Cisco, TX 76437 | Oil & Gas Operator | Oct 2025 |
| 536 | Orville S Slaughter Jr | Denver, CO 80205 | Oil & Gas Operator | Aug 2000 |
| 537 | Orwig Oil Company Inc | Bradenton, FL 34212 | Oil & Gas Operator | Dec 2022 |
| 538 | Orx Resources, Inc. | | Oil & Gas Operator | Dec 2009 |
| 539 | Orx Resources, L.L.C. | Houston, TX 77067 | Oil & Gas Operator | Oct 2025 |
| 540 | Oryx Energy Comp | | Oil & Gas Operator | Apr 1991 |
| 541 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 542 | Os&S Operating Inc. | Electra, TX 76360 | Oil & Gas Operator | Oct 2025 |
| 543 | Osa Oil & Gas LLC | Tulsa, OK 74131 | Oil & Gas Operator | Aug 2023 |
| 544 | Osage Energy Resources LLC | Bartlesville, OK 74005-2527 | Oil & Gas Operator | Jun 2025 |
| 545 | Osage Energy, LLC | Colony, KS 66015 | Oil Operator | Nov 2023 |
| 546 | Osage Exploration & Development Inc | San Diego, CA 92131-3807 | Oil & Gas Operator | Oct 2016 |
| 547 | Osage Hot Oil Service | Newcastle, WY 82701 | Oil & Gas Operator | Jul 1997 |
| 548 | Osage Oil & Transportation Inc | Cleveland, OK 74020 | Oil & Gas Operator | Nov 2000 |
| 549 | Osage Operating Company LLC | Seattle, WA 98133 | Oil Operator | May 2006 |
| 550 | Osage Partners LLC | | Oil & Gas Operator | Aug 2025 |
| 551 | Osage Petroleum Corporation | Saint Louis, MO 63131-4691 | Oil & Gas Operator | Mar 2009 |
| 552 | Osage Resources, LLC | Wichita, KS 67202 | Oil & Gas Operator | May 2025 |
| 553 | Osair Inc | Mentor, OH 44061 | Oil & Gas Operator | Dec 2021 |
| 554 | Osborn Energy, L.L.C. | Bucyrus, KS 66013 | Oil & Gas Operator | Jul 2017 |
| 555 | Osborn Heirs Co | San Antonio, TX 78217 | Oil & Gas Operator | Aug 2025 |
| 556 | Osborn Heirs Com | | Oil & Gas Operator | May 1995 |
| 557 | Osborn Heirs Company LTD | San Antonio, TX 78217 | Oil & Gas Operator | Jun 2025 |
| 558 | Osborn Oil & Gas | | Oil & Gas Operator | Jun 1991 |
| 559 | Osborn,W.B. Oil & Gas Operations | San Antonio, TX 78217 | Oil & Gas Operator | Oct 2025 |
| 560 | Osborne Oil Co. | Dallas, TX 75244 | Oil & Gas Operator | Aug 2003 |
| 561 | Osburn Gerald Dba Ozzy & Son Oil & Gas | Drumright, OK 74030-5467 | Oil Operator | Oct 2020 |
| 562 | Oscar Oil Company | Iowa Park, TX 76367 | Oil & Gas Operator | Sep 2004 |
| 563 | Oscar'S Well Service Inc | Okemah, OK 74859 | Oil & Gas Operator | Apr 1998 |
| 564 | Osceola Oil & Gas Corporation | Somerset, TX 78069 | Oil & Gas Operator | Aug 1994 |
| 565 | Osci Oil And Gas, Inc. | Parker, KS 66072 | Oil Operator | Jun 1998 |
| 566 | Oshtah Oil Company LLC | Stratford, OK 74872 | Oil & Gas Operator | Sep 2018 |
| 567 | Osman Global Services LLC | | Oil & Gas Operator | Jan 2025 |
| 568 | Oso Exploration & Production, LLC | Houston, TX 77269 | Oil Operator | Oct 2025 |
| 569 | Oso Exploration Co. | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2011 |
| 570 | Oso Oil & Gas Properties LLC | Price, UT 84501 | Gas Operator | Jun 2016 |
| 571 | Oso Perdido Services LLC | Flatonia, TX 78941 | Oil Operator | Jul 2025 |
| 572 | Oso Resources LLC | Edmond, OK 73003 | Oil & Gas Operator | Jun 2025 |
| 573 | Ososki Edward D Dba Federal Oil Company | | Oil & Gas Operator | Jun 2025 |
| 574 | Osprey Petroleum Company, Inc. | Manvel, TX 77578 | Oil & Gas Operator | May 2020 |
| 575 | Osr Oil & Gas Company | Victoria, TX 77902 | Oil & Gas Operator | Jul 2000 |
| 576 | Osr Oil & Gas Corp | Midland, TX 79710 | Oil & Gas Operator | Dec 2024 |
| 577 | Osterhout Phillip L | Drumright, OK 74030-0693 | Oil & Gas Operator | Jan 2014 |
| 578 | Ostrich Oil & Gas, LLC | Midland, TX 79701 | Oil & Gas Operator | Oct 2025 |
| 579 | Oswego Arbuckle Enterprise Inc | S Coffeyville, OK 74072-9702 | Oil & Gas Operator | Mar 2015 |
| 580 | Oswego Oil & Gas | | Oil & Gas Operator | Jun 1984 |
| 581 | Oswego, Inc. | Amarillo, TX 79109 | Oil & Gas Operator | Jun 2004 |
| 582 | Osyka Oil & Gas, Inc. | Metairie, LA 70004 | Oil & Gas Operator | Oct 2025 |
| 583 | Osyka Permian, LLC | Houston, TX 77079 | Oil & Gas Operator | Oct 2025 |
| 584 | Osyka Producing Company, Inc. | Houston, TX 77242 | Oil & Gas Operator | Oct 2025 |
| 585 | Otb Operating, LLC | Stanton, TX 79782 | Oil & Gas Operator | Oct 2025 |
| 586 | Otc Investors Inc | | Oil Operator | Jun 2025 |
| 587 | Otc Petroleum Corporation | Nichols Hill, OK 73116 | Oil & Gas Operator | Mar 2015 |
| 588 | Otc/Occ Not Assigned | | Oil & Gas Operator | Dec 2024 |
| 589 | Otex Inc | N Canton, OH 44720 | Oil & Gas Operator | Dec 1988 |
| 590 | Otex LLC | Santa Anna, TX 76878 | Oil & Gas Operator | Oct 2025 |
| 591 | Otex Resources LLC | Baytown, TX 77520 | Oil & Gas Operator | Oct 2025 |
| 592 | Otis C. Coles, Jr. | | Oil & Gas Operator | Jan 1998 |
| 593 | Oto, Co. | Woodward, OK 73802 | Oil & Gas Operator | Jun 1998 |
| 594 | Ott Inc | Casper, WY 82602 | Oil Operator | Jul 2025 |
| 595 | Otter Exploration Inc | Warren, PA 16365-9689 | Oil & Gas Operator | Dec 2021 |
| 596 | Ouachita Development Corp. | | Gas Operator | Mar 2014 |
| 597 | Ouachita Exploration Inc | Chickasha, OK 73018 | Oil & Gas Operator | Jun 2025 |
| 598 | Ouida Oil | Rowlett, TX 75030 | Oil & Gas Operator | Mar 2008 |
| 599 | Ouida Oil Co. | | Oil & Gas Operator | Apr 1999 |
| 600 | Outback Oil, Inc. | Pratt, KS 67124 | Gas Operator | Sep 2019 |