| 501 | Mid Center Oil Company | | Oil & Gas Operator | Mar 2014 |
| 502 | Mid-Con Central Expl Co | Tulsa, OK 74136 | Oil & Gas Operator | Aug 2014 |
| 503 | Mid-Continent Energy Operating Company | Tulsa, OK 74103 | Oil & Gas Operator | Feb 2026 |
| 504 | Middle Bay Production Co. Inc. | Houston, TX 77010 | Oil & Gas Operator | Sep 2014 |
| 505 | Midgard Energy Company | The Woodlands, TX 77380 | Oil & Gas Operator | Dec 2014 |
| 506 | Midnight Hour LLC | Enid, OK 73702 | Oil & Gas Operator | Apr 2020 |
| 507 | Midwestern Exploration Company | Edmond, OK 73013 | Oil & Gas Operator | May 2025 |
| 508 | Mikco Inc | Tulsa, OK 74133 | Oil & Gas Operator | May 2001 |
| 509 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 510 | Minihan Production Co | Seminole, OK 74868 | Oil & Gas Operator | Jan 1997 |
| 511 | MJM Oil & Gas, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Aug 2003 |
| 512 | Mobil Exp & Prod Us Inc | Houston, TX 77060-1991 | Oil & Gas Operator | May 2001 |
| 513 | Monexco | Edmond, OK 73034-3776 | Oil & Gas Operator | Mar 2008 |
| 514 | Monexco LLC | Dallas, TX 75204-2634 | Oil & Gas Operator | Jan 2026 |
| 515 | Monroe Natural Gas Inc | Norman, OK 73071 | Oil & Gas Operator | Feb 2026 |
| 516 | Monterey Production Company LLC | Tulsa, OK 74136 | Oil & Gas Operator | Jan 2026 |
| 517 | Montgomery Exploration Co LTD | Dallas, TX 75204-2634 | Oil & Gas Operator | Jan 2026 |
| 518 | Moran Oil Enterprises LLC | Seminole, OK 74818 | Oil & Gas Operator | Dec 2019 |
| 519 | Morgan Petroleum Company | Edmond, OK 73083 | Oil & Gas Operator | Mar 1993 |
| 520 | Moss Ted A Operating Company | Oklahoma City, OK 73126-0187 | Oil & Gas Operator | Jun 1997 |
| 521 | Mustang Fuel Corp. Of Oklahoma | Oklahoma City, OK 73106 | Oil & Gas Operator | Nov 2016 |
| 522 | Nadel And Gussman LLC | Tulsa, OK 74119 | Oil & Gas Operator | Apr 2026 |
| 523 | National Cooperative RFG Assoc | McPherson, KS 67460-1404 | Oil & Gas Operator | Oct 2025 |
| 524 | National Energy Group Inc | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 525 | National Oil Company | Garden City, KS 67846 | Oil & Gas Operator | Jun 2024 |
| 526 | Native Gas Company LLC | Edmond, OK 73083-7435 | Oil & Gas Operator | Mar 2015 |
| 527 | Natural Gas Anadarko Company | Perryton, TX 79070 | Oil & Gas Operator | Apr 2026 |
| 528 | Natural Gas Anadarko Inc | Perryton, TX 79070 | Oil & Gas Operator | May 1999 |
| 529 | Natural Gas Compression Corp | Cleveland, OK 74020 | Oil & Gas Operator | Jan 2025 |
| 530 | Natural Gas Pipeline Co Of Am LLC | Downers Grove, IL 60515-3708 | Oil & Gas Operator | Mar 2015 |
| 531 | Naylor Operating Company LLC | Perryton, TX 79079-9703 | Oil & Gas Operator | Sep 2012 |
| 532 | Nbi Services, Inc. | Tulsa, OK 74159 | Oil & Gas Operator | Apr 2026 |
| 533 | Neas Operating | Pampa, TX 79065 | Oil & Gas Operator | Oct 2011 |
| 534 | New London Oil Inc. | Houston, TX 77253 | Oil & Gas Operator | Aug 2002 |
| 535 | Nichols Water Service Inc | Forgan, OK 73938 | Oil & Gas Operator | May 2018 |
| 536 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Apr 2026 |
| 537 | Noble Energy Production Inc | Houston, TX 77067 | Oil & Gas Operator | Apr 2026 |
| 538 | North Lake Resources LLC | Oklahoma City, OK 73132 | Oil & Gas Operator | Apr 2026 |
| 539 | Northport Production Company | Oklahoma City, OK 73113 | Oil & Gas Operator | Feb 2026 |
| 540 | Northwest Disposal Corporation | Laverne, OK 73848-0504 | Oil & Gas Operator | Jul 2014 |
| 541 | O K Swabbing Inc | Hennessey, OK 73742 | Oil & Gas Operator | Feb 2026 |
| 542 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Apr 2026 |
| 543 | O'Neill Properties, LTD. | Midland, TX 79702 | Oil & Gas Operator | Apr 2026 |
| 544 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Apr 2026 |
| 545 | Oakwood Resources Inc | Dallas, TX 75374 | Oil & Gas Operator | May 1998 |
| 546 | Oexco, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2015 |
| 547 | Oil Producers, Inc. Of Kansas | Wichita, KS 67206 | Oil & Gas Operator | Apr 2026 |
| 548 | Oil Property Management Inc | Attica, KS 67009 | Oil & Gas Operator | Feb 2021 |
| 549 | Oil Recovery Systems Inc | Tulsa, OK 74145-4619 | Oil & Gas Operator | Jan 2026 |
| 550 | Oilsearch Corporation | Albuquerque, NM 87109 | Oil & Gas Operator | Feb 1994 |
| 551 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2026 |
| 552 | Oklahoma Energy Acquisitions LP | Houston, TX 77094-1900 | Oil & Gas Operator | Feb 2026 |
| 553 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Feb 2026 |
| 554 | Olympic Petroleum Co | Tulsa, OK 74114 | Oil & Gas Operator | Jun 1998 |
| 555 | Omimex International Corp | Fort Worth, TX 76103-2300 | Oil & Gas Operator | Jan 2026 |
| 556 | Oneok Exploration Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 557 | Oneok Field Services Company | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2026 |
| 558 | Oneok Resources Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 559 | Opal Operating Company LLC | Edmond, OK 73013 | Oil & Gas Operator | Apr 2026 |
| 560 | Osterhout Phillip L | Drumright, OK 74030-0693 | Oil & Gas Operator | Jan 2014 |
| 561 | Otc Petroleum Corporation | Nichols Hill, OK 73116 | Oil & Gas Operator | Mar 2015 |
| 562 | Overflow Energy, LLC | Perryton, TX 79070 | Oil & Gas Operator | Apr 2026 |
| 563 | Ovintiv Mid-Continent Inc. | The Woodlands, TX 77380-2764 | Oil & Gas Operator | Feb 2026 |
| 564 | Oxford Oil Inc | Cleveland, OK 74020 | Oil & Gas Operator | Feb 1997 |
| 565 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Apr 2026 |
| 566 | P & P Producing Inc | Midland, TX 79702 | Oil & Gas Operator | Feb 2015 |
| 567 | P F Beeler LLC | Norman, OK 73072-7522 | Oil & Gas Operator | Jan 2026 |
| 568 | P.O.&G. Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Apr 2026 |
| 569 | Pacific Enterprise Oil Co USA | Los Angeles, CA 90071-2005 | Oil & Gas Operator | Aug 2012 |
| 570 | Pal Kids Inc | Coronado, CA 92118 | Oil & Gas Operator | Nov 2000 |
| 571 | Paloma Operating Co Inc | Houston, TX 77002-5220 | Oil & Gas Operator | Feb 2026 |
| 572 | Panenergy Services Inc | Houston, TX 77525 | Oil & Gas Operator | May 2001 |
| 573 | Panhandle Eastern Pipeline Company LP | Houston, TX 77002-6803 | Oil & Gas Operator | Oct 1999 |
| 574 | Panhandle Oil & Gas Consultants Inc | Woodward, OK 73802-5011 | Oil & Gas Operator | Jul 2015 |
| 575 | Panhandle Oilfield Service Companies Inc | Liberal, KS 67905-1256 | Oil Operator | Sep 2000 |
| 576 | Pantera Energy Company | Amarillo, TX 79101 | Oil & Gas Operator | Apr 2026 |
| 577 | Pardee Production Co. | Skiatook, OK 74070 | Oil & Gas Operator | Mar 2021 |
| 578 | Park Avenue Exploration Corp | Oklahoma City, OK 73102-5604 | Oil & Gas Operator | Sep 2011 |
| 579 | Parker & Parsley Dev Co | Midland, TX 79702 | Oil & Gas Operator | Mar 2015 |
| 580 | Parker & Parsley Dev LP | Irving, TX 75039-3745 | Oil & Gas Operator | Mar 2015 |
| 581 | Parwest Land Exploration Inc | Oklahoma City, OK 73112 | Oil & Gas Operator | Jan 2026 |
| 582 | Patina Oil & Gas Corporation | Denver, CO 80202 | Oil & Gas Operator | May 2016 |
| 583 | Patina Oklahoma Corp | Duncan, OK 73533-9523 | Oil & Gas Operator | Nov 2014 |
| 584 | Patrick R J & Jack H Vaughn | Oklahoma City, OK 73154 | Oil & Gas Operator | Feb 2002 |
| 585 | Patrick RJ Operating Co | Liberal, KS 67905-1157 | Oil & Gas Operator | Nov 2014 |
| 586 | Patton Dale | Stillwater, OK 74074 | Oil & Gas Operator | Dec 2011 |
| 587 | Payne Exploration Company | Crescent, OK 73028 | Oil & Gas Operator | Jan 2026 |
| 588 | Payne W C Family Trust | Oklahoma City, OK 73116-9044 | Oil & Gas Operator | Mar 2015 |
| 589 | Pennzoil Petroleum Company | Houston, TX 77252 | Oil & Gas Operator | Nov 1999 |
| 590 | Perkins Nova | Atwood, OK 74827-9738 | Oil Operator | Feb 2014 |
| 591 | Pet-Ex Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | Dec 2025 |
| 592 | Petra Petroleum Inc | Littleton, CO 80160-0319 | Oil & Gas Operator | Jun 2005 |
| 593 | Petro Speed Inc | Norman, OK 73069-8116 | Oil & Gas Operator | Mar 2015 |
| 594 | Petro-Haley | Borger, TX 79008 | Oil & Gas Operator | Apr 2026 |
| 595 | Petro-Management Assoc., Inc. | Edmond, OK 73083-2346 | Oil & Gas Operator | Jun 2007 |
| 596 | Petrocorp Incorporated | Tulsa, OK 74170 | Oil & Gas Operator | Nov 2021 |
| 597 | Petroglyph Operating Co | Boise, ID 83709 | Oil & Gas Operator | Jul 2017 |
| 598 | Petrohawk Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2021 |
| 599 | Petroleum Inc | Wichita, KS 67202 | Oil & Gas Operator | Oct 2021 |
| 600 | Petroleum Reserve Corporation | Plymouth MTNG, PA 19462 | Oil & Gas Operator | May 2008 |