| 401 | Monterey Pipeline Co. | | Oil Operator | Aug 1993 |
| 402 | Moore McCormack Energy, Inc. | | Oil & Gas Operator | Jul 1988 |
| 403 | Mosbacher Energy Company | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 404 | Munday Operating Co., L.L.C. | | Oil & Gas Operator | May 2007 |
| 405 | Murray J. Evans | | Oil Operator | Mar 1985 |
| 406 | Natural Resource MGMT. Corp. | | Oil & Gas Operator | Jun 1989 |
| 407 | Navitas Resources, LLC | | Oil & Gas Operator | May 2016 |
| 408 | Nearburg Producing Company | Dallas, TX 75380 | Oil & Gas Operator | Oct 2025 |
| 409 | Neuhoff Oil & Gas Corp. | | Oil & Gas Operator | Dec 1986 |
| 410 | Newfield Exploration Company | The Woodlands, TX 77380 | Oil & Gas Operator | Jun 2017 |
| 411 | Nexen Petroleum U.S.A. Inc. | Houston, TX 77024 | Oil & Gas Operator | Jul 2012 |
| 412 | Nicco Operating Co. | | Oil & Gas Operator | May 1990 |
| 413 | Nicklos Oil & Gas Co. | Dallas, TX 75201 | Oil & Gas Operator | Nov 1986 |
| 414 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Oct 2025 |
| 415 | North Central Oil Corp | Houston, TX 77252 | Oil & Gas Operator | Dec 2005 |
| 416 | O'Boyle Energy Corporation | | Oil Operator | Feb 1991 |
| 417 | O. D. Maybrier | | Oil Operator | Dec 2011 |
| 418 | O.I.L. Energy, Inc. | | Oil & Gas Operator | Dec 1984 |
| 419 | Ocean Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 420 | Ody Oil Corp. | | Oil & Gas Operator | Oct 1994 |
| 421 | Oil Country Management, Inc. | | Oil & Gas Operator | Jan 2005 |
| 422 | Oil Recovery, Inc. | | Oil Operator | Sep 1992 |
| 423 | Oleum Incorporated | | Oil & Gas Operator | Mar 1996 |
| 424 | Oleum Operating Company, L.C. | Longview, TX 75606 | Oil & Gas Operator | Dec 2021 |
| 425 | Oleum Operating La LLC | | Oil & Gas Operator | Nov 2022 |
| 426 | Olipdp II, LLC | Lafayette, LA 70503 | Oil & Gas Operator | Oct 2025 |
| 427 | Omni Operating Company | Osage, WY 82723 | Oil & Gas Operator | Sep 2001 |
| 428 | Onyx Energy Dev Of Texas Inc. | | Oil Operator | Dec 1996 |
| 429 | Onyx Energy Of Texas Inc. | | Oil Operator | Dec 1996 |
| 430 | Ops Group Limited | Houston, TX 77060 | Oil & Gas Operator | Jun 2014 |
| 431 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 432 | Oxtex Inc | | Oil & Gas Operator | Oct 1989 |
| 433 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |
| 434 | P & P Producing Inc | Midland, TX 79702 | Oil & Gas Operator | Feb 2015 |
| 435 | P. B. Operating Company | | Oil & Gas Operator | Feb 1978 |
| 436 | P.C.S.I. | | Oil & Gas Operator | Jun 1987 |
| 437 | Pacific Enterprises Oil Co. (USA) | Dallas, TX 75201 | Oil & Gas Operator | Feb 2001 |
| 438 | Painter Oil And Gas LTD. | | Oil & Gas Operator | Jun 1986 |
| 439 | Pan-Ok Production Company | | Oil & Gas Operator | Nov 2024 |
| 440 | Parker & Parsley Development Co. | Midland, TX 79702 | Oil & Gas Operator | May 1995 |
| 441 | Parker & Parsley Devpt L P | | Oil & Gas Operator | Oct 1997 |
| 442 | Parker & Parsley Petroleum Co. | | Oil & Gas Operator | Dec 1990 |
| 443 | Parker & Parsley Producing L.P. | Midland, TX 79702 | Oil & Gas Operator | Oct 1997 |
| 444 | Partners Oil Company | Tulsa, OK 74135 | Oil & Gas Operator | Aug 1995 |
| 445 | Pawnee Oil And Gas, Inc. | Richardson, TX 75083 | Oil & Gas Operator | May 2023 |
| 446 | Pel-Tex Oil Company, Inc. | | Oil & Gas Operator | Jul 1995 |
| 447 | Pennzoil Exploration & Production Co. | Carthage, TX 75633 | Oil & Gas Operator | Mar 2008 |
| 448 | Peoples Energy Prod.-TX, L.P. | Houston, TX 77002 | Oil & Gas Operator | Sep 2007 |
| 449 | Perdido Energy Louisiana, LLC | | Oil & Gas Operator | Dec 2024 |
| 450 | Petro-Hunt, L.L.C. | Dallas, TX 75201 | Oil & Gas Operator | Oct 2025 |
| 451 | Petro-Lewis Corp. | | Oil & Gas Operator | Feb 1994 |
| 452 | Petrodome Operating, LLC | Houston, TX 77265 | Oil & Gas Operator | Jun 2025 |
| 453 | Petrofunds, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jun 1996 |
| 454 | Petroglen Company, Inc. | | Oil & Gas Operator | Jul 1990 |
| 455 | Petrohawk Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2021 |
| 456 | Petroleum Futures-Chapman Oil | | Oil & Gas Operator | Jul 1981 |
| 457 | Petroleum Resources MGMT Corp. | | Oil & Gas Operator | Mar 2002 |
| 458 | Petroquest Energy, Inc. | Lafayette, LA 70505 | Oil & Gas Operator | Feb 2001 |
| 459 | Petroquest Energy, L.L.C. | Lafayette, LA 70505 | Oil & Gas Operator | Oct 2025 |
| 460 | Petroquest Exploration, Inc. | Dallas, TX 75251 | Oil & Gas Operator | Mar 2008 |
| 461 | Petrus Oil Company., L.P. | | Oil & Gas Operator | Dec 1989 |
| 462 | Petrus Operating Co., Inc. | | Oil & Gas Operator | Dec 1986 |
| 463 | Pharaoh Oil & Gas, Inc. | MC Camey, TX 79752 | Oil & Gas Operator | Oct 2025 |
| 464 | Phillips Oil Company | Casper, WY 82602 | Oil & Gas Operator | Sep 1986 |
| 465 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |
| 466 | Phoenix Energy, Inc. | Oilmont, MT 59466 | Oil & Gas Operator | May 2025 |
| 467 | Phoenix Exploration Company LP | | Oil & Gas Operator | Sep 2011 |
| 468 | Phoenix Oil & Gas LTD., L.L.P. | Houston, TX 77010 | Oil & Gas Operator | Jun 2004 |
| 469 | Pioneer Natural Resources USA Inc | Irving, TX 75039 | Oil & Gas Operator | Jun 2025 |
| 470 | Pioneer Prod. Corp. | | Oil & Gas Operator | Jun 1986 |
| 471 | Pioneer Production Corp-Huggs | | Oil & Gas Operator | Jun 1986 |
| 472 | Pioneer Resources Producing, L.P | Irving, TX 75039 | Oil & Gas Operator | Feb 2001 |
| 473 | Planet Operating, LLC | | Oil & Gas Operator | Dec 2024 |
| 474 | Plano Corp. | | Oil & Gas Operator | Mar 2005 |
| 475 | Playa Oil & Gas, LP | | Oil & Gas Operator | Apr 2009 |
| 476 | Plymouth Resources Group II Inc | | Oil & Gas Operator | May 2007 |
| 477 | Polaris-MRM Production Co. | | Oil Operator | Nov 1985 |
| 478 | Power Reserves, Inc. | | Oil Operator | Feb 1999 |
| 479 | Prairie Producing Company | | Oil & Gas Operator | Dec 1992 |
| 480 | Premience Energy LLC | | Oil & Gas Operator | Dec 2024 |
| 481 | Premience Tepetate LLC | | Oil & Gas Operator | Jul 2014 |
| 482 | Presidio Exploration, Inc. | Englewood, CO 80155 | Oil & Gas Operator | May 1999 |
| 483 | Pride Energy Company | Tulsa, OK 74170 | Oil & Gas Operator | Oct 2025 |
| 484 | Prime Operating Company | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 485 | Prize Operating Company | Grapevine, TX 76051 | Oil & Gas Operator | Aug 2016 |
| 486 | Proton Energy, L.L.C. | Houston, TX 77002 | Oil & Gas Operator | Jun 2005 |
| 487 | Quanah Petroleum, Inc. | | Oil & Gas Operator | Sep 1983 |
| 488 | Quarles Drilling Corporation | Tulsa, OK 74136 | Oil & Gas Operator | Feb 2008 |
| 489 | Quest Exploration L.L.C. | | Oil & Gas Operator | Jul 2014 |
| 490 | Quinoco Petroleum Inc | | Oil & Gas Operator | Dec 1990 |
| 491 | Quintana Petroleum Corporation | Denver, CO 80265 | Oil & Gas Operator | Mar 1998 |
| 492 | Quintana-H H Cullen-Carl O&G | | Oil & Gas Operator | Jul 1984 |
| 493 | R & B Oil Company, LLC Of Texas | | Oil & Gas Operator | Jan 2025 |
| 494 | R. J. Davenport | | Oil Operator | May 1985 |
| 495 | Radke Oil Co., Inc. | | Oil Operator | May 2001 |
| 496 | Ramco Exploration, Inc. | | Oil & Gas Operator | Feb 1998 |
| 497 | Ramco, Inc. | | Oil & Gas Operator | May 1992 |
| 498 | Range Production Company | Fort Worth, TX 76102 | Oil & Gas Operator | Sep 2021 |
| 499 | Red River Oil & Gas Inc. | | Oil & Gas Operator | May 2012 |
| 500 | Red Wing Oil & Gas, Inc. | | Oil Operator | Sep 1990 |