| 3401 | O.B., Keith & Owen B. Whatley | | Oil Operator | Jul 1989 |
| 3402 | O.G.P. Operating, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Feb 2026 |
| 3403 | O.I.L. Energy, Inc. | | Oil & Gas Operator | Dec 1984 |
| 3404 | Oak Energy, LLC | Houston, TX 77027 | Oil & Gas Operator | Feb 2026 |
| 3405 | Oak Valley Operating, LLC | The Woodlands, TX 77380 | Oil & Gas Operator | Jun 2015 |
| 3406 | Oakfield Energy LLC | | Oil Operator | Jun 2019 |
| 3407 | Oakland Corporation | | Oil & Gas Operator | Dec 1981 |
| 3408 | Oakley Oil & Gas, L.L.C. | | Oil & Gas Operator | Mar 2012 |
| 3409 | Oasis Production Co., Inc. | | Oil & Gas Operator | Jun 1988 |
| 3410 | Occ Operating Co. | | Oil & Gas Operator | Apr 2019 |
| 3411 | Occidental Energy Company, Inc. | Houston, TX 77282 | Oil & Gas Operator | Jul 2021 |
| 3412 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 3413 | Octagon Resources Corporation | | Oil Operator | Apr 2005 |
| 3414 | Ody Oil Corp. | | Oil & Gas Operator | Oct 1994 |
| 3415 | Odyssey Operating Company | Shreveport, LA 71106 | Oil & Gas Operator | Sep 2020 |
| 3416 | Offshore Oil & Gas Inc | Houston, TX 77063 | Oil & Gas Operator | Sep 1994 |
| 3417 | Offshore Shelf LLC | | Oil & Gas Operator | Dec 2007 |
| 3418 | Oil & Gas Development Company | | Oil & Gas Operator | May 1991 |
| 3419 | Oil & Gas Producers, Inc | Topeka, KS 66604 | Oil Operator | Jun 2004 |
| 3420 | Oil & Gas Property MGMT., Inc. | Dallas, TX 75201 | Oil & Gas Operator | Jul 1996 |
| 3421 | Oil And Gas Futures, Inc. | | Oil & Gas Operator | May 1977 |
| 3422 | Oil Country Management, Inc. | | Oil & Gas Operator | Jan 2005 |
| 3423 | Oil Lift Inc | Metairie, LA 70002 | Oil & Gas Operator | Apr 2020 |
| 3424 | Oil Palace, Inc. | | Oil Operator | Jun 2016 |
| 3425 | Oil Patch Operators, LLC | | Oil & Gas Operator | Jul 2005 |
| 3426 | Oil Recovery, Inc. | | Oil Operator | Sep 1992 |
| 3427 | Oil Reserves Corp Of America | | Oil & Gas Operator | May 2002 |
| 3428 | Oil Well Buyers Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 2024 |
| 3429 | Oil,Gas & Other Minerals, Inc. | | Oil & Gas Operator | Apr 1996 |
| 3430 | Oilfield Technical Services, Inc. | | Gas Operator | Jun 2018 |
| 3431 | Oilwell Acquisition Co | | Oil & Gas Operator | Jun 1999 |
| 3432 | Ok Oil Company, Inc. | Bivins, TX 75555 | Oil & Gas Operator | Feb 2013 |
| 3433 | Ok-La-Tex Production, Inc. | | Oil & Gas Operator | Jan 1982 |
| 3434 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Nov 2025 |
| 3435 | Okie Operating Company, LTD. | Tulsa, OK 74103 | Oil & Gas Operator | Feb 2026 |
| 3436 | Okkatahula, Inc. | | Oil Operator | Nov 1978 |
| 3437 | Oldfield Operating Corporation | | Oil Operator | Dec 2013 |
| 3438 | Oleum Inc | | Oil & Gas Operator | Mar 1996 |
| 3439 | Oleum Operating Company, L.C. | Longview, TX 75606 | Oil & Gas Operator | Dec 2021 |
| 3440 | Oleum Operating La LLC | | Oil & Gas Operator | Nov 2022 |
| 3441 | Oliditt Corporation | | Gas Operator | Mar 2022 |
| 3442 | Oliditt Production Inc. | | Gas Operator | Sep 1998 |
| 3443 | Olipdp II, LLC | Lafayette, LA 70503 | Oil & Gas Operator | Feb 2026 |
| 3444 | Olympic Natural Gas Company | | Oil & Gas Operator | Oct 1990 |
| 3445 | Olympic Oil & Gas Co., Inc. | | Oil Operator | Apr 1991 |
| 3446 | Olympic Oil & Gas Expl. Co. | | Oil & Gas Operator | Nov 1987 |
| 3447 | Olympic Petroleum Co | Tulsa, OK 74114 | Oil & Gas Operator | Jun 1998 |
| 3448 | Olympic Production Company | | Oil & Gas Operator | Jul 1994 |
| 3449 | Omeara Bros. | | Oil & Gas Operator | Oct 1982 |
| 3450 | Omega Energy Corp. | Graham, TX 76450 | Oil & Gas Operator | Feb 2026 |
| 3451 | Omega Energy Incorporated | | Oil & Gas Operator | May 1998 |
| 3452 | Omni Operating Company | Osage, WY 82723 | Oil & Gas Operator | Sep 2001 |
| 3453 | Onshore Exp Cor-La Nat Res Inc | | Oil & Gas Operator | Oct 1978 |
| 3454 | Onshore Pipeline Const Co Inc | | Oil & Gas Operator | Aug 1998 |
| 3455 | Onyx Energy Corporation | Oklahoma City, OK 73157 | Oil & Gas Operator | May 1994 |
| 3456 | Onyx Energy Dev Of Texas Inc. | | Oil Operator | Dec 1996 |
| 3457 | Onyx Energy Of Texas Inc. | | Oil Operator | Dec 1996 |
| 3458 | Onyxx Energy LLC | | Oil & Gas Operator | Mar 2017 |
| 3459 | Opal Oil Inc. | | Oil Operator | Sep 2021 |
| 3460 | Opmi Operating Company | Houston, TX 77057 | Oil & Gas Operator | Jun 2008 |
| 3461 | Ops Group Limited | Houston, TX 77060 | Oil & Gas Operator | Jun 2014 |
| 3462 | Optimistic Oil Co. | | Oil & Gas Operator | Dec 1991 |
| 3463 | Ora Oil Company | | Oil & Gas Operator | May 2017 |
| 3464 | Oracle Oil, LLC | | Oil & Gas Operator | Jul 2013 |
| 3465 | Orb Exploration, L.L.C. | | Oil & Gas Operator | Jun 2017 |
| 3466 | Orion Oil & Gas, LLC | Houston, TX 77042 | Oil & Gas Operator | Oct 2007 |
| 3467 | Orleans Exploration Co., Inc. | | Oil & Gas Operator | Aug 1990 |
| 3468 | Orx Resources, Inc. | | Oil & Gas Operator | Dec 2009 |
| 3469 | Orx Resources, L.L.C. | Houston, TX 77067 | Oil & Gas Operator | Feb 2026 |
| 3470 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 3471 | Osman Global Services LLC | | Oil & Gas Operator | Jan 2025 |
| 3472 | Osr Oil & Gas Corp | Midland, TX 79710 | Oil & Gas Operator | Dec 2024 |
| 3473 | Osyka Permian, LLC | Houston, TX 77079 | Oil & Gas Operator | Feb 2026 |
| 3474 | Otis C. Coles, Jr. | | Oil & Gas Operator | Jan 1998 |
| 3475 | Ouachita Development Corp. | | Gas Operator | Mar 2014 |
| 3476 | Ouida Oil Co. | | Oil & Gas Operator | Apr 1999 |
| 3477 | Output Acquisition Corp. | | Oil & Gas Operator | Jul 2010 |
| 3478 | Owen Production Co | | Oil Operator | May 2001 |
| 3479 | Owl Creek Production Co., Inc. | Houston, TX 77027 | Oil & Gas Operator | Apr 2006 |
| 3480 | Oxbow EP LLC | Mathis, TX 78368 | Oil Operator | Feb 2026 |
| 3481 | Oxford Exploration Company | Denver, CO 80237 | Oil & Gas Operator | Aug 1995 |
| 3482 | Oxtex Inc | | Oil & Gas Operator | Oct 1989 |
| 3483 | Oxy Petroleum Inc | | Oil & Gas Operator | Jan 1986 |
| 3484 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Feb 2026 |
| 3485 | Ozark Production Company, Inc. | | Oil & Gas Operator | Jan 2025 |
| 3486 | P & A Oilfield Services, Inc. | | Oil & Gas Operator | Jan 1998 |
| 3487 | P & A Well Service | | Oil & Gas Operator | Jan 1994 |
| 3488 | P & M Petroleum | | Oil Operator | Mar 1998 |
| 3489 | P & P Producing Inc | Midland, TX 79702 | Oil & Gas Operator | Feb 2015 |
| 3490 | P D Parker | | Oil & Gas Operator | Aug 1985 |
| 3491 | P E Trichel | | Gas Operator | May 1980 |
| 3492 | P. B. Operating Company | | Oil & Gas Operator | Feb 1978 |
| 3493 | P. K. Smith | | Oil Operator | Mar 1997 |
| 3494 | P. S. & G., Incorporated | | Gas Operator | Aug 1983 |
| 3495 | P.C.S.I. | | Oil & Gas Operator | Jun 1987 |
| 3496 | P.T.L. Operating Co. | | Oil Operator | Jun 2003 |
| 3497 | Pace Royalty Trust Fund, Inc. | Shreveport, LA 71135 | Oil & Gas Operator | Nov 2001 |
| 3498 | Pacific Atlantic Oil Co. | | Oil & Gas Operator | Dec 2003 |
| 3499 | Pacific Enterprises Oil Co USA | Dallas, TX 75201 | Oil & Gas Operator | Feb 2001 |
| 3500 | Pacific Enterprises Royalty Co | Oklahoma City, OK 73101 | Oil & Gas Operator | Feb 2002 |