| 21401 | Oil Recovery, Inc. | | Oil Operator | Sep 1992 |
| 21402 | Oil Reserves Corp Of America | | Oil & Gas Operator | May 2002 |
| 21403 | Oil Rock Energy Inc. / O.R.E. | Dallas, TX 75208 | Oil & Gas Operator | Apr 2025 |
| 21404 | Oil Rock Oil Company, Inc. | Elizabeth, WV 26143 | Oil & Gas Operator | Dec 2021 |
| 21405 | Oil Rock Resources, LLC | Weatherford, TX 76088 | Oil & Gas Operator | Jan 2024 |
| 21406 | Oil Search Inc | Brookfield, OH 44403 | Oil & Gas Operator | Dec 2023 |
| 21407 | Oil Securities Inc. | | Gas Operator | Dec 2003 |
| 21408 | Oil State Petroleum Inc | Jennings, OK 74038 | Oil & Gas Operator | Jan 2025 |
| 21409 | Oil Tech Producers Corporation | Moundridge, KS 67107 | Gas Operator | Dec 2024 |
| 21410 | Oil Ventures LTD | | Oil & Gas Operator | Jan 2013 |
| 21411 | Oil Well Buyers Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 2024 |
| 21412 | Oil Well Management Co. | | Oil & Gas Operator | Dec 1989 |
| 21413 | Oil, Gas, Etc. LLC | Katy, TX 77449 | Oil & Gas Operator | Apr 2025 |
| 21414 | Oil,Gas & Other Minerals, Inc. | | Oil & Gas Operator | Apr 1996 |
| 21415 | Oil-Tech Prod Co | | Oil & Gas Operator | Oct 1992 |
| 21416 | Oil-X Corp., The | FT Stockton, TX 79735 | Oil & Gas Operator | Apr 2025 |
| 21417 | Oilbank Production LLC | Norman, OK 73072 | Oil Operator | Jan 2025 |
| 21418 | Oilcat Production Co Inc | McLeansboro, IL 62859 | Oil Operator | Dec 2023 |
| 21419 | Oilco Energy Inc | Duncan, OK 73533 | Oil & Gas Operator | Mar 2015 |
| 21420 | Oilco Gas Co LC | Duncan, OK 73534 | Oil & Gas Operator | Dec 2014 |
| 21421 | Oildigger Resources Fund L LLLP | Billings, MT 59101 | Oil & Gas Operator | Feb 2025 |
| 21422 | Oilex Int'L Investments, Inc. | Luling, TX 78648 | Oil & Gas Operator | Apr 2025 |
| 21423 | Oilfield Consultants | | Oil & Gas Operator | Dec 1987 |
| 21424 | Oilfield Leasing Inc | Cushing, OK 74023-0967 | Oil & Gas Operator | Aug 2018 |
| 21425 | Oilfield Management, Inc. (A) | Midland, TX 79702 | Oil & Gas Operator | Apr 2025 |
| 21426 | Oilfield Operating Company | Cushing, OK 74023-1347 | Oil & Gas Operator | Jan 2018 |
| 21427 | Oilfield Research, Inc | | Oil Operator | Dec 2021 |
| 21428 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | Feb 2025 |
| 21429 | Oilfield Search | | Oil Operator | Mar 1990 |
| 21430 | Oilfield Services And Supply Co. Inc. | | Oil Operator | Sep 1989 |
| 21431 | Oilfield Services, LLC | Winfield, KS 67156 | Oil Operator | Nov 2017 |
| 21432 | Oilfield Truck Service | | Oil Operator | Jun 2014 |
| 21433 | Oilrox Resources LLC | San Antonio, TX 78258 | Oil & Gas Operator | Feb 2025 |
| 21434 | Oilsearch Corporation | Albuquerque, NM 87109 | Oil & Gas Operator | Feb 1994 |
| 21435 | Oiltech Inc | Yuba City, CA 95991 | Oil & Gas Operator | Dec 1984 |
| 21436 | Oiltex, Inc. | Baltimore, MD 21221 | Oil & Gas Operator | Dec 2013 |
| 21437 | Oilton Petroleum Inc | Oilton, OK 74052-0459 | Oil & Gas Operator | Oct 2001 |
| 21438 | Oilton Resources, Inc. | Laredo, TX 78041 | Oil & Gas Operator | Apr 2025 |
| 21439 | Oilwell Acquisition Co. | | Oil & Gas Operator | Jun 1999 |
| 21440 | Oilwell Operator | | Gas Operator | Dec 1994 |
| 21441 | Oilwell Operators, Inc. | Pampa, TX 79066 | Oil & Gas Operator | Apr 2025 |
| 21442 | Oily Dog Operators Texas, LLC | Austin, TX 78746 | Oil Operator | Apr 2025 |
| 21443 | Ojai Oil Company | Camarillo, CA 93012 | Oil & Gas Operator | Dec 2024 |
| 21444 | Ojb, Inc. | Buda, TX 78610 | Oil & Gas Operator | Mar 2013 |
| 21445 | Ojt, LLC | Richmond, TX 77469 | Oil Operator | Apr 2025 |
| 21446 | Ok Arena Operating Company | Oklahoma City, OK 73101 | Oil & Gas Operator | Apr 2025 |
| 21447 | Ok Oil Company, Inc. | Bivins, TX 75555 | Oil & Gas Operator | Feb 2013 |
| 21448 | Ok Operating Co | Midland, TX 79702 | Oil & Gas Operator | Aug 1999 |
| 21449 | Ok-La-Tex Production, Inc. | | Oil & Gas Operator | Jan 1982 |
| 21450 | Okc Energy Corporation | Oklahoma City, OK 73120-3119 | Oil & Gas Operator | Nov 2014 |
| 21451 | Okemah Production Inc | | Oil Operator | Dec 2005 |
| 21452 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2025 |
| 21453 | Okie Oil Inc | Sapulpa, OK 74067-0290 | Oil & Gas Operator | Mar 2011 |
| 21454 | Okie Operating Company, LTD. | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2025 |
| 21455 | Okkatahula, Inc. | | Oil Operator | Nov 1978 |
| 21456 | Okla Petroleum Energies Corp | | Oil Operator | Jan 2013 |
| 21457 | Okla Petroleum Reclaimers Inc | Kellyville, OK 74039 | Oil Operator | Jul 2020 |
| 21458 | Okla Sub-Surface Pump & Supply Co | Seminole, OK 74804 | Oil & Gas Operator | Sep 2024 |
| 21459 | Okla. Magic Circle Energy Corp. | Shawnee, OK 74801 | Oil & Gas Operator | Jul 2004 |
| 21460 | Oklahoma & Northwestern Co. | Oklahoma City, OK 73102 | Oil & Gas Operator | Jan 1997 |
| 21461 | Oklahoma Arrowhead Energy, Inc. | Nichols Hill, OK 73116 | Oil & Gas Operator | Sep 1996 |
| 21462 | Oklahoma Basic Economy Corp | Houston, TX 77002-6003 | Oil & Gas Operator | Apr 2020 |
| 21463 | Oklahoma Cellulose Inc | Cleveland, OK 74020 | Oil Operator | Jan 2025 |
| 21464 | Oklahoma Crude Inc | Broken Arrow, OK 74012 | Oil & Gas Operator | Apr 2024 |
| 21465 | Oklahoma Crude Reclaimers, LLC | | Oil Operator | Feb 2025 |
| 21466 | Oklahoma Ea II, L.L.C. | Oklahoma City, OK 73102 | Oil & Gas Operator | Dec 2004 |
| 21467 | Oklahoma Energy & Exploration, Inc. | Tulsa, OK 74114 | Oil Operator | Jan 1996 |
| 21468 | Oklahoma Energy Acquisitions LP | Houston, TX 77094-1900 | Oil & Gas Operator | Jan 2025 |
| 21469 | Oklahoma Energy Development Co | | Oil & Gas Operator | Sep 2008 |
| 21470 | Oklahoma Energy Exchange LLC | Duncan, OK 73534-1105 | Oil & Gas Operator | Sep 2012 |
| 21471 | Oklahoma Energy LLC | Skiatook, OK 74070-3998 | Oil Operator | Nov 2024 |
| 21472 | Oklahoma Equipment & Salvage | Oklahoma City, OK 73120-5903 | Oil & Gas Operator | Mar 2015 |
| 21473 | Oklahoma Gas & Oil Corporation | Okemah, OK 74859 | Oil Operator | Oct 2018 |
| 21474 | Oklahoma Liquid Resources Inc | Collinsville, OK 74021 | Oil & Gas Operator | Dec 2024 |
| 21475 | Oklahoma Marlin Oil Corporation | Oklahoma City, OK 73113 | Oil & Gas Operator | Feb 2020 |
| 21476 | Oklahoma Natural Resources Inc | Woodward, OK 73801 | Oil & Gas Operator | Sep 1996 |
| 21477 | Oklahoma O & G Royalties Inc | Duncan, OK 73533 | Oil & Gas Operator | Nov 2000 |
| 21478 | Oklahoma Oil & Gas MGMT Inc | Edmond, OK 73083-6786 | Oil & Gas Operator | Jan 2025 |
| 21479 | Oklahoma Oil And Gas Resources LLC | Guthrie, OK 73044-8095 | Oil & Gas Operator | Feb 2025 |
| 21480 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 21481 | Oklahoma Oil Tactics Inc | Edmond, OK 73003-1351 | Oil & Gas Operator | Mar 2015 |
| 21482 | Oklahoma Operating Company | Midland, TX 79708 | Oil & Gas Operator | Apr 2025 |
| 21483 | Oklahoma Operating, LLC | Holliday, TX 76366 | Oil Operator | Nov 2003 |
| 21484 | Oklahoma Petroleum Allies LLC | Ardmore, OK 73401 | Oil Operator | Oct 2023 |
| 21485 | Oklahoma Petroleum MGMT Corp | Tulsa, OK 74119 | Oil & Gas Operator | Jun 1993 |
| 21486 | Oklahoma Prime Energy LLC | Ardmore, OK 73401 | Oil Operator | May 2020 |
| 21487 | Oklahoma Prod & Exp Co | Broken Arrow, OK 74012 | Oil & Gas Operator | May 2013 |
| 21488 | Oklahoma RB Operating Company | Midland, TX 79701 | Oil & Gas Operator | Jan 1998 |
| 21489 | Oklahoma Rig & Salvage, Inc. | Oklahoma City, OK 73114 | Oil & Gas Operator | Mar 2015 |
| 21490 | Oklahoma Sterling Oil & Gas Corp | Tulsa, OK 74170 | Oil & Gas Operator | Jun 1997 |
| 21491 | Oklahoma SWD Systems Inc | Odessa, TX 79762-8132 | Oil & Gas Operator | Jan 2025 |
| 21492 | Oklahoma Tank Service Inc | Oklahoma City, OK 73143 | Oil Operator | Aug 1997 |
| 21493 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Feb 2025 |
| 21494 | Oklaoleum Oil And Gas Inc | Bristow, OK 74010-0057 | Oil Operator | Jan 2016 |
| 21495 | Oklatex Energy, Inc. | Beaumont, TX 77702 | Oil Operator | Apr 2025 |
| 21496 | Okmar Oil Compan | | Oil & Gas Operator | Feb 1995 |
| 21497 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 21498 | Okreek Oil Company | Weatherford, TX 76086 | Oil & Gas Operator | Apr 2025 |
| 21499 | Okt Petroleum Company Inc | Oklahoma City, OK 73118-7425 | Oil & Gas Operator | Oct 2013 |
| 21500 | Okt Resources, LLC | Edmond, OK 73013 | Oil & Gas Operator | Apr 2025 |