| 4201 | Oil Capital Operating, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2026 |
| 4202 | Oil Center Operating Inc | Fort Worth, TX 76102-5108 | Oil & Gas Operator | Apr 2014 |
| 4203 | Oil Creek Production Company | Prague, OK 74864-0667 | Oil & Gas Operator | Dec 2025 |
| 4204 | Oil Exploration Of America Inc | Sisseton, SD 57262-9503 | Oil & Gas Operator | Jun 2001 |
| 4205 | Oil Investors Inc | Crescent, OK 73028 | Oil & Gas Operator | Jan 2026 |
| 4206 | Oil Lift Inc | Metairie, LA 70002 | Oil & Gas Operator | Apr 2020 |
| 4207 | Oil Operations Inc | | Oil & Gas Operator | Apr 2011 |
| 4208 | Oil Patch Energy LLC | Broken Arrow, OK 74014 | Oil & Gas Operator | Nov 2025 |
| 4209 | Oil Pool Inc | Tulsa, OK 74132-2659 | Oil & Gas Operator | Jan 2026 |
| 4210 | Oil Producers, Inc. Of Kansas | Wichita, KS 67206 | Oil & Gas Operator | Mar 2026 |
| 4211 | Oil Production Management Inc | Squaw Valley, CA 93675-9725 | Oil & Gas Operator | Dec 2002 |
| 4212 | Oil Production Systems Inc | Cushing, OK 74023 | Oil & Gas Operator | Jan 2013 |
| 4213 | Oil Property Management Inc | Attica, KS 67009 | Oil & Gas Operator | Feb 2021 |
| 4214 | Oil Recovery Systems Inc | Tulsa, OK 74145-4619 | Oil & Gas Operator | Dec 2025 |
| 4215 | Oil State Petroleum Inc | Jennings, OK 74038 | Oil & Gas Operator | Jan 2026 |
| 4216 | Oil Ventures LTD | | Oil & Gas Operator | Jan 2013 |
| 4217 | Oilbank Production LLC | Norman, OK 73072 | Oil Operator | Dec 2025 |
| 4218 | Oilco Energy Inc | Duncan, OK 73533 | Oil & Gas Operator | Mar 2015 |
| 4219 | Oilfield Leasing Inc | Cushing, OK 74023-0967 | Oil & Gas Operator | Aug 2018 |
| 4220 | Oilfield Operating Company | Cushing, OK 74023-1347 | Oil & Gas Operator | Jan 2018 |
| 4221 | Oilrox Resources LLC | San Antonio, TX 78258 | Oil & Gas Operator | Jan 2026 |
| 4222 | Oilsearch Corporation | Albuquerque, NM 87109 | Oil & Gas Operator | Feb 1994 |
| 4223 | Oilton Petroleum Inc | Oilton, OK 74052-0459 | Oil & Gas Operator | Oct 2001 |
| 4224 | Oilwell Operators, Inc. | Pampa, TX 79066 | Oil & Gas Operator | Mar 2026 |
| 4225 | Ok Production Services Inc | Broken Arrow, OK 74014 | Oil & Gas Operator | Dec 2025 |
| 4226 | Okc Energy Corporation | Oklahoma City, OK 73120-3119 | Oil & Gas Operator | Nov 2014 |
| 4227 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Dec 2025 |
| 4228 | Okie Oil Inc | Sapulpa, OK 74067-0290 | Oil & Gas Operator | Mar 2011 |
| 4229 | Okla Sub-Surface Pump & Supply Co | Seminole, OK 74804 | Oil & Gas Operator | Sep 2024 |
| 4230 | Oklahoma Basic Economy Corp | Houston, TX 77002-6003 | Oil & Gas Operator | Apr 2020 |
| 4231 | Oklahoma Cellulose Inc | Cleveland, OK 74020 | Oil Operator | Dec 2025 |
| 4232 | Oklahoma Crude Inc | Morris, OK 74445 | Oil & Gas Operator | Nov 2025 |
| 4233 | Oklahoma Crude Reclaimers, LLC | | Oil Operator | Jan 2026 |
| 4234 | Oklahoma Energy Acquisitions LP | Houston, TX 77094-1900 | Oil & Gas Operator | Dec 2025 |
| 4235 | Oklahoma Energy Exchange LLC | Duncan, OK 73534-1105 | Oil & Gas Operator | Sep 2012 |
| 4236 | Oklahoma Energy LLC | Skiatook, OK 74070-3998 | Oil Operator | Apr 2025 |
| 4237 | Oklahoma Equipment & Salvage | Oklahoma City, OK 73120-5903 | Oil & Gas Operator | Mar 2015 |
| 4238 | Oklahoma Gas & Oil Corp | | Oil Operator | Oct 2018 |
| 4239 | Oklahoma Liquid Resources Inc | Collinsville, OK 74021 | Oil & Gas Operator | Dec 2025 |
| 4240 | Oklahoma Natural Resources Inc | Woodward, OK 73801 | Oil & Gas Operator | Sep 1996 |
| 4241 | Oklahoma O & G Royalties Inc | Duncan, OK 73533 | Oil & Gas Operator | Nov 2000 |
| 4242 | Oklahoma Oil & Gas MGMT Inc | Edmond, OK 73083-6786 | Oil & Gas Operator | Dec 2025 |
| 4243 | Oklahoma Oil And Gas Resources LLC | Guthrie, OK 73044-8095 | Oil & Gas Operator | Jan 2026 |
| 4244 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 4245 | Oklahoma Oil Tactics Inc | Edmond, OK 73003-1351 | Oil & Gas Operator | Mar 2015 |
| 4246 | Oklahoma Petroleum MGMT Corp | Tulsa, OK 74119 | Oil & Gas Operator | Jun 1993 |
| 4247 | Oklahoma Prime Energy LLC | Ardmore, OK 73401 | Oil Operator | May 2020 |
| 4248 | Oklahoma Prod & Exp Co | Broken Arrow, OK 74012 | Oil & Gas Operator | May 2013 |
| 4249 | Oklahoma Rig & Salvage Inc | Oklahoma City, OK 73114 | Oil & Gas Operator | Mar 2015 |
| 4250 | Oklahoma SWD Systems Inc | Odessa, TX 79762-8132 | Oil & Gas Operator | Dec 2025 |
| 4251 | Oklahoma Tank Service Inc | Oklahoma City, OK 73143 | Oil Operator | Aug 1997 |
| 4252 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Jan 2026 |
| 4253 | Oklaoleum Oil And Gas Inc | Bristow, OK 74010-0057 | Oil Operator | Jan 2016 |
| 4254 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 4255 | Okt Petroleum Company Inc | Oklahoma City, OK 73118-7425 | Oil & Gas Operator | Oct 2013 |
| 4256 | Oktex Operating LLC | Edmond, OK 73013-1961 | Oil & Gas Operator | May 2020 |
| 4257 | Oky Investments, Inc. | Edmond, OK 73013 | Oil & Gas Operator | Sep 2021 |
| 4258 | Old Dominion Oil Corporation | Oklahoma City, OK 73107 | Oil & Gas Operator | Apr 2009 |
| 4259 | Ole Crow Operating | Wichita Falls, TX 76308 | Oil Operator | Dec 2025 |
| 4260 | Oleum Inc | | Oil & Gas Operator | Mar 1996 |
| 4261 | Olia Oil & Gas Services LLC | Cedar Park, TX 78630-2049 | Oil & Gas Operator | Aug 2022 |
| 4262 | Oliphant Gertrud | Holdenville, OK 74848-0849 | Oil Operator | Aug 2013 |
| 4263 | Oliphant Operating Co,LTD,LLC | | Oil Operator | Dec 2025 |
| 4264 | Olive Oil & Gas Inc | Jennings, OK 74052 | Oil & Gas Operator | Oct 2025 |
| 4265 | Olympia Oil Inc | Edmond, OK 73083-7088 | Oil & Gas Operator | Jul 2020 |
| 4266 | Olympic Petroleum Co | Tulsa, OK 74114 | Oil & Gas Operator | Jun 1998 |
| 4267 | Omega Energy, LLC | Corpus Chrsti, TX 78418 | Oil & Gas Operator | Mar 2026 |
| 4268 | Omimex International Corp | Fort Worth, TX 76103-2300 | Oil & Gas Operator | Dec 2025 |
| 4269 | Omimex Petroleum Inc | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2022 |
| 4270 | Omni Oil & Gas, Inc. | San Antonio, TX 78229 | Oil & Gas Operator | Oct 2017 |
| 4271 | On-Line Oil Inc | Oklahoma City, OK 73105-5208 | Oil & Gas Operator | Mar 2015 |
| 4272 | Onapa Gas Company LLC | Tulsa, OK 74136-7253 | Gas Operator | Nov 2019 |
| 4273 | Oneok Exploration Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 4274 | Oneok Field Services Company | Tulsa, OK 74103 | Oil & Gas Operator | Jul 2022 |
| 4275 | Oneok Gas Processing LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2018 |
| 4276 | Oneok Gas Transportation Co | Tulsa, OK 74121-2089 | Oil & Gas Operator | Oct 2014 |
| 4277 | Oneok Resources Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 4278 | Onpoint Oil & Gas, LLC | Oklahoma City, OK 73170-4848 | Oil & Gas Operator | Jan 2026 |
| 4279 | Onshore Royalties LLC | Houston, TX 77269 | Oil & Gas Operator | Jan 2026 |
| 4280 | Onyx Energy Corporation | Oklahoma City, OK 73157 | Oil & Gas Operator | May 1994 |
| 4281 | Onyx Properties Corp | Oklahoma City, OK 73114 | Oil & Gas Operator | May 2006 |
| 4282 | Opal Operating Company LLC | Edmond, OK 73013 | Oil & Gas Operator | Mar 2026 |
| 4283 | Open Door Holdings Inc | Surprise, AZ 85387-2015 | Oil & Gas Operator | Feb 2024 |
| 4284 | Open Door Productions Inc | Muskogee, OK 74401-1032 | Oil & Gas Operator | Apr 2020 |
| 4285 | Open Range Energy LLC | Jones, OK 73049-8744 | Oil & Gas Operator | Mar 2025 |
| 4286 | Optima Exploration LLC | Tulsa, OK 74116-5664 | Oil & Gas Operator | Mar 2015 |
| 4287 | Opubco Resources Of TX Inc | Dallas, TX 75231 | Oil & Gas Operator | Sep 2005 |
| 4288 | Oracle Resources Oklahoma LP | Dallas, TX 75240-5751 | Oil & Gas Operator | Feb 2008 |
| 4289 | Orason Resources Inc | Tulsa, OK 74169-1225 | Oil & Gas Operator | Nov 2006 |
| 4290 | Orca Operating Company LLC | Houston, TX 77056 | Oil & Gas Operator | Jan 2026 |
| 4291 | Oren Stone | Erick, OK 73645-4542 | Gas Operator | Jun 2022 |
| 4292 | Orion Exploration LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Apr 2015 |
| 4293 | Orion Exploration Partners LLC | Tulsa, OK 74105-5153 | Oil & Gas Operator | Nov 2025 |
| 4294 | Orloski John C | Bartlesville, OK 74006 | Oil & Gas Operator | Jun 2025 |
| 4295 | Osa Oil & Gas LLC | Tulsa, OK 74131 | Oil & Gas Operator | Aug 2023 |
| 4296 | Osage Energy Resources LLC | Bartlesville, OK 74005-2527 | Oil & Gas Operator | Dec 2025 |
| 4297 | Osage Exploration & Development Inc | San Diego, CA 92131-3807 | Oil & Gas Operator | Oct 2016 |
| 4298 | Osage Oil & Transportation Inc | Cleveland, OK 74020 | Oil & Gas Operator | Nov 2000 |
| 4299 | Osage Petroleum Corporation | Saint Louis, MO 63131-4691 | Oil & Gas Operator | Mar 2009 |
| 4300 | Osborn Heirs Co | San Antonio, TX 78217 | Oil & Gas Operator | Jan 2026 |