| 21101 | Oil Reserves Corp Of America | | Oil & Gas Operator | May 2002 |
| 21102 | Oil Rock Energy Inc. / O.R.E. | Dallas, TX 75208 | Oil & Gas Operator | Jun 2025 |
| 21103 | Oil Rock Oil Company, Inc. | Elizabeth, WV 26143 | Oil & Gas Operator | Dec 2021 |
| 21104 | Oil Rock Resources, LLC | Weatherford, TX 76088 | Oil & Gas Operator | Jan 2024 |
| 21105 | Oil Search (Alaska), LLC | | Oil & Gas Operator | Apr 2025 |
| 21106 | Oil Search Inc | Brookfield, OH 44403 | Oil & Gas Operator | Dec 2024 |
| 21107 | Oil Securities Inc. | | Gas Operator | Dec 2003 |
| 21108 | Oil State Petroleum Inc | Jennings, OK 74038 | Oil & Gas Operator | Mar 2025 |
| 21109 | Oil Tech Producers Corporation | Moundridge, KS 67107 | Gas Operator | Feb 2025 |
| 21110 | Oil Ventures LTD | | Oil & Gas Operator | Jan 2013 |
| 21111 | Oil Well Buyers Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 2024 |
| 21112 | Oil Well Management Co. | | Oil & Gas Operator | Dec 1989 |
| 21113 | Oil, Gas, Etc. LLC | Katy, TX 77449 | Oil & Gas Operator | Jun 2025 |
| 21114 | Oil,Gas & Other Minerals, Inc. | | Oil & Gas Operator | Apr 1996 |
| 21115 | Oil-Tech Prod Co | | Oil & Gas Operator | Oct 1992 |
| 21116 | Oil-X Corp., The | FT Stockton, TX 79735 | Oil & Gas Operator | Jun 2025 |
| 21117 | Oilbank Production LLC | Norman, OK 73072 | Oil Operator | Mar 2025 |
| 21118 | Oilcat Production Co Inc | McLeansboro, IL 62859 | Oil Operator | Dec 2023 |
| 21119 | Oilco Energy Inc | Duncan, OK 73533 | Oil & Gas Operator | Mar 2015 |
| 21120 | Oildigger Resources Fund L LLLP | Billings, MT 59101 | Oil & Gas Operator | Apr 2025 |
| 21121 | Oilex Int'L Investments, Inc. | Luling, TX 78648 | Oil & Gas Operator | Jun 2025 |
| 21122 | Oilfield Consultants | | Oil & Gas Operator | Dec 1987 |
| 21123 | Oilfield Management, Inc. (A) | Midland, TX 79702 | Oil & Gas Operator | Jun 2025 |
| 21124 | Oilfield Operating Company | Cushing, OK 74023-1347 | Oil & Gas Operator | Jan 2018 |
| 21125 | Oilfield Research, Inc | | Oil Operator | Dec 2021 |
| 21126 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | Apr 2025 |
| 21127 | Oilfield Search | | Oil Operator | Mar 1990 |
| 21128 | Oilfield Services And Supply Co. Inc. | | Oil Operator | Sep 1989 |
| 21129 | Oilfield Services, LLC | Winfield, KS 67156 | Oil Operator | Nov 2017 |
| 21130 | Oilfield Truck Service | | Oil Operator | Jun 2014 |
| 21131 | Oilrox Resources LLC | San Antonio, TX 78258 | Oil & Gas Operator | Apr 2025 |
| 21132 | Oilsearch Corporation | Albuquerque, NM 87109 | Oil & Gas Operator | Feb 1994 |
| 21133 | Oiltech Inc | Yuba City, CA 95991 | Oil & Gas Operator | Dec 1984 |
| 21134 | Oiltex, Inc. | Baltimore, MD 21221 | Oil & Gas Operator | Dec 2013 |
| 21135 | Oilton Petroleum Inc | Oilton, OK 74052-0459 | Oil & Gas Operator | Oct 2001 |
| 21136 | Oilton Resources, Inc. | Laredo, TX 78041 | Oil & Gas Operator | Jun 2025 |
| 21137 | Oilwell Acquisition Co. | | Oil & Gas Operator | Jun 1999 |
| 21138 | Oilwell Operator | | Gas Operator | Dec 1994 |
| 21139 | Oilwell Operators, Inc. | Pampa, TX 79066 | Oil & Gas Operator | Jun 2025 |
| 21140 | Oily Dog Operators Texas, LLC | Austin, TX 78746 | Oil Operator | Jun 2025 |
| 21141 | Ojai Oil Company | Camarillo, CA 93012 | Oil & Gas Operator | Mar 2025 |
| 21142 | Ojb, Inc. | Buda, TX 78610 | Oil & Gas Operator | Mar 2013 |
| 21143 | Ojt, LLC | Richmond, TX 77469 | Oil Operator | Jun 2025 |
| 21144 | Ok Arena Operating Company | Oklahoma City, OK 73101 | Oil & Gas Operator | Jun 2025 |
| 21145 | Ok Oil Company, Inc. | Bivins, TX 75555 | Oil & Gas Operator | Feb 2013 |
| 21146 | Ok Operating Co | Midland, TX 79702 | Oil & Gas Operator | Aug 1999 |
| 21147 | Ok-La-Tex Production, Inc. | | Oil & Gas Operator | Jan 1982 |
| 21148 | Okc Energy Corporation | Oklahoma City, OK 73120-3119 | Oil & Gas Operator | Nov 2014 |
| 21149 | Okemah Production Inc | | Oil Operator | Dec 2005 |
| 21150 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2025 |
| 21151 | Okie Oil Inc | Sapulpa, OK 74067-0290 | Oil & Gas Operator | Mar 2011 |
| 21152 | Okie Operating Company, LTD. | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2025 |
| 21153 | Okkatahula, Inc. | | Oil Operator | Nov 1978 |
| 21154 | Okla Sub-Surface Pump & Supply Co | Seminole, OK 74804 | Oil & Gas Operator | Sep 2024 |
| 21155 | Okla. Magic Circle Energy Corp. | Shawnee, OK 74801 | Oil & Gas Operator | Jul 2004 |
| 21156 | Oklahoma Arrowhead Energy, Inc. | Nichols Hill, OK 73116 | Oil & Gas Operator | Sep 1996 |
| 21157 | Oklahoma Basic Economy Corp | Houston, TX 77002-6003 | Oil & Gas Operator | Apr 2020 |
| 21158 | Oklahoma Cellulose Inc | Cleveland, OK 74020 | Oil Operator | Mar 2025 |
| 21159 | Oklahoma Crude Inc | Broken Arrow, OK 74012 | Oil & Gas Operator | Apr 2024 |
| 21160 | Oklahoma Crude Reclaimers, LLC | | Oil Operator | Apr 2025 |
| 21161 | Oklahoma Ea II, L.L.C. | Oklahoma City, OK 73102 | Oil & Gas Operator | Dec 2004 |
| 21162 | Oklahoma Energy & Exploration, Inc. | Tulsa, OK 74114 | Oil Operator | Jan 1996 |
| 21163 | Oklahoma Energy Acquisitions LP | Houston, TX 77094-1900 | Oil & Gas Operator | Jan 2025 |
| 21164 | Oklahoma Energy Exchange LLC | Duncan, OK 73534-1105 | Oil & Gas Operator | Sep 2012 |
| 21165 | Oklahoma Energy LLC | Skiatook, OK 74070-3998 | Oil Operator | Nov 2024 |
| 21166 | Oklahoma Equipment & Salvage | Oklahoma City, OK 73120-5903 | Oil & Gas Operator | Mar 2015 |
| 21167 | Oklahoma Gas & Oil Corp | | Oil Operator | Oct 2018 |
| 21168 | Oklahoma Liquid Resources Inc | Collinsville, OK 74021 | Oil & Gas Operator | Mar 2025 |
| 21169 | Oklahoma Marlin Oil Corporation | Oklahoma City, OK 73113 | Oil & Gas Operator | Feb 2020 |
| 21170 | Oklahoma Natural Resources Inc | Woodward, OK 73801 | Oil & Gas Operator | Sep 1996 |
| 21171 | Oklahoma O & G Royalties Inc | Duncan, OK 73533 | Oil & Gas Operator | Nov 2000 |
| 21172 | Oklahoma Oil & Gas MGMT Inc | Edmond, OK 73083-6786 | Oil & Gas Operator | Mar 2025 |
| 21173 | Oklahoma Oil And Gas Resources LLC | Guthrie, OK 73044-8095 | Oil & Gas Operator | Apr 2025 |
| 21174 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 21175 | Oklahoma Oil Tactics Inc | Edmond, OK 73003-1351 | Oil & Gas Operator | Mar 2015 |
| 21176 | Oklahoma Operating Company | Midland, TX 79708 | Oil & Gas Operator | Jun 2025 |
| 21177 | Oklahoma Operating, LLC | Holliday, TX 76366 | Oil Operator | Nov 2003 |
| 21178 | Oklahoma Petroleum MGMT Corp | Tulsa, OK 74119 | Oil & Gas Operator | Jun 1993 |
| 21179 | Oklahoma Prime Energy LLC | Ardmore, OK 73401 | Oil Operator | May 2020 |
| 21180 | Oklahoma Prod & Exp Co | Broken Arrow, OK 74012 | Oil & Gas Operator | May 2013 |
| 21181 | Oklahoma RB Operating Company | Midland, TX 79701 | Oil & Gas Operator | Jan 1998 |
| 21182 | Oklahoma Rig & Salvage, Inc. | Oklahoma City, OK 73114 | Oil & Gas Operator | Mar 2015 |
| 21183 | Oklahoma Sterling Oil & Gas Corp | Tulsa, OK 74170 | Oil & Gas Operator | Jun 1997 |
| 21184 | Oklahoma SWD Systems Inc | Odessa, TX 79762-8132 | Oil & Gas Operator | Mar 2025 |
| 21185 | Oklahoma Tank Service Inc | Oklahoma City, OK 73143 | Oil Operator | Aug 1997 |
| 21186 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Apr 2025 |
| 21187 | Oklaoleum Oil And Gas Inc | Bristow, OK 74010-0057 | Oil Operator | Jan 2016 |
| 21188 | Oklatex Energy, Inc. | Beaumont, TX 77702 | Oil Operator | Jun 2025 |
| 21189 | Okmar Oil Compan | | Oil & Gas Operator | Feb 1995 |
| 21190 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 21191 | Okreek Oil Company | Weatherford, TX 76086 | Oil & Gas Operator | Jun 2025 |
| 21192 | Okt Petroleum Company Inc | Oklahoma City, OK 73118-7425 | Oil & Gas Operator | Oct 2013 |
| 21193 | Okt Resources, LLC | Edmond, OK 73013 | Oil & Gas Operator | Jun 2025 |
| 21194 | Oktex Operating LLC | Edmond, OK 73013-1961 | Oil & Gas Operator | May 2020 |
| 21195 | Oky Investments, Inc. | Edmond, OK 73013 | Oil & Gas Operator | Sep 2021 |
| 21196 | Ol' Boys Operations LLC | Pampa, TX 79065 | Oil & Gas Operator | Jun 2025 |
| 21197 | Ol' Oily LLC | | Oil Operator | Jan 2025 |
| 21198 | Old Acres Farm, Inc. | Perry, NY 14530 | Gas Operator | Dec 2023 |
| 21199 | Old Cedron, L.L.C. | Lubbock, TX 79410 | Oil & Gas Operator | May 2004 |
| 21200 | Old Chief Oil, LLC | New Braunfels, TX 78132 | Oil Operator | Jun 2025 |