| 21101 | Oi Auburn, Inc. | Tulsa, OK 74135 | Gas Operator | Dec 2023 |
| 21102 | Oil & Gas Acquisition Group Inc | Austin, TX 78716 | Oil & Gas Operator | May 2003 |
| 21103 | Oil & Gas Development Company | | Oil & Gas Operator | May 1991 |
| 21104 | Oil & Gas Exploration Inc | Cleveland, OK 74020 | Oil & Gas Operator | Aug 2013 |
| 21105 | Oil & Gas MGMT Inc | Mount Pleasant, PA 15666-3304 | Oil & Gas Operator | Dec 2024 |
| 21106 | Oil & Gas Operations | Midland, TX 79706 | Oil & Gas Operator | May 2025 |
| 21107 | Oil & Gas Producers, Inc. | Topeka, KS 66604 | Oil Operator | Jun 2004 |
| 21108 | Oil & Gas Properties | Midland, TX 79704 | Oil & Gas Operator | May 2025 |
| 21109 | Oil & Gas Property MGMT., Inc. | Dallas, TX 75201 | Oil & Gas Operator | Jul 1996 |
| 21110 | Oil & Gas Servic | | Oil Operator | Jun 1983 |
| 21111 | Oil & Gas Solutions LTD | Wooster, OH 44691 | Oil & Gas Operator | Dec 2007 |
| 21112 | Oil & Gas SVC Inc | Reelsville, IN 46171-9686 | Gas Operator | Dec 1991 |
| 21113 | Oil & Gas Unlimited Inc | | Oil & Gas Operator | May 2013 |
| 21114 | Oil & Realty Devlop Inc | Columbus, OH 43212 | Oil Operator | Dec 1986 |
| 21115 | Oil And Gas Futures, Inc. | | Oil & Gas Operator | May 1977 |
| 21116 | Oil Capital Corporation | Littleton, CO 80122 | Gas Operator | May 2009 |
| 21117 | Oil Center Operating Inc | Fort Worth, TX 76102-5108 | Oil & Gas Operator | Apr 2014 |
| 21118 | Oil Coast Corp. | S Houston, TX 77587 | Oil & Gas Operator | May 2025 |
| 21119 | Oil Company Of America, Inc. | Hays, KS 67601 | Oil Operator | Dec 2009 |
| 21120 | Oil Country Management, Inc. | | Oil & Gas Operator | Jan 2005 |
| 21121 | Oil Creek Production Company | Prague, OK 74864-0667 | Oil & Gas Operator | Feb 2025 |
| 21122 | Oil Development Co | | Oil & Gas Operator | Jan 1979 |
| 21123 | Oil Drillers & D | | Oil & Gas Operator | Feb 1992 |
| 21124 | Oil Enterprises | Logan, OH 43138 | Oil & Gas Operator | Dec 2024 |
| 21125 | Oil Equipment As | | Gas Operator | Jun 1989 |
| 21126 | Oil Exploration Of America Inc | Sisseton, SD 57262-9503 | Oil & Gas Operator | Jun 2001 |
| 21127 | Oil Field Manage | | Oil Operator | Jun 1991 |
| 21128 | Oil Field Production Inc | Tulsa, OK 74133 | Oil Operator | Feb 2025 |
| 21129 | Oil Gas Management, Inc. | Kansas City, MO 64106 | Oil Operator | Apr 2011 |
| 21130 | Oil Inc | | Oil & Gas Operator | Dec 1971 |
| 21131 | Oil Internationa | | Oil Operator | Jun 1986 |
| 21132 | Oil Investors Inc | Crescent, OK 73028 | Oil & Gas Operator | Mar 2025 |
| 21133 | Oil Lease Operating Co. | Coldspring, TX 77331 | Oil & Gas Operator | Aug 2003 |
| 21134 | Oil Lift, Incorporated | Metairie, LA 70002 | Oil & Gas Operator | Apr 2020 |
| 21135 | Oil Management Corporation | Dallas, TX 75206 | Oil & Gas Operator | Apr 2022 |
| 21136 | Oil Mountain Energy Inc | Casper, WY 82609 | Oil Operator | Apr 2025 |
| 21137 | Oil Operations Inc | | Oil & Gas Operator | Apr 2011 |
| 21138 | Oil Operators Inc. | | Oil & Gas Operator | Nov 2024 |
| 21139 | Oil Palace, Inc. | | Oil Operator | Jun 2016 |
| 21140 | Oil Partners | Salina, KS 67401 | Oil Operator | Jun 2001 |
| 21141 | Oil Partners, LLC | Salina, KS 67401 | Oil Operator | Jan 2025 |
| 21142 | Oil Patch Energy LLC | Broken Arrow, OK 74014 | Oil & Gas Operator | Jan 2025 |
| 21143 | Oil Patch Operators Co., L.L.C. | Kilgore, TX 75663 | Oil & Gas Operator | May 2025 |
| 21144 | Oil Patch Operators, LLC | | Oil & Gas Operator | Jul 2005 |
| 21145 | Oil Pool Inc | Tulsa, OK 74132-2659 | Oil & Gas Operator | Jan 2025 |
| 21146 | Oil Producers In | | Oil & Gas Operator | Dec 1996 |
| 21147 | Oil Producers, Inc. Of Kansas | Wichita, KS 67206 | Oil & Gas Operator | May 2025 |
| 21148 | Oil Production Management Inc | Squaw Valley, CA 93675-9725 | Oil & Gas Operator | Dec 2002 |
| 21149 | Oil Production S | | Oil Operator | Sep 1993 |
| 21150 | Oil Production Systems Inc | Cushing, OK 74023 | Oil & Gas Operator | Jan 2013 |
| 21151 | Oil Projects, LLC | Houston, TX 77027 | Oil & Gas Operator | May 2025 |
| 21152 | Oil Prop Company | | Oil & Gas Operator | Sep 1995 |
| 21153 | Oil Prop Investm | | Oil Operator | Dec 1995 |
| 21154 | Oil Properties Co., Inc. | Wichita, KS 67208 | Gas Operator | Dec 2009 |
| 21155 | Oil Property Man | | Oil & Gas Operator | Jun 1995 |
| 21156 | Oil Property Management, Inc. | Attica, KS 67009 | Oil & Gas Operator | Feb 2021 |
| 21157 | Oil Recovery Systems Inc | Tulsa, OK 74145-4619 | Oil & Gas Operator | Feb 2025 |
| 21158 | Oil Recovery, Inc. | | Oil Operator | Sep 1992 |
| 21159 | Oil Reserves Corp Of America | | Oil & Gas Operator | May 2002 |
| 21160 | Oil Rock Energy Inc. / O.R.E. | Dallas, TX 75208 | Oil & Gas Operator | May 2025 |
| 21161 | Oil Rock Oil Company, Inc. | Elizabeth, WV 26143 | Oil & Gas Operator | Dec 2021 |
| 21162 | Oil Rock Resources, LLC | Weatherford, TX 76088 | Oil & Gas Operator | Jan 2024 |
| 21163 | Oil Search Inc | Brookfield, OH 44403 | Oil & Gas Operator | Dec 2024 |
| 21164 | Oil Securities Inc. | | Gas Operator | Dec 2003 |
| 21165 | Oil State Petroleum Inc | Jennings, OK 74038 | Oil & Gas Operator | Jan 2025 |
| 21166 | Oil Tech Producers Corporation | Moundridge, KS 67107 | Gas Operator | Jan 2025 |
| 21167 | Oil Ventures LTD | | Oil & Gas Operator | Jan 2013 |
| 21168 | Oil Well Buyers Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 2024 |
| 21169 | Oil Well Management Co. | | Oil & Gas Operator | Dec 1989 |
| 21170 | Oil, Gas, Etc. LLC | Katy, TX 77449 | Oil & Gas Operator | May 2025 |
| 21171 | Oil,Gas & Other Minerals, Inc. | | Oil & Gas Operator | Apr 1996 |
| 21172 | Oil-Tech Prod Co | | Oil & Gas Operator | Oct 1992 |
| 21173 | Oil-X Corp., The | FT Stockton, TX 79735 | Oil & Gas Operator | May 2025 |
| 21174 | Oilbank Production LLC | Norman, OK 73072 | Oil Operator | Feb 2025 |
| 21175 | Oilcat Production Co Inc | McLeansboro, IL 62859 | Oil Operator | Dec 2023 |
| 21176 | Oilco Energy Inc | Duncan, OK 73533 | Oil & Gas Operator | Mar 2015 |
| 21177 | Oildigger Resources Fund L LLLP | Billings, MT 59101 | Oil & Gas Operator | Apr 2025 |
| 21178 | Oilex Int'L Investments, Inc. | Luling, TX 78648 | Oil & Gas Operator | May 2025 |
| 21179 | Oilfield Consultants | | Oil & Gas Operator | Dec 1987 |
| 21180 | Oilfield Leasing Inc | Cushing, OK 74023-0967 | Oil & Gas Operator | Aug 2018 |
| 21181 | Oilfield Management, Inc. (A) | Midland, TX 79702 | Oil & Gas Operator | May 2025 |
| 21182 | Oilfield Operating Company | Cushing, OK 74023-1347 | Oil & Gas Operator | Jan 2018 |
| 21183 | Oilfield Research, Inc | | Oil Operator | Dec 2021 |
| 21184 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | Mar 2025 |
| 21185 | Oilfield Search | | Oil Operator | Mar 1990 |
| 21186 | Oilfield Services And Supply Co. Inc. | | Oil Operator | Sep 1989 |
| 21187 | Oilfield Services, LLC | Winfield, KS 67156 | Oil Operator | Nov 2017 |
| 21188 | Oilfield Truck Service | | Oil Operator | Jun 2014 |
| 21189 | Oilrox Resources LLC | San Antonio, TX 78258 | Oil & Gas Operator | Mar 2025 |
| 21190 | Oilsearch Corporation | Albuquerque, NM 87109 | Oil & Gas Operator | Feb 1994 |
| 21191 | Oiltech Inc | Yuba City, CA 95991 | Oil & Gas Operator | Dec 1984 |
| 21192 | Oiltex, Inc. | Baltimore, MD 21221 | Oil & Gas Operator | Dec 2013 |
| 21193 | Oilton Petroleum Inc | Oilton, OK 74052-0459 | Oil & Gas Operator | Oct 2001 |
| 21194 | Oilton Resources, Inc. | Laredo, TX 78041 | Oil & Gas Operator | May 2025 |
| 21195 | Oilwell Acquisition Co. | | Oil & Gas Operator | Jun 1999 |
| 21196 | Oilwell Operator | | Gas Operator | Dec 1994 |
| 21197 | Oilwell Operators, Inc. | Pampa, TX 79066 | Oil & Gas Operator | May 2025 |
| 21198 | Oily Dog Operators Texas, LLC | Austin, TX 78746 | Oil Operator | May 2025 |
| 21199 | Ojai Oil Company | Camarillo, CA 93012 | Oil & Gas Operator | Feb 2025 |
| 21200 | Ojb, Inc. | Buda, TX 78610 | Oil & Gas Operator | Mar 2013 |