| 1 | Halgas Inc | Tulsa, OK 74101-3012 | Oil & Gas Operator | May 2013 |
| 2 | Hall Energy Company LLC | Oklahoma City, OK 73120-5020 | Oil & Gas Operator | Jul 2022 |
| 3 | Hall Resources Corporation | Independence, MO 64057-2158 | Oil & Gas Operator | Jun 2016 |
| 4 | Hallwood Petroleum, Inc. | Midland, TX 79701 | Oil & Gas Operator | Aug 2024 |
| 5 | Hamilton Brothers Oil Co. | Houston, TX 77057 | Oil & Gas Operator | Mar 2015 |
| 6 | Hanna Oil And Gas Company | Fort Smith, AR 72901 | Oil & Gas Operator | Sep 2024 |
| 7 | Harrison Oil & Gas Inc | Houston, TX 77019 | Oil & Gas Operator | Oct 2024 |
| 8 | Hawkins Oil & Gas Inc | Tulsa, OK 74103 | Oil & Gas Operator | Dec 2016 |
| 9 | HCG Energy Corporation & Subs | | Oil & Gas Operator | Mar 2015 |
| 10 | Helmerich & Payne, Inc. | Tulsa, OK 74114 | Oil & Gas Operator | Sep 2024 |
| 11 | Henry Petroleum Of Oklahoma LP | Midland, TX 79703-5000 | Oil & Gas Operator | Feb 2017 |
| 12 | Heritage Exploration LLC | Oklahoma City, OK 73120-5622 | Oil & Gas Operator | Jan 2020 |
| 13 | Heston Oil Company | Tulsa, OK 74108 | Oil & Gas Operator | Mar 2005 |
| 14 | Highland Energy Co | Dallas, TX 75201 | Oil & Gas Operator | Jun 1994 |
| 15 | Highland Oil & Gas LLC | Houston, TX 77079-7220 | Oil & Gas Operator | Feb 2015 |
| 16 | Hiland Energy LP | Enid, OK 73701-0032 | Oil & Gas Operator | Dec 2022 |
| 17 | HK Energy Operating, LLC | Houston, TX 77002 | Oil & Gas Operator | May 2023 |
| 18 | Horizon Natural Gas Company | Tulsa, OK 74170 | Oil & Gas Operator | Sep 2024 |
| 19 | Horizon Natural Resources, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Jan 2019 |
| 20 | Horton Oil Company, Inc. | Independence, KS 67301 | Oil & Gas Operator | Jul 2000 |
| 21 | Howell Bill J | Calvin, OK 74531-0248 | Oil & Gas Operator | Sep 2016 |
| 22 | HRB Operating Company Inc | Bridgeport, TX 76426 | Oil & Gas Operator | Dec 2024 |
| 23 | Hsumy Oil & Gas Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2007 |
| 24 | Hughes Drilling Co. | Enid, OK 73702 | Oil & Gas Operator | Apr 1998 |
| 25 | Hunt Oil Company | Dallas, TX 75201 | Oil & Gas Operator | Dec 2024 |
| 26 | Huntington Energy LLC | Nichols Hill, OK 73116 | Oil & Gas Operator | Dec 2024 |
| 27 | Hutton Gas Operating Company | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2015 |