| 1 | H & D Operating Company | Refugio, TX 78377 | Oil & Gas Operator | May 2015 |
| 2 | H & T Oil & Gas Company, Inc. | Alice, TX 78333 | Oil & Gas Operator | Mar 2008 |
| 3 | H&K Energy | Stockdale, TX 78160 | Oil & Gas Operator | Jul 2005 |
| 4 | Halcon Operating Co., Inc. | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 5 | Hamman Oil & Refining Company | Houston, TX 77098 | Oil & Gas Operator | Oct 2025 |
| 6 | Hankey Oil Company | Houston, TX 77027 | Oil & Gas Operator | Feb 2010 |
| 7 | Hankey Operating, Inc. | Houston, TX 77027 | Oil & Gas Operator | Mar 2016 |
| 8 | Hanson Minerals Co. | Houston, TX 77042 | Oil & Gas Operator | Oct 1993 |
| 9 | Hanson Production Company | Cuero, TX 77954 | Oil & Gas Operator | Jul 2009 |
| 10 | Hardwick Oil Company | Sugar Land, TX 77478 | Oil & Gas Operator | Nov 2014 |
| 11 | Harper Hefte, Inc. | Corpus Chrsti, TX 78410 | Oil & Gas Operator | Oct 2025 |
| 12 | Harrison Interests, LTD. | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 13 | Hawthorn Energy Partners, LLC | Nichols Hill, OK 73116 | Oil & Gas Operator | Oct 2025 |
| 14 | Headington Oil Company | Dallas, TX 75231 | Oil & Gas Operator | Dec 2016 |
| 15 | Hemco Development, LLC | Dallas, TX 75201 | Oil & Gas Operator | Nov 2020 |
| 16 | Henry Petroleum Corp. | Midland, TX 79703 | Oil & Gas Operator | Mar 2001 |
| 17 | High Plains Gas Systems, Inc. | Houston, TX 77019 | Oil & Gas Operator | Oct 2025 |
| 18 | Hilcorp Energy Company | Houston, TX 77208 | Oil & Gas Operator | Oct 2025 |
| 19 | Hinton Production Company | MT Pleasant, TX 75455 | Oil & Gas Operator | Aug 1995 |
| 20 | Hollimon Oil Corporation | Castroville, TX 78009 | Oil & Gas Operator | Nov 2016 |
| 21 | Horizon Prod. And Operating, LLC | Houston, TX 77019 | Oil & Gas Operator | Oct 2025 |
| 22 | Huber J M Corp | Edison, NJ 08837 | Oil & Gas Operator | Oct 2025 |
| 23 | Hughes, Dan A. Company | Beeville, TX 78104 | Oil & Gas Operator | May 2006 |
| 24 | Hughes, Dan A. Company, L.P. | Beeville, TX 78104 | Oil & Gas Operator | Oct 2025 |
| 25 | Hunt Oil Company | Dallas, TX 75201 | Oil & Gas Operator | Oct 2025 |
| 26 | Hunt Petroleum Corporation | Dallas, TX 75201 | Oil & Gas Operator | Nov 2008 |
| 27 | Hunter Petroleum Inc. | Alice, TX 78333 | Oil & Gas Operator | May 2014 |
| 28 | Huntington Resources Inc | Tulsa, OK 74103 | Oil & Gas Operator | Oct 2006 |
| 29 | Hurd Enterprises, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Oct 2025 |