| 1 | H & S Operating Co., Inc. | Winesburg, OH 44690 | Oil & Gas Operator | Dec 2024 |
| 2 | Hadson Petroleum (USA), Inc. | | Oil & Gas Operator | Dec 1992 |
| 3 | Harkins & Co. | | Oil & Gas Operator | Oct 1986 |
| 4 | Hawkeye Oil & Gas, Inc. | | Gas Operator | Jun 1995 |
| 5 | Haynehead Operating Company, LLC | | Gas Operator | Feb 2016 |
| 6 | Herlihy, John D. | | Oil & Gas Operator | May 1997 |
| 7 | Hickox, I. N. | | Oil Operator | Nov 1967 |
| 8 | Highland Oil Co. | | Oil Operator | Mar 1953 |
| 9 | Highmount Black Warrior Basin, LLC | | Gas Operator | Jul 2010 |
| 10 | Hilcorp Energy Company | Houston, TX 77208 | Oil & Gas Operator | Mar 2025 |
| 11 | Hodge, T.F. & Morrow Oil & Gas Co. | | Oil & Gas Operator | Sep 1993 |
| 12 | Houser, R. G. | | Oil Operator | Mar 1953 |
| 13 | Houston Oil & Gas Company, Inc. | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 14 | Howell Petroleum Corporation | Houston, TX 77251 | Oil & Gas Operator | Oct 2015 |
| 15 | Hughes & Hughes | | Oil & Gas Operator | May 1984 |
| 16 | Hughes Eastern Corporation | Ridgeland, MS 39157 | Oil & Gas Operator | Dec 2024 |
| 17 | Hughes Eastern Petroleum, LTD. | | Oil & Gas Operator | Jun 1986 |
| 18 | Hughes Petroleum Corp. | | Oil Operator | Dec 1972 |
| 19 | Humble Oil & Refining Co. | Houston, TX 77252 | Oil & Gas Operator | Jan 2000 |
| 20 | Hunt Oil Company | Dallas, TX 75201 | Oil & Gas Operator | Mar 2025 |
| 21 | Huseman Oil International, Inc. | | Oil & Gas Operator | Feb 1992 |