| 1 | H & N Operating Co., Inc. | | Oil & Gas Operator | Oct 1997 |
| 2 | Hallwood Petroleum, Inc. | Midland, TX 79701 | Oil & Gas Operator | Jun 2025 |
| 3 | Harkins And Co., Et Al | | Oil & Gas Operator | Dec 1980 |
| 4 | Harmony Producing Co Inc | | Oil & Gas Operator | Dec 1995 |
| 5 | Harrington Oil Inc. | | Oil & Gas Operator | Apr 1978 |
| 6 | Harris & Payne-Randel Drilling | | Oil & Gas Operator | Dec 1989 |
| 7 | Harrison Drilling Co | | Oil & Gas Operator | Mar 1981 |
| 8 | Hassie Hunt Expl. Co. | | Oil & Gas Operator | Aug 2008 |
| 9 | Hawkeye Drilling Co. | Waskom, TX 75692 | Oil & Gas Operator | Feb 2023 |
| 10 | Hayes & Assoc Inc | | Oil & Gas Operator | Oct 1991 |
| 11 | Herlihy John D. | | Oil & Gas Operator | May 1997 |
| 12 | Heron Operating, LLC | | Oil & Gas Operator | Jul 2025 |
| 13 | High Plains Operating Co | | Oil & Gas Operator | Nov 1993 |
| 14 | High-Line Production Services LLC | | Oil & Gas Operator | Aug 2025 |
| 15 | Highmark Energy Operating LLC | Dallas, TX 75222 | Oil & Gas Operator | Nov 2025 |
| 16 | Hilcorp Energy Company | Houston, TX 77208 | Oil & Gas Operator | Nov 2025 |
| 17 | Holleman & Parks Oil & Gas Inc | | Oil & Gas Operator | May 1995 |
| 18 | Houston Oil & Minerals Corp. | Houston, TX 77002 | Oil & Gas Operator | Aug 1996 |
| 19 | Howell Petroleum Corporation | Houston, TX 77251 | Oil & Gas Operator | Oct 2015 |
| 20 | Hughes & Hughes | | Oil & Gas Operator | May 1984 |
| 21 | Hughes & New Oil Co. | | Oil Operator | Jul 1993 |
| 22 | Hughes Eastern Corporation | Ridgeland, MS 39157 | Oil & Gas Operator | Sep 2025 |
| 23 | Humble Oil & Refining Co. | Houston, TX 77252 | Oil & Gas Operator | Jan 2000 |
| 24 | Hunt Oil Company | Dallas, TX 75201 | Oil & Gas Operator | Nov 2025 |
| 25 | Huseman Oil International Inc | | Oil & Gas Operator | Feb 1992 |