| 1 | Sandefer Petroleum Co. | | Oil & Gas Operator | Apr 1994 |
| 2 | Seaboard Pipe & Equip. Co. | | Oil & Gas Operator | May 1977 |
| 3 | Seaboard Well Service, Inc. | | Oil & Gas Operator | Jan 1978 |
| 4 | Senior G&A Operating Co Inc | | Oil & Gas Operator | Nov 1991 |
| 5 | Sevarg Company, Inc. | | Oil & Gas Operator | Feb 2016 |
| 6 | Shelf Energy, LLC | | Oil & Gas Operator | Dec 2024 |
| 7 | Shell Oil Company | Houston, TX 77210 | Oil & Gas Operator | Apr 2015 |
| 8 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 9 | Sklar &Phillips-Great Southern | | Oil & Gas Operator | Aug 1980 |
| 10 | Sohio Petroleum Co. | Casper, WY 82602 | Oil & Gas Operator | Apr 1986 |
| 11 | Source Petroleum Inc. | San Antonio, TX 78265 | Oil & Gas Operator | Oct 2025 |
| 12 | Southeastern Public Service Co | | Oil & Gas Operator | Sep 1982 |
| 13 | Southern Bay Operating, L.L.C. | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 14 | Southern Production & Expl Co. | | Oil & Gas Operator | Apr 2008 |
| 15 | Southern Union Exploration Co. | Austin, TX 78701 | Oil & Gas Operator | Feb 2002 |
| 16 | Southland Royalty Company | Houston, TX 77210 | Oil & Gas Operator | Sep 2011 |
| 17 | Southwest Oil Properties, Inc. | | Oil & Gas Operator | Feb 1996 |
| 18 | St. Mary Land & Exploration Co | Denver, CO 80201 | Oil & Gas Operator | Jun 2010 |
| 19 | St. Mary Operating Company | Denver, CO 80203 | Oil & Gas Operator | Mar 2019 |
| 20 | St. Paul Oil And Gas Corp. | | Oil & Gas Operator | Aug 1991 |
| 21 | Stone Petroleum Corporation | | Oil & Gas Operator | Dec 1996 |
| 22 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Oct 2025 |
| 23 | Summit Energy Company | | Oil & Gas Operator | Mar 2009 |