In order to improve the seismic monitoring of the Soultz-sous-Forêts geothermal site, a new seismic observation well was drilled in 2000. After two months of drilling, OPS4 reached the final depth of 1537m. Location of the OPS4 wellhead (in WGS84): - Latitude: 48.92108705 | 48° 55' 15" N - Longitude: 7.88306364 | 7° 52' 59" E - Altitude: 204m

The 4616 well was an old oil well drilled in 1950-1951. The well was recovered and used as seismic observation well of the Soultz-sous-Forêts geothermal project from 1987. It has been deepened in the framework of the project to 1414m in 1990. Location of the 4616 wellhead (in Lambert coordinates): - Latitude: 48.93879707 | 48° 56' 19" N - Longitude: 7.86502087 | 7° 51' 54" E - Altitude: 155.4m

The 4601 well was an old oil well drilled in 1951. It has been deepened in the framework of the Soultz-sous-Forêts project from 1010m to 1604m. A seismic probe was deployed at the bottom of the well to monitor the microseismic activity induced by the several experiments conducted on the geothermal site of Soultz-sous-Forêts. Location of the 4601 wellhead (in WGS84): - Latitude: 48.92805654 | 48° 55' 41" N - Longitude: 7.84882476 | 7° 50' 55" E - Altitude: 169m

The 4550 well was an old oil well drilled in 1949-1950. It has been deepened in the framework of the Soultz-sous-Forêts project from 1050m to 1500m in 1990. A seismic probe was deployed at the bottom of the well to monitor the microseismic activity induced by the geothermal site of Soultz-sous-Forêts. Location of the 4550 wellhead (in WGS84): - Latitude: 48.93750535 | 48° 56' 15" N - Longitude: 7.86972203 | 7° 52' 10" E - Altitude: 151m

In 1990/1991, an old oil well, EPS1 has been deepened and cored to characterize the granite reservoir and perform some deep hydraulic tests in view of a future experimental doublet. Unfortunately, the well had an important not controlled deviation and could not reach the expected depth. However, it was cored from 930 m to the bottom hole at 2227 m depth and provided a lot of scientific data. Location EPS1 WGS84: Latitude: 48.93118507 | 48° 55' 52'' N Longitude: 7.86766157 | 7° 52' 3'' E