The world's deepest Enhanced Geothermal System (EGS) project was carried out by the company St1 in Espoo, Finland, 2014 - 2022. The project comprised drilling two deep wells to >6 km depths, and carrying out hydraulic stimulation and monitoring of induced seismicity with downhole seismic arrays and satellite stations. The St1 drill site in Otaniemi, Espoo, is a world-class site, where superdeep wells are accessible in an urban area. Excellent research has been already done providing in-depth background knowledge. The St1 deep holes provide a unique possibility to establish a deep borehole observatory and geothermal laboratory offering unprecedented possibilities for research in induced seismicity, geothermics, hydraulic properties, deep fluids and gas as well as deep biosphere, helping to understand the behavior of crystalline bedrock at extreme depth.
Our aim is to apply the boreholes and data sets for a thorough analysis of the crystalline bedrock conditions at 5 – 6 km depth, solving problems related to developing EGS in crystalline rock.

KEYWORDS: Europe, Finland, Induced Seismicity, Geothermics, Fluid, Geochemistry, Deep Biosphere