The transition to a climate-neutral society by 2050 is to be achieved by reducing greenhouse gas emissions. The accompanying decline in production of the hydrocarbon industry leaves behind an enormous intact infrastructure and thousands of highly skilled workers. The project creates a techno-economic validation system for different methods of reusing existing wells and infrastructure for geothermal use. Depending on the location and depth, the nature of the geological subsurface and the heat output varies. The following applications are planned as reuse options: The boreholes will be converted and used

• as deep borehole heat exchangers (DBHE)
• as underground heat storage (e.g. for seasonal heat storage, Aquifer Thermal Energy Storage-ATES)
• as borehole thermal energy storage, close to the surface (borehole thermal energy storage-BTES)
• to use hot water for heating or electricity generation (hydrothermal geothermal energy)
• to use water supplied to the depths and thus heated (Enhanced Geothermal Systems-EGS).

The theoretically developed concepts will be tested and validated in site-specific feasibility studies at 8 pilot sites in Central Europe (D, AT, HU, SLO, CR). Finally, transnational strategies and a transnational action plan will be developed to create a policy, legal and incentive framework and specific measures to enable the transition to sustainable growth through the use of geothermal energy. This will promote the structural shift from a fossil fuel producing hydrocarbon industry to a sustainable green energy supply through geothermal energy by reusing existing infrastructure.