Geothermal Exploration in Switzerland for Heat Production and Storage: The Key Role in Knowledge and Technology Transfer From the Hydrocarbon Industry

Abstract

A full range of regional-scale evaluation activities of geothermal energy resources and subsurface heat-storage potential are being carried in the entire Molasse Plateau in Switzerland in the framework of both Federal research programs such as Swiss national SCCER SoE programs and Canton-driven initiatives such as the ‘GEothermie2020’ program in the Geneva Canton aimed at implementing a nuclear-free 2050 energy strategy.

A large data set of 2D seismic lines from different surveys mostly acquired for hydrocarbon exploration carried in the 70s and 80s, have been collected and in part re-processed to enhanced potential shallower stratigraphic targets. New walk-around and walk-above VSP were acquired in abandoned wells in order to establish a better control on velocity model and reservoir heterogeneity. All these seismic data, together with newly-acquired Bouger-anomaly gravity data, calibrated with few deep boreholes have been integrated in a single data base which served as basis for establishing a sound subsurface stratigraphy framework. The latter spans from the Permo-Carboniferous (P-C) to the Tertiary age, including potential geothermal reservoirs in the P-C sandstones, and the Jurassic and Cretaceous limestones.

The mapping of fault system has been carried out to identify deeply rooted lineaments which may connect the crystalline basement to shallower formations, including especially those ones controlling the P-C extensional structures, possibly reactivated, at later stages, during the Alpine inversion and present day tectonic regime.

Preliminary data of downhole temperatures suggest a gradient of 25-30°C/km. The examination of these different data sets, including the distribution of historical earth-quakes epicenters and results of ongoing passive seismic monitoring, aims at 1) supporting further evaluation and risk assessment (including the possible undesired occurrence of hydrocarbons and seismic ) of the regional geothermal potential and 2) identifying a number of most suitable subsurface targets for both heat direct-use and storage, using a play fairway analysis approach.

The knowledge and technology transfer from the HC industry in this exploration phase could be key to accelerate the learning curve and meet the energy strategy objectives. This can provide the geothermal players with the necessary best practice and workflows which however, need to be adapted to a very different and challenging business environment if compared to the HC industry.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018