Gravity survey in delineating geologic features of interest for deep geothermal use at Campus North of KIT.

The seasonal mismatch of the thermal energy demand can be addressed by thermal energy storage systems of high capacity (e.g. Lee 2013). In this scenario, High-temperatures aquifer thermal energy storage systems (HT-ATES), which commonly supply domestic needs could expand to meet heating or industrial processes demands by storing excess heat. DeepStor is a planned scientific infrastructure that address the demonstration the concept of HT-ATES in former hydrocarbon reservoirs of deep sedimentary rocks. Specifically, the concept development of the use of deep geothermal energy at Campus North (CN) of KIT. The latter is located on the largest known thermal anomaly in Germany (up to 140°C at 2 km depth), and in the central part of the Upper Rhine Graben (URG). In order to improve the understanding of the depleted oil reservoir conditions, a gravity survey is being carried out to support the modeling of geological structures. The gravity data in and around the CN is being acquired in an area of ~10 km2 using a CG-6 Autograv Gravity Meter (Scintrex Ltd) has a measurement range of over 8000 mGals and a resolution of 0.0001 mGal. This enable to study in both detailed local and large scale regional structures. Previous works in the URG have shown that temperatures above 100°C located in the central part of the graben superpose with areas of low values of Bouguer anomaly (Baillieux et al., 2013). On the other hand, the gravity observations on the URG have been interpreted in terms of subsurface density variation due to lithological heterogeneities. The results of the new gravity data at a local scale will improve the understanding of the local lithological heterogeneities and fracture porosity, giving feedback for the improvement of the new geological model in this area.