The stress regime in a Rotliegend reservoir of the Northeast German Basin

In-situ stresses have significant impact, either positive or negative, on the short and long term behaviour of fractured reservoirs. The knowledge of the stress conditions are therefore important for planning and utilization of man-made geothermal reservoirs. The geothermal field Gro Schonebeck (40 km north of Berlin/Germany) belongs to the key sites in the northeastern German Basin. We present a stress state determination for this Lower Permian (Rotliegend) reservoir by an integrated approach of 3D structural modelling, 3D fault mapping, stress ratio definition based on frictional constraints, and slip-tendency analysis. The results indicate stress ratios of the minimum horizontal stress S (hmin) being equal or increasing 0.55 times the amount of the vertical stress S (V) (S (hmin) a parts per thousand yen 0.55S (V) ) and of the maximum horizontal stress S (Hmax) a parts per thousand currency sign 0.78-1.00S (V) in stress regimes from normal to strike slip faulting. Thus, acting stresses in the 4,100-m deep reservoir are S (V) = 100 MPa, S (hmin) = 55 MPa and S (Hmax) = 78-100 MPa. Values from hydraulic fracturing support these results. Various fault sets of the reservoir are characterized in terms of their potential to conduct geothermal fluids based on their slip and dilatation tendency. This combined approach can be adopted to any other geothermal site investigation.