Results of Stimulation Treatments at the Geothermal Research Wells in Groß Schönebeck, Germany

Abstract

The aim of this paper is to present the results of previously performed fracture treatments in the new geothermal research well GtGrSk4/05 at Groß Schönebeck. The fracture treatments included three hydraulic stimulations, two in the sandstone section of the Lower Permian (Upper Rotliegend) and one in the volcanic section (Lower Rotliegend). In the low permeable volcanic rocks we performed a cyclic waterfrac treatment over 6 days in conjunction with adding low sand concentrations. Flow rates of up to 150 l/s during the high stages were realized with a total amount of injected water of 13,170 m³. Monitoring the water level in the offsetting well EGrSk3/90, which is 475m apart at the final depth, showed a very rapidly water level increase due to the stimulation treatment. A possible explanation is a natural fracture system or a fault zone in the volcanic rocks, which connects the two boreholes via the new fractures. It was known from previous treatments in the offsetting well that the high permeable sandstones do not show a self propping effect, hence we carried out two gel proppant treatments in these sandstones to maintain long-term access to the reservoir. A total amount of 100 to of high strength proppant with 500 m³ of cross-linked gel were injected during each treatment. The subsequent production test in conjunction with flowmeter logging to obtain the inflow intervals showed the success of the fracture treatments.