Downhole Monitoring During Hydraulic Experiments at the In-Situ Geothermal Lab Groß Schönebeck

Abstract

During the current project phase the geothermal water loop at the Groß Schönebeck site is being set up and short- to long-term hydraulic experiments are performed in the well doublet in order to assess the hydraulic properties and the sustainability of the engineered reservoir. Downhole measurements are carried out during production in order to observe the performance of the stimulated zones and the naturally occurring permeable intervals. The production string has been constructed in order to allow for access to the reservoir with logging tools during fluid production using a new developed Y-tool to bypass the submersible pump. In addition a novel hybrid wireline production logging system for combined measurements with electrical tools (pressure, temperature, flow meter, gamma ray, casing collar locator) and fiber-optic distributed temperature sensing (DTS) has been developed. The results of the first measurement campaigns show that valuable data for the observation and understanding of reservoir flow dynamics can be collected with the new system. The observed hydraulic behavior is mainly controlled by a variable contribution from a hydraulic fracture zone, which appears to be influenced by the production history and induced reservoir processes.