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Abstract:
During hydraulic stimulation as well as during production of deep geothermal wells induced seismicity might occur. To keep perception of seismicity and seismic risk at a low level, the use of local seismic networks is an established monitoring measure. Based on its results, parameters of operation of wells like injection pressure can be adjusted to maintain acceptable levels of seismicity. The joint research project SEIGER was part of the 7th Energy Research Programme of the German federal government. It was a collaboration of 27 scientists from universities, research institutes and private companies in Germany. Their work included automation of monitoring, optimization of the seismic research network in the area of Landau in the Upper Rhine Graben in southwestern Germany as well as the use of seismic arrays. The latter can serve as supplement or alternative in respect of local seismic networks and they can monitor a larger area than local networks. Geomechanical modelling techniques were extended to investigate possible triggering of existing faults near geothermal wells. Induced seismic events were attributed to existing fault patterns by improvement of seismic location techniques using 3D seismic velocity models. Passive and active seismic methods were adopted to reveal the shallow ground structure and to estimate the possible amplification of seismic motion (site effect) efficiently, for instance in the urban area of Munich. The data base of seismic hazard assessment of induced seismicity was improved in respect of local ground motion prediction equations, temporal changes of seismicity and consideration of site effects.
