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The GEISER (Geothermal Engineering Integrating Mitigation of Induced Seismicity in Reservoirs) project was funded by the
European Commission from 2010 until 2013. The project addressed one of the major challenges the development of geothermal energy is facing: the mitigation of induced seismicity to an acceptable level. To address this objective, induced seismicity from representative geothermal reservoirs throughout Europe was analyzed (Soultz, Basel, Gross Schoenebeck, Iceland, Campi Flegrei).
In addition, data from regions outside continental Europe were made available by companies and partners working in the respective caountries (Berlín, El Salvador; The Geysers, USA; Paralana and Cooper Basin, Australia). Induced earthquakes were analyzed with respect to their relationship with injection parameters, local stress fields, and geological settings. These analyses demonstrated
that locating the hypocentres of the observed seismic events (seismic cloud) is dependent on the design of the installed network, the used velocity model and the applied location technique. Understanding the geomechanics and processes involved in creating induced seismicity. The influence of factors such as temperature, poro-elasticity, fluid injection rate, existing fault segments, and time dependent effects were investigated to better constrain the mechanisms involved during fluid injection. The project also addressed consequences of induced seismicity by providing an assessment of the seismic hazard presented by earthquakes triggered through human activity in comparison to hazards triggered by natural seismicity. Combining a statistics based approach – the classic probabilistic hazard assessment applied in seismology - with input from hydraulic and mechanical models about stress transfer and the rupture process, a dynamic forward-looking traffic light system is proposed to better mitigate large induced seismic events during geothermal operations. In addition, guidelines are proposed for licensing and site development for local authorities and industry. On the basis of these results and recommendations, strategies for soft injection have been proposed to mitigate large induced seismic events. Experience of past seismic events caused by the mining and the oil and gas industries have been included to address the proper handling of risk.
Abstract:
injection, induced seismicity, mitigation strategies
