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Multi-stage hydraulic stimulation, Zonal isolation, Realtime seismic monitoring, Fluid injection induced seismicity, Adaptive traffic light system, enhanced geothermal systems (EGS)
Abstract:
Reykjavik is almost entirely heated by geothermal energy. Yet, recent growth of the city significantly increased
the heat demand. Past experiences in Iceland’s capital region showed that hydraulic stimulation of existing
geothermal wells is suited to improve hydraulic performance and energy supply. However, fluid injection may
also trigger felt or even damaging earthquakes, which are of concern in populated areas and pose a significant
risk to stimulation operations. Consequently, soft stimulation concepts have been developed to increase
geothermal well performance while minimizing environmental effects such as induced seismicity. In a demonstration
project of hydraulic soft stimulation in October 2019, more than 20.000 m3 of water were injected into
well RV-43 in Reykjavik in multiple stages and with different injection schemes. The hydraulic performance of
the well was improved without inducing felt seismicity. An a priori seismic risk assessment was conducted and
for the first time the risk was continuously updated by an adaptive traffic light system supported by a sophisticated
realtime microseismic monitoring. Our results confirm that it is possible to improve the performance of
geothermal wells in Reykjavik and worldwide with acceptable technical, economic, and environmental risks.
Here we provide an overview of the entire stimulation project including site description, stimulation design,
zonal isolation, logging, seismic risk assessment and mitigation measures, realtime seismic, hydraulic and
chemical monitoring, and stimulation results and challenges.
