Preliminary Modelling Activities for an Adaptive Traffic Light System for the Hengill Geothermal Field

Monitoring micro-seismicity during operations of a geothermal field is crucial for the understanding of seismic hazard and the reservoir evolution. Induced earthquakes in the context of geothermal projects are on the one hand an important tool to enhance the permeability and thus productivity of reservoirs and to image structure and processes. On the other hand, felt and in particular damaging induced earthquakes are a major threat to societal acceptance and regulatory license to operate. With the adaptive data-driven ATLS (Adaptive Traffic Light System), we aim at managing and mitigating the risk posed by induced earthquakes during stimulation and operations, while at the same time ensuring and optimising the productivity. RISC is developed as part of the EC Geothermica project COSEISMIQ (www.geothermica.eu/projects/coseismiq/) and will demonstrate the full potential of adaptive tools for risk mitigation and reservoir optimisation on the Hengill volcanic region. There, two power plants (Hellisheiði and Nesjavellir) have a total production capacity of 423 MWe and 433MWth, but to maintain this energy output, new production wells and reservoir stimulations are needed, often associated with induced seismicity. RISC integrates the entire processing chain, from automated picking of waveforms and data processing to seismic hazard and risk forecasting, including a strong seismicity modelling component. The seismicity forecasting module routinely computes and weights different models, ranging from purely statistical to fully coupled, 3D hybrid models. To implement such complex data-driven risk mitigation tool in Hengill, we performed a preliminary analysis of the past seismicity at two re-injection sites and provide preliminary numerical modelling for one of the sequences using the hybrid simulator TOUGH2-Seed. Future analysis will aim, on the one hand, at understanding the physical processes happening at the different sites, and on the other hand, at evaluating the performance of such code for future real-time application