Abstract
Abstract. The rapid increase in energy demand in the city of Reykjavik has posed the need for an additional supply of deep geothermal energy. The deep-hydraulic (re-)stimulation of well RV-43 on the peninsula of Geldinganes (north of Reykjavik) is an essential component of the plan implemented by Reykjavik Energy to meet this energy target. Hydraulic stimulation is often associated with fluid-induced seismicity, most of which is not felt on the surface but which, in rare cases, can be a nuisance to the population and even damage the nearby building stock. This study presents a first-of-its-kind pre-drilling probabilistic induced seismic hazard and risk analysis for the site of interest. Specifically, we provide probabilistic estimates of peak ground acceleration, European microseismicity intensity, probability of light damage (damage risk), and individual risk. The results of the risk assessment indicate that the individual risk within a radius of 2 km around the injection point is below 0.1 micromorts, and damage risk is below 10−2, for the total duration of the project. However, these results are affected by several orders of magnitude of variability due to the deep uncertainties present at all levels of the analysis, indicating a critical need in updating this risk assessment with in situ data collected during the stimulation. Therefore, it is important to stress that this a priori study represents a baseline model and starting point to be updated and refined after the start of the project.
Highlights
The city of Reykjavik, the capital and center of population of Iceland, meets 99.9 % of its district heating demand by geothermal energy (Gunnlaugsson et al, 2000)
The exceptional geothermal gradient in this area triggered the drilling of a well (RV-43) in 2001 after a gabbro body was identified as potential heat source and drilling target for this deviated well
As for the individual risk (IR), in the presence of epistemic uncertainties, the median of the damage risk (DR) distribution is taken as a reference metric to be compared with the selected safety standard, i.e., qDR,0.5 ≤ DRST
Summary
The city of Reykjavik, the capital and center of population of Iceland, meets 99.9 % of its district heating demand by geothermal energy (Gunnlaugsson et al, 2000). Another source of concern stems from the fact that deep geothermal projects in Europe – the Geldinganes stimulation is no exception – are often located close to consumers and in densely urbanized areas with historical and vulnerable buildings and infrastructures In these contexts, the problem of assessing and managing induced seismicity is critical (Bommer et al, 2015; Giardini, 2009; Majer et al, 2007, 2012; Mignan et al, 2015, 2019a, b, Trutnevyete and Wiemer, 2017; van Elk et al, 2017; Walters et al, 2015).
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