Deep geothermal energy (∼3-6 km depth) is a candidate for sustainable and carbon-free energy supply. One of the main concerns of deep geothermal systems is induced seismicity that may produce earthquakes of economic concerns, challenging the development of this form of alternative energy. So far, cold water injection has been overlooked but may contribute to induced seismicity due to fault reactivation through thermal stresses also beyond the cooling region. This can be of importance, in particular, in fractured and faulted geothermal reservoirs. In this study, we first compare different approaches to estimate induced seismic risk from slip-tendency analysis, rate-and-state friction theory and modified Gutenberg-Richter statistics based on frictional Coulomb-stress perturbations. Then, we systematically investigate effects of both, intrinsic geological parameters (e.g., fault-, host rock properties and in-situ stress), and operational parameters (e.g., well geometry and placement, injection schemes, induced pressure perturbation) on induced seismicity.
One of today's greatest challenges is the energy transition from fossil fuels to low-carbon renewables. Geothermal energy is a local solution for base load heat and electricity supply. As such it has the potential to provide safe and clean energy for the growing urban areas worldwide. In the Netherlands, geothermal energy is conventionally extracted from deep sedimentary aquifers that may be intersected by fractures and faults. While fault zones may serve as fluid pathways, thereby improving fluid production from and injection to a reservoir, they also pose the risk of hosting seismic events caused by geothermal operations (Muntendam-Bos et al. 2022, Buijze et al. 2020, Zang et al. 2014). The risk of induced seismicity is a major factor that currently hinders the widespread development of geothermal energy. Injection-induced seismic risk must thus be better understood to develop methods to assess and mitigate the risk of larger induced seismic events (Bommer 2022).
