Managing Induced Seismicity Risks From Enhanced Geothermal Systems: A Good Practice Guideline

Geothermal energy is a green source of power that could play an important role in climate-conscious energy portfolios; enhanced geothermal systems (EGS) have the potential to scale up exploitation of thermal resources. During hydraulic fracturing, fluids injected under high-pressure cause the rock mass to fail, stimulating fractures that improve fluid connectivity. However, this increase of pore fluid pressure can also reactivate pre-existing fault systems, potentially inducing earthquakes of significant size. Induced earthquakes are a significant concern for EGS operations. In some cases, ground shaking nuisance, building damages, or injuries have spurred the early termination of projects (e.g., Basel, Pohang). On the other hand, EGS operations at Soultz-sous-For & ecirc;ts (France), Helsinki (Finland), Blue Mountain (Nevada, USA), and Utah FORGE (USA) have adequately managed induced earthquake risks. The success of an EGS operation depends on economical reservoir enhancements, while maintaining acceptable seismic risk levels. This requires state-of-the-art seismic risk management. This article reviews domains of seismology, earthquake engineering, risk management, and communication. We then synthesize "good practice" recommendations for evaluating, mitigating, and communicating the risk of induced seismicity. We advocate for a modular approach. Recommendations are provided for key technical aspects including (a) a seismic risk management framework, (b) seismic risk pre-screening, (c) comprehensive seismic hazard and risk evaluation, (d) traffic light protocol designs, (e) seismic monitoring implementation, and (f) step-by-step communication plans. Our recommendations adhere to regulatory best practices, to ensure their general applicability. Our guidelines provide a template for effective earthquake risk management and future research directions. Geothermal energy could play an important role in the future of climate-conscious energy. Enhanced geothermal systems (EGS) have the potential to unlock thermal energy trapped in impermeable rocks; hydraulic fracturing injects fluids under pressures high enough to stimulate fractures, increasing permeability. However, this process also has the potential to cause earthquakes. Induced earthquakes have the potential to end operations or cause development moratoriums. On the other hand, there are EGS operations that were able to adequately manage these risks. Here, we review the literature of cases, to synthesize material into a state-of-the-art understanding of seismic risk management. We provide "good practice" guidelines that spans multiple domains. Because of this breadth of topics, we advocate for a modular framework that covers seismic risk pre-screening, seismic hazard and risk evaluation, design of traffic light protocols, seismic monitoring considerations, and detailed communication plans. Overall, this review provides a template for future EGS projects to consider, while highlighting research directions needed for improved management of earthquake risks. Induced seismicity can be caused by geothermal operations. These earthquakes can be operation-ending, or spur development moratoriums We review the breadth of literature and then synthesize "good practice" recommendations, in a modular format for simplicity Our guidelines provide a template for safe and responsible enhanced geothermal systems operations, while highlighting future research directions