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Combining 3D Dynamic Rupture Modeling and Thermo-Hydro-Geomechanical Modeling Towards Physics-Based Induced Earthquake Simulations

Description: 

Geothermal systems, offering sustainable sources of energy, are important building blocks of climate change mitigation strategies, but are challenged by the possible occurrence of induced earthquakes of potentially large societal and economic impact. Hence, the operational success of geothermal systems depends on the development of effective strategies to mitigate the hazard of induced earthquakes. Physics-based numerical modeling can allow a holistic understanding of injection and production operations, earthquake nucleation, propagation, and arrest, and complement empirical guidance, e.g. provided by traffic light systems. However, the physical processes associated with cold water injection and earthquakes occur on vastly different time scales and are governed by distinct physics, challenging numerical models. Here, we demonstrate the feasibility of linking complex 3D thermo-hydro-geomechanical (THM) and dynamic earthquake rupture models. We model exemplary pore pressure, temperature, and stress evolution during injection over decades using the open-source THMC sImulator for GEoscience Research (TIGER), which solves the THM coupled processes in geothermal reservoirs. Our model results suggest that stress can deviate significantly from the background stress at the reservoir scale. Specifically, a localized pore pressure increase of several MPa builds up near the injection well, which results in a sizable effective normal stress change, able to nucleate an earthquake. Using the dynamic rupture and seismic wave propagation code SeisSol, we initialize 3D dynamic rupture simulations from the stress state of the geomechanical models. Depending on the assumed friction law parameterization, a wide range of rupture behavior, including spontaneously arrested or runway ruptures, are modeled. We discuss how geomechanically constrained dynamic rupture simulations can address key problems, such as the maximum physically plausible earthquake magnitude in a georeservoir, and coupling strategies for multiple events towards digital twins of geothermal systems.

Session: Understanding and Managing Induced Seismicity

Type: Oral

Date: 4/19/2023

Presentation Time: 02:15 PM (local time)

Presenting Author: Thomas Ulrich

Student Presenter: No

Invited Presentation: 

Authors