Exploring Whether Subsurface Fluid Production can Minimize Triggered Seismicity in Geothermal Fields

Project Overview

Fluid injection and production related to energy recovery and other industrial operations alter the pressure and stress state of subsurface reservoirs, which can lead to induced seismicity. Here, the primary goal is to investigate the hypothesis that the modulation of stress state in subsurface reservoirs through fluid injection/production operations can reduce the likelihood of inducing seismicity. Validation of this mitigation strategy will provide an active operational method to control induced seismicity in subsurface-reservoir exploitations such as geothermal-energy recovery and carbon storage. In this project, we analyze the relationship between extensive fluid production and the paucity of aftershock activity at the Coso geothermal plant (CGP) following the 2019 Ridgecrest earthquake sequence, where high rates of aftershock triggering were expected. We developed a high-fidelity multiphase coupled thermo-hydro-mechanical (THM) model to simulate fluid injection/production activities at the CGP between 1986 and 2020. THM results of surface subsidence due to high rates of fluid production agree well with field observations from global positioning system (GPS) and interferometric synthetic-aperture radar (InSAR). Subsequently, the variations of pore pressure, temperature, and stress state were used to drive numerical earthquake simulations of the aftershock response to the 2019 Ridgecrest earthquakes. The earthquake simulations show that seismic quiescence may occur following the Ridgecrest event, depending on the initial stress state at the time of the mainshock and at the initiation of geothermal-energy production. Seismic quiescence occurs in 20% of the cases we explored, where rates are decreased by 50% of the background rate in the two years following the mainshock. In circumstances where aftershock rates increase near the CGP following Ridgecrest, the average rate change is a factor of two larger than background rates from simulations with no operations. These findings indicate that, unlike many other operations that bring faults closer to failure, operations at the CGP are acting to stabilize faults such that triggering in the current stress state is minimal.

Mission Impact

Through this work, we have improved our simulation capabilities for many subsurface applications, including geothermal-energy system, carbon and/or gas storage, and nuclear-waste repositories. These capabilities are of strategic interest to DOE and align with LLNL's mission goals in energy and climate resilience and core competencies in sustainable energy production and HPC innovation. Specific impacts include demonstration of state-of-the-art capability to simulate thermo-hydro-mechanical processes and multiphase flow coupled with 3D physics-based simulations of induced and natural, based on pore pressure, poroelastic stress changes, and tectonic stress conditions. This end-to-end modeling capability will position us to compete for external funding in the application areas listed above.

This project established a relationship with the Coso Operating Company and the Navy Geothermal Program office, where both organizations entrusted LLNL with proprietary datasets that are not publicly available. This relationship may prove fruitful for future collaborations with industrial operators.

This project will produce a high-visibility publication and noteworthy presentations that will further advance LLNL's reputation for advanced simulation capabilities and high-performance computing related to these application areas.

Lessons learned from this project will be directly advantageous to upcoming FORGE projects led by LLNL PIs Kroll and Fu.

Publications, Presentations, and Patents

Kroll, K. A. et al. 2021. "Understanding the Interaction Between Tectonic and Anthropogenic Stresses at the Coso Geothermal Field." Presentation, Navy Geothermal Program Office Review Meeting, November 2021.

Kroll, K. A. et al. 2021. "Understanding the Role of Tectonic and Anthropogenic Stresses in Controlling Aftershock Activity at the Coso Geothermal Field." American Geophysical Union Annual Meeting, New Orleans, LA, December 2021.