Permeability heterogeneity controls fluid migration and microseismicity evolution in The Geysers geothermal field, California

Abstract

Fracture networks directly govern the efficiency of geothermal energy extraction and play a critical role in fluid migration and microearthquake generation. Using deep learning and Markov clustering, we build a high-resolution microseismic catalog covering the past decade for The Geysers geothermal field, California. Our observations reveal distinctive clustering patterns and inferred fracture systems tightly correlated with injection operations. Source mechanism analyses and pore pressure simulations indicate that the inferred connected fracture network provides pathways for rapid and directional pore pressure diffusion, highlighting that heterogeneous permeability controls the localized migration of fluids and the associated microseismic response. Our study highlights the importance of continuous and integrated seismic monitoring for ensuring the sustainability of long-term reservoir development and exploitation. Continuous seismic observations and numerical simulations reveal that, over the past decade, fluid migration and microseismic responses at The Geysers geothermal field have been primarily controlled by heterogeneous permeability.