Towards Subsurface Stress and Strain Monitoring at the Patua Geothermal Field

Abstract

Geothermal resources have the potential to provide clean energy, and the understanding of subsurface stress and strain changes becomes crucial for geothermal operations. We demonstrate the effort to combine seismic (earthquakes and ambient noise), surface deformation (InSAR and GPS) and numerical modeling for characterizing subsurface stress and strain. We have deployed five shallow-borehole seismometers for monitoring the microearthquake activities at the Patua Geothermal Field since June 2021. Patua is a conventional (non EGS) geothermal field; however, the field has a potential to apply a near-field EGS well stimulation to stimulate the reservoir. This local array lowers the magnitude completeness of earthquake detection, which can characterize fault distribution and their criticalness, as well as records ambient-noise data to detect time-lapse changes of subsurface velocities using coda-wave interferometry. Time-lapse changes in velocities provide a unique view of subsurface elastic changes between each receiver pair. Surface deformation estimated from InSAR shows a clear trend of subsidence in addition to the annual cycle. The cumulative deformation from 2018 to 2022 correlates with mapped faults, which suggests that the north-northeast trending faults may be permeable pathways. We will jointly interpret the results of seismic and surface deformation for subsurface stress changes, which could be used for the numerical modeling of future well stimulation activities and evaluating fluid migration within the existing geothermal field.