Episodic Ground Deformation Associated with Fluid Extraction for Geothermal Energy Production, in Costa Rica.

Abstract:

The ground response to the production of energy in geothermal fields can be detected in the form of ground displacement and seismic activity. Changes in the temperature, volume, pressure of the reservoir can culminate in surface deformation. Satellite remote sensing (InSAR) permits the study of the deformation at these sites with high spatial and temporal resolution. Here we study the Dr Alfredo Mainieri Protti geothermal field, located near Miravalles Volcano in the Northern Costa Rica volcanic arc. We measure the deformation associated with geothermal energy production using data from two satellites (ALOS-2 and Sentinel 1A) between January 2015 and January 2017. The ALOS-2 data was used to obtain the extent of the affected area, and multi-temporal methods such Persistent Scattering, and Small Baselines were applied to the Sentinel 1A data, to obtain the temporal pattern of the ground displacements. Results show a direct response of the ground to the extraction of fluids. The pattern of deformation obtained with ALOS-2 is spatially correlated with the geothermal field, and with the recorded seismicity. Between April 2015 to October 2016, periods of uplift and subsidence were observed with values between∼2 to 3 cm every 120 days, linked to changes in the amount of fluids extracted from the reservoir. The results also show the ability of the reservoir to recover rapidly following a decrease in extraction rate. This work has shown that even in this tropical region it is possible to monitor anthropogenic ground motion using InSAR. This is beneficial for the Central American region, as satellite images are becoming more frequently acquired and available, and can be used to boost the monitoring of seismic regions, volcanic activity and anthropogenic activities.