Seismic Sensor Configuration Design for a Geothermal Field to Monitor High-Resolution Seismicity

Abstract

Micro-seismicity has been reported to be induced by both developing or operating geothermal field. In the developing stage, to create underground cracks for water circulation within geothermal wells, hydraulic fracturing is frequently employed. High pressure water fluid will be injected into borehole to create fractures. In the producing stage, continuous extraction hot water and injection cool water fluid is a standard procedure. Condition monitoring of seismic activity of geothermal field is important to re-modulate, interrupt and restart of industrial activities. To monitoring micro-seismic activity, dense seismic stations on surface and sub-surface are usually deployed to track high-resolution seismicity spatial-temporal evolution. To optimize the design of a seismic network and increase the detection/location resolution of a small event. In this study, a multiple station earthquake method based on grid search technique has been developed. This algorithm has employed to evaluate the travel time residuals of earthquake within networks of special layouts. Based on the message of distribution size of travel time residual pattern, network performance of event location is calculated. We evaluated and compared the performance of different layouts (surface deployment and small seismic arrays) in terms of detection/location threshold and location errors to design optimize array. The proposed design procedure has been suggested to plan the seismic network of a geothermal field in Taiwan.