SEGJ Technical Conference

Feasibility study of seismic imaging of supercritical reservoir(s) using DAS and DTS methods in the Ibusuki geothermal field

Abstract We conducted a feasibility study in 2018 in a geothermal field, Kyushu, Japan. We installed a fiber-optic cable down to 977 m in the borehole and measured the temperature and acquired seismic data in the borehole by distributed temperature sensor (DTS) and distributed acoustic sensor (DAS) modes, respectively. The measured highest temperature was 264 degC at the 914 m depth. We obtained 4.5 days of the continuous seismic monitoring via DAS and surface seismometers. The seismic system observed seven natural earthquakes occurring in surrounding region. One of the earthquakes with M5.2 at 100 km south of the DAS system occurred at 123 km depth and were observed by a whole depth of 977 m to 0 m. It is identified that less or no attenuation of seismic amplitudes at high temperature zone and Vp is approximately 4 km/s at this zone. By semblance analysis of all earthquakes, we obtained Vp profile in the borehole.