Geophysical characteristics of a fault system in the northern Central Range of Taiwan and its applications for geothermal energy exploration

Abstract The northern Central Range of Taiwan is a high-potential geothermal region. Since the formations are mainly tight metasandstone and slate, permeable structures associated with faults commonly considered as conduits fluids. This study determines characteristics orientations fault zones by analyzing geophysical logs microresistivity formation image log (FMI) JT-4 well in Jentse, an important area Range. Between 720 1480 m measured depth (MD), effective porosity intact host rock mostly below 3% calculated log. Zones greater than 5% only clustered within few thin intervals. FMI interpretations show these porous interior fractured faulted These comprise damage high density open fracture planes cores breccias. There highly brecciated core 1334–1339 MD, which would be most interval well. Additionally, some healed sealed fractures observed. picked drilling-induced tensile signify that direction present-day maximum horizontal principal stress N40–50°E, also strike parallel to NE–SW direction. results concentrated four belonging one major normal system. After integrating locations zones, we propose system about 200 wide, trends N50–70°E, dips 70–80° NW. development may controlled current rifting Okinawa Trough offshore northeastern Taiwan. exhibits fluid regional system, will benefit future exploration