Takigami geothermal system, northeastern Kyushu, Japan

Abstract The Takigami geothermal reservoir is bounded by a system of faults and fractures oriented along two main directions, north to south and east to west. The Noine fault has a large vertical displacement and trends north to south, dividing the subsurface characteristics of resistivity, permeability, temperature and reservoir depth. The Takigami geothermal fluid has a near neutral pH and is of the Na–Cl type, with a chloride content ranging from 400 to 600 ppm. The southwestern part of the area has the highest subsurface temperature, up to 250°C. The deep fluid originates from the southwest, and flow is mainly to the north and partly to the east along faults and fractures, decreasing in temperature with increasing lateral flow.

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