The Use of Fluid Inclusion Geothermometry as an Indicator of Reservoir Temperature and Thermal History in the Hatchobaru Geothermal Field, Japan

Abstract

Fluid inclusions provided of a fast and easy method for estimating underground temperatures, which in turn are very useful for defining the thermal history of a geothermal system. The lowest value of fluid inclusion temperature at each depth is quite close to the present temperature of fluid conduits and reservoirs. The distribution of fluid inclusion temperatures from producing zones has a relatively narrow range up to 40°C in the Hatchobaru geothermal field. The minimum of them give an estimate of 260-290°C for the reservoir temperature. On the other hand, the fluid inclusion temperature form a reinjecting zone show a bimodal distribution. The minimum value (230°C) of the lower temperature peak agrees well with the present temperature, where as the value (273°C) of the higher temperature peak seem to be equal to the original reservoir temperature.