Sustainable Development of Geothermal Energy-A Case Study of Hatchobaru Geothermal Field, Central Kyushu, Japan-

Abstract

Geothermal energy is renewable but its sustainability is not self-evident. Therefore it is very important to manage geothermal reservoir in order to realize sustainable production of geothermal energy. We estimated the mass balance in the geothermal reservoir during exploitation at Hatchobaru geothermal field, central Kyushu, Japan, based on the changes in gravity and Gauss’s theorem. Combining the estimated mass change and the rates of produced and re-injected geothermal fluids, we calculated the rate of natural recharge to the geothermal reservoir from outside. As a result, we estimated that the rate of natural recharge is nearly same as the rate of steam discharged to the atmosphere from the cooling towers. The above result is consistent with the mass balance estimated from numerical modeling. Therefore we conclude that the sustainable production of geothermal energy is realized at Hatchobaru Geothermal Power Station.