An Estimate of the Resources Potential of Ungaran Geothermal Prospect for Indonesia Power Generation

Abstract

Numerical analysis has been performed to assess the geothermal potential of Ungaran volcano located in Central Java Indonesia using a 3-D finite difference simulator. A conceptual model was constructed based on the results of geophysical studies such as gravity, spontaneous-potential, micro-earthquake, infrared imagery and shallow ground temperature. Geophysical studies found deep geothermal fluids which are supplied from　below of the central volcano was changed into　lateral flows. A part of the geothermal fluids reaches the ground surface and forms the Gedongsongo fumarole area. The background temperature distributions and mass flux patterns were calculated for 150,000 years to obtain the quasi-steady state. The meteoric water flow pattern demonstrates predominant downward flow, with mass flux varying between 10-8 g/cm2sec up to 10-7 g/cm2sec. The thermal evolution was calculated for up to 30,000 years. The deep geothermal fluids supplied from　below of the central volcano have enthalpy of 1085 kJ/kg and　mass flow rates of 230 kg/s to 250 kg/s. In order to estimate the geothermal potential for conventional electric power production, we employed the minimum reservoir temperature is 150oC and the performance of the reservoir was predicted for 30 years production. Depths of the reservoir are assumed from 0.5 km to 3 km beneath mean sea level. The result shows that the estimated geothermal potentials are 2.3 MWe up to 40.4 MWe depending on the difference of thicknesses of the reservoir.