Perpustakaan Digital ITB

Ulumbu Geothermal Field is located in Flores Island, Indonesia. It is approximately 13 km south southwest of the city of Ruteng. The geothermal system of this field is steam dominated at the upper part and liquid dominated at the bottom part with temperature of 230oC to 240oC. From the thermal features, this field has area of approximately 28 km2 and possible reserve of 187.5 MWe (ESDM, 2005) and potential recoverable reserve of 150 MWe (WJEC, 2007). TOUGH2 simulator is a numerical simulator which can carry the modelling of fluid flow in porous and fractured media, this simulator could help engineer to determine the characteristics of the reservoir such as area, thickness, pressure, temperature, and permeability distribution, those results could be used to determine the potential reserve of the field. The objective of this study is to present numerical modelling of Ulumbu Geothermal Field based on published geological, geophysical, and geochemical, and wells data. The model was matched with available temperature data from three drilled wells, mass flow, and heat flow to achieve natural state condition. After the natural state model had been achieved, the reservoir characteristics were determined, from the characterization, the area of the reservoir is about 28 km2, the reservoir thickness is 1500-1700 m, temperature is in range of 235-244oC and the final permeability of reservoir is ranging from 25-65 mD. Potential reserve of the field was also calculated using heat stored method with Monte Carlo simulation, the P10 of the field reached value of 137 MWe showing this field has good capability to support current installed capacity with high level of confidence. This is the first natural state reservoir modelling of Ulumbu Geothermal Field that has been established successfully.