Resource assessment of Tompaso geothermal field, Indonesia

Abstract

The Tompaso geothermal field is one of the prospect fields being developed by PT. Pertamina Geothermal Energy. The Tompaso prospect is located in North Sulawesi, Indonesia about 30 km from the Lahendong geothermal field which currently produces about 60 MWe. In 2008, the first exploration well was drilled in Tompaso and today there are a total of 8 wells divided into 3 clusters. The purpose of the drilling activity is to develop a 2×20 MWe power plant, i.e. units 5 and 6 in Tompaso Prospect. This paper describes a resource assessment of the Tompaso geothermal field that consists of volumetric calculations for 20, 25 and 30 year production scenarios. A well test analysis for the purpose of calculating transmissivity and storativity values is also described. The well testing utilised all existing data from step drawdown tests in the Tompaso geothermal field. The last chapter describes pressure drawdown calculations using the Monte Carlo method to simulate pressure decline in the Tompaso prospect for different production scenarios in order to optimise future production.