Numerical modelling of the Kamojang geothermal system, Indonesia

Abstract

Kamojang geothermal field on the island of Java in Indonesia is in a large volcanic chain, 15 km long and 4.5 km wide. It is a steam-dominated field located at 1500 m a.s.l. The field has been exploited since 1983, currently supplying steam for 140 MWe power production but production will be raised to 200 MWe, scheduled in 2006. To date, 72 wells have been drilled in the field. Reservoir simulation is a numerical method used to simulate the performance of a geothermal reservoir either at natural state conditions (before exploitation) or under a variety of exploitation schemes and future predictions. The TOUGH2 simulator was used for a 2-dimensional numerical modelling of the Kamojang geothermal system to study different boundary conditions from what has been practiced in the past. The model consists of 394 elements in 13 layers. The natural state of the model simulates quite well the reservoir’s temperature and pressure down to 1 km depth as observed in well KMJ-11. The model was used to make a 27 year forecast on reservoir response to the 200 MWe production, starting in 2006. The model needs, however, to be recalibrated and compared to more field data to give a more confident estimate of the field’s future performance.