Reservoir Modeling of the Northern Vapor-Dominated Two-Phase Zone of the Wayang Windu Geothermal Field, Java, Indonesia

Abstract

The Wayang Windu geothermal field is located 35 km southeast of Bandung, Indonesia and started commercial operation in June 2000 at 110 MWe. A second unit came on line in March 2009, to produce a total of 227 MWe. More than 90% of the steam production for the two units is supplied from a vapor-dominated two-phase zone in the north of the field.
A numerical simulation was developed to establish if this production from the two-phase zone is sustainable. The model uses TOUGH-2 simulation software. Initial and boundary conditions were defined based on available data from the drilled area. The distribution of porosity, pressure, temperature and water saturation, and their respective changes in response to exploitation were assessed. The model was verified by matching measured downhole temperatures prior to exploitation and downhole pressure and flowing enthalpies during exploitation. There is good agreement between field data and the simulation for the two-phase zone.