| Abstract |
The Patuha vapor-dominated geothermal resource occurs within a Quaternary volcanic highland in west Java, Indonesia. The productive reservoir shows a close relationship with a west-northwest trending structural zone or "volcanic axis" defined by an alignment of late-stage volcanic domes, craters and lava flows. Fumaroles occur in several areas at higher elevations in the field, including a localized area of magmatic gas discharge at Kawah Putih. Magnetotelluric and gravity surveys have defined a region of high resistivity and shallow basement which bounds the south and east margins of the reservoir. Geophysical data has proved less useful in defining the north and west flanks of the productive resource, due to the presence in these areas of shallow outflows of chloride-bearing condensates and clay-rich volcaniclastic sediments. Deep temperature gradient data provided the most reliable initial indication of the extent of the reservoir, as verified by subsequent production test drilling. The productive vapor-dominated reservoir proven by drilling to date near Kawah Ciwidey is about 700 meters thick and covers about 5.5 square kilometers. The total reservoir area may reach up to 20 square kilometers, as indicated by an elongate, deep thermal anomaly which overlaps the volcanic axis. |