| Abstract |
Recent assessment provides a high probability that the Wayang Windu geothermal resource can support organic growth opportunities such as adding power plant unit to the existing 227 MW power plant operations until year 2040. This resource assessment is based on an integrated conceptual model of geothermal field based upon evaluations of geology, geochemistry, geophysics, downhole well and discharge well data. A large number of big-hole development wells and several slim-hole exploratory wells have been drilled in and around the field, providing data on subsurface temperatures, pressures, fluid chemistry, subsurface geology and reservoir properties. Therefore, the location, shape and approximate extent of the geothermal system have been defined reasonably well and many important characteristics of the system have been interpreted with a reasonable degree of confidence. The proven resource covers an area of 22 km square and is closely associated with northeasterly trending volcanic domes on the southern slope of Gunung Malabar. The reservoir is a moderately saline brine that is overlain by commercially exploitable steam caps. The most likely conceptual model has been converted into a numerical model to evaluate the resource performance under different generation scenarios. The numerical model is constructed as dual porosity model using TOUGH2 reservoir simulator and consists of 30,680 regular grid blocks. The numerical model has been calibrated against initial (pre-exploitation) reservoir pressure and temperature. In addition, it has also been calibrated against historical production parameters such as steam cap pressure, liquid reservoir pressure, discharge enthalpy and superheat evolutions during 18 years of commercial operations at 110 MW and 227 MW loads. |