Geologic Conceptual Model Update of the Darajat Geothermal Field, Indonesia

Abstract

Darajat is a volcanic geothermal reservoir located in West Java, Indonesia, that currently supplies steam to generate 260 MWe from 3 power plant units. Thorough reservoir characterization and modeling was conducted in 2001-2004 as part of the Darajat Unit III reserves assessment. Since that study, additional resource information was obtained from a Magneto Telluric / Time Domain Electro Magnetic (MT/TDEM) survey conducted in 2004, a micro-earthquake (MEQ) array that was established in 2005, and a make-up drilling campaign conducted in 2007-2008. The new information obtained from the geophysical surveys and drilling results has led to an improved understanding of the geology of the reservoir, including the distribution of low porosity reservoir rock, the permeability distribution, and reservoir boundaries. This new information, together with down-hole pressure, temperature, and production logs, has been integrated into an updated geologic conceptual model and incorporated into a 3D earth model through the application of geostatistical modeling tools. The 3D earth model provides the geologic input into the numerical simulation model which is being used to evaluate reservoir performance and to assess the capacity of the reservoir to support additional generation.