Spatial Correlation Model Between Resistivity Data and Subsurface Permeable Zones to Optimize the Existence of a Geothermal Reservoir
Awwab HAFIZH, Mohamad Nur HERIAWAN, SURYANTINI, Taiki KUBO, Katsuaki KOIKE, Chevy ISKANDAR
[Bandung Institute of Technology, Indonesia]
Indonesia as a country that is crossed by the tectonic paths has potential disasters related to the presence of volcanic and earthquake zones. It also has natural resources potential, one of which is the presence of geothermal potential. One location that has potential geothermal resources is Mt. Patuha, located in the south of Bandung, West Java, Indonesia. Although the geothermal potential that exists in these locations has been partially produced, it is suspected that there are still other parts of the location that have the potential for increasing the production targets in the future. One parameter that can be used as an indication of the geothermal prospect area is the presence of surface manifestations i.e. hot springs and fumaroles. Hot springs occur due to the fractures that carry hot fluids from the subsurface. Areas with high fracture intensity in subsurface will certainly be the main target in geothermal exploration. High fracture intensity shows high permeability in the presence of fluid and hot steam from the influence of magmatism. In addition, the heat effects of fluids and vapours caused the alteration of rocks as caprock which are usually characterized by the very low resistivity zones. The geothermal reservoir itself will be characterized by relatively low to moderate resistivity zones. Distribution of the subsurface resistivity is generally obtained from the results of geophysical surveys such as the MT (magneto-telluric) method carried out in the fairly regular grids and covered wide area. The surface fracture zones could be identified from the satellite images or digital terrain model data, while the subsurface permeability data in the study site were obtained from the results of exploration drilling in term of the presence of TLC (total lost circulation) data. The drilling in geothermal exploration commonly was carried out in irregular grids and only covered specific area due to its high cost. Multivariate geostatistical method with conditional co-simulation such as Sequential Gaussian Co-Simulation could generate 3-dimensional model of subsurface permeable zones by considering their spatial correlation with the resistivity data as secondary variable. This method was effective to optimize the existence of geothermal reservoir in the Patuha geothermal field.
|        Topic: Exploration||Paper Number: 11070|