Development of Indonesia version Geothermal Expert Modeling System (iGEMS)

Abstract

The iGEMS was developed as an Indonesian version of the NEDO-developed Geothermal Expert Modeling System (GEMS), which had been developed for a national project "Nationwide Geothermal Resources Exploration Project (Phase3）" in Japan. The iGEMS was developed by improving GEMS to work on a commercially available personal computer with a minimum set of data. It enables an easy analysis, narrowing its function down to the two core functions of GEMS, which are "estimation of a 3 dimensional thermal structure that takes account of geothermal upflow" and "calculation of the geothermal resource by means of the volumetric method". The iGEMS is composed of two main programs, which are the main body of iGEMS and Surfer. The GEMS provides such main functions as analyses, generation of cross-section data, and receiving user inputs of analytic parameters and cross-section line on a simplified map displayed. Surfer is a contouring and surface mapping software to display the survey results and analyzed data in plan map or cross section on the screen. The analysis function of the system contains (1) placing heat sources, (2) calculating the conductive thermal structure, (3) calculating the activity index at each hot spring, (4) placing the discharge area, (5) calculating the activity distribution within the discharge area, (6) modifying the thermal structure taking into account the upflow and (7) calculating the geothermal resource and selecting promising areas by the volumetric method. According to the calculation result of geothermal resource in the Bajawa geothermal area using iGEMS, 74 MW of geothermal resource per 3 km² (25 MW /km²) was estimated in the Mataloko area and 92 MW per 4 km² (23 MW /km²) in the Nage and Wolo Bobo areas. Indonesia is one of the world's leading geothermal power generating countries. It is expected that iGEMS will realize a smooth and easy evaluation of geothermal resources in future geothermal development projects.