DETERMINATION OF THE GEOTHERMAL SYSTEM BOUNDARY BASED ON GEOLOGICAL STUDY AND WATER GEOCHEMISTRY IN KARAHA-BODAS AREA, WEST JAVA AND ITS IMPLICATION ON CONCEPTUAL MODEL

• Main Author: Bilhan Danakusumah, Grandy
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/41904
• Institution: Institut Teknologi Bandung

The Karaha-Bodas geothermal field is in Garut regency, West Java, Indonesia. This field is a partially vapour dominated system with reservoir temperatures ranging from 250oC - 350oC. The Karaha-Bodas geothermal field is divided into two areas, namely Karaha in the north and Bodas Lake in the south. This conceptual model of the geothermal field was previously made and shows that the Karaha-Bodas geothermal system is one system which has the same heat source coming from Telaga Bodas. However, the conceptual model is considered to be incompatible with the manifestation characteristics that appear in the Karaha and Telaga Bodas regions which both characterize the upflow zone. The purpose of this study is to review the Karaha-Bodas geothermal system based on the determination of the system boundary which is then taken into consideration in the estimation of the actual conceptual model. The method used in this study is the grouping of cold springs and thermal springs which are integrated with geological analysis, in the form of geomorphology and volcanostratigraphy. Meanwhile, the grouping referred to is based on the physical and chemical properties of springs which are thought to have experienced thermal water contamination. Based on the results of the study, there are some cold springs that are contaminated with thermal water with characteristics such as the presence of anomalies of temperature, pH, and TDS. The contaminated springs are also supported by enrichment of anions and cations and isotopes of oxygen-18. This grouping of contaminated springs can estimate the boundaries of the Karaha-Bodas geothermal system into 2 system boundaries, namely Karaha and Telaga Bodas. The boundaries of the Karaha geothermal system are controlled by the G. Putri Eweranda Crown, while the boundaries of the Telaga Bodas geothermal system are controlled by the Telaga Bodas Crown. The alleged existence of the Sadakeling system limits which is controlled by the Sadakeling Crown. This system boundary division can estimate the conceptual model of the Karaha-Bodas geothermal system which shows the presence of different rocks, reservoirs and heat sources.