Patuha geothermal field is one of the geothermal fields in West Java. Developed by PT Geo Dipa Energi (Persero) since 2014, the geothermal field produced electricity, with installed capacity amounted to 55 MWe. Patuha geothermal system is vapour-dominated system. The geothermal manifestations are located at approximately 2,100 m asl. The Patuha field consists of three main upflow zones, namely Kawah Putih, Kawah Ciwidey, and Kawah Cibuni. This study analyzed the drill cuttings from 3 wells as the primary data with total depths ranging from 1,581 to 2,166 m with the well’s highest stable temperatures measured of ±230°C. The three wells selected for this research—PPL 02, PPL 04, and PPL 07—were analyzed to describe the rock properties and estimate the prospect areas of present-day geothermal exploration in Patuha. The objective of this paper is to develop a better understanding of the subsurface geology and its correlation to the dynamic processes (i.e., hydrothermal alteration) in Patuha geothermal field. The hydrothermal minerals are formed by near-neutral pH fluids and are characterized by quartz, calcite, clays (smectite, illite, chlorite), wairakite, epidote, and actinolite. The existence of acidic fluids is evident by the formation of acidic hydrothermal minerals e.g., anhydrite at various depth of the studied wells, particularly at PPL 07 which is located around Sugihmukti-Urug area. Moreover, the previous studies by Reyes (1990), Layman and Soemarinda (2003), Rachmawati et al. (2016), Elfina (2017) on hydrothermal minerals, geothermal manifestation characteristics, fluid geochemistry, and conceptual model are adapted to improve the analysis and interpretation of this paper.
Geothermal exploration in Indonesia based on Mineralogy and Hydrothermal Alteration
