1 PROCEEDINGS, 2 nd ITB Geothermal Workshop 2013 Institut Teknologi Bandung, Bandung, Indonesia, March 4-8, 2013 CURRENT TEMPERATURE STUDIES IN KAMOJANG GEOTHERMAL FIELD WEST JAVA INDONESIA Emmy Suparka ( 1 ), D.F.Yudiantoro ( 2 ), Isao Takashima ( 3 ) Johanes Hutabarat ( 4 ) and M.Yustin Kamah ( 5 ) ( 1 ) Geological Engineering Institute of Technology Bandung, Indonesia ( 2 ) Geological Engineering UPN “Veteran” Yogyakarta, Indonesia ( 3 ) Centre for Geo-Environmental Science, Akita University, Japan ( 4 ) Faculty of Geology, University of Padjadjaran, Indonesia ( 5 ) Pertamina Geothermal Energy, Indonesia e-mail: emmy@gc.itb.ac.id, d_fitri4012@yahoo.com, takasima@gipc.akita-u.ac.jp, johaneshutabarat@unpad.ac.id, yustinkamah@pertamina.com ABSTRACT Kamojang geothermal field is located in Garut approximately 42 Km south-east of Bandung city. This area is vapor dominated system and high temperature around 235-250 o C. Geographically, the area is located on a series of active volcanoes, such as: G.Rakutak, G.Gandapura, G.Guntur and G.Masigit. This volcanoes series are Quaternary volcanoes about 0.452 to 1.2 Ma. G.Guntur is the most active volcano compared to the surrounding volcanoes until now. The complex volcanoes around the Kamojang geothermal field as heat source of the geothermal system. The resulting temperature of the magma interacts with the fluid produced alteration rock. Alteration zone in this field are crystobalite- montmorillonite, illite-montmorillonite and chlorite- epidote. By doing thermoluminescence analysis on the rock alteration and comparing with temperature mineral and temperature measurements from wells, it can be seen distribution temperature geothermal until now. Based on the analysis this method indicates that the current temperature in Kamojang geothermal field divided into three, that are: old, medium and young. The young temperatures are expected to contribute good heat on the geothermal systems. Identify the current of paleo temperature to temperature it now using petrography, X-ray diffraction and thermoluminescence methods. The results of this analysis are expected to be used as consideration in the area development of Kamojang geothermal field. INTRODUCTION Kamojang geothermal field located in Garut, West Java Province, which is about 42 km to the southeast of Bandung. Geographically, geothermal field is located in the Quaternary volcanic series lined from west to east. The volcanoes are G.Rakutak, Ciharus Lake, Pangkalan Lake, G.Gandapura, G.Guntur and G. Masigit. G.Rakutak is the older than G.Guntur and both are still active. While the Kamojang geothermal field boundaries limited by several morphologies, ie: G.Gandapura in the east, S. Ciwalirang in northern, western section of Lake Ciharus and S. Citepus in the south. Kamojang geothermal field is steam dominated with high temperature around 235-250 o C. This area was first discovered by the Dutch in 1920 and the early exploration in 1973 with the cooperation between the Government of Indonesia and New Zealand. After 10 years of exploration, this field produces in 1983 to producing 140 MWe, and in 1997 expanded to 220 MWe (Sudarman et al., 1995). This study focused on the study of geothermal temperature distribution obtained from the petrography analysis, X-ray diffraction, fluid inclusion and thermoluminescence. Some of the core and cutting samples from wells KMJ-6, 10, 25, 26, 35, 47, 52,78 and CHR-1 to analysis by the method. By studying the current temperature is expected to learn the history of paleo heat until now. GEOLOGY OF KAMOJANG GEOTHERMAL FIELD Robert et al. (1983) and Robert (1987) compiled Kamojang stratigraphy and geology of the area based on the correlation between lithology and lithologic