This research was conducted as one of the major annual events to introduce and train students to geothermal exploration. Kamojang geothermal field is a local area of PT Pertamina. Geothermal exploration is the object of research this time. The purpose of this research is to model the subsurface zone that includes cap rock, reservoir zone, and fault structure of the support system kamojang geothermal areas.
Kamojang geothermal area is one area of vapor dominated geothermal system that has been exploited in Indonesia since 1983 and its management are under PERTAMINA. Understanding of the geology of the geothermal reservoir area and the distribution of rock types, fault structures, and alteration are considered important when determining the type of geothermal reservoir. Through studies it is known that wells in the reservoir parameters such as porosity geothermal, connectedness, and permeability of rocks below the surface may help the interpretation of geothermal reservoir (Pri Utami 1999; Wood, 1975; Browne, Purba, 1994). Determining zone of cap rock, reservoir, and heat source can be used as a guideline for geothermal reserves calculation and as a basis for well drilling. One of the geophysical methods that can be used to determine the subsurface resistivity values that can predict these zones is the method Audiofrekuensi Magnetotelluric (AMT).
Kamojang geothermal area along the 15 km with a width of 4.5 km is located in Guntur Rakutak-volcanic ring. Kamojang area consists of 7 units litologi from the oldest to the youngest who produce G. Cibatuipis (hornblende,andesite lava), G. Base (labradorit lava and tuff), G. Gandapura (piroksen andesite lava and tuff), G. Buttons (pyroclastic and basaltic andesite lava), G. Masigit and G. Elephant (basaltic lava), G. Guntur (piroksen andesite lava). Volcanic sediments consist of colluvial deposits, alluvial deposits, and volcanic debris to fill Lake Base (Working Group Team Kamojang, 1995). Based on the description of Petrology, core and cutting the availability of existing and combine them with descriptions that have been made by other researchers (Pri Utami 1999; Wood, 1975; Browne, Purba, 1994) the main litologi wells in the study is andesite ash, lava andesite, andesite breccia, and andesite tuff.
Kamojang area was first operational in 1982. Kamojang Field is one of the geothermal field is owned by Pertamina with the largest energy production compared with other field has. Total capacity of PLTP currently consists of 200MW of Geothermal Power Plant Unit 1,2,3. Total 140MW owned and operated by Indonesia Power, and Geothermal Power Plant Unit 4 of 60MW owned & operated by PT PGE.
Survey AMT (Audio-Frequency Magnetotelluric) has been conducted in the area Kamojang geothermal prospect, West Java, on April 24 to 26, 2009, with a version 26716-01 Rev. Stratagem-D. Acquisition of data resulted in five points in a single highly directional path southeast - northwest with the distance between points is 200 meters. Positioning with GPS Etrek. Processing of data for each point using 2D analysis with Imagem, resistivity values as a function of depth.
