Overview of the petrophysical and geochemical properties of the Ungaran Quarternary Volcano in relation to geothermal potential

Abstract

Ungaran geothermal field is estimated to have a potential of 15 MWe. The volcano is located in the middle of Java Island which is a range of Quaternary volcanoes. As in other islands in Indonesia that indicate that this volcano has a potential energy of geothermal. This volcano is a strato volcano with andesitic composition. The Ungaran volcano geothermal system is located within a young cone depression, overgrown by Mount Gugon and Mount Megi that form the depressive ring. Geothermal manifestations contained in Gedongsongo include: fumarola, hot springs, travertine, steaming ground and alteration rocks. The temperature of the hot springs is about 50°C, the pH of hot water is acidic (ranging from pH 1.5 to 5.5), bubble gas and around fumarola are found sublimation of sulfur and pyrite.This research uses analytical methods of geochemistry (water and rock), petrography and petrophysics. Based on geothermometer analysis shows that the reservoir temperature is 300°C. The composition of fumaroles is strongly influenced by magmatic elements with temperatures greater than 300°C. While petrography analysis yields that the material of Ungaran volcano rock is andesite-basaltic. Knowing the geothermal potential of this area is expected to increase the Java-Bali power supply.