Geochemical Study of the WKP Ungaran, Central Java

Abstract

This study aims to analyze the composition, origin, and characteristics of thermal fluids in the Ungaran geothermal field, Central Java, and to estimate the reservoir temperature using geothermometers. The methods used include geochemical surveys, chemical analysis of water and gas, and interpretation of geoindicators. The results show that the thermal fluids in this field have chloride, bicarbonate, and sulfate water types, with the upflow zone dominated by sulfate water and the outflow zone by bicarbonate water. Stable isotope analysis indicates water-rock interaction in the subsurface. Reservoir temperature estimates based on silica geothermometers range from 110-179°C, while gas geothermometers indicate temperatures between 220-270°C. The conceptual model produced depicts a geothermal system controlled by geological structures such as normal faults and calderas. This study provides significant insights into the Ungaran geothermal system and can serve as a basis for further exploration.