Geothermal Resource Estimation of Ulubelu Area Based on Volcanostratigraphic Studies

Abstract

The Ulubelu Geothermal Area is one of the Geothermal Working Area owned by PT. Pertamina Geothermal Energy (PGE) located in Tanggamus Regency, Lampung Province. To determine the geothermal potential of the Ulubelu area, a scientific study is needed to explain the relationship between volcanism in the Ulubelu area and the formation of the geothermal system in that region. The topographic maps at the scales of 1:100,000 and 1: 50,000. The study focues on determining Ulubelu’s volcanic characteristic parameters, which included volume as primary data and geological structure patterns, volcanic age, and magma evolution as secondary data. The Randingan caldera I Ulubelu has a volcanic volume of 120km³, indicating a sufficiently large magma chamber as heat source (Q=1.9x10^15J). The youngest volcanism is 200,000 years old, which falls within the ideal age range forming a mature geothermal system. The geological structure pattern is homogenous, with radial vent distribution is going towards the Randingan dome’s top. Given these characteristics, it is reasonable to assume that the Ulubelu Geothermal Area has promising geothermal prospects for exploration and development.