Identification of Geothermal System Structure Based on Derivative Analysis and 3D Model of Gravity Satellite Data of Mount Rajabasa Area, South Lampung

Abstract

Indonesia has the second largest geothermal potential with 40% (24 GigaWatt) or 331 points of geothermal reserve locations, this is because Indonesia is traversed by the ring of fire so there are many volcanoes in Indonesia. One of the areas is the Rajabasa Mountain, located in the south of Lampung Regency, with the manifestation of thermal springs and fumaroles. This study aims to provide information related to the existence of geothermal potential using the gravity method, find out the subsurface structure using the First Horizontal Derivative (FHD), Second Vertical Derivative (SVD) methods and conduct 3D modelling. Based on the FHD and SVD analysis, four faults controlling the geothermal system were obtained, distributed in the Northwest – Southeast direction in the form of shear faults, and North-South in the form of normal faults with high anomaly values on residual maps of suspected lava rock intrusions. The 3D modelling results obtained indicate the presence of clay rock which is assumed to be caprock with a density of 2.5 – 2.58 gr/cc at a depth of up to ± 1500 m, and andesite rock which is suspected to be a reservoir with a density of 2.64 – 2.7 gr/cc at a depth of 750 – 2000 m.