INVESTIGATION OF GEOTHERMAL SYSTEM USING ADVANCED PROCESSING AND INVERSION OF GRAVITY DATA IN LAINEA NON-VOLCANIC GEOTHERMAL FIELD, INDONESIA

Indonesia is a country that has abundant geothermal resources. The purpose of this research is to investigate the geothermal system in the Lainea non-volcanic geothermal field, Southeast Sulawesi Province, Indonesia. This includes (i) estimating the geothermal reservoir basins, cap rocks, and basements; (ii) estimating the heat source; and (iii) evaluating the subsurface faults. The first two objectives were achieved by using the improved structural gravity inversion. The third objective was achieved by using advanced processing techniques, namely 3-D Euler deconvolution, tilt angle of horizontal gradient (TAHG), and fast sigmoid edge detection (FSED). Inversion of gravity data exhibits the reservoir basins that are located at depths from 600 m to 900 m with a density range of 2865 ≤ ρ < 2942 kg/m³. Several rock blocks with densities ranging from 2608 to 2865 kg/m³ function as caprock. The caprock is located at depths ranging from several tens of meters to 1000 m. The basement underlying the reservoir rock is the integration of rock layers with densities of 2948 ≤ ρ < 3045 kg/m³ and 3046 ≤ ρ ≤ 3122 kg/m³. The upper boundary of the basement is located at a depth of several ten meters to 1500 m below sea level. Intrusive plutonic rocks with maximum density of 3174 kg/m³ are located at depths ranging from 1500 m to more than 3000 m. The TAHG and FSED demonstrate the presence of subsurface faults with northwest-southeast and southwest-northeast trends. Euler deconvolution results support the fault model of the TAHG and FSED.