3D Geological Model Reconstruction and Fault Permeability Assessment at Muara Laboh Geothermal Prospect, South Solok Regency, West Sumatra, Indonesia

Abstract

Sumatra is an island formed by tectonic activity of the Indo-Australian plate subducting beneath the Eurasian plate (Barber et al., 2005). This tectonic activity has resulted in the formation of geological structures such as faults and fractures, which serve as migration pathways for fluids from reservoirs to the surface. One of the manifestations of geothermal energy found is located in Sapan Maluluang, South Solok, West Sumatra. The objectives of this study are to determine the geological conditions and surface structures in the study area, reconstruct a 3D geological model of the study area, and determine the permeability of each fault in the study area. The research stages conducted include initial interpretation of spatial data using DEM, field observations, 3D model reconstruction, and assessment of fault permeability. The methods used involved integrating primary and secondary data, followed by data analysis using several software tools. The parameters used included distance from the fault intersection, distance from the fault, fault length, and fault slip tendency. Based on field data combined with tentative data, there are 6 rock units and 8 faults in the study area. The results of fault reconstruction and permeability assessment show 5 ranks based on permeability levels, with the first order is Alam Pauh Duo Fault with highest weight value > 0.8, the second order is North Bangko Keruh Fault with highest weight value of 0.75–0.8, the third order is Bangko Putih Fault, Pinang Awan Fault, and Taratak Tinggi Fault with highest weight value of 0.65–0.7, the fourth is South Bangko Keruh Fault and Pauah Duo Fault with highest weight value of 0.55–0.6, and the fifth is Sapan Bawah Fault with highest weight value of 0.45–0.5. The most permeable faults are the Alam Pauh Duo Fault and North Bangko Keruh Fault, as well as the intersection between North Bangko Keruh Fault and South Bangko Keruh Fault.