Perpustakaan Digital ITB

The Silangkitang (SIL) geothermal system is a fault-controlled and liquid-dominated reservoir associated with a deep heat source. Subsurface data from recent development drilling and reservoir monitoring demonstrated that the high permeability is concentrated within the zone between two strands of the Great Sumatra Fault (GSF). Existing producers and injectors targeted the same geological structure. Consequently, the cooling injected fluid returned to the production area. This phenomenon could provide negative impacts on the sustainability of the SIL field. For that reason, an integrated evaluation to characterize subsurface geologic structure is critical. This research aims to define the distribution and geometry of faults in the subsurface. The study starts with surface data evaluation using LiDAR and field-mapping database. The interpretation of surface lineament and tectonic geomorphology are integrated with field data to develop surface lithology and fault maps. To constrain the geometry of surface fault in the subsurface, secondary data, including well and non-well, are assessed. Combined analysis on the well data such as drilling loss, drilling break, PTS log feedzone, and inter-well tracer improves the understanding of permeability and connectivity distribution, particularly in the current exploitation area. On the other hand, non-well data analysis such as gravity, magnetotelluric, and microearthquake significantly delineate structures in unexplored areas. At the end, the structural framework is constructed to explain better the subsurface condition of fault distribution and geometry and its implication to permeability and connectivity. This research's structural framework defines the area of interest for future make-up production and injection.