GEOTHERMAL CONCEPTUAL MODEL OF TALU-TOMBANG, WEST PASAMAN, WEST SUMATRA BASED ON GEOSCIENCE STUDY

• Main Author: Alzaid Ponka, Muhammad
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/78461
• Institution: Institut Teknologi Bandung

Talu-Tombang Geothermal Field is one of the potential geothermal resources in West Sumatra. The objective of this study is to make a conceptual model of the TaluTombang geothermal system using geology, geochemistry, gravity, and directcurrent resistivity data. The geology study used the Digital Elevation Model, Landsat, and the result of surface geological mapping data to make. Geochemistry analysis of water (? 18O and ?2H) is to understand fluid type, equilibrium in reaction of water and rock, fluid origin, mixing model, and reservoir temperatures. Soil geochemistry analysis (Hg and CO2) is to determine the permeability zone and related to the presence of geothermal surface manifestation. Geophysics studies include gravity modeling, geomagnetic data anomaly analysis, and resistivity zones. The geothermal system of the study area is characterized by the presence of warm water pools with temperatures ranging from 40 to 50°C at Talu and Tombang areas. The apperance of manifestations in the area is associated with NW-SE and NE-SW fault systems. Lithology present in the study area is Pre-Tertiary metamorphic rock, Tertiary sedimentary rock, Quaternary volcanic rock and alluvial. The chemical analyses show that warm water are immature HCO3-Cl and SO4-HCO3 type. The geothermal system in study area has two reservoirs with temperature between 110 and 150±10°C. The reservoir is predicted at ~250m depth. The reservoir fluid is meteoric water origin. Near the surface, the reservoir fluid mixes with groundwater. Result from the gravity survey shows the high residual anomalies of 25 to 50 mGal in the middle of the study area indicating an intrusion rock; the intrusion might act as a heat source. The Talu-Tombang geothermal field has a resource area of 2 km2 (minimum) and 33 km 2 (maximum). The geothermal resource capacity calculated using the volumetric stored heat method (Monte Carlo Simulation) shows that the Talu-Tombang geothermal field has resource between 6 MWe (minimum) and 25 MWe (maximum).