SUBSURFACE GEOLOGICAL MODELING BASED ON THE GRAVITY DATA OF LIMBONG’S GEOTHERMAL FIELD, NORTH LUWU, SOUTH SULAWESI

• Main Author: Aldiansyah Siregar, Naufal
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69817
• Institution: Institut Teknologi Bandung

The Limbong geothermal area in North Luwu Regency has geothermal indications characterized by the appearance of hot springs and fumaroles. Therefore, this study was conducted to determine the subsurface model of the Limbong geothermal field system to determine the Limbong geothermal potential. In this study, data processing was carried out in the form of observational gravity data from measurements from the PSDMBP Subsurface Research Program Team in 2010 to obtain a Complete Bouguer anomaly. The Complete Bouguer Anomaly value of the Limbong geothermal area has a range of -82 mGal to -54 mGal. Then the anomaly is separated using the Moving Average, Butterworth, and Gaussian filters. Regional and residual anomaly values obtained have the same range and trend of the pattern. From the three residual anomaly maps produced, the residual anomaly map was chosen using the Moving Average method because it has much compatibility with surface geological conditions. Next, 2D forward modeling and 2D inversion modeling are carried out on two tracks trending Northwest – Southeast directions. The modeling results show that there is a layering that is following the geological map where the high anomaly value comes from igneous rock intrusion with a density contrast of +0.48 gr/cc and some locations of low anomaly value are caused by a lower-density rock (young rock) that penetrates continuously so that it is destroyed. and weathering of rocks due to active geological structures. Based on the results of the research, it can be identified the heat source from the intrusion of igneous rock, the metamorphic rock unit is suspected as a reservoir, the old granite rock unit undergoing hydrothermal alteration as caprock, and the existing geological structure is the main factor controlling the permeability which is the driving force for fluid flow in the limbong geothermal system.