GEOTHERMAL SYSTEM MODELLING BASED ON GRAVITY DATA OF KEPAHIANG GEOTHERMAL FIELD, BENGKULU, INDONESIA

• Main Author: Firdian Saputra, Anggi
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/65797
• Institution: Institut Teknologi Bandung

Indonesia government has made a target to increase the generating capacity of Renewable New Energy (EBT) to 11,791 MW and made a roadmap to develop geothermal power with the aim to increase geothermal capacity from 2.13 GW in 2019, to 7.87 GW by 2030, and to 9.3 GW by 2035. To reach this target, the exploration and exploitation of geothermal areas in Indonesia must be increased. The Kepahiang geothermal area in Bengkulu Province is one area that has not been exploited, even though it has potential resources of up to 180 MW. Potential geothermal sources are estimated to be in the Kaba Volcano area, where there are geothermal manifestations in the form of solfatara-fumarole. The purpose of this study is to analyze and determine the conceptual model of the geothermal system in the Kepahiang geothermal area using the gravity method. Gravity data was obtained from the gravity data acquisition by The Kepahiang Integrated Geophysical Survey Team in 2010 which can be accessed at the library of the Center for Coal and Geothermal Mineral Resources (PSDMBP). Gravity data processing will produce a Complete Bouguer Anomaly Map with a value range of 18 mGal to 52 mGal. Then, the regional and residual anomalies are separated using the Moving Average and Quadratic Polynomial methods, where the window width is determined by performing a 1-dimensional spectral analysis. The anomaly results using Quadratic Polynomial method showed high and low anomalous values in the northeast and southwest areas, which are thought to be due to the intrusion of residual andesit-basalt I from the volcanism of Mount Kaba and weathered rocks, so this method was considered to have a correlation with the geology of the study area. 2.5D modeling shows that high anomaly values can be indicated as intrusion andesit-basalt I with a density contrast of +0.59 gr/cc. The presence of intrusion andesit-basalt I is thought to be a heat source, pyroclastic flow of old Kaba 2 unit is thought to be the reservoir. and pyroclastic flow of old Kaba 3 and Pyroclastic flow of young Kaba units is thought to be the caprock.