GEOTHERMAL SYSTEM MODELLING BASED ON GRAVITY DATA OF ARJUNO-WELIRANG GEOTHERMAL FIELD, EAST JAVA, INDONESIA

• Main Author: Ires Bujana, Malta
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/61955
• Institution: Institut Teknologi Bandung

The government has made a roadmap to increase geothermal capacity to 9.3 GW by 2035. To reach this target, exploration and exploitation of geothermal areas in Indonesia must be increased. The Arjuno-Welirang geothermal area in East Java 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 Welirang Volcano area, where there are geothermal manifestations in the form of solfatara-fumarola. The purpose of this study is to analyze and determine the conceptual model of the geothermal system in the Arjuno-Welirang geothermal area using the gravity method. Gravity data was obtained from the gravity data acquisition by The Arjuno-Welirang 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 -5 mGal to 70 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 low anomaly is seen in the southern area, which is an area of interest where possible geothermal locations are located. 2.5D modeling shows that low anomaly values can be indicated as magma with a density contrast of -0.3 gr/cc, which may act as a heat source. The outflow zone is likely to be in the hot spring manifestation area.