Available online at: Al-Fiziya: Journal of Materials Science, Geophysics, Instrumentation and Theoretical Physics Website: http://journal.uinjkt.ac.id/index.php/al-fiziya Vol.6 No. I 2023, 41-50 ©2023 The Author (s) This is an Open-access article under CC-BY-SA license (https://creativecommons.org/licenses/by sa/4.0/) Al-Fiziya: Journal of Materials Science, Geophysics, Instrumentation and Theoretical Physics P-ISSN: 2621-0215, E-ISSN: 2621-489X 3D Visualization of Geothermal System Structure Based on Inversion Model of Gravity Data. Case Study: Mt. Salak Region, West Java Nanda Ridki Permana 1,* , Belista Gunawan 2 1 PT Minelog Services Indonesia, Industrial Estate and Warehouse Techno Park, Indonesia. 2 GeoXplore Indonesia, Indonesia. * nandaridki836@gmail.com Submitted: July ; Revised: July ; Approved: August ; Available Online: September Abstract. The geothermal power plant located in Mount Salak plays a crucial role in increasing the electricity supply transmitted to the Java-Bali region, as the energy demand continues to rise. The objective of this research is to determine the 3D subsurface structure of Mount Salak, specifically the distribution of the reservoir as the target for geothermal energy using the Gravity method. Gravity data, including gravity disturbance (gd), geoid, and Digital Elevation Model (DEM), were obtained from the ICGEM website with a total of 48740 data each. Based on the results of the residual anomaly map, the low anomalies beneath Mount Salak have values from -5.15 to -1.88 mGal, which are suspected to be associated with the magma chamber. The high anomalies beneath the manifestations have values from 0.92 to 5.01 mGal, indicating andesitic basalt intrusive rocks believed to be the reservoir rock. Through the 3D inversion modeling of the subsurface structure of the Mount Salak geothermal system, a clay cap with a density from 2.47 to 2.5 gr/cc at depths of 0 to 700 m and andesitic basalt rock as the reservoir with a density from 2.74 to 2.91 gr/cc at depths of 700 to 3000 m have been identified. Keywords: Geothermal, Gravity, Inversion, Mt. Salak, Reservoir DOI : 10.15408/fiziya.v6i1.33439 INTRODUCTION Geothermal is a renewable energy source that shows an increasing role and mix of primary energy supply in Indonesia [1], because it is relatively environmentally friendly for electricity generation compared to other sources such as fuel oil [2]. Geothermal potential in Indonesia is estimated to reach more than 27,000 Mw or the equivalent of 219 million barrels of petroleum [3]. Where almost 40% of the world's geothermal potential is in Indonesia [4] and around 21.7% is in West Java [5]. Geothermal power plants have an important role in the Java-Bali network as they require a large supply of electricity for the local population. The Geothermal Power Plant in Mount Salak supplies electricity to the surrounding areas, particularly in the Jawa-Bali region, with a capacity of not less than 180 MWe. [6]. The Geothermal Power Plant in Mount Salak consists of three units with a capacity of 60 MW each. Electrical power from these three units is transmitted to the New Bogor 150 kV transmission network for interconnection with the Java- Madura-Bali system. Part of the generated power is also used for self-consumption [7].