Optimizing the Gravity Data and Geological Observation for Mapping the Local Fault around the Jaboi Volcano

Abstract

Geothermal is a very expensive investment industry. Therefore, it is necessary to map a geological structure in the sub-surface, i.e., faults, and rock formations that control volcanic hydrothermal systems to reduce investment risk in the exploitation of geothermal. On the other hand, the hydrothermal system aims for flow paths connecting reservoir wells for fluid production. The Jaboi Volcano, with an estimated 80 MWe located on Weh Island, Indonesia, has been planned by the government to develop electrical energy, where the excess energy will be exported to Banda Aceh via undersea cables. We use global gravity model plus (GGM+) in a resolution of ~230m/px for mapping the geological structure of Jaboi volcano. Based on GGM+ data analysis, the Bouguer anomaly data shows low gravity values in volcanic areas, namely 46 – 69 mGal. These data only represent rock density values with low density in geothermal areas. We also calculate the residual anomaly from the Bouguer data using the high-pass-filtering technique, wherein the volcanic area, several high-gravity anomalies (1 – 1.4 mGal) correspond to the Leumomate fault in the direction of NW-SE. The same pattern is also obtained in the area with a suspected Ceunohot fault in the SW – NE direction. This research demonstrates the optimization of gravity satellite that free access to be used in mapping geological structures in geothermal Jaboi. Finally, we conclude that GGM+ data is a very efficient and cost-effective technique to detect geological structures around the Jaboi volcano, which developing countries can use as a preliminary study for evaluating and exploring geothermal energy