Analysis and Interpretation of Gravity data to modelling ‘PB’ Geothermal Field

Abstract

The ‘PB’ field is located on the island of Sumatra which is related to the volcanic activity of Kaba hill which still retains residual heat from the magma. One of the geophysical methods used in this case is the gravity method where this method can be applied to determine the location of reservoirs, possible locations for reservoirs, and even to examine geological features and heat sources. In this paper, gravity data is used to interpret the structure and possibility of modelling the heat source in the ‘PB’ geothermal field. The gravity data was analyzed using integrated gradient interpretation techniques such as Horizontal Gradient (HG) and Euler Deconvolution (ED) methods. The CBA map produced shows two dominants high Bouguer anomalies underlying the ‘PB’ geothermal field associated with the presence of dacite and andesitic rocks. Analysis of fault structure based on geological data, HG and ED enhancement data on gravity anomalies was used as a reference for the initial model of subsurface conditions in the inversion model. The 2-D modelling results reflected high-density rocks associated with active ‘PB’ mountain volcanism. The conclusion obtained from the analysis and interpretation of the ‘PB’ geothermal system is that this area still has active volcanism, which is a heat source, with the presence of diatreme found through 2D gravity inversion modeling. The conceptual model results obtained by combining the integration of each reference and existing research show that the upflow zone is at the top of Kaba Hill and the outflow zone is at Babakan Bogor hot spring and Suban hot spring. Thus, these results can provide comprehensive information in analyzing and interpreting as well as the use of enhancement data gravity HG, ED and 2D slice inversion in the description of structures and modelling in the Geothermal ‘PB’ field.