Modelling of Heat Source in the Geothermal field based on Euler Deconvolution and Occam Inversion using GGMPlus Gravity data
Author: Fanzly Togap Z. Lase, Istifani Ferucha, Patria Ufaira Aprina, Susanti Alawiyah
Applied and Exploration Geophysics ITB, Geothermal Engineering ITB
togaplase8668@gmail.com
The component of the geothermal system that plays an important role is a heat source. Heat sources can be a magma intrusion from volcanic activity or a geothermal gradient from sedimentation. Identification of heat source can be conducted using gravity anomaly modeling in the Sumbersari Geothermal Field, Southeast Sulawesi. In this study, inversion modeling was undertaken using the occam approach. The input data, Complete Bouguer Anomaly (CBA), was acquired from satellite data processing (GGM Plus). The estimation of heat source depth was established through spectral analysis of CBA data, to obtain regional and residual anomalies, as well as estimates of rock density in the study area. The geometry of the rock body in the inversion process uses a rectangular prism arrangement in the form of a 3D regular grid which represents the distribution of subsurface density. This inversion process uses ZondGM2D software. To improve the subsurface model of the inversion process, data enhancement was also carried out. Fault structure analysis based on geological data and Horizontal Gradient Magnitude (HGM) enhancement data on gravity anomalies was used as a reference for the initial model of subsurface conditions in inversion modeling. Not only horizontal gradient magnitude, but Euler Deconvolution is also carried out to determine the lineament of the geological structure in the study area. Based on the CBA map, low anomalies are associated with sedimentary rock and high anomalies are metamorphic rock with NW-SE and NE-SW trends. The presence of high and low anomalous contrasts in the CBA data indicates the presence of faults that control the geothermal system in the Sumbersari potential area. This is in accordance with the findings of manifestations in the study area which are correlated with geological structures. In addition, the high anomalous contrast resulting from the occam inversion also indicates the presence of altered rock, which is considered as heat source with an estimated very deep heat source. Thus, the results of this 3D gravity inversion can provide comprehensive information and are expected to be a reference in the development of the Sumbersari geothermal field, Southeast Sulawesi.
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