Heat Source Identification by Reprocessing Geoscience Data to Update Conceptual Model of Pentadio Geothermal Prospect Area

Abstract

The Pentadio Geothermal Prospect Area, Gorontalo, has been studied for geothermal development in the exploration stage. The previous conceptual model that has been produced shows that magma is the heat source of the geothermal system only based on geochemistry of manifestations that had high SO4 2- concentrations. However, the presence of tertiary intrusion based on regional geological data and high SO4 2- concentration cannot be strong evidence to prove the heat source is associated with magmatic system. The purposes of this research are updating the conceptual model, defining the heat source, and producing a different perspective from the previous study for the geothermal system in Pentadio Geothermal Prospect Area by providing a further analysis based on geoscience data reprocessing that had been acquired before. The methods consist of geological structure analysis that involves defining the permeability and geochemistry analysis for interpreting the type of reservoir fluid. Gravity data were reprocessing produced the regional and residual maps, and 3D modelling analysis for determining subsurface condition and heat source possibility in Pentadio Geothermal Prospect Area. The Pentadio Geothermal System is correlated with Gorontalo Graben which controls the permeability in the system. The fluid from geothermal manifestations near Limboto Lake has alkaline pH even though it has high SO4 2- content and low magnesium content. Gravity data shows the regional fault (NW-SE) has a depth of more than 4 km and seems to have the possibility of producing heat influx to the near surface. It is suspected as a heat source of the geothermal system in this area. There is no evidence for magma intrusion to be a heat source in the subsurface by geology and geophysics model. The high concentration of SO4 − in manifestations was influenced by sediment contamination in this area.