Characterization of Naturally Fracture Geothermal Reservoir with Electrical Borehole Image in Central Sumatera Basin

Abstract

Abstract Prospective area of a geothermal field in central sumatera basin lies in step over transtensional between two segments, Suliti and Siulak, Sumatra faults. Geological structure in this prospect area shows structural pattern controlled by pull apart basin system as a proceed of embraced movement from transform fault system (SFZ) and establishes dilation zone between those two segments, forming negative flower structure in direction of NW-SE and N-S. The pattern of geological structure is predicted to control the availability of geothermal system which in this case related to presence of surface manifestation. Surface manifestation indicates good permeability zone that can be used as flow path of geothermal fluid from reservoir. Heterogeneity encompasses the specific rock mechanical properties which is diverse overtime and how it changes the deformation process and resultant of the structure itself. The pattern of geological structure and fracture channel properties in this study is predicted and modelled using analysis of fracture zone by combination of electrical borehole image log and petrophysical analysis methods, then confirmed by geomechanical model. The objective of this research is to perform detailed subsurface analysis on a geothermal field in Central Sumatera basin so control the availability of geothermal system which in this case related to presence of surface manifestation.