SPATIAL CORRELATION BETWEEN SUBSURFACE PERMEABLE ZONE AND RESISTIVITY IN THE PATUHA GEOTHERMAL FIELD, WEST JAVA

• Main Author: Hafizh, Awwab
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43763
• Institution: Institut Teknologi Bandung

Determining permeable zone is imperative to object the reservoir especially when in geothermal field, permeable zone is translated into either structure or lithologyderived-permeability that may result in Total Loss Circulation (TLC). The recorded data of TLC locations in Patuha geothermal field are very limited compared to widely-spread resistivity data from megnetotelluric survey (MT). Despite being limited, TLC data can be paired with MT to estimate the reservoir boundary by using multivariate geostatistics method: Sequential Gaussian Cosimulation (SGCS). Although reservoir modelling has been done in more sophisticated methods, inferring permeability zone from this ‘enhanced’ TLC in the view point of exploration is more relevant, hence, the reservoir zone will be obtained. Prior to this, lineament density was extracted from satellite imagery data by using modified Segment Tracing Algorithm (mSTA) to see the surface permeable zone. It is confirmed that high lineament density correlates to existing geological structures and surface manifestations alignment in Patuha geothermal field. This algorithm can overcome the time-consuming manual lineament extraction for the same permeable zone determination. The parameter for SGCS method is Markov Model II resulting in the subsurface permeable zones model. The correlation value between the high permeable zone and low to moderate resistivity (15-100 ohm.m), within which the resistivity values of reservoir zone is known to be, is R = 0.74. Surface Trancient Electromagnetic (TEM) survey was conducted to provide the validation for near-surface permeable zones. The SGCS results near the surface showed the existence of 4 (four) permeable zones; amongst them TEM Point PPL6 and PPL8 prove the conductive zone at this location. While the high permeable zone SGCS results are at 1250-500 masl which is suspected as the reservoir zone.