Subsurface structure identification of ‘X’ geothermal prospect area based on gravity and magnetotelluric data

Abstract

Exploration stage has the highest risk, due to discover the interest reservoir zone include high temperature and pressure, middle to high permeability, and non-acidic fluid. Permeability is one of the most difficult parameters to be determined in this stage. Fault zone could be able to control and provide fluid flow within reservoir. It is usually related to high permeability zone. Fault identification become an important and interesting parameter in to be explore. The aim of this research is identified subsurface structure to build up a conceptual model of geothermal system. The methods include magnetotelluric data analysis and 3D MT structure interpretation together with first horizontal derivative and second vertical derivative analysis of gravity data. Geochemistry and geology data are used as supporting data. There are structure types of normal and reverse fault identified in the research area. MT and gravity interpretation show that structures are direct to northeast-southwest and northwest-southeast. Up-flow zone is predicted between TPP-TPB manifestations. Structures supposed to highly contribute in providing permeability zone in the research area. Manifestations fluid have the characteristics of meteoric and magmatic fluid (volcano-hydrothermal system). The clay cap thickness average is predicted between 500–700 m. The reservoir thickness average is predicted between 1500–2000 m. Temperature estimation of the reservoir is 240–280 °C. Heat source might be located between TPB and TPP manifestations. Subsurface structure analysis might be useful to increase success ratio in drilling.