Airborne Magnetic Surveys to Investigate High Temperature Geothermal Reservoirs

Abstract

Airborne magnetic survey is an effective geophysical exploration method in terms of cov‐ erage, resolution and cost, particularly for area with restricted or difficult ground access. Research studies in New Zealand have shown airborne magnetic surveys can indicate the regions of high reservoir permeability and thermal up-flow of active geothermal systems. However, the method has not been extensively used in the geothermal investigations, probably because the interpretation of airborne magnetic data has so far been seen as dif‐ ficult and requires a complex quantitative 3D modelling of subsurface magnetisation. This chapter introduces a new approach to use airborne magnetic survey to investigate high temperature geothermal resources without the need of 3D magnetic modelling. This new approach takes advantage of data processing packages that during the last few years have become accessible through the internet. A simple but comprehensive explanation is given on the physics background of the airborne magnetic surveys. Examples are provid‐ ed from interpretations of real airborne magnetic data from the North Island of New Zea‐ land and the Java Island of Indonesia. This chapter is aimed to provide the readers a sufficient level of knowledge and confidence to organise and/or run investigation of high temperature geothermal reservoirs using airborne magnetic surveys.