Massiot, C.; McNamara, D.D.; Lewis, B. 2013 Interpretive review of the acoustic borehole image logs acquired to date in the Wairakei-Tauhara Geothermal Field. Lower Hutt, N.Z.: GNS Science. GNS Science report 2013/04 26 p.
Abstract: Targeting structurally controlled permeability remains a challenge in high temperature geothermal fields, because of the difficulties in characterising faults and fractures and their behaviour within the reservoir. Acoustic televiewer logs provide direct data on structure (fractures and faults), in-situ stress orientations and lithology from within the boreholes. In 2009, a high temperature acoustic televiewer (the ABI85-92), capable of operating in temperatures up to 300°C, was developed by Advanced Logic Technologies (ALT) and made available to the industry. This tool is operated in New Zealand by Tiger Energy Services under the trade name ‘Acoustic Formation Imaging Technology (AFIT)’ tool. Between 2009 and 2012, ten AFIT logs have been acquired across the Wairakei-Tauhara Geothermal Field operated by Contact Energy Ltd., representing 7294 metres of acoustic borehole image. Of this, 4765 metres have been analysed and interpreted, and 7130 natural and induced features have been identified. Results and insights on the structural character and permeability are summarised here. (auth)