Processing and analysis of high temperature geothermal acoustic borehole image logs in the Taupo Volcanic Zone, New Zealand

• We analysed 23 acoustic borehole televiewer (BHTV) logs in the Taupo Volcanic Zone.
• We propose a new classification for lithological, structural and stress features.
• Patterns of volcano-sedimentary lithologies are presented.
• The accuracy and applicability of the BHTV interpretation results are discussed.
• The new techniques provide better input for geothermal reservoir characterisation.

Acoustic borehole televiewer (BHTV) logs provide direct observations of lithology, structure and in situ stress in reservoirs, essential for successful well targeting and field management. Analyses of BHTV logs acquired in twenty-three high temperature (≤288 °C) geothermal wells in the Taupo Volcanic Zone, New Zealand, resulted in the modification of BHTV processing techniques and the creation of a descriptive feature classification for hydrothermally altered, volcano-sedimentary-basement type reservoirs lacking other complementary information common in hydrocarbons or lower temperature geothermal systems. Lithological characteristics observed on these BHTV logs are presented, alongside an assessment of the reliability of the structural measurements and image interpretation.