EXPANDING THE BOUNDARIES AT KAWERAU: NEW DATA FROM THE TE AHI O MAUI PROJECT

Abstract

The Te Ahi o Maui drilled one production well (TP-1) and two injection wells (TI-1, TI-2) in 2016, and then in 2017 side-tracked TP-1 (TP1-ST), and drilled a second production well (TP-2). These wells were drilled for a new 25 MWe power plant development on the western side of the Kawerau reservoir.
The geology encountered in these wells was largely as expected, with greywacke basement deepening to the north and west. The clay cap, as defined by methylene blue results, is at 200-500m in the production wells, and up to 650 m in the injection wells. There is evidence of both NE and NW striking faults in this area, with all formations below the Matahina Ignimbrite offset between TP-1 and TP-2 by an inferred NW striking fault.
Very good permeability was found in four of the five wells, mostly occurring between Kawerau Andesite and the top of greywacke basement. The highest temperatures (up to 265°C) were seen above greywacke, with an inversion beneath. Temperatures are higher than expected in the injection wells. These higher temperatures and good permeability in the injection wells that were sited beyond the previously recognized resistivity boundary indicate an extension of the deep geothermal system in this part of the field.