The Geology, Mineralogy and Geothermometry of the Broadlands Geothermal Field, Taupo Volcanic Zone, New Zealand

Abstract

Following the commissioning of the Wairakei geothermal power station, several areas in the Rotorua-Taupo Volcanic Zone were investigated for their power-producing potential. One of these was the Broadlands district, where a resistivity survey had located a sizeable area of subsurface water. The first hole, east of the Waikato River (Fig. 2), was drilled in late 1965, but although the temperature at hole bottom is 278°*, rock permeability is low and the bore is a poor steam producer. However, further drillholes (Br 2, 3 and 4) in the Ohaki area tapped good supplies of high temperature water and prompted a fullscale scientific and exploratory drilling programme. This was completed in mid-1971 after 25 holes had been drilled and it was estimated that the field could produce about 150 megawatts of electricity.