Chemistry of the Well Discharges at Ngawha

Abstract

Discharge and downhole water and gas samples from four of the six deep wells drilled at Ngawha, namely NG2, NG4 and have been analysed. The last two of these tapped a reservoir calculated to be of total discharge composition of 1240 ppm 410 ppm silica, 870 ppm boron and about 190 ppm bicarbonate. The gases are about 1. 1 4 w t of the total discharge, about twice that of Broadlands, and ten times that of Wairakei. Geothermometers indicate two reservoirs, one at about and one at Other indicators show that the system is old, sealed, and in proximity to a magma body.