Discharge of Thermal Fluids at Te Aroha (A Case History of CO2 Geysering Wells)

Abstract

Te Aroha is a small thermal prospect in the North Island of New Zealand where surface manifestations have been monitored over the past 100 years. Its main attraction is the 67 m deep Mokena well which discharges sodium-bicarbonate fluids periodically at a maximum temperature of with a long term rate of 0.7 since 1936. Two other wells have also discharged fluids by geysering, but at lower flow rates of 0.1 The discharging wells are driven by a periodic C02 gaslift. The Mokena well deposits aragonite and requires reaming at half-yearly intervals to maintain production. Discharge characteristicsof the wells and fluid chemistry data are presented which allow an estimate of C02 concentrations required to maintain the periodic gaslift (about 3 g C02per of fluid).