Conceptual Model Evolution of the Tauhara Geothermal Reservoir from 1960-2020

Abstract

At the early stages of reservoir exploration the conceptual model for the geothermal resource is of necessity simple. As a reservoir is developed the conceptual model will be refined as new spatial and temporal information becomes available from additional drilling and extended monitoring of the reservoir response to production and reinjection. Pressure response of the early exploration wells at the Tauhara reservoir, drilled in the 1960s some 5-10 km distance from production areas at Wairakei (first power generation 1958), indicated the existence of a relatively shallow and laterally extensive hydraulic connection between the Tauhara and Wairakei reservoirs. The pressure difference between the reservoirs implied that part of the Wairakei hot recharge was derived from Tauhara. Over time, the conceptual model has evolved, incorporating data from new, deeper wells, together with geophysical surveys, and the reservoir response to changing volumes of production and reinjection fluids. The evolution of the conceptual model for the Tauhara reservoir over the last 60 years is presented along with the current understanding of the nature of the interconnections between Wairakei and Tauhara.