Modelling the Rotorua Geothermal System

Abstract

The Rotorua Geothermal Field is an area of major geyser activity in Aotearoa New Zealand. The field was subjected to extraction of geothermal fluid by hundreds of households for heating and other purposes from the 1950’s. After the decline of some of the thermal features was recognised in the mid-1980’s an extensive monitoring programme was developed to provide an understanding of the system dynamics. Many aspects of that monitoring programme continue through to the current day including pressure and temperature monitoring. The Bay of Plenty Regional Council are currently undertaking a review of the Rotorua Geothermal Plan. Alongside of that review an update of a numerical reservoir model that was developed in 2004 has been carried out.
One of the challenges with modelling the Rotorua system is that very few wells have been drilled to more than 200m. As a consequence, the data is strongly biased towards the shallow parts of the system. In this paper we will use new data from Rotorua and information from other producing geothermal systems to inform a conceptual model that incorporates the deeper reservoir at Rotorua. We will also present a review of monitoring data collected at Rotorua, describe the conceptual model and the updated numerical reservoir model.