3-D Geoscience Modelling: Why Is It Essential? A Case Study of the Rotorua Geothermal Field in New Zealand

Abstract

The Rotorua Geothermal Field, New Zealand, is renowned for its spectacular natural features and cultural heritage around geothermal uses by local Maori people. Rotorua City is built on top of the geothermal resource. It is a thriving city and a key destination for geothermal tourism. To optimize the use of the resource without compromising safety nor affecting its natural geothermal surface expressions, the local authorities have supported many geoscientific studies in that area to understand and monitor the dynamics of the field. Building 3-D geoscientific models that integrate multidisciplinary geological, geochemical, geophysical and reservoir datasets into one model is essential to better understand geothermal resources and has become standard practice in the New Zealand geothermal industry. A 3-D geoscientific model of the Rotorua Geothermal Field has been developed starting with a geological model as its foundation that combines surface and subsurface geological and structural data/interpretation. The surface features, bore locations, bore temperatures, chemical composition of the fluids and geophysical data (seismic, magnetotellurics, gravity, and thermal infra-red) have been added and used to enhance the model. Combined use of the datasets has enabled detailed lithological modelling within key geothermal reservoir units to an extent that fluid flow pathways through these units can be identified. This data-driven 3-D conceptual representation of the geothermal field aims to better inform numerical models that simulate the reservoir behaviour. In this paper, we present the impact a comprehensive 3-D geoscience model is having on the development of our understanding of the Rotorua geothermal resource and its applications for sustainable field management.