Improved Visualisation of Reservoir Simulations: Geological and Fluid Flow Modelling of the Tauranga Low-Enthalpy Geothermal System, New Zealand

Abstract

The low-enthalpy geothermal system at Tauranga, on the north coast of the North Island of New Zealand, is widely used for hot springs, commercial pools, aquaculture and direct heating. As pressure on the system increases, the need to carefully manage its use is becoming more important. By creating a Leapfrog Geothermal geological model and incorporating it into a TOUGH2 reservoir model, a fairly detailed simulation of the system can be created. Outputs from the TOUGH2 model can then be read back into Leapfrog Geothermal, facilitating direct comparison between measured and modelled temperatures, and highlighting regions that need to be better modelled. Using a 2-layer geological model comprising sediments overlying volcanic rocks, we created a TOUGH2 model covering 130 km by 70 km and extending down to 2 km depth. Relatively low thermal conductivity of 1-1.5 W/m°C from the literature appears to give a good fit to the data, but both permeability and heat flux at depth are important parameters that our modelling shows need to be better constrained. Integrating Leapfrog Geothermal and TOUGH2 software creates a useful tool in geothermal reservoir simulation, facilitating model calibration and allowing reservoir models to be more easily disseminated to a much wider audience.