An updated model of Ohaaki geothermal field, New Zealand

• New numerical model of Ohaaki based on an updated conceptual model. • The updated conceptual model includes 12 faults and the alteration zone (clay cap). • The new model maintains the good match to the natural state data and achieves a better match to some of the production history data. The University of Auckland has been collaborating with Contact Energy Limited (and its predecessors) for many years on computer modelling of the Ohaaki Geothermal Field. This paper describes the latest model that has been developed over the last 4 years. It is based on an updated digital conceptual model that is used, with our modelling framework, to set up a reservoir model that can be run in either AUTOUGH2 (our version of the well-known simulator TOUGH2) or in Waiwera, our own highly parallelized simulator. The new digital conceptual model gives an improved representation of the geological formations, the faults and the alteration zone and the corresponding numerical model gives an improved match to most of the data. The new model produces much better results for temperature decline and pressure decline followed by pressure recovery in the deep wells, such as BR59, BR60 and BR61, on the West Bank of the Waikato River.