Reservoir modelling of the Ohaaki geothermal system

Abstract

A large three-dimensional numerical model of Ohaaki geothermal system has been developed at the University of Auckland in collaboration with Contact Energy Limited (and its predecessors) over many years. The model is calibrated against data from the natural state, the well testing period, the recovery period and the production period. Recently the model was reviewed and re-calibrated to improve the match between model results and measured data. This was done by changing the heat input at the base of the model and by adjusting the permeability structure. However, although the deep temperatures obtained in the re-calibrated model were closer to those indicated by deep drilling, the shallower temperature profiles, in general, needed further improvement. Model refinements are being worked on to further improve the match.