Recent Computer 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. The production history data was also updated to the end of 2004. A match between model results and the production history was obtained for the enthalpy and carbon dioxide content of individual wells and for reservoir pressures. Matching the carbon dioxide content of individual wells required further adjustment to the carbon dioxide flux in the natural state model. A significant improvement to the match of the model results with the production data was obtained with the 2006 model compared to the previous (2004) model.