MODELLING OF THE OHAAKI GEOTHERMAL SYSTEM

Abstract

The Ohaaki Geothermal field is situated in the Taupo Volcanic Zone of New Zealand. It was the second geothermal field in New Zealand to be developed and is used primarily for electricity generation. Wells were first drilled in the Ohaaki field during the early 1960's. After a period of well testing following drilling, there was a long period of field recovery until steam production for electricity generation started in 1988. A large three-dimensional numerical model of the Ohaaki geothermal field is presented. It is implemented with the geothermal simulator TOUGH2 (Pruess, 1991). The model is used to investigate the natural state, the well testing and recovery period and the recent production period. The model is calibrated by matching natural state temperatures in the wells, pressure data from the well testing and recovery period and enthalpy and pressure data from the recent production period.