Abstract:
This thesis presents a numerical model for simulating the natural state of a geothermal reservoir and its response to production. The model is able to describe reservoirs in which there is a significant amount of carbon dioxide. A large number of numerical experiments are carried out to investigate the interaction between the thermal state, hydrology and reservoir properties in determining the natural state of a geothermal reservoir and to study the production behaviour of a geothermal reservoir. These experiments show that the processes occurring during exploitation are too complex to allow the production behaviour to be quantified in terms of a few parameters which could be estimated during exploration or early production. Models, of the Wairakei reservoir and the gassy Broadlands reservoir in New Zealand are presented. These 2-D radial models give a good fit to the past production histories of the fields. The model of Wairakei predicts a slow decrease in pressure and enthalpy up to the year 2000, however the model of Broadlands suggests that the proposed output from the field may be very close to the maximum which can be maintained.