Numerical modelling of production from the Poihipi dry steam zone: Wairakei geothermal system, New Zealand

The Poihipi power station utilizes dry steam from a shallow zone near the margin of the Wairakei geothermal reservoir. The station has been in operation for several years, with daily variations in the fluid production rate following variations in time-of-day pricing of electricity. The corresponding varying pressure history provides a good database for testing models of the geothermal reservoir.Three different types of model were calibrated, namely, uniform porous medium, dual-porosity, fractured medium, and fractional dimension. The best match to the pressure data was achieved with the fractional dimension model.