Estimating Wairakei’s 50 Years and 100 Years Mwe Potential Capacity from a Calibrated Natural State Model Using Experimental Design (ED) and Response Surface Methodology (RSM)

Abstract

Wairakei geothermal field has been operating since 1958, which is years beyond the initial expected production life. There is still significant hot geothermal fluid available for electricity generation that can sustain production for many more years. It is interesting to estimate the theoretical capacity (MWe) of the field assuming it runs for another 40 years, a total production life of 100 years since commissioning.
Two different resource assessment methods were investigated: the volumetric (stored heat) method, and also Experimental Design (ED) and Response Surface Methodology (RSM). In particular, the use of the Plackett-Burman design for building a polynomial model using a calibrated natural state reservoir model with minimum number of required simulation runs was investigated.
Results obtained from Plackett-Burman suggest that Wairakei could sustain a P50 of 294 MWe for 50 years and 219 MWe for 100 years since commissioning. Findings also reveal that permeability and injection parameters are critical to sustain operation for the first 50 years while sufficient permeability and porosity are crucial to support the operation up to 100 years.