| Abstract |
Production from liquid dominated high temperature geothermal systems such as Wairakei have the potential to induce boiling in the reservoir, resulting in increased steam flows to the surface. At Karapiti thermal area, Wairakei, reservoir boiling has caused a large increase in surface heat flow demonstrated by increased areas of steaming and warm ground, increased fumarolic activity and hydrothermal eruptions. Despite the obvious qualitative indications, such an increase in heat and steam flow is difficult to measure. Because of the likelihood of altered surface activity, potentially involving violent phenomena (hydrothermal eruptions) it is important with respect to preserving the natural surface features, and also for public safety, to improve our understanding of shallow heat and mass transfer above boiling geothermal systems. Four simple mathematical models are used to investigate shallow subsurface heat and mass transfer in geothermal soil. The models are calibrated with a time series of soil temperature data from the Karapiti geothermal area, Wairakei, New Zealand. The modelling results show that simple models can produce reasonable estimates of heat flow and soil diffusivity in geothermally heated soil. |