MODELLING GEOTHERMAL POWER GENERATION FROM THE WAIOTAPU – WAIKITE – REPOROA GEOTHERMAL FIELDS

Abstract

The Taupo Volcanic Zone in New Zealand is a cradle of geothermal systems, of which some, such as Waiotapu, are renowned as geo-tourism destinations. Due to its cultural significance, Waiotapu is classified as a protected geothermal system, where no geothermal production is allowed. Geothermal systems with hydrological linkage to Waiotapu such as Waikite and Reporoa are also treated differently than other systems. The Waikato Regional Plan classified Waiotapu – Waikite as protected systems and Reporoa as a research system (Waikato Regional Council, 2019).
The natural state numerical model developed by Kaya et al. (2014) was used to investigate possible strategies from Reporoa area under different production and reinjection scheme for optimum power generation while monitoring the pressure near the surface features to avoid any induced changes in the thermal activity and avoid the adverse effect of development. Investigations were done both on the production side, such as the amount of power generation, location, depth and number of production wells, and also on the injection side, such as the location, depth and number of injection wells, including injection rate. The configuration of production and injection wells was also tested. A monitoring well was located between Reporoa and Waiotapu with the purpose of safeguarding Waiotapu from any potential changes due to production activity.
Based on the test results, the recommended scenario is to set up a 25 MW production in Reporoa, with five production wells and one injection well. The production wells have a maximum steam flow of 47 kg/s from each well, and all injection wells inject both brine and condensate at 100% injection rate. According to our modelling study, the goal of preserving surface manifestations in Waiotapu area is achievable.