We have passed the half-way mark in the Geothermal: The Next Generation research programme. Today, there are more questions than answers as to what the supercritical geothermal future for Aotearoa New Zealand might look like, but our research is moving the knowledge forward.
Below are some highlights of activities and changes from the last year, by project:
Goal: searching for prospective locations for accessing supercritical fluids, and delineating potential resources in the Taupō Volcanic Zone (TVZ).
- We have been improving our geophysical and computer modelling to de-risk and target future exploration areas. Working with stakeholders to combine social and science feasibility, we have selected target sites to focus our geophysics, structural, geological and modelling work in preparation for a potential supercritical exploration well.
- A new Total Magnetic Intensity grid that includes offshore magnetic data has been constructed and is used to model the Curie Point Depth and heat flow.
- The magnetotelluric team have implemented the FEMTIC MT inversion code. This more advanced mesh design allows topography to be incorporated, and for the mesh to be adaptively refined around areas of interest. The first use of this capability at Mt Tongariro was presented at the 2022 Japanese Geophysical Union meeting.
- The ETH-Zurich team successfully modelled the thermal condition of a deep cooling mush and is progressing the modelling of possible supercritical fluid resources in the TVZ.
- All analytical data on basement xenoliths has been acquired and the data interpretation is well underway.
- The fractures in Marlborough schist (surface analogue for subsurface low-grade schist) have been digitised and 3D visualisations of the fracture systems published.
- The team welcomed the collaboration of masters students Siru Jylhänkangas and Keiha Nicols from Victoria University of Wellington.
Goal: investigating chemical characteristics of supercritical fluids and their interactions with rocks and minerals under supercritical conditions.
- The research facility for experimentation on fluid-rock, fluid-infrastructure interactions under supercritical conditions is providing a fundamental resource for the testing of materials. The team have been conducting continuous flow through experiments at supercritical pressure and temperature conditions similar to those expected in NZ supercritical reservoirs (high temperature but low pressure).
- Several water-rock interaction experiments used NZ basement greywacke rock (the likely injection aquifer for TVZ supercritical geothermal resources) and geothermal brine. Subcritical (conventional geothermal) and supercritical reactions differ markedly due to the low density of the water phase at supercritical conditions.
- The supercritical high-temperature reactor was used to measure the solubility of quartz (a ubiquitous mineral in geothermal systems both subcritical and supercritical). We have now successfully measured the solubility of quartz in the 375 – 600°C and 200 – 270 bar ranges, and this new data provides fundamental information for engineers and geochemists working on supercritical fluid production and utilisation.
- An experimental study was completed on the potential of Rhenium and Indium as geothermal tracers under both subcritical, super-hot and supercritical conditions (200–400°C, and in presence of a NZ greywacke rock substrate). The results show that Rhenium is potentially a suitable candidate at subcritical conditions, however both are unsuitable at supercritical conditions.
- A comprehensive reactive transport model was built and calibrated in TOUGHREACTTM to numerically simulate fluid-rock reactions between basalt and water at subcritical conditions (350°C, 500 bar). The results represent the calibration of a numerical model with actual laboratory experimental results.
Goal: translating supercritical research and forming an engaged stakeholder community.
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