Drilling deeper: New Zealand explores supercritical geothermal

New Zealand’s government has allocated NZ$60 million to accelerate exploration of supercritical geothermal energy, aiming to access reservoirs at extreme temperature and pressure conditions that could transform the country’s baseload renewable capacity.

Under the “Geothermal: The Next Generation” research programme, GNS Science and collaborating institutions are working to identify exploratory drilling targets in the Taupō Volcanic Zone (TVZ), where high heat flow and active crustal processes suggest accessible supercritical conditions at depths between 3.5 and 6 km.

Supercritical geothermal refers to a fluid state in which water exceeds 373 °C and 220 bars of pressure, resulting in energy densities up to three to seven times greater than conventional geothermal systems operating at 200–300 °C. Such enhanced enthalpy could allow significantly more power generation per well, reducing the number of boreholes needed for comparable output.

However, engineering challenges include the uncertainty of permeability at these depths and conditions. Drilling to 5–6 km may encounter rock so ductile that natural fractures collapse, preventing flow; past experiences in Japan and Italy have observed such behavior. Corrosive fluids in superheated zones could demand advanced materials, fluid handling systems, or reinjection strategies to manage chemical aggression and thermal stresses.

New Zealand’s commitment to deep geothermal is intended to diversify its renewable portfolio beyond solar, wind, and hydro, offering continuous 24/7 generation that is less variable than intermittent sources. The country’s design of a governance group and site identification process also underscores the strategic effort to de-risk early exploratory investment.