Radiogenic Iron Oxide (RIO) Model

This model focuses on areas where ancient volcanic and granitic rocks released hot sub-surface fluids that permeated through the surrounding rocks and altered their composition. Olympic Dam is an example of this. Natural, low-level radiogenic decay results in extremely high heat production rates.

Measured heat production rates in RIO bodies may be as much as 50 times greater than those from average granite, and thermal modelling shows that under favourable conditions temperatures in excess of 200°C may be generated at depths of around three kilometres. Petratherm has a number of techniques, developed by MNGI Pty Ltd, to identify RIO bodies by using detailed gravity (measuring density changes) and magnetic data to detect the iron oxide associated with these systems.

Enhanced Natural Thermal System (ENTS)

In some instances, the heat transfer from a RIO body may be enhanced by favourable geological conditions. Specifically, pre-existing faults may already focus natural superheated groundwater. These fault-controlled heat reservoirs telescope potential resources much closer to the surface, allowing cheaper development costs. Development of a heat exchanger is also much simpler, as there is already a natural flow system, which can be enhanced to maximize heat extraction.