Geothermal Exploration and Development in Australia

Professor Richard Hillis

This talk will first present an overview of the recent boom in geothermal exploration and development activities in Australia and then focus on the influence of in situ stress on the engineering of geothermal reservoirs in the subsurface.

The installed global electricity generation capacity of geothermal energy is around 9 GW, less than 1 % of demand. Both in the USA and Australia there are bold predictions that geothermal energy could supply 10 % of demand by 2020. Delivery of this prediction would require technically more challenging geothermal resources (deeper and tighter) to be commercialised. This talk will discuss how Australian geothermal companies intend to commercialise such resources. The Australian geothermal boom is in part driven by the CO2 emissions-free nature of geothermal electricity and the talk will also discuss the cost of electricity generation versus CO2 emissions for various types of electricity generation.

The in situ stress field is a key variable in any geothermal development, principally because of its control on the direction of subsurface fluid flow. The talk will present some field examples that illustrate that fluid flow along fractures in the subsurface (both natural and hydraulically stimulated) is focused on fractures that are suitably aligned for failure within the in situ stress field. An understanding of such control on fluid flow is critical to placement of injection and production wells in geothermal developments.

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