Australian mean land-surface temperature

The mean land-surface temperature represents an important boundary condition for many geothermal studies. This boundary is particularly important to help constrain the models made to analyse resource systems, many of which are shallow in nature and observe relatively small thermal gradients. Consequently, a mean land-surface temperature map of the Australian continent has been produced from 13 years of MODIS satellite imagery, for the period 2003–2015. The map shows good agreement with independent methods of estimating mean land-surface temperature, including borehole surface-temperature extrapolation and long-term, near-surface ground measurements. In comparison to previously used methods of estimating mean land-surface temperature, our new estimates are up to 12 °C warmer. The MODIS-based method presented in this study provides spatially continuous estimates of land-surface temperature that can be incorporated as the surface thermal boundary condition in geothermal studies. The method is also able to provide a quantification of the uncertainties expected in the application of these estimates for the purposes of thermal modelling

Developing Australian Enhanced Geothermal Systems and Hot Sedimentary Aquifer Models For Reducing Risk

ABSTRACT Reducing uncertainty at an early stage of resource development is a key necessity to attract project finance. Risk analysis frameworks exist in the petroleum industry for quantifying risk and expected returns At a basic level, any geothermal system comprises two independent components: heat, and a heat transport mechanism. Practically, these translate to temperature, and a heat transfer fluid (or vapor) with a transport pathway (i.e. permeability). Australia has low heat flow relative to 'traditional' geothermal countries, requiring extensive thermal insulation provided by thick sedimentary accumulations in order to reach temperatures high enough for power generation. Because of the depth at which hot reservoirs occur, matrix permeability in sediments is compromised meaning that permeability enhancement is needed for most projects, and exploration is difficult and expensive. Estimating temperature at depth has so far proven to be robust using heat flow or extrapolation of temperature-where such measurements are available. However, these data are sparse. Approaches such as TherMAP The lack of examples of working deep EGS or HSA reservoirs is an outstanding issue. A study is needed to compile the fracture characteristics of existing projects in Australia and internationally. A complementary conceptual study using discrete fracture network modelling in a stochastic sensitivity analysis may provide constraints on the range of geological environments (lithologies, geodynamic history including uplift, compaction, metamorphism, thermal history, previous deformation, present stress regime) favorable for the development of optimal fracture networks for geothermal exploitation. This paper proposes how some of the key parameters around permeability may be derived from proxy data sets, and how modelling using statistical methods may be used in predictive exploration and associated risk analysis