Geothermal Structural Permeability Map

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The Geothermal Structural Permeability Map project delivered a national database and map of natural fractures and subsurface permeability in critical Australian basins to better exploit geothermal resources across Australia.Key resultsWhile it was expected the permeability anisotropy (directional permeability) would be reflected in directional resistivity of the magnetotelluric survey acquired as part of this project, results were inconclusive. Previous studies in the Otway Basin had shown promise for magnetotellurics as a cheap, non- invasive survey mechanism for identifying the same permeability anisotropy identified in well and/or seismic datasets. Whether this is a result of fractures lacking an interconnectivity at depth, non-saline fluid filling them, or the fractures showing as open to conductive fluids in image logs being a false positive.A key road block to achieving all outcomes of the project was that we found the initial budgeted cost and time input insufficient for the development of an interactive GIS website to host the structural permeability map content. While the project had intended to keep website development in-house for ease of data management, we had to outsource this to a specialist who could provide a simplified version of our original template, as well as building a template and quote for a fully interactive GIS hosting platform in the future.Recent studies in active geothermal areas have identified a variety of “geothermal favourability proxies” for identifying zones and/or pathways where permeability, heat, and fluids overlap. Focussing on the permeability, and permeability pathway proxies, this project demonstrated how regional-scale map data could also be interrogated in this was to provide more a broader, regional exploration tool to identify areas for more detailed investigation.

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