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.
Permeability affects how easily liquids and gases can move through and be extracted from the earth, including hot water that can be used to generate geothermal power. A greater understanding of structural permeability at depth is critical to identifying resources and de-risking geothermal projects ahead of drilling.
In 2014, the International Geothermal Expert Group‘s forward looking report recommended ‘rebooting’ Australia’s geothermal industry. The report highlights a need for greater support of technological innovation and research in finding prospective geothermal resources without drilling and developing technologies to increase flow-rate from geothermal wells.
The Geothermal Structural Permeability Map project deliver an unprecedented, continent-scale archive of natural fracture distributions and attributes that can be used to predict subsurface permeability within Australia’s energy basins.
It was the first ever investigation of the structural permeability of the Australian continent achieved by applying advanced geophysical, geomechanical, and petrological techniques in a cross-disciplinary approach. This integration of datasets delivered a unique database of natural fracture properties, as well as helping to develop new methods for the detection of fractures beneath the Earth’s surface and predicting how fluids will move through them.
The project assists project development in engineered geothermal systems, in both sedimentary basins and crystalline basement regions. Better understanding of natural fracture distributions, attributes, and permeability provides data and insight for carbon capture and storage, unconventional gas resources, and groundwater resources.
A key outcome of the project delivered a workflow ‘toolkit’ for the prediction of permeability pathways in critical Australian basins. This is aimed at reducing the risk of drilling failure through better predictions prior to drilling, as well as giving developers the best chance of targeting areas where well flow-rates are highest.
- While 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.