Bailey, Adam1, Jarrett, Amber1, Wang, Liuqi1, Dewhurst, David2, Esteban, Lionel2, Kager, Shane2, Monmusson, Ludwig2, Carr, Lidena1, Henson, Paul1
1Geoscience Australia, Canberra, Australia; 2CSIRO Energy, Perth, Australia
Exploring for the Future (EFTF) is an Australian Government initiative focused on gathering new data and information about potential Northern Australian mineral, energy and groundwater resources. Northern Australia is generally under-explored yet offers enormous potential for industry development, as it hosts many prospective regions and is located close to infrastructure and major global markets. In June 2020 a four year extension to the EFTF program was announced, expanding the scope to include the whole of Australia.
The energy component of EFTF aims to improve our understanding of the petroleum potential of Australian frontier basins. The Kidson Sub-basin, located within Western Australia’s Canning Basin, is an EFTF primary area of interest. A large, underexplored depocentre, it is likely that the proven petroleum systems of the Canning Basin extend into this frontier region. Geoscience Australia and partners recently acquired significant new data over the Kidson Sub-basin, including the L211 Kidson Sub-Basin 2D Seismic Survey and the deep stratigraphic borehole, Waukarlycarly 1.
This study brings together the geomechanical studies undertaken in the Canning Basin, including the Kidson Sub-basin, as part of EFTF. This includes interpretation of the regional stress regime and its context within the Australian continent, detailed analysis of present-day stress magnitudes, and geomechanical rock testing undertaken by CSIRO-Energy on samples recovered from Waukarlycarly 1.
Wireline log data, including wellbore image logs, were interpreted from open-file petroleum and stratigraphic wells to define stress orientations and magnitudes across the Canning Basin. A NE-SW regional present-day maximum horizontal stress orientation is interpreted from observed wellbore failure in image logs, and is in broad agreement with both the Australian Stress Map and previously published earthquake focal mechanism data. A strike-slip faulting stress regime is interpreted through the basin, however, when analysed in detail there are three distinct stress zones identified: 1) a transitional reverse to strike-slip faulting stress regime in the top ~1.0 km of the basin, 2) a strike-slip faulting stress regime from ~1.0 km to ~3.0 km depth, and, 3) a transitional strike-slip to normal faulting regime at depths greater than ~3.0 km. Detailed mechanical earth models demonstrate a variable present-day state of stress within the Canning Basin. Significant changes in stress within and between lithological units, due to the existence of discrete mechanical units, form numerous inter- and intra- formational stress boundaries that are likely to act as natural barriers to fracture propagation.
Rock testing targeted potential reservoir-seal pairs and intervals with identified unconventional hydrocarbon potential, characterising mechanical and petrophysical properties through unconfined compressive stress (UCS) tests, desktop ultrasonic testing, mercury injection capillary pressure (MICP), road-ion-beam milling and scanning electron microscopy (BIB-SEM), and gas porosity and permeability experiments. Hence, conventional and unconventional reservoir rock properties are characterised.
These data provide geomechanical and petrophysical insights into intervals with identified or potential hydrocarbon prospectivity and allow for extrapolation of rock properties. Although the Kidson Sub-basin is underexplored, these results demonstrate that should Canning Basin petroleum systems extend into the Kidson Sub-basin, geomechanical properties are likely to be favourable for the development of shale resources.
Adam Bailey graduated with a PhD in 2016 from the Australian School of Petroleum and currently works with the Onshore Energy Systems team at Geoscience Australia and has expertise in petroleum geomechanics, structural geology and basin analysis. Adam is currently working on the flagship Exploring for the Future Program.