AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Reassessing the In Situ Stress Regimes of Australia’s Petroleum Basins
(1) Centre for Tectonics, Resources and Exploration (TRaX), University of Adelaide, Adelaide, SA, Australia.
(2) Deep Exploration Technologies Cooperative Research Centre, Adelaide, SA, Australia.
Previous in-situ stress studies across many of Australia’s petroleum basins demonstrate normal fault and strike-slip fault stress regimes, despite the sedimentary successions demonstrating evidence for widespread Miocene-Recent reverse faulting.
Seismic and outcrop data demonstrate late Miocene-Recent reverse or reverse-oblique faulting in the Carnarvon, Otway and Gippsland basins. In the Otway Basin a series of ~NE-SW trending anticlines related to reverse-reactivation of deep syn-rift normal faults, resulting in deformation of Cenozoic post-rift sediments are observed. Numerous examples of late Miocene-Recent reverse faulting in the offshore Gippsland Basin have been observed, with contractional reactivation of previously normal faults during these times partially responsible for formation of anticlinal hydrocarbon traps that host the Barracouta, Seahorse and Flying Fish hydrocarbon fields.
A new method for interpreting leak-off test data demonstrates that the in-situ stress data from the Carnarvon, Otway and Gippsland basins can be reinterpreted to yield reverse fault stress regimes, consistent with the present-day tectonic settings of the basins. This reinterpretation has significant impact on the petroleum exploration and development in the basins. Faults and fractures previously believed to be at low risk of reactivation in a normal fault or strike-slip fault stress regime are now considered at high risk in the reinterpreted reverse fault stress regime.