A stratigraphic study of the Crayfish Group in the
Penola Trough, Otway Basin!
Jonathan Conti - 2013
Honours Degree of Bachelor of Science (Petroleum Geology & Geophysics)
Australian School of Petroleum
The University of Adelaide
The Early Cretaceous Crayfish Group in the Penola Trough, Otway Basin, was deposited as part of the early syn-rift graben-fill succession overlying the Late Jurassic to Early Cretaceous Casterton Formation. Commercial volumes
of hydrocarbons have been produced from formations within the Crayfish Group. However, correlation of the Crayfish Group stratigraphy across the Penola Trough has been difficult due to lateral facies variations, significant
faulting and variable quality seismic data.
A multidisciplinary approach has been applied in this study towards developing a better understanding of the lateral extent, and relationships between the Crayfish Group formations in the South Australian and Victorian
sections of the Penola Trough. Analysis of the formations through a workflow which included petrological investigations, core logging, palynostratigraphy,
lithostratigraphy and seismic stratigraphic interpretation, has provided a comprehensive overview of the connectivity between formations, as well as an improved understanding of the palaeogeographic environment at the time
of deposition. The application of a sequence stratigraphic framework to the Crayfish Group has enabled a new way of interpreting the temporal and spatial characteristics of the formations, as well as the key surfaces between
the assigned depositional system tracts.
In this study, chemostratigraphy, has been used to assess the geochemical variations in the Crayfish Group formations, between wells in South Australia and Victoria. The results from the use of this method provide chemicallycharacteristic correlations between formations across the trough, and enable a high-resolution subdivision of strata. In addition, variations in chemical ratios have been found to represent changes in the palaeoclimate during the
Crayfish Group deposition, and the possibility of two sources of provenance.
The findings in this study support a new approach to defining the stratigraphy of the Crayfish Group formations, providing a platform for future exploration and reservoir development in the Penola Trough.