Seismic Interpretation Of Structure And Stratigraphy, Permit T-15-P, Durroon Sub-Basin, Off-Shore Northeastern Tasmania.
Brincat, Mark P.
Honours Degree, 1992
University of Adelaide
Permit T-15-P is located offshore northeastern Tasmania with a total area of 16500 square kilometres and covers the majority of the newly named Durroon Sub-basin. The dominant features in the Durroon Sub-basin are the Bark, Anderson and Boobyalla half-grabens which are bounded by large listric normal faults. Major tectonism of the area occurred during the breakup of the Antarctic and Australian continental plates in the Late Jurassic and Early Cretaceous. Later structural development, which is only evident in the southeast of the Boobyalla half-graben as a dominant north- south fault trend, is associated with the Tasman rifting event.
Interpretation of a regional seismic grid shows that a basement high separated the Durroon Sub-basin from the Bass Basin and existed at least until the end of the Cenomanian. This basement high was covered by the Durroon Formation and from this time on the Durroon Sub-basin has acted as a near source extension of the Bass Basin. The Boobyalla and Anderson fault blocks acted as local fault-controlled depressions until at least the Late Cretaceous.
Deposition of the Durroon Formation coincided with the Tasman rifting event. The fault-barred lacustrine setting and conditions associated with the Tasman rifting created an environment in the Boobyalla and Anderson half-grabens ideal for the production of organic matter. Consequently, over most of the sub-basin, the Durroon Formation exhibits a very high organic (particularly algal) content, which makes it a potentially very good oil source rock off-structure in the deeper sections of the basin. It may also act as a seal for the Cenomanian sandstone and Otway Group reservoirs. The Durroon Sub-basin contains potentially significant, but high risk, deep, fault- controlled hydrocarbon plays. The largest risk for potential traps is the breaching of the seal by the extremely large displacements of the faults bounding the half-grabens.