Publication Name: Second South-Eastern Australia Oil Exploration Symposium - Technical Papers
Authors: J.K. Davidson and K.C. Morrison
Date Published: December 1986
Number of Pages: 21
Reference Type: Book Section
Abstract:A modified version of the Global Basin Classification (Kingston et al., 1983) can be used to identify the geological controls of hydrocarbon plays in, and between, sedimentary basins. The input data are descriptive, requiring minimal interpretation with generalisations appropriate to the scale of the plays and basins being analysed.
The Top Latrobe, Eastern View and Kapuni plays, in Gippsland, Bass and Taranaki Basins respectively, are not similar. The vast differences in quantities of hydrocarbons in these plays are less dependent on structure size, reservoir extent and quality, and source rock than they are on seal effectiveness and degree of exploration. The latest Eocene-earliest Oligocene compression in Gippsland was intense enough to cause an unconformity between the excellent reservoirs and the overlying Oligocene sealing shales. The same event in Bass was of much lower intensity and resulted in Upper Eocene sealing shales disconformably overlying excellent reservoirs. Folding is not appararent at this time in the Taranaki. The top porosity play in the Kapuni Group is time transgressive with very good reservoirs and seals ranging from Palaeocene in the northwest to uppermost Eocene in the south. PostMiddle Miocene compressional events generated large, easily explorable anticlinal traps in Gippsland, induced minor wrench components to small normal fault blocks and may have locally aided vertical migration in Bass, and formed large anticlines and generally breached the seal in Taranaki. This seal
breach has contributed to a play at the top of a Middle Miocene turbidite sequence, itself often breached to
cause migration into plays in Pliocene clastics.
A Base Tertiary play is recognised in Bass. Increased shaliness and enhanced seal and source characteristics of the Early Eocene and Palaeocene form a play on unconformably underlying Late Cretaceous reservoirs. This play is virtually absent in Gippsland and Taranaki.
In Otway, the lowest Tertiary and Upper Cretaceous comprise clastics which provide a limited onshore play on the Otway Group gas-prone source rocks. In general offshore, the thick Upper Cretaceous reservoir and source rocks were breached, often to the seabed, by normal faults associated with gravity slumping, and they provide little chance of success.