Publication Name: Second South-Eastern Australia Oil Exploration Symposium - Technical Papers
Authors: G.C. Smith
Date Published: December 1986
Number of Pages: 41
Reference Type: Book Section
Abstract:
The Bass Basin is an intracratonic rift basin located offshore between Victoria and Tasmania. The tectonosedimentary history is controlled by Otway rifting between Australia and Antarctica and to a lesser extent by Tasman Sea rifting. A Lower Cretaceous volcanogenic synrift sequence (Otway Group) and a TasmanSea Cenomanian to Santonian shale dominated synrift sequence (Durroon Formation), occurring in large tilted fault blocks, are recognizable on seismic. These are overlain by a post-rift sequence comprising a Campanian to Eocene non-marine coal measure sequence (Eastern View Group) and a marine sequence (Demons Bluff Formation and Torquay Group) which drowned and filled the basin during its sag phase with shallow-water mudstones, marls and carbonates.
The burial history records the effects of rapid subsidence, sedimentation and low T -P metamorphism in the rift and early post-rift phases, waning in the Tertiary. The rift sequences are confined to a narrow NW-SE basin axis and exhibit the highest metamorphic ranks except on basement highs. The post-rift sequences onlap the older sequences and basement rocks extending over the basin margins, and range from lower ranks on the margins to moderately high ranks at depth along the basin axis. Maturation in the Eastern View Group is mainly controlled by the Cretaceous to Eocene burial. The exinite organic matter is mature only at depth along the basin axis being immature on the basin margins, whereas the vitrinite and inertinite are mature or overmature throughout most of the basin.
The Upper Eastern View Group has good reservoirs, seal and source rocks but lacks structure and is low in
maturity. The Lower Eastern View Group has good intraformational seals and reasonable structure but poor source rocks and poor reservoirs. Overall the Bass Basin has a low probability for discovery of large commercial oil or gas fields and only a moderate probability for discovery of small commercial oil or gas fields.