Areas AC07-1, AC07-2, AC07-3, AC07-4 and AC07-5
Ashmore Platform, Bonaparte Basin
Petroleum Potential
Few wells have been drilled on the Ashmore Platform and exploration has been sporadic, with exploration concentrating on the proven Vulcan Sub-basin. Having said this, hydrocarbon discoveries have been made close to the release areas. Of note is the Puffin accumulation where oil is reservoired within Late Cretaceous sub-marine fans that extend from the Vulcan Sub-basin onto the southeast margin of the platform. The Puffin oil field is currently undergoing development.
Source rocks
The proven Late Jurassic source rocks of the Vulcan Sub-basin are either absent or thin and immature across the Ashmore Platform. Hence, plays largely rely on long distance migration from depocentres in the Cartier Trough and Swan Graben. The source potential of the Early Triassic and Early Permian section in these depocentres is largely untested.
Timing of expulsion and migration
Various models have been proposed to predict oil migration onto the Ashmore Platform. The modelling undertaken by Kennard et al (1999) predicted relatively restricted migration onto the Ashmore Platform, whereas modelling reported by Chen et al (2002) showed a more widespread migration towards and onto the platform. Significantly, Chen et al (2002) modelled some oil charge migrating towards the Douglas, Rainbow and Warb structures on the Ashmore Platform, whereas Kennard et al (1999) predicted little or no charge. Indeed, residual oil was found in the Miocene Oliver Formation.
Play types
Drilling to date on the Ashmore Platform has focussed on the Cretaceous Puffin Sandstone and the Triassic reservoirs immediately underlying the Base Cretaceous Unconformity (Nome and Challis formations in the Triassic and the Upper Swan Formation in the Early Jurassic).
One possible new play for the Ashmore Platform is interpreted Jurassic/Triassic reef or mound structures (Figure 7). These features appear to be unfaulted and to be unaffected by reactivation of the faults in the area, thereby potentially overcoming the preservation issue present elsewhere on the Ashmore Platform.
Critical risk factors for the Ashmore Platform are suitable migration pathways from adjacent or underlying mature source rocks as well as trap integrity, since many Late Miocene–Pliocene reactivated faults extend to the sea-floor.