AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Sub-salt Petroleum Potential of the Neoproterozoic Adelaide Rift, South Australia
(1) PIRSA Petroleum & Geothermal Group, Adelaide, SA, Australia.
The Adelaide Rift is a Neoproterozoic to Cambrian rift complex extending over 1000 km in South Australia. The northern-most extension of the Adelaide Rift outcrops in the Peake and Denison Ranges, and underlies the younger Permo-Carboniferous Arckaringa Basin west of the Ranges. In the Peake and Denison Ranges the Neoproterozoic section comprises basic volcanics, evaporites, carbonates and clastics, deposited in a rift valley, overlain by a sequence of clastics and platform carbonates, including glacial sediments recording two periods of glaciation.
Seismic data acquired over the Arckaringa Basin in the 1980’s shows distinct salt-tectonic features in the underlying Neoproterozoic section. Salt withdrawal basins indicate significant syn-deposition salt movement during the Neoproterozoic and early Cambrian. Minor salt-remobilisation during later deformation events is also evident. Interpreted salt withdrawal basins adjacent to disturbed diapiric breccias are exposed in the Peake and Denison Ranges to the east.
The presence of tilted fault blocks sealed by inferred massive salt horizons are tantalising, given the success of sub-salt rift block plays elsewhere in the world. Overmaturity may be an issue, however significant oil shows intersected in nearby Permo-Carboniferous sediments suggest that the sub-salt play is worth further consideration. The Permo-Carboniferous section is not sufficiently mature for oil generation, hence the oil shows are assumed to have been sourced from the older sediments.