A New Look at the Offshore Canning Area: Locality of the Largest Offshore Oil Discovery in Australia in Over 30 Years

Abstract

In August 2014, Apache Energy announced a significant oil discovery at Phoenix South-1 in the Bedout sub-basin on the Northwest Shelf of Australia. The well recovered light oil (46 deg API) from Early Triassic sandstones. Preliminary results indicate potential for 300 Mmbbls of oil in place with additional structures in the area, making it potentially the most significant offshore oil discovery in Australia for over 30 years. Of particular significance is the demonstration that there now appears to be an effective oil source within the Lower Triassic in an area previously considered gas-prone. A new regional study of the prospectivity of the area offshore from the onshore Canning Basin was recently undertaken to assess the impact of the Phoenix South-1 discovery. The study area covers over 200,000 km² and incorporates over 130,000 km of seismic data and 70 wells. Although Jurassic petroleum systems predominate over most of the Northwest Shelf, the prospectivity of the study area is defined by Lower Triassic, Permian and Carboniferous petroleum systems. The Lower Triassic interval, the most likely source of the oil in Phoenix South-1, has a substantial areal extent. It is underlain by a thick potential Permian section that could provide a significant gas source, potentially generating the gas found in Phoenix-1. Further northeast the offshore extension of the Fitzroy Graben contains a thick sequence of Permian and Carboniferous rocks associated with recognised petroleum systems in the adjacent onshore Canning Basin. These three potential source intervals provide considerable scope to charge traps over a large region. Substantial potential exists not only around Phoenix South-1 in the Triassic, but also on the flanks of the sub-basins and over the Broome Platform, where multiple reservoir/seal pairs in the Jurassic and Cretaceous sequences offer potential targets analogous to the Stag, Wandoo Gwydion and Cornea accumulations. Direct hydrocarbon indicators observed on the Broome Platform provide evidence of long distance migration. Prior to Phoenix South −1 well, industry consensus tended towards viewing the majority of the North West Shelf as a gas province with limited potential for further significant oil discoveries. In the offshore Canning area of the shelf there is now the possibility of a new oil province. The next 50 years look interesting indeed.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015