Multi-scale characterisation of the Paaratte Formation, Otway Basin, for CO2 injection and storage

Abstract

A resurgent interest in the gas potential of the Gulf of Papua has been enhanced by the recent announcement of developing new LNG facilities in Port Moresby. Petroleum Geo-Services (PGS) has recently acquired a 6,000-km2Multi-Client 3D (MC3D) survey in the gulf. Although most of the discoveries in PNG are from the highland areas, the gulf is a proven hydrocarbon province with gas/condensate accumulations previously discovered in several reef build-ups. It is thought that sediments from the Papuan Fold Belt produced clastic dominated deltas in the Gulf area. Although this play is untested offshore, there is evidence these sandy facies exist and could contain hydrocarbons. On the first phase of acquisition/interpretation, an efficient screening workflow called Prospect Scanner, developed to highlight areas of AVO effects in large 3D seismic datasets, was tested. It uses pre-stack seismic time migrated (PSTM) gathers to extract AVO attributes that are then inverted to derive relative acoustic and shear impedance volumes. Using idealised cross-plots, the relationship between Vp/Vs ratio and the Ip values gives a good indication of the fluid and lithology of the tested interval. The results are loaded into a conventional interpretation package for interpretation/visualisation. Prospect Scanner has highlighted previously undrilled turbidite and basin floor fan prospects in the region. The Vp/Vs versus Ip cross-plot shows clustering ofthe sand anomaly and good separation from the majority of the plot. These points correspond to the idealised location for a gas sand. Past concerns about lateral prediction of reservoir presence and quality associated with the basin floor fans can be addressed through this workflow.