Geoscience Visual Presentation G09: Rock physics and seismic amplitudes of the Kingia Sandstone, North Perth Basin

Geoscience Visual Presentation G09 The Kingia Sandstone in the northern Perth Basin is a significant gas reservoir, with potential to become a geothermal resource and a candidate for CO2 storage. Several challenges to exploitation, however, have been identified, including difficulties in predicting depositional and diagenetic facies. Deposited in the Early Permian within shoreface and estuarine environments, the Kingia unconformably overlies the Bit Basher Shale and grades upwards into the Irwin River Coal Measures (IRCM). Porosity in the Kingia is primarily destroyed by burial compaction and quartz cementation but can be preserved where early coating of quartz grains by iron-rich clays inhibits development of quartz cement. The distribution of preserved porosity is highly variable both vertically and laterally. Seismic amplitude interpretation away from well control is complicated as the sandstones with preserved porosity exhibit unusually high Poisson’s ratios, increasing with porosity in both gas- and brine-filled conditions. Contrary to expectations, low Poisson’s ratios do not indicate high porosity or gas presence. When porous and wet, the sandstones have similar elastic properties to shales, resulting in significant overlap with rocks in the bounding formations. The seismic signature of the Kingia is, thus, dependent on the interplay of several factors, including lateral heterogeneity in the overlying IRCM, the distribution and thickness of tight vs porous Kingia sands, fluid fill, the thickness of the Bit Basher, and the properties of the underlying High Cliff sandstone and Holmwood Shale. Forward 2D scenario modelling is recommended to provide guidance to interpret the complex seismic amplitudes. To access the Visual Presentation click Supplementary data’ below. To read the full paper click here