Publication Name: Eastern Australian Basins Symposium 2001
Authors: P.J. Boult and J. Donley
Date Published: November 2001
Number of Pages: 32
Reference Type: Magazine Article
Abstract:A 3D seismic volume of porosity logs, calibrated to wells, was generated by multi-attribute trace inversion of seismic data over an area containing five producing gas Fields in the Pretty Hill Formation of the onshore Otway Basin, South Australia. From this 3D volume, calibrated maps of net pay pore space and the original gas-in-place were calculated for the Katnook and Redman Fields.
The problem of integrating high vertical resolution well data with high lateral resolution seismic data was overcome by establishing a statistically valid, non-linear, probabilistic neural network-based relationship between well bore porosity logs and seismic data at eight well locations. Removing each wel l in turn and establishing the relationship from the remaining wells validated the relationship. Using the validated relationship, a 3D volume of porosity was calculated from the 3D seismic volume.
Using trace mathematics this porosity trace-volume was converted into a cumulative-beneath-top-reservoir pore-space trace-volume for net pay. For each individual field, a slice of this trace-volume at the free water
level, which represents the cumulative pore space between free water level and the seal, was input into original gas-in-place calculations.
For the Katnook Field, original gas-in-place calculations, based on this 3D porosity volume, show an excellent agreement with that based on production simulation after ten years of production.