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Forward Modelling and Seismic Inversion for Unmasking of Gas Reservoir Sandstones in the Patchawarra Formation, South Australia.

Sundsby, Ole

Honours Degree, 1998

University of Adelaide

Abstract

This study investigates the application of seismic modelling and inversion for gas reservoir detection in the Permian Patchawarra Formation of the Cooper Basin in South Australia. The seismic response of these reservoirs is typically hidden or `masked' by much stronger reflections from surrounding interbedded coals. Primary goals were the detection of modelled changes on synthetic seismograms, characterisation of these changes and evaluation of seismic inversion for detailed interpretation and unmasking. Log blocking and editing incorporating petrophysical control was used to create models containing lateral variations at the reservoir or coal levels. Identification of modelled seismic events was attempted using the known wavelet and resolution principals. The pseudo 2D synthetic sections were then inverted using different inversion algorithms. Real 3D seismic data were also inverted to compare and calibrate the inversions. Recursive and GLI (Generalised Linear Inversion) inversion algorithms gave a range of impedance solutions, which were evaluated using modelled logs as a check. The study shows that changes in Patchawarra reservoirs and surrounding rocks may be recognised on seismic data and on inverted sections. With certain limitations, the reservoir log responses are unmasked by inversion.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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