Modelling Of Thin Bed Sands In Fluvial-Deltaic Environments Of The Southern Cooper Basin, South Australia.

Crimes, Angela C.

Honours Degree, 1995

University of Adelaide

Abstract

The current belief that most of the Cooper Basin structural traps have been identified has resulted in stratigraphic traps becoming the focus for recent exploration.

Environmental conditions in the basin were ideal for the formation of swamps during the Permian, and thus coals are present in many of the formations within the basin. The coals generate high amplitude reflections. It has been considered problematic as to whether thickness variations across a stratigraphic trap in thin reservoir sandstones, which have a relatively weak reflection response, would be detectable on seismic data in the presence of the surrounding strong coal reflections.

In order to investigate the detectability of such thin sands, 1.5D seismic modelling was performed for three typical thin sandstones delineated by drilling on the flank of the Moomba High and Daralingie Shelf. The models were varied by adding or removing the sand, varying the section thickness, and varying the coal distribution to examine the effect on the seismic response. By comparing the outputs, the conclusion has been reached that variations in reservoir sandstone thicknesses cause observable amplitude changes on synthetic seismic data. However, a detailed knowledge of the local geology will be needed to interpret such changes. Furthermore, real seismic data is contaminated by noise, and in more cases than not the expectation would be that the detection of thin bed sands would not be possible unless the sand amplitude variations were marked.