A SEISMIC MODEL OF FAULTS IN THE COOPER BASIN

Abstract

A synthetic seismic section was modelled to help in the interpretation of Cooper Basin seismic lines which cross major faults and exhibit shadow zones.

A major fault bounding the northwest flank of the Packsaddle Structure in the Merrimelia-Innamincka Farmout Block in South Australia was selected for modelling. A geological cross-section postulated on the basis of wells on either side of the fault was fed into the seismic modelling package AIMS (Advanced Interpretive Modelling System — licensed by Geoquest International Inc.) to produce a synthetic seismic line. This synthetic line provided a realistic match with an actual seismic line across the fault. Pre-stack migration of the actual seismic data is suggested to provide additional evidence for the reliability of the model.

The shadow zone in the synthetic section is caused by dipping events in the fault shadow zone created by compaction of the Toolachee and Patchawarra Formations along the hanging wall of the fault plane. The dipping events cause reflected energy to be detected outside the fault zone. The large component of compaction within the Permian section is largely ascribed to thick coal horizons. The possibility of petroleum traps in the hanging wall of the fault is inferred and drilling is recommended.