OFF-END SEISMIC DATA ACQUISITION IN THE EROMANGA BASIN

Abstract

During late 1988 and early 1989 Shell conducted a land seismic survey in permit ATP 267P in the Eromanga Basin, in fulfilment of farm-in obligations. Against traditional wisdom in the Eromanga Basin Shell decided for an off-end acquisition geometry.

An acquisition geometry design rationale is presented which leads to an optimum stack response. Depending on geological and economical constraints on maximum offset and shot and receiver station spacing this may result in either a split spread or an off-end geometry.

For Shell's Eromanga seismic campaign it was decided that, given a 120 channel seismic recording instrument, an off-end spread with 15m source and receiver station spacing and 1800 m maximum offset presented the best compromise between optimal achievement of exploration objectives and available resources.

For comparison an 8 km portion of a nearby 1988 centre spread line was overshot using the off-end technique, and was processed by the same contractor with a similar processing sequence. The improvements in data quality obtained demonstrate that off-end data acquisition is a viable technique which can be optimally suited to meet lateral sampling and noise suppression requirements.