A SEISMIC AMPLITUDE VERSUS OFFSET STUDY IN THE SOLE AREA, GIPPSLAND BASIN

Abstract

Analysis of amplitude versus offset (AVO) variations in shallow reservoirs can be a powerful tool, and has been used to determine the nature and distribution of hydrocarbons in the Sole area.

The Sole-1 well was drilled in 1973 on the northern margin of the Gippsland Basin. The well encountered a 16 m dry gas column at the top of the Latrobe Group, within a fault-bounded anticline.

Seismic line GS88B-97 was acquired in 1988 over the crest of the Sole Anticline. A dipping reflection event cross-cutting the geological structure was interpreted as a reflection emanating from the base of the gas column. Structural interpretation is ambiguous at the field's northern bounding fault and potential was recognised for a significant extension of the field northwards.

An AVO study comparing variations in measured reflection amplitudes on common depth point (CDP) gathers and substacks with modelled results has been successful in unambiguously delineating the field extent and shows that the field is bounded to the north by the main fault. This successful use of AVO techniques at Sole has permitted a more precise estimate of gas in place and has potential for application to other accumulations along the northern margin of the Gippsland Basin.