Near-surface seismic expression of gas chimneys in the Perth Basin

Abstract

Shallow anomalous high speed events, evident on the shot gathers, are observed to be associated with gas chimneys in the Central Perth Basin. Shot gathers in the vicinity of gas chimneys display these events, which have apparent speeds of around 3000 m/s in the uppermost 300 ms, and appear to localised around the gas chimneys. These high speed events have been investigated using existing seismic data from the region, with these high speed events modelled using wide aperture seismic (WAS) techniques. Understanding the effect of these shallow high speed layers is important for the following reasons - 1. they may provide support for a petroleum prospect; 2. they may represent a possible geohazard during drilling; 3. these high speed layers can have a profound effect on the seismic imaging of the underlying strata.