AVO polarization attributes and hodograms.

Abstract

A case study using seismic data from the Gorgon field of the NW Shelf of Australia is done to validate the methodology. Application of this new scheme can help one recognize AVO anomalies and enhances AVO interpretation.

New attributes resulting from this methodology include (1) the polarization angle, (2) the polarization angle difference, (3) the AVO strength, (4) the linear-correlation coefficient, and (5) the product of AVO strength and polarization angle difference. These different attributes can then be used to enhance or to show the AVO effects for any given event on of a seismic trace (seismic section). The results obtained from a flat-layered model made of a succession of gas and brine sand layers encased in shale units are shown. Processing and wave propagation effects, and thin-layer modeling are also investigated.

An alternative approach to identifying AVO anomalies is to consider the AVO polarization in the intercept-gradient (A-B) plane. This method does not require deviations or separations from a background trend exhibited in traditional crossplots such as intercept-gradient (A-B) or near trace-far trace (N-F). A benefit of the hodogram or polarization method is that the wavelet is taken into consideration as it is convolved with the reflection coefficient series. Crossplotted intercept and gradient are polarized along a "background trend" for non-anomalous events and at angles different from the "background trend" for anomalous events.