Processing Through to Stack in the τ-ρ Domain

Abstract

Improved seismic sections can be obtained by processing through to stack in the τ-ρ domain. This approach provides significant improvements over routine processing, using hyperbolic velocity filtering (HVF) to suppress the τ-ρ transform artefacts. HVF is a form of time and offset variant filtering that only allows each point in the t-x domain to contribute to a small number of p traces during a τ-ρ transform. HVF can be incorporated into a point-source τ-ρ transform, extending previous implementations that applied HVF during the slant stack. This assists gap deconvolution by providing plane-wave amplitudes in a τ-ρ gather where reverberations are exactly periodic along p traces and where S-wave reflections and long period multiples are suppressed. The τ-ρ domain also offers improved velocity analysis through the use of wide-angle reflections and because primary reflection ellipses never cross each other. The τ-ρ transform of a CMP gather can then be stacked with further advantages resulting from the elliptical moveout correction, which minimises wavelet stretch and approximates the exact reflection traveltime better than NMO. Examples from the Carnarvon and Gippsland Basins confirm that the cumulative theoretical advantages of τ-ρ domain processing are achieved in practice.