Publications

One objective for acquiring multi-azimuth seismic has been said to be improved illumination. We attempt to acquire regularly sampled data at the surface, but due to velocity overburden and raybending the effective coverage or illumination is less regular at our target. Some examples published in the literature indicate that parts of our target surface may only be visible from specific sourcereceiver azimuths. Ray-tracing was applied to a real data model and acquisition configuration to investigate illumination at the target horizon. The result is intuitive: - structure in the shooting direction is illuminated best and is shadowed when shooting perpendicular. Areas with no illumination i.e. that were in the shadow zones of structural hills will remain low amplitude even after prestack depth migration. The only way to gain amplitude information in these areas is to acquire data which illuminates them.A second objective proposed by Keggin et al was multiple diffraction attenuation. This aspect can become significant in areas where residual-multiple energy left after processing is of similar or higher amplitude to primary reflections. The concept is that primary reflection data will tend to add constructively and the diffraction multiple cancel.It turns out that in order to address both these objectives, a regularly sampled input is preferable, and this needs to be taken into account while acquiring multi-azimuth data. With multi-azimuth acquisition, this includes regularly sampled sourcereceiver azimuth. An added benefit of regularly sampled azimuth is the potential to measure and correct for azimuthal anisotropy.