Sub-basalt Multiple and Noise Suppression Using a Dense, Marine Wide-azimuth Recording Geometry

A dense, wide-azimuth marine seismic line was recorded in the W. Shetland region of the Atlantic Margin starting in an area with no basalt and extending over an increasing thickness of basalt. Conventional seismic surveys have found difficulty in imaging beneath the basalt because of strong and complex multiple generation, scattering of energy and attenuation of signal frequencies above approximately 20Hz. The azimuthal diversity of a well sampled wide-azimuth stack provides an additional means of suppresssing both multiples of dipping events and short wavelength scattered energy. The shot line spacing was 100m thus providing symmetrical offset samppling within CMP gathers. This is much denser than production wide-azimuth surveys in the GOM. On-board stacks of the wide-azimuth data show significant suppression of the multiples and noise compared to a 2D stack. Procecssing tests show that this is primarily caused by azimuthal diversity rather than increased fold or non-linear offset distribution