3D surface-related multiple prediction offshore Australia

Experience coupled with technology enables innovative solutions for extremely challenging situations. In a recent survey offshore Australia, water layer multiple attenuation was required to meet the survey objectives. However the acquisition configuration did not allow the water bottom to be imaged due to 30m water depth and a 240 meter near offset. This would normally prevent the successful application of either 2D or 3D SRME approaches.

In addition geology produced significant interbeds due to the presence of coal beds at various depths. This situation indicated that traditional tau-p deconvolution approaches could potentially harm the seismic signal. Furthermore, the downward reflection points of the multiples were often laterally offset from the cable, indicating a full 3D approach was necessary.

WesternGeco analyzed the geophysics and applied a novel 3D-SMP workflow to the entire (>1,000km²) survey area using several complimentary demultiple methods. Their combination provided a demonstrable improvement by reducing remnant multiple energy (water-layer multiples and interbeds generated by the sea floor) while leaving the signal relatively unaltered. This workflow performed significantly better than other, more traditional demultiple applications that were tested.

The result was an enhanced structural image with reduced multiple contamination across the reservoir interval.