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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association

Abstract


IPA-AAPG Deepwater and Frontier Symposium, 2004
Pages 39-49

Seismic Previous HitFrequencyNext Hit Bandwidth Constraints in Deepwater Locations

Andrew Long, Iain Buchan

Abstract

Deepwater environments typically involve an undercompacted overburden with low quality factor (Q) values associated with high rates of anelastic seismic attenuation. Rugose water bottom characteristics and complex stratigraphic styles collectively yield surface seismic data that has a small Previous HitfrequencyNext Hit bandwidth and a poor signal-to-noise content.

A common misconception associates shallow seismic source and streamer towing depth with increased high Previous HitfrequencyNext Hit amplitudes, larger Previous HitfrequencyNext Hit range, larger Previous HitfrequencyNext Hit bandwidth, and hence, better vertical and lateral resolution. We show how this misconception arises, and provide a quantitative demonstrate of the true factors affecting Previous HitfrequencyNext Hit content in deepwater seismic data.

Overall, any pre-survey decision on source and streamer depths is a compromise between the pursuit of maximum Previous HitfrequencyTop bandwidth (shallower source and streamer depths) and useful/recoverable S/N ratios in the data (deeper source and streamer depths), allowing for all possible noise mechanisms and operational constraints. It is unsurprising that the experience of the seismic industry in deepwater or high attenuation areas has consistently endorsed deeper rather than shallower source and streamer depths for yielding optimal data quality. As demonstrated in a deepwater 3D seismic example from the Philippines, the use of tight spatial sampling in both the inline and cross-line directions (i.e., the use of high-density 3D acquisition) is critical to avoid the loss of recorded high frequencies during processing, and to avoid noise and artifacts degrading both resolution and image quality. Furthermore, significant increases in trace density per square kilometre translate to significant increases in image quality, S/N ratio, and resolution.


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