Finely sampled 3D angle gathers from sparse OBN data

Abstract

Large-scale deepwater ocean-bottom node (OBN) surveys typically use a node spacing of about 400 m. We make 3D angle gathers from OBN data by mapping image traces to the reflection azimuth and reflection angle domain. Large node spacing may coarsely sample the seismic data in these angles. This may result in degraded and noisy angle gathers unless we properly account for the sampling during processing. We describe a method for making high-quality 3D angle gathers on finely sampled angle grids. We do this by properly band limiting the mapping operator with sinc functions defined in the angle domain. This method allows us to oversample the 3D angle gathers accurately in the angle domain and obtain high-quality results. We demonstrate our method with deepwater Gulf of Mexico node data and show that we can produce high-quality gathers even with 800 m node spacing. The angle gathers derived from these wider node data preserve residual moveout and therefore are suitable for model building. Our results add confidence that data acquired with nodes spaced farther apart than 400 m can be processed and imaged successfully.