Deep-Water Ocean-Bottom PP and PS Modelling to Optimize Future Acquisition Parameters

With nodes replacing cables in ocean-bottom systems, the flexibility of the receiver layout and how far to push its sparsity is regularly revisited. In a deep-water environment in which the nodes must be individually placed using a remotely operated vehicle, reducing their number is desirable to constrain the survey cost. While planning a future ocean-bottom node (OBN) survey in deep water, we evaluated the impact of the layout sparsity and extent on the seismic image quality in order to optimize the acquisition geometry.

Compared with conventional towed-streamer surveys, OBN surveys have several advantages: a rich content of azimuth and the ability to record converted waves (PS data) in addition to the P-wave. PS data have long been recognized to provide improved images below shallow gas. Recent examples have confirmed the uplift and are one reason behind the increasing demand for seabed acquisition.

In the current study, we modelled several OBN layouts using a combination of elastic finite-difference modeling and ray tracing to understand the impact of wavefield sampling on the image produced by PP and PS data, and the effect that the gas has on the amplitudes at reservoir level.