TopSeis - shooting over the seismic spread

In this paper we present a new source-over-cable marine seismic acquisition technique that initially was developed to meet imaging challenges of the Loppa High in the Norwegian Barents Sea. Two seismic vessels operate in tandem; one streamer vessel towing a spread of deep, densely spaced streamers, and one source vessel with two or more sources. The source vessel is shooting on top of the seismic spread which facilitates acquisition of zero-offset, as well as split-spread data. This creates a unique illumination of the subsurface, especially in the shallow but also to intermediate target depths. The solution has been developed and tested in close cooperation between CGG and Lundin through a comprehensive modelling and field trial program involving a series of safety and mechanical tests and also a small 3D test survey.