Shooting over the seismic spread

Conventional marine seismic surveys typically mobilize a single vessel towing two airgun source arrays in front of a spread of ten or more streamers. The data acquired in this way are narrow-azimuth and lack near offsets owing to the distance between the sources and the streamers which can be in the range of 100 to 200 m for the inner cables and up to 500 m for the outer cables. Several solutions, such as coil shooting (French, 1984; Ross, 2008) or advanced multi-vessel operations (Mandroux et al., 2013), have been proposed and deployed to improve azimuth coverage and fold. Although these are excellent solutions for achieving wide-azimuth data, they are generally expensive and/ or time-consuming, and none of them record zero-offset data. Near- and zero-offset data are, however, especially critical for imaging shallow geological targets and of great benefit for multiple attenuation. In this paper, we present a tailored solution to this challenge that allows the recording of both zero-offset data and dual azimuths in an effective and safe way. We call this acquisition solution TopSeis. This solution was created in close co-operation between Lundin Norway and CGG and is designed to deliver excellent broadband (2.5-200 Hz) imaging of shallow to intermediate targets at depths of up to 3000 m or more.