Presurvey Design and Acquisition

When borehole seismic data is acquired in conjunction with surface seismic data, a typical geometry is to have an array tool clamped downhole and have the vessel stream in a series of parallel lines over a grid. For a stand-alone 3D VSP survey, however, spiral patterns are the preferred sailing geometry. This technique enables continuous source shooting, and acquisition downtime while the vessel turns at the line ends is eliminated. On land, a source arrangement on the surface is sometimes preferred.