Sparse 3D marine seismic surveys


1. Sparse 3D surveys are widely accepted for land data acquisition. It greatly reduces acquisition cost while achieving imaging objectives. The flexible GNS™ acquisition technology removes restrictions for streamer offshore surveys and allows to acquire sparse 3D data not only at land, but at sea.

2. In the areas with azimuthally anisotropic subsurface the acquisition geometry design can orient the array along a geological strike. Wide line spacing with fewer receivers and fewer number of shots means lower acquisition expenditures. The acquired network will have different shot and receiver spacing along acquisition lines (for instance 25x200 m). Such sparse geometry data shows good results at the West Siberia exploration targets (with 50x400m bin size and 12 fold).

3. Performing sparse 3D with low fold we will need fewer GNS™ SPNs, and they can fairly quickly be deployed over a large exploration area.


When sparse 3D is effective and provides good results:


1. Imaging of relatively deep targets requires wide-aperture (up to 10 km) and multi-azimuth data;

2. CDP bin size is selected according to frequency and maximum dip of target horizon to avoid migration aliasing. Various dips of target beds in orthogonal direction allow utilization of asymmetric bin. Modern algorithms provide imaging of the geological objectives basing on seismic data with asymmetric bin pattern up to 1:4;

3. Fast simultaneous coverage of a large area, which is very important in Arctic sea highly dependent on ice and weather conditions and logistical constraints.