Conventional 3D marine acquisition records a limited subset of the reflected wavefield because of its narrow range of source-receiver azimuths. This method of recording just a small percentage of the total wavefield provides limited illumination and resolution.
On the other hand, land and seabed acquisition have sometimes used wide-azimuth geometries but only at the expense of large spacing of either shots or receivers, or both. This coarse sampling can lead to an aliased representation of the wavefield and hence noisy and misleading images of the earth.
To achieve an optimum image of the sub-surface, we need both wide-azimuth recording and sufficiently dense sampling to obtain a full representation of the seismic wavefield. In the marine environment, CGGVeritas' Wide Azimuth (WAZ) recording provides this by using a wide array of receivers for every shotpoint; for land and seabed surveys, our technology provides dense shotpoint sampling designed to sample the wavefield adequately. A good analogy is the use of very large arrays for radio telescopes that give unparalleled, high-resolution images of outer space.
Benefits:
- More accurate imaging of the sub-surface
- Improved signal-to-noise ratio
- Improved fracture and reservoir characterization
Think of the shot as analogous to dropping a stone into a pond. The waves propagate outwards in all directions and if we want to record the whole wavefield adequately we must have receivers over the entire area. Conventional 3D surveys record only a narrow off-end swath (illustrated by the yellow box above). This is a poor representation of the wavefield, typically sampling only about 5-10% of the total energy from the sub-surface.
