3D marine streamer seismic surveys frequently have excess coverage; for example, in areas where the recorded data from different sail lines overlap as a result of streamer feathering, where infill lines have been acquired, or where an overlapped acquisition strategy is being pursued.
Excess coverage on a single 3D survey is conventionally handled by selecting the traces that best meet certain criteria, such as how close the midpoint is to bin-centre, or how close the azimuth is to the survey azimuth.
4D binning extends this concept by comparing simultaneously the coverage on a pair of time-lapse surveys. The procedure chooses the survey-to-survey trace pairs that are offer the best repeatability according to user-selected similarity criteria such as the most similar midpoint location, azimuth, offset, source / receiver location, or the minimum sum or average of the distance between the sources and the distance between receivers. Such trace selection based on appropriate similarity criteria can significantly improve the repeatability of time-lapse seismic datasets.
WesternGeco has recently enhanced its 4D binning technology to allow the display of multiple QC attributes. This provides the ability to easily evaluate the effect of different selection criteria and give an objective measure of how well surveys have been repeated.
The same 4D binning routines may now be used online during acquisition of a monitor survey to evaluate how well the baseline is being repeated. The effect on repeatability of proposed lines can be tested before they are acquired, so maximizing acquisition efficiency. Because the onboard QC software is identical to that used in WesternGeco seismic processing centers, we can be sure that decisions made during acquisition will be honored during subsequent 4D processing.
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