A New Approach to Efficient 4D Acquisition

To acquire good 4D it is important to repeat acquisition parameters and especially the baseline’s source and receiver positions. If one cannot compensate for feather one will have to shoot 4D infill, which adds to the cost of the monitor survey. We present a novel approach to pre-plot planning and positioning QC during acquisition. From analysis of the baseline’s post-plot data for unique coverage contribution of each source-receiver pair and using a field specific tolerable positioning error we derive uniqueness criteria. Lines not matching these criteria will be removed from the pre-plot. From analysis of the baseline data we define how much feather deviation we can tolerate and introduce a robustness criterion, the feather aperture. All pre-plot lines for the monitor survey will now have an associated, line specific, feather aperture value. The feather aperture concept assists in choosing lines with a wide feather aperture for periods of unpredictable currents and can also help to reduce time spent waiting on unnecessarily tight feather matching criteria. This paper shall demonstrate a technique that should change 4D QC and also significantly improve acquisition efficiency.