Repeatability of 3-D ocean-bottom cable seismic surveys

Recent advances allow time‐lapse 3-D (sometimes called 4-D) seismic surveys to map gas‐oil and oil‐water contacts. Some have used “legacy” 3-D data (i.e., data not originally acquired for a 4-D study) and found that the varying quality of the different vintages of the data limited the resolution that could be attained. How then, do we best carry out acquisition and processing for a 4-D seismic program so that the data are repeatable to the extent that differences are attributable to movement of the reservoir fluids and not to the acquisition, processing, or other factors?