Abstract

AbstractA processing method is presented to attenuate the surface ghost using marine twin streamer data. It is an extension to the dephase and sum method which corrects for the phase of the ghost in both streamer outputs and then adds them in an attempt to fill the notches in the amplitude spectrum. The method presented corrects both the phase and the amplitude effect of the surface ghost by combining both signals as a weighted sum.This method is applicable to all types of twin streamer data, ranging from deep exploration data to very shallow high‐resolution surveys. Both the synthetic and real data examples shown are of the high‐resolution type, using frequencies above 2 kHz and short streamers (active sections of the order of one metre).Both the dephase and sum method and the weighted sum method are applied to synthetic high‐resolution data and the results are compared. This has been done for noise‐free data, data with a high noise level and data with strong geometrical spreading on the ghost reflections. From these test results it can be concluded that in general the weighted sum method gives better results. The improvement in the signal‐to‐noise ratio appears to be the same, due to the additive character of both methods. In the case of high‐resolution twin streamer data recorded in shallow water, the delay time of the ghost reflection can be of the same order of magnitude as the traveltime of the primary. For this situation, geometrical spreading can have a considerable effect on the amplitude of the ghost reflection. If no correction can be made for the spreading function, it might be better to use the dephase and sum method.Both methods are also applied to a real data set recorded in a high‐resolution survey. Because the ghost delay is of the same order of magnitude as the arrival time of the primary, the ghost reflection is strongly affected by geometrical spreading. Since the spreading function of the source is unknown, it cannot be corrected for. This causes the result of the weighted sum method to be less reliable compared to the case where no spreading is involved.

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