ghost reflections and reverberations that occur before the seismic energy is reflected by the target geological structure. (Indeed it will be noted that the path of seismic energy shown in FIG. 2(d) does not involve a reflection by the target geological structure.) Ghost reflections and reverberations can also occur after the seismic energy has been reflected from the target geological structure, and these are known as receiver-side ghost reflections or reverberations.

 

 

F. J. Barr and J. J. Saunders have proposed, in a paper presented at the 59th SEG Meeting (1989), a method of attenuating ghost reflections and reverberations by recording the reflected seismic signal using two different types of seismic receivers, namely using both hydrophones and geophones. The up-going wave field is recorded by the hydrophone and the geophone with the same polarity, while the down-going wave field is recorded by the hydrophone and the geophone with opposite polarities. The difference between the signal recorded by the hydrophone and the signal recorded by the geophone allows the up-going wavefield to be separated from the down-going wavefield.

An alternative method for attenuating ghost reflections and reverberations is to use two receivers located at different depths. This method is based on the principle that waves travelling in different directions will have spatial derivatives of different signs, so that comparing the signal obtained at one receiver with the signal obtained by the other receiver will allow the up-going wavefield to be separated from the down-going wavefield.

These prior art methods separate the up-going and down-going wave fields at the receiver location. That is, they attempt to remove the ghost reflections and reverberations that arise after the seismic energy has been reflected by the target geological structure. This is known as receiver-side deghosting. These prior art methods do not, however, address the problem of the ghost reflections and reverberations that occur before the seismic energy is reflected by the target geological structure.

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