The Research Of Method To Suppressing Ghost Wave Based On Boundary Value Inversion In Variable-depth Streamer

The most common method is to sink the receiving cable to a constant depth in the acquisition of seismic data on the ocean.The shortage of this method is that the frequency of the seismic data is serious trap effect,and the notch trap frequency is fixed.Therefore the method of seismic data acquisition of variable depth cable is introduced first in order to obtain the wideband seismic data.Variable-depth streamer seismic data acquisition is a kind of acquisition method that the depth of the streamer increases gradually with the increase of offset distance.The seismic data obtained by using the variable-depth streamer can give consideration to the both high and low frequency information to broaden the frequency band.However,the seismic data obtained by this method are more seriously influenced by the ghost wave.Ghost waves are the accompanying waves generated by the reflection of the sea surface in the seismic data,also known as virtual reflection.The existence of ghost waves can generate notch effect in frequency domain and reduce the frequency band of seismic data In serious cases,it can even produces false coaxial axis to increase the difficulty of interpretation of seismic data.This paper researched the method based on boundary value inversion to suppressing ghost waves in Variable-depth streamer.The method firstly sets a datum in depth below the maximum depth streamer then the propagation of the wave field on the datum surface is divided into two parts,which are transmitted directly to the receiving cable,and the other part is reflected by sea surface first and then propagated to the receiving cable.The seismic wave field that received on the cable will contain ghost waves.The method of suppressing the ghost wave is to use the iterative inversion method to obtain the boundary value of the datum,and thus the value is the seismic data after the ghost wave is suppressed.This method can effectively suppress ghost wave in the seismic data of Variable-depth streamer and improve the frequency band width of seismic data.Through simple model,complex model and actual data processing,this paper proves that this method can effectively suppress the ghost wave in the seismic data of Variable-depth streamer.