The Research Of Shallow Water Multiple Elimination Processing

Multiple attenuation is always one of the most important problems in marine seismic data processing.If the multiples are not eliminated well,it will seriously affect the authenticity of seismic profile imaging.In the marine data,the sea surface and the seabed are two strong reflective interfaces.The strong multiple waves will be formed by the concussion between the seismic waves,which will seriously affect the accuracy and characteristics of the seismic section imaging.In deep water conditions,multiples are usually long periods,so there is a great difference in time difference and velocity with primary,which is easier to identify.However,in the shallow waters,usually less than 200 meters,the seabed related multiples and primary waves will interfere with each other together,or even conceal the primary reflection.The traditional free surface multiple attenuation method(SRME)uses the data convolution method to predict the multiple wave model,the premise is that the acquisition data records the complete information.For deep water seismic data,this method can better attenuate multiple waves.However,in shallow water,because the time difference between the seabed primary and the direct wave is very small and overlaps interference,it is difficult to identify primary seabed reflection.The minimum offset of the seismic data from the towing cable of the sea is usually more than 150 meters,and the seafloor's primary can not be identified on the minimum offset channel.It is difficult to predict the seafloor multiples due to the difficulty of obtaining the seafloor's primary reflection.Therefore,it is difficult to effectively suppress the short periodic multiple wave of shallow water seismic data by using the conventional SRME method.A better prediction method of seafloor multiples is studied in this paper,and a set of easy and effective shallow water surface free surface multiple elimination technology is formed.In this paper,the characteristics of the seabed multiple wave in shallow water seismic data are analyzed.The principle and problems of SRME free surface multiple elimination method are analyzed and discussed.The key to predict seafloor related multiples in shallow water is to reconstruct the seafloor's primary reflection.In this paper,the Green function method is used to reconstruct the seafloor reflection.After that,the seafloor related multiples model is predicted by convolution with the original seismic data,and then multiples are subtracted from the original data.The simulation data and actual data are used to test and verify,and good results have been achieved.The method of this paper:(1)It is suitable for shallow water seismic,can better eliminate seafloor related short period multiples.(2)it can be used in combination with other multiples attenuation methods such as de-convolution,SRME,Radon transformation and so on.(3)Data driven,with better amplitude protection,only need water depth for the prior information.