The Research Of Model-based Water-layer Demultiple

Multiples' problem has always been one of the important problem in seismic data processing,in Marine seismic exploration,multiples' problem is more obvious.If the multiples are not be identified and suppressed,the subsequent processing of seismic data and the results of explaining will be affected seriously.Therefore,how to suppress multiples effectively and preserve primary reflection is an important subject in Marine seismic data processing.In Marine seismic data,water-layer related multiples are the most domainant interference wave,we can use conventional SRME method which convolutes the original data to predict multiples,and using the method of adaptive subtraction to suppress multiples.In the shallow-water,due to the lack of near-offset data and effective reflection information which cause that this method can not obtain ideal suppression effect.First,this article expounds the development present situation of the multiples' suppression technology and demultiple methods systematically,including filtering and wave-equation method,analyzes the principles of various and problems,then focuses on the method of surface-related multiple elimination(SRME).The method of SRME convolutes the original seismic data to predict multiples,but due to its own defects and shortcomings that restrict the application of this method in the shallow water.This article mainly studies the model-based water-layer demutiple method(MWD),this method is the improvement of SRME method,according to the water-layer model to construct the green's function and convolute raw seismic data to predict multiples so as to the suppress the multiples,this method can effectively make up for the inadequacy of SRME method,and shows a great advantage in the water-layer(especially the shallow water)multiples' prediction.In addition,this article studies the method of adaptive subtraction,including the single channel matching method based on the principle of least squares,multi-channel matching method and the method of curvelet transform,then derives the formula and analyses the theory.I test the algorithm through simple submarine model,complex seabed model and real dataset on the sea.First I predict the multiples with the MWD method,as we can see,MWD method can predict the water-layer multiples accurately,but there are certain differences between the predicted multiples and the original seismic record,such as time,amplitude,phase.Then the predicted multiples are cut from the original data,the primary reflection and multiples are separated performly.The processing results show that this method can effectively attenuate water-layer related multiples in shallow water.Finally,I develop the software module based on the Qt platform on the procedures of the algorithms in this paper,then it is easy to apply and promote in the future.