Research On Internal Multiple Suppression Method Based On Horizon Separation

Multiple is one common noise in seismic data,which can cause false reflection events in seismic profiles,interfering with effective signals and affecting seismic interpretation.Therefore,multiple attenuation is an important data processing step for both marine and land data.Techniques for surface-related multiple elimination have been improving rapidly in past years,however,with the increasing requirements of exploration accuracy and the prominent influence of internal multiples,seismic data processing have to focus on the research of an effective suppression method.In this thesis,the technology of internal multiple suppression is studied on the basis of previous research.Firstly,a theoretical foundation is laid for the internal multiple suppression in this paper by investigating the existing research results,understanding the relevant theoretical knowledge of multiples,and summarizing the existing methods of multiples suppression.Then the theory and formula derivation process of the WRW model and the surface-related multiple elimination(SRME)method are introduced,on which the calculation formula of the internal multiples prediction based on horizon separation is extended from SRME.Three primary wave fields are separated from the surface data to directly predict the formation horizons of internal multiples,which has advantages of high computational efficiency and less prior information.In order to solve the problem of data separation in this method,an improvement was made on the basis of seismic DNA horizon picking method,in which the gene bank was established by double fivepoint sampling,and the secondary window cross-correlation algorithm was used to identify and connect the same events,so as to avoid the manual setting of searching genes and improve the accuracy of data separation.Finally,an adaptive subtraction method based on 2D blind separation of convolved mixtures(BSCM)to suppress internal multiples is adopted,whose optimization objective is to maximize the non-Gaussian properties of primary waves without orthogonality assumption of primary and multiple to protect primary and subtract internal multiple.According to the geological structure related to the generation of internal multiples,this thesis simulates the marine salt dome model,the low-velocity coal seam model and the western region model.The processing results of the model and actual data show that the method of internal multiple prediction can effectively predict internal multiple of the multiple generating horizon by using the separated surface data.At the same time,it is verified that the adaptive subtraction method based on 2D BSCM can suppress the internal multiples and protect the primaries by comparing different adaptive subtraction methods.