High Resolution And Nonlinear AVA Inversion For Pre-stack Seismic Data

AVA inversion which is based on the scattering matrix in layered elastic medium,use non-stack or partial angle stack seismic data,to extract the elastic parameters of the underground rock,so as to realize the purpose of the reservoir prediction and fluid identification.In practical application,there is still existing the following problems:(1)the ability of the inversion result to distinguish the underground geological body is low,and the specific performance is that the vertical resolution is not too high and the formation boundary edge location and geological body can not show clearly,and it is difficult to meet the needs of the small geologic body's seismic and geological description;(2)in the process of AVA inversion,it is often to make some approximation assumptions for the ratio of S-wave velocity to P-wave velocity to linearize the nonlinear AVA problem,for example,it is often takes 0.5.However,in practical application,we often meet the situation that it is not satisfy the assumptions;(3)at present,the prestack seismic inversion which is based on the hypothesis of small jump formation parameters and use the first order approximation of the layered elastic medium scattering matrix,is only applicable to weak reflection interface.When the local layer elastic parameters change is bigger,the inversion method based on the first-order approximate is difficult to get a reasonable inversion result(to adapt the situation when the changes in the elastic parameters become larger).According to the above problem,this paper has done in-depth research on the basis of conventional AVA inversion method.Take the implicit AVF information in seismic data as the complete dictionary of seismic signal representation and introduce these AVF informations into the inversion and make full use of the amplitude of seismic data in every change with frequency information,especially in high frequency and low frequency information to improve the resolution of inversion.By introducing the total variation regularization constraint,we can get an inversion result which can show the formation boundary edge location and geological body clearly.Regard the velocity ratio as an unknown quantity,and take the nonlinear inversion method and strategy to solve the problem that the ratio does not meet the constant assumptions.Using series expansion,we infer the expression of high order approximation for scattering matrix.It breaks the limitation of conventional pre-stack seismic inversion due to the assumption of small elastic parameter contrasts.