Numerical Simulation And Attenuation Characteristics Of Wave Field In Viscoelastic Orthotropic Porous Media

As the nation's demand for oil and gas resources continues to rise,seismic exploration targets have gradually shifted to thin interbedded,fractured,and other complex reservoirs.Previous elastic media theory has failed to provide a reasonable description of the effects of actual formation media on seismic wave propagation..The actual earth reservoir medium is often very complicated.The medium composition not only contains the solid skeleton,but also the medium generally has pores.Because the pores are filled with various fluids,it has a significant impact on the propagation characteristics of seismic waves.Therefore,it is very important to carry out research on complex porous media that conform to the properties of the actual reservoir medium.It lays a solid foundation for subsequent seismic exploration and seismic data interpretation.Therefore,based on the predecessor's theory of porous media,this paper establishes an orthotropic media model of viscoelastic porosity and deeply studies the propagation characteristics of seismic waves.The traditional Biot theory is based on the Gassman equation and takes into consideration the frictional losses caused by the relative flow between the fluid in the pores and the solid rock skeleton under pressure gradients.It describes macroscopic phenomena and lays the foundation for the propagation of seismic waves in porous media.The theoretical basis.A large number of subsequent studies have shown that the Biot theory does not provide a reasonable explanation for the strong attenuation and high frequency dispersion of seismic waves in rock media.With the in-depth study of the Biot theory and numerous experiments,it was found that microscopic Squirt jet effects in porous media.It is the main factor that causes the strong wave attenuation and high frequency dispersion of seismic waves.Therefore,the Biot theory and the Squirt injection mechanism are combined to establish a unified BISQ model.Although the BISQ theory better describes the strong attenuation and high-frequency dispersion of seismic waves in porous media,this phenomenon mainly occurs in the higher frequency bands,and the effective frequency bands for seismic exploration are mainly concentrated in the low-frequency bands,so this is related to practical work.There is still a large deviation.In this paper,through the in-depth study of the BISQ theory,the viscoelastic mechanism of the rock solid frame of the generalized Zener linear body is introduced into the BISQ model,and the influence of the anisotropy of the medium is fully considered.An example of orthotropic media conforming to the actual formation media is taken as an example.The wave equations of orthotropic media in viscoelastic pores based on the BISQ model are deduced.By staggered-grid high-order finite-difference techniques,the seismic wave field in the medium is numerically simulated in two dimensions.The viscoelastic mechanism of the solid skeleton,crack parameters,and the influence of the thin interbed on propagation of the wave field are discussed.The wave field snapshots and seismic synthesis records are compared to analyze the effects of various media parameters on wave field propagation.At the same time,by solving the plane wave solution of the model,the equations of phase velocity and inverse quality factor are deduced,and the influence of different model parameters in the seismic frequency range on the propagation of seismic waves in the medium is analyzed.