The Research Of Attenuation Mechanism In Multiphase Media Based On General Liner Solid Model

Due to the inelasticity of the Earth materials,the dispersion and attenuation of seismic wave occur when it propagates.The research on the dispersion and attenuation mechanism of seismic wave has always been a difficult and central issue in seismic exploration.The commonly used attenuation models include fluid flow model and viscoelastic model.The two kinds of attenuation models reflect different attenuation mechanisms with different angles,different frequency bands,different scales and different fluid distribution,so they are different under the same theoretical framework.How to build a unified theoretical framework is of great significance to explain the dispersion and attenuation characteristics of seismic waves in rock.In this paper,based on Biot poroelastic model,energy is used to describe the mechanical system,Lagrange function L is used to describe the dynamic characteristics of the conservative system,and dissipation function D is used to describe the effect of converting dynamic energy into thermal energy,which is equivalent to an external friction acting on this conservative system.The motion equation of elastic wave in fluid saturated porous media is reconstructed with displacement vector matrix and elastic parameter matrix of solid phase and fluid phase.Based on this mechanical system,firstly t,he internal friction effect caused by microscopic and mesoscopic fluid flow is regarded as the viscosity coupling between the rock skeleton and the fluid in hard pores,and these non-macroscopic fluid flow effects are characterized by adding the equivalent macroscopic viscosity matrix term in the dissipation function D.Then,define the observable deformation parameters and multiple internal defor mations as well as their coupling parameters,so that the viscoelastic effect of solid is characterized by expanding the elastic parameter matrix and viscous parameter matrix.By adding the macroscopic equivalent parameter term or expanding the dimension of parameter matrix,the Biot poroelastic model is extended to General Liner Solid Model,and the expansion and extension of Biot poroelastic model is realized under the framework of Lagrangian continuum mechanics.This General Linear Solid Model integrating fluid flow theory and viscoelastic theory can describe squirt flow model,mesoscopic wave induced fluid flow model and viscoelastic model,which provides a theoretical basis for the study of the attenuation mechanism of elastic waves in multiphase media.In order to verify the validity of the General Liner Solid Model,by introducing the equivalent squirt viscosity matrices ηK and ημ,the model was compared with two different types of BISQ models and Tang model in the 1 k Hz frequency band,which shows the rationality and interpretability of the General Liner Solid Model.Based on this model,the core data of sandstone samples from an oil field in the east of China under different saturation and pressure in the 10-1000 Hz frequency band was tested and fitted in the laboratory,and the parameter modeling is carried out under the framework of General Liner Solid Model combined with rock physical characteristics.The numerical results are in good agreement with the experimental data,which shows that this model can effectively and reasonably explain the experimental data under different water saturations and effective pressures.