Analysis Of Elastic Wave Propagation Characteristics In Formations With Fluid Saturated Porous Media

The subject is supported by National Nataural Science Foundation of "The theoretical research on the fine detection of reflective channel wave in coal seam based on continuous source".The purpose of this thesis is to study and analyze the propagation characteristics of elastic waves in fluid-saturated porous media and to provide the basic theoretical support for the exploration of elastic wave in actual coal measures strata in the fund project.Porous media contain more parameters to describe the properties of strata,so compared with single-phase elastic media,the strata containing porous media are closer to the actual structure of strata,so they can be widely used in coal measures strata exploration.At present,the research on the theory of porous media mainly focuses on the BISQ model and the improved BISQ model.The BISQ model and the improved BISQ model always study the elasticity from the perspective of a single pore when discussing the elastic wave wave equation of porous media.This thesis attempts to analyze the elastic wave propagation characteristics of fluid-saturated porous media formations from the perspective of the entire formation by establishing a simulation model.In this thesis,the channel characteristics of porous media formations are studied.The reflection,transmission and refraction of elastic waves between the solid framework of the porous media and the fluid interface are analyzed.The propagation attenuation,dispersion and group velocity of the porous media channel are studied.This provides a theoretical basis for analyzing the propagation of elastic waves from the perspective of the entire formation.Then,by studying the theory of elastic wave propagation in porous media,the relationship between stress and strain,strain and displacement,stress and displacement in porous media is deduced.The relationship between physical properties of porous media and the effect of solid skeleton on elastic wave propagation are analyzed theoretically,and the waveguide effect of elastic wave propagation in porous media is studied.Finally,based on the perfect matching layer(PML)absorption boundary condition,the elastic wave propagation in the infinite layer is simulated.Using the COMSOL Multiphysics multiphysics modeling and simulation software,the fluid saturated pore medium layer is established based on the improved BISQ theoretical model.The three-dimensional simulation model is used to analyze the influence of fluid-saturated porous media with different porosity,solid skeleton permeability and fluid viscosity on elastic wave propagation,and the influence of waveguide effect in porous media is compared and analyzed.The research in this thesis is beneficial to the elastic wave as the main means of detecting the formation structure,has certain guiding significance for coalfield exploration and seismic exploration,and can contribute to the further development of the formation exploration field.