Research On Elastic Wave Propagation In Multi-scale Porous Media

Oil or gas reservoirs and subsea media are typical porous media.Seismic exploration and acoustic detection technologies are important means of oil and gas resource exploration and subsea investigation,respectively.The dispersion and attenuation of elastic waves are particularly prominent in the wave propagation process of porous media,and are important attributes for oil and gas seismic prediction and acoustic inversion of seabed bottom parameters.Therefore,it is of great scientific and practical significance to study the law of elastic wave propagation in porous media.The main reasons for the dispersion and attenuation of elastic waves during the propagation in porous media are caused by the relative movement of solid and fluid phases in porous media,which include macroscopic global flow,microscopic squirt flow and meso-local flow.In this paper,we integrate the effects of three-scale fluid flow in porous media on elastic wave propagation into the same theoretical model.The model equivalently represents the pore medium as a"cross-shaped"structure,consisting of a solid skeleton and two types of pore fluids,where the inside and outside of the"cross-shaped"are saturated with different fluids,respectively.Based on the dynamics mechanism,we derived the basic potential energy,kinetic energy,and dissipation function of the model,and obtained the wave equation of the model.We calculated the complex wave number of the elastic wave by plane wave analysis method,and obtained the solutions of the three types of wave velocities and inverse quality factors.Finally,through numerical calculations,we analyzed propagation characteristics such as elastic wave propagation speed and attenuation under different parameters.The frequency range of oil and gas seismic exploration is generally between 5Hz and 2kHz.The frequency of elastic waves used in submarine acoustic detection technology is generally 5kHz to hundreds of kHz.Therefore,in this paper,we study the dispersion and attenuation characteristics of elastic waves with different physical parameters in the frequency range from 1 to 10~8Hz.