Reflection And Refraction Of Elastic Wave And SH Wave In Layered Porous Media Based On Virtually Enlarged Pore Acoustic Model

Understanding the propagation laws and characteristics of elastic waves in fluid-saturated porous media is of great importance to the fields of seismic exploration,soil engineering,and petrophysics,and therefore related research has received the attention of many researchers in this field.The propagation characteristics of elastic waves can be affected by many factors,among which slip is prevalent between pore fluids and solids due to the wetting effect of the medium.In this paper,the virtually enlarged pore acoustic model considering slip is used to study the effect of slip on the reflection and refraction of elastic waves at the interface between fluid and fluid-saturated porous media with the dispersion and attenuation of SH waves.First,this paper investigates the propagation characteristics of elastic waves in fluid-saturated porous media that considering slip based on the virtually enlarged pore model(VEP model for short).And the viscous correction factor ′()containing the slip length is brought into the Biot displacement field equation to obtain the fluctuation equations satisfied by two types of longitudinal waves and one type of transverse waves.The variation of elastic wave velocity and attenuation with slip length is calculated.The results show that the slip in the high frequency range affects the elastic wave propagation characteristics,and the velocity and attenuation of fast longitudinal and transverse waves increase with the increase of the slip length.The velocity of slow longitudinal waves increases with the increase of slip length,but the effect of slip length on attenuation is smaller.Secondly,the VEP model is used to study the reflection and refraction of elastic waves at the interface between fluid and fluid-saturated porous media.The Helmholtz decomposition of the fundamental field quantities is performed to give the energy reflection and refraction coefficients of elastic waves by introducing the potential function.The variation of the energy reflection and refraction coefficients with the incident angle when the slip length is different is examined.The sensitivity of the elastic wave reflection and refraction coefficients to the permeability and fluid viscosity coefficient after taking into account the slip is investigated.The results show that the slip length affects the energy refraction and reflection coefficients of elastic waves and increases the sensitivity of the energy reflection and refraction coefficients of elastic waves to the static permeability and fluid viscosity coefficients.Finally,the VEP model is used to study the propagation characteristics of SH waves and Love waves in fluid saturated porous media.Starting from the fluctuation equation of SH waves with slip length,the potential function is introduced,and the SH wave dispersion equation is obtained by solving the equation with boundary conditions,and the intuitive analytical expression of SH guided wave velocity dispersion is given.The variation characteristics of velocity dispersion curve and decay curve under different slip lengths are examined.In a certain frequency range,the velocity of SH wave increases with the increase of slip length,and the attenuation of SH wave increases with the increase of slip length near the cut-off frequency of each order,and decreases with the increase of slip length in the high frequency region.The attenuation of the Love wave at the interface between the fluid-saturated pore medium and the elastic plate increases and then decreases with the increase of the slip length,and the dispersion of the Love wave velocity does not change significantly with the slip length.The findings of this paper are of great scientific significance and reference value for an in-depth understanding of the propagation laws and characteristics of elastic waves in fluid saturated pore media.