Reflection And Transmission Of The Plane Wave At A Fluid/Fluid-saturated Poroelastic Solid Interface With Seismoelectric Effect

The research on seismoelectric effect which is the changing effect of the electromagnetic field which is caused by elastic wave field is becoming the hot concerned by exploration geophysics, especially oil and gas exploration and development of the industry. This paper is aimed to study Reflection and transmission of the plane wave at a fluid/fluid-saturated poroelastic solid interface with seismoelectric effect.So we launch the following research around this one theme.Biot established the mechanics theory of elastic wave in fluid-saturated porous media, which to be called Biot's theory. This theory made some assumptions to the porous media to be research: (1)the scale of pore and solid-phase particle is far less than the wavelength; (2)the pore is connected; (3) Solid-phase are connected. In these assumptions, Biot obtained the stress-strain relations and equations of motion, and gived the plane wave's solutions in the uniform pore medium The theory forecasted whether exist slow P wave in porous media.This article simply introduces the production mechanism of seismoelectric effect. The elastic waves are coupled with the electromagnetic waves if there is an electric double layer (EDL) at the mineral-water interface. It is explained why such a coupling occurs when a fast P wave or a slow P waves, or a shear wave propagates. It is noted that electrokinetic effect is related to fluid motion, and is primarily related to ion migration in the movable fluid.Pride established the coupling equations of sound field and electromagnetic. To solve the Pride's governing equations, the Helmholtz potential functions are used to express the frame and fluid displacement vectors and the electric field vector,transforming the governing equations into wave equations about the potential functions. Under rectangular coordinate system the formal solution of the coupling field in fluid-saturated porous media is derived. Through the boundary conditions of the coupling problem, the reflection and transmission coefficient of energy fluxes are calculated in theory. By numerical simulation, we learned that changing incident angle and frequency can obtain the coefficients which are needed, and after achieving maximum at a frequency value the reflection and transmission coefficients of electromagnetic energy are gradually decrease as the frequency increasing. In different boundary conditions, there are some differences on the energy reflection coefficients.The reflection and transmission coefficient is not only related with the incident angle and frequency, but also related with the other parameters, This model and procedures provided a theoretical basis for further detailed in-depth study of their relationship.If sound field is solved independently, the reflection and transmission problem can be studied by non-coupling method and the seemingly stable law. Non-coupling rule is that ignoring electromagnetic fields induced by acoustic effecting on the sound field, and make the Pride coupled equations reduce to solving the Maxwell's equations with fluctuations in the current source; Then cited Hertz vector, the problem solving the Maxwell's equations with fluctuations in the current source is transformed into solving the problem on the Hertz vector of the non-homogeneous vector Helmholtz equation; Using the solutionof scalar Helmholtz equation, to find a special solution of non-homogeneous vector Helmholtz equations and then superposition with general solution of homogeneous Helmholtz equation, drawing the expression of electric and magnetic fields, getting the accuracy of this method through simulation results. The seemingly stable method is also ignoring electromagnetic fields induced by acoustic effecting on the sound field, making the low-frequency electromagnetic fields as seemingly stable field, after the introduction of electric potential, using the boundary conditions to solve electric field, and then using electric fields to further define the current density and magnetic field strength, and similarly, used FORTRAN software simulation, the method also seems to be accuracy.The numerical simulations in this paper show that plane layered media twists and turns the sound reflection coefficient of coupling with the incident angle, frequency, and the formation parameters, to further clarify the sense of sound field coupling with electromagnetic, it is necessary to carry out the following research projects: characteristic of sound field coupling with electromagnetic wave in level mezzanine media; acoustic-electric well logging and simulation; rock parameters effect on the Electrokinetic coupling coefficient.