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Staggered Grid Finite Difference Numerical Simulation Of Two-Phase Isotropic Medium Elastic Wave Based On Biot Theory

Posted on:2019-09-30Degree:MasterType:Thesis
Country:ChinaCandidate:Y W DuanFull Text:PDF
GTID:2370330545956465Subject:Earth Exploration and Information Technology
Abstract/Summary:PDF Full Text Request
The two-phase medium model is closer to the actual underground media than the single-phase medium.Therefore,the seismic wave propagation path and attenuation of the two-phase medium are more meaningful to be researched than the single-phase medium.The finite difference method of the staggered grid converts the odd-order derivative of velocity into the stress-to-space derivative without increasing the computational mass and the storage space,and the high order difference and the staggered grid are organically combined.Compared with general difference method,the finite difference method has superiority for its characteristics of small dispersion,high precision and high efficiency.In this paper,the stability condition of the staggered grid and the boundary conditions of the perfectly matched layer are discussed in detail at first.the researches and applications of PML boundary conditions in the field of seismic wave forward modeling over the past 20 years are summarized,and classified the different absorption and attenuation functions in PML absorption boundary conditions,the staggered grid finite difference method is used to realize the numerical simulation of two-dimensional first order velocity-stress acoustic equation in the PML boundary conditions.The parameters such as time step,space grid length,absorption layer number and spatial difference precision are changed.The influences of each parameter on the finite difference numerical simulation is analyzed.The different attenuation functions in the PML boundary conditions are used to simulate,and the effects of different attenuation functions on the reflection of boundary are further analyzed.Secondly,the elastic wave field in the two-phase isotropic medium is simulated numerically,and the influence of the main frequency and the dissipation coefficient of the elastic wave is analyzed.Last and most important,the propagation law and attenuation of elastic wave in viscous biphasic medium interface are simulated emphatically.The results show that,improve the spatial difference accuracy can suppress some of the numerical dispersion in PML absorption boundary.The number of boundary absorption layers directly affects the absorption effect of absorption on boundary reflection in numerical simulation.And the larger the number of absorption layers is,the better the absorption effect of boundary reflection will be,but it may increase the calculation points,and lower the computational efficiency;the attenuation function directly affects the numerical simulation.In the two-phase isotropic medium,fast P-wave,slow P-wave and S-wave reflect and transmit at the boundary of double-layer two-phase porous media,there is mutual conversion between the wave modes,which is consistent with the actual acquisition of seismic data.And the numerical simulation of two-phase medium is of great significance to understand the propagation law of seismic wave in actual underground,and the double layered viscous medium model fits the actual formation situation better.
Keywords/Search Tags:two-phase medium, Biot theory, Staggered grid finite difference method, PML
PDF Full Text Request
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