The Impact Of Seismic Waves On The Pore Fluid Migration

This thesis studies the effect of seismic wave pressure boosting the pore fluid’spermeability.Wave’s propagation differs in different medium, and also differs withpropagation equations. The more complex the medium model is, the morecomplicated the equation is. Medium model develops generally from simple tocomplex, which like homogeneous, isotropic and ideal elastic medium is a simplemodel. This paper conducts acoustic seismic wave equation and full seismic waveequation based on the theories of elastic waves; then establishes the high accuracydifference scheme by the characteristic of elastic wave, the full matching layerabsorbing boundary conditions and stability conditions of seismic wave equation arecombined to perform forward numerical wave equation simulation. Analysis of thesimulation result is followed.The pore medium’s fluid mechanism while seismic wave propagates through thelocal reservoir is discussed, and which the elastic wave propagation theory is based onsuch mechanism. BISQ(Boit-Squirt) model is studied from Boit model to Carcionemodel. The characters of BISQ model is discussed from the pore elastic waveequation as follows:1it describes how the fluid-structure coupling effects the seismicwave;2it, which take full account of2-phase porous media, indicates that the relativemovement controlled by vicious force is the main mechanism of elastic waveattenuate through the porous media;3there behaves as scalar flow when pressuregradient exists in two types of porous media. And finite difference numericalsimulation of elastic wave in a fluid-containing porous media is applied to extract thepressure of the fluid by the fluid-structure coupling model.Re-fit the seismic wave recorded by the seism stations, recovers aneasy-mathematically source-time variant function. Associating the real situation of theLongmen Mountain, the simulated area is divided into clastic rock, carbonate rockand basement. Courant stability condition and full matching absorbing layer are combined to activate the cross-grid high-order full wave numerical simulation. Forfull wave equation, appling Professor Ma Detang’s P-wave and S-wavedecomposition method, mix-wave, P-wave, S-wave field snapshot, and seismic phasediagram of the target fluid is obtained. And use it as initial source of thefluid-structure coupling effect; perform the numerical simulation on BISQ model, sothe distribution of the seismic pressure on target fluids is acquired.Studies on the Well1Well2, Well3and Well4of west of Sichuan gas fieldnotice that significant abnormality exist after the earthquake. It reveals that due to aninstantaneous pressure boost, the pore pressure increase, the well dynamic productionperformed abnormally. Earthquake, introduce a seismic wave pressure to the fluid(calculated by the numerical simulation of fluid-structure interaction) and when theseismic pressure is higher than the formation stress, fluid may migrate along theseismic waves.