| With the increasing of complex reservoir development needs, correspondingtheory and technology of hydrocarbon reservoir exploration and development hasbecome an important research subject. Biot(1956) set up two-phase porous mediatheory of fluid saturation in order to accurately describe fluid porosity, firstly. Thisprinciple established two-phase porous media theory of wave propagation, initiatedthe road of porous media research. The Biot mechanism considers the fluid is forcedto participate in the solid’s motion by viscous friction and inertial coupling, andpredict the existence of the second category of P wave (slow P wave), this is one ofthe important findings about porous media. In order to further understand the theoryof porous media, this thesis deduced two-phase porous medium wave equation basedon Biot model, understood the physical significance of the parameters of the equationto understand the theory more profoundly.In view of the complexity of pore medium wave equation based on Biot model,this article first reviewed the theory of micro-fluid equation derivation process,including the fluid pressure and the poroelastic coefficient tensor of effective stress;Then the staggered grid finite difference algorithm is used to simulate seismic wavefield in two-phase porous media based on Biot model, and to analyze the seismicwave propagation characteristics in pore medium. We also study the propagationcharacteristic of reflection and transmission of seismic wave of pore media. A largenumber of studies have shown that the correctness of the Biot theory, but a certainscope. Although the Biot theory in explaining various aspects of elastic wavepropagation characteristic in pore medium obvious deficiencies, but it laid thefoundation of pore medium wave theory, still there is no doubt its classic status.Squirt flow mechanism is independent of the Biot flow mechanism of anotherimportant mechanics, mainly considers that the fluid is squeezed out of thin pores deformed by a passing wave. For making up for the limitations of Biot model,Dvorkin and Nur (1993) proposed a unified Biot-Squirt (BISQ) theory dealing bothBiot and squirt-flow mechanisms simultaneously. This thesis deduced two-phaseporous medium wave equation based on BISQ model and squirt-flow coefficient S.We fund this coefficient is a plural, associated with angular frequency which isderived from the displacement of solid phase and flow phase displacement of planarsimple harmonic solution. The wave equations based on BISQ model became partialdifferential equations with complex coefficient. And generally source function (suchas Ricker wavelet) is a composite wave containing a lot of frequency componentswhich is given by simulation, even the actual seismic waves. The indications are thatbased on BISQ model in numerical simulation of elastic wave field, should be done infrequency domain. So, this thesis adopts the25-points of high precisionfrequency-space domain finite difference algorithm for two-phase porous media basedon BISQ model to carry on the numerical simulation, analyzes the Biot flow andsquirt flow coupling effect how to influence the seismic wave propagationcharacteristics of two-phase porous media and propagation law in the ideal fluid andviscous fluid.In order to fully understand seismic wave dispersion, attenuation and othercharacteristics in reservoirs, this paper carry out seismic wave propagationcharacteristics research in two-phase porous media based on BISQ model. First, beginwith frequency domain wave equation for porous media based on BISQ model, theChristoffel equation in the two-phase porous media based on BISQ model is derivedby assuming plane harmonic solution of various wave. Then, through solving thedispersion relation equation to determine the complex velocity and give theexpressions of phase velocity and quality factor. On this basis, researching the effectof porosity, permeability and viscosity on seismic wave dispersion and attenuation. |
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