Finite Difference Numerical Simulation Of Elastic Wave Biphase Media

With the continuous development of oil and gas exploration and development work, the object of exploration and the development conditions faced are becoming increasingly complex and the requirement on the precision of reservoir prediction is more and more higher. As the reservoir is actually two-phase medium or multi-phase medium, the traditional theory of seismic wave regarded underground medium as the single phase medium, so it is not well applied to fluid porosity and it also can not accurately calculate the fluid parameters related to reservoir rocks, therefore, it is of great significance to establish two-phase medium (or fluid porosity) or the elastic wave propagation theory in fluid saturated porous media on the development of seismology and geophysics.According to foreign and domestic research of the two-phase medium, this paper firstly discussed the establishment of elastic wave equation, double longitudinal wave phase velocity, the reflection and transmission equation of elastic interface and the transformation of elastic parameters based on the Biot theory of two-phase medium and the elastic wave equation of BISQ theory, the improved BISQ theory. At the same time it introduced the finite difference method and discussed difference format, source, dispersion, boundary conditions of elastic wave in single-phase medium with staggered grid. Secondly, it used the staggered mesh finite difference method to solve the first-order rate-stress equation based on Biot theory of two-phase isotropic medium and analyzed the characteristics of wave field which was numerically simulated, then used first-order rate-stress equation based on the improved BISQ theory of two-phase isotropic medium to study the influence of physical parameters such as porosity, permeability, viscous coefficient on wave field and fulfilled wave field separation numerical simulation based on the two kinds of two-phase medium theory, which had a certain guiding significance to understand the propagation rules of elastic wave in two-phase medium and recognize multi-wave information. Finally, the reservoir model was established based on the field horizon data according to the Biot theory which had no the dissipative conditions and the high order staggered grid finite difference technology was used to numerically simulate the reservoir model, meanwhile numerically simulated it with the changed porosity and pore fluid and analyzed the characteristics of wave field, then studied the AVA curves corresponding to the surface of two-phase medium and compared with the wave field numerically simulated in the reservoir model.Numerical simulation results showed that using two-phase medium had important practical significance to the understanding of the seismic wave propagation theory, provided the basis of further research to study the change of reservoir parameters, identifying fluid and AVO inversion etc.