Wave Propagation In Unsaturated Porous Media

The subject on elastic wave propagation in unsaturated porous media is an important subject in Civil Engineering, Petroleum Engineering, Bioengineering, Earthquake Engineering and Geophysics. Based on the Mechanics of Fluids in Porous Media and the Continuum Mechanics, a continuum theory of three-phase porous media was developed to analysis the propagation, reflection and transmission of elastic waves in a porous medium saturated by two immiscible, viscous, compressible fluids.In the first chapter, the phylogeny and present status of the theory of elastic wave propagation in unsaturated porous media were generalized systematically. The theoretical models were sorted to six types, and the merits and demerits of each theoretical model were discussed. For the first time it was emphasized that different models should be employed for differently saturated states. According to the capillary pressure curve, the states of saturation could be differentiated to three models: water insular saturation, funicular saturation and air insular saturation.Taking into account of influence of inertia couple, viscosity couple between solid phase, liquid phase and gas phase, and capillary pressure, the governing equations for waves propagation in funicular saturated porous media were established. Solving the equations, it was found that there are three compressible waves and one shear wave in funicular saturated porous media. The contribution of variation of saturation on the waves speed and attenuation were studied in detail, and the theoretical results are plotted and compared with the experimental data available in the literature.On account of different saturation procedure, drainage or imbibition, there are two saturation patterns in air insular saturation porous media. At the same global saturation, the properties of the porous media vary depending on the saturation pattern. We offer two governing equations for the two deferent saturation patterns. The results showed that the properties of elastic waves in porous media were markedly diverse. However, the properties of elastic wave tend to be accordant while saturation decreases to funicular saturation zone. The theoretical results are plotted and compared with the experimental data available in the litera- ture. In addition, the outcomes of two saturation patterns match the experimental data available in the literature well.In fact, the stratum is remarkably anisotropic, and is usually represented as transversely isotropic poroelastic media. This dissertation carried out to investigate the features of elastic wave in funicular saturated and air insular saturated porous media. The influences of saturation fluctuation, anisotropy, propagation direction and frequency on the elastic wave speed and attenuation were all adopted.By reason of the macrostructures of natural rock and stratum usually are layered, the properties of elastic wave in layered partially saturated porous media were studied in this paper. In chapter 4, funicularly saturated porous media was used to simulate unsaturated soil which is often used in Civil Engneering, and the relationship between waves' reflection factor, transmission factor and the displacement caused by incident waves and saturation, frequency, and angel of incidence while P1 wave or SV wave incident in any angle. In chapter 7, air insularly saturated porous media was used to simulate reservoir and fully saturated porous media was used to describe cap rock in Petroleum Engneering. Theoretical formulation is developed for the computation of amplitude reflection/transmission coefficients and energy density flux reflection/transmission coefficients at the interface, which are considered as functions of the degree of saturation and the angle of incidence. All the coefficients are studied over a wide range of frequencies and angles of incidence. Numerical results are given to illustrate the influence of saturation on amplitude reflection/transmission coefficients and energy splitting at plane interfaces.