The Study On Rock Physics Considering The Effect Of The Fluids In The Pores

The study of the elastic wave propagation in porous media has so far been one of the hot spots of the geophysics and oil prospecting. And elastic wave velocity dispersion and attenuation caused by the wave-induced fluid flow(WIFF) is the key problem. The diversification of the rock components, the irregularity of the pore structures and the differences among the properties of different pore fluids lead to the heterogeneity of the rocks, which makes it difficult to construct a universal porous medium model that based on real physical mechanisms.This paper carried out a detailed review of six theoretical models about the wave-induced fluid flow, to find out the main research directions and the latest developments of the velocity dispersion and attenuation which related to the wave-induced flow. Then the squirt model which plays a role in ultrasonic and logging frequencies and the White patchy saturation model which causes the significant attenuation in seismic frequencies are considered. These two attenuation mechanisms can not be expected to be independent. In the context of squirt flow, the stiffness of the modified dry frame is complex-valued and frequency dependent and these frame parameters play a key role in the energy loss mechanism related to the presence of mesoscopic heterogeneities. We propose a simple but effective procedure to estimate the seismic attenuation and velocity dispersion behaviour associated with wave-induced fluid flow due to both microscopic and mesoscopic heterogeneities. To determine the combined effects of wave-induced fluid flow at both microscopic and mesoscopic scales, the modulus of the modified dry frame are introduced into the Biot theory, then the two-scale model(White-Squirt model) is obtained.The attenuation and dispersion characteristics of the elastic wave are analysized with three models, concluding that the microscopic and the mesoscopic mechanisms are relevant and the White-Squirt model is quite accurate than White model.In this paper, because of the complex pore system in the carbonate rocks, the effect of the local flow between the cracks and other shapes of pores is considered in the well logging frequency. We combine the effective medium theory with the full frequency Mavko-Jizba model, which only needs simple parameters, to construct the two-phase model of the carbonate rocks. The model is involved in attenuation and dispersion. Then the model is employed to analysize the frequency-dependent velocities and attenuation by considering porosity, frequency diffusivity parameter, crack aspect ratio and crack density. Finally the model is employed to estimate the S-wave velocity for the practical carbonate area and the velocities and attenuation in seismic frequency are also estimated approximately, which provides more materials for the reservoir fluid identification and prediction.