The Research Of Seismic Rock Physics Model In Saturated Porous Media

Compressional and shear wave velocities play an important role in the reservoir prediction and fluid identification.Rock physics theory and models are approaches and ways to obtain elastic parameters such as compressional and shear velocities of underground reservoir rocks.In this paper,considering the effect of rock skeleton and pore fluid,we build the rock physics model for porous medium containing fluid,that can reflect the characteristics of underground rock reservoir more truly.We analyze the influence of petrophysical parameters,fluid property and other factors on elastic wave velocity dispersion and attenuation as well as reflection coefficient,and explore the construction of rock physics model for medium containing viscous fluid.In the process of calculating the compressional and shear velocities of saturated rocks,dry rock skeleton elastic moduli are key parameters.In this paper,based on the relationship between the ratio of dry rock bulk modulus to shear modulus and porosity,decoupling the differential equivalent medium equation,we get the a nalytic expression of dry rock skeleton equivalent bulk modulus and shear modulus for the single pore shape and multiple pore shape types.Then we build corresponding dry rock skeleton models and apply our models to the experimental data and actual logging data,achieving good effect.On the basis of dry rock skeleton model,using the White patch saturated thoughts,we construct the rock physics model for porous medium saturating fluid.Then we analyze the influence of petrophysical parameters(such as poro sity,permeability,saturation),fluid property and other factors on elastic wave velocity dispersion and attenuation as well as reflection coefficient.Using the finite difference numerical simulation method,we simulate the elastic wave velocity dispersion and attenuation in seismic exploration frequency band,expecting to provide theoretical guidance for the quantitative characterization of the relation between seismic wave field and petrophysical parameters and fluid property and future predicting the physical property and hydrocarbon potential of underground reservoir rock.Heavy oil(viscous fluid)is an important unconventional resources with abundant reserves.Due to its viscoelastic properties,conventional Gassmann equation is not applicable.In this paper,we analyze the relation of shear modulus of viscous fluid with temperature and frequency.In the light of the feature of viscous fluid,we establish the rock physics model for estimating the effective elastic parameters of medium saturated viscous fluid and apply the model to actual logging data.