Abstract
Abstract Understanding the dependence of the rock properties on temperature is essential when dealing with heavy oil reservoirs. Reported rock physics models can hardly capture the effect of temperature on wave velocities. We propose a dual-porosity temperature-dependent model based on the coherent potential approximation, combining temperature- and frequency-dependent empirical equations for pore fluids with the David-Zimmerman model. The Maxwell model is adopted to obtain the complex shear modulus as a function of temperature and frequency. To verify the validity of the model, a glycerol-saturated tight sandstone and three heavy oil sand samples are considered. The comparison between the predicted and measured wave velocities shows that the model can quantitatively describe the behavior as a function of temperature. We find that there is a viscosity threshold (liquid point), where the P- and S-wave velocity variation trends change, while the porosity has no effect.
Highlights
Reservoir rocks can be considered as heterogeneous porous viscoelastic media, fully or partially saturated with fluids which have a dissimilar behavior as a function of depth, temperature, and pressure
Seismic wave attenuation and velocity dispersion are sensitive to the fluid types and corresponding environmental conditions [1, 2] and can be used to obtain information about the rock properties
We develop a temperature-dependent rock physics model based on the double-porosity CPA method and the micropore structure theory proposed by David & Zimmerman [27]
Summary
Reservoir rocks can be considered as heterogeneous porous viscoelastic media, fully or partially saturated with fluids which have a dissimilar behavior as a function of depth, temperature, and pressure. A large number of theoretical and experimental studies have been performed on the elastic wave velocities in rocks under different environmental (temperature and pressure) conditions [7,8,9,10]. Modeling on the physical properties of heavy oil is difficult due to its high viscosity. Appropriate viscoelastic models can be adopted to obtain the properties of heavy oil-saturated rocks [11, 17,18,19,20,21,22], and the shear modulus of the fluid cannot be neglected in this case [23]. The CPA method allows us to consider a pore fluid of high viscosity described by the Maxwell viscoelastic model. The temperature-dependent wave velocities are compared to experimental data
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