A Mathematical Model for Prediction of Gas Diffusivity in Reservoir Oil With Considering Swelling Effect

In petroleum reservoirs, estimation of the rate of mass transfer caused by molecular diffusion is necessary for determining the amount of gas diffusing into oil in gas injection projects. The key parameter for calculating the mass transfer rate is diffusion coefficient of gas into oil. Hence in EOR Projects, the knowledge of this key parameter for designing the injection projects is essential. Oil swelling is a common phenomenon which is observed in gas injection projects and should be taken into consideration for modeling of diffusion process in EOR projects. Mathematical modeling is a good tool which may help predicting this parameter. In this study, it has been tried to develop a mathematical model based on the real mechanism that happens in gas injection processes in porous media for predicting the gas diffusion coefficient for the system in which the gas is injected into oil through a water blocking film. The model equation has been solved with approprate initial and boundary conditions to obtain a series of type curves similar to those which are used in well testing. The results are classified in two groups, oil and water phases and are presented in dimensionless form. The effect of swelling varies with the variation of Peclet number.It may be concluded that by increasing Peclet number the role of convection mechanism is more prominent.