DIFFUSION-CONTROLLED SWELLING OF RESERVOIR OIL BY INDIRECT CONTACT WITH INJECTION GAS

The diffusion-controlled swelling of reservoir oil, when the oil is indirectly contacted by an injection gas such as CO2 by diffusion through a water barrier film, is presented. The solutions are based on the method of the variable powered profile to describe the distribution of CO2 in the oil and water phases. This technique greatly reduces the mathematical complexity of the moving boundary problem which is represented by a system of coupled partial differential governing equations, to a system of coupled ordinary differential equations. The present solution is compared with the numerical solution for CO2 diffusion into an oil phase through a diminishing water barrier. This study demonstrates that the water-blocking phase produces the major mass transfer resistance. The increase in time for the oil phase to saturate with CO2 is highly non-linear. It increases rapidly with increasing water phase thickness.