Experimental Study of Carbon Dioxide Diffusion in Oil-Saturated Porous Media under Reservoir Conditions

Abstract

For both CO2 enhanced oil recovery and CO2 sequestration in oil reservoirs, the diffusion of injected CO2 into oil-saturated porous media is of great significance in project design, risk assessments, economic evaluation, and performance forecast. However, the measurement of CO2 diffusion coefficient in liquid-saturated porous media under reservoir conditions has not been well-established due to the complications caused by density-induced natural convection in the CO2−oil systems. This paper presented a new method for measuring the effective CO2 diffusion coefficient in oil-saturated porous media under reservoir conditions. A core plug with the two end faces sealed was designed as the physical model for radial diffusion process. The measurement was conducted in a high-pressure diffusion cell with an oil-saturated core sample placed in the middle and the remaining void space of the cell filled by high-pressure CO2 sample. A small-pressure decay technique was employed to record the pressure change of the gas...