Experimental and modeling study on the effect of molecular diffusion during CO2 injection

Abstract

In this work, a new approach based on the effect of molecular diffusion on oil recovery during CO2 injection in naturally fractured reservoirs has been proposed to examine the best condition for oil recovery in the matrix block. A homogeneous matrix block from one of Iran’s naturally fractured reservoirs has been investigated. The matrix block is filled with oil and connate water surrounded by fractures filled with injection gas from the top, bottom and right side. In which matrix block oil saturation and behavior of matrix block from inside for specific time are examined simultaneously. Sensitivity analyses on the matrix block at different saturation pressures showed first the positive effect of increasing saturation pressure could be seen when diffusion was involved. Secondly, as the pressure increased, the side of recovery changed from the top to the bottom just absolutely more effective when we had diffusion in the system. Third, gravity drainage at lower saturation pressures was dominant for 2 cases with and without diffusion and at higher saturation pressures capillary force becomes more involved.