Experimental and theoretical studies on gravity assisted inert gas injection for the recovery of waterflood residual oil in homogeneous and layered porous media

Gravity drainage has been found to be a very efficient oil recovery mechanism in a significant number of oil reservoirs. The process of inert gas injection into the waterflooded reservoirs is well-known for its high oil recovery efficiency when it is assisted by the gravity forces. The success of this technique stems from the continuity of the oil phase in the bulk film contained in pores invaded by the gas and the gravity stabilized oil bank moving toward the production well. This study is focused on the experimental and theoretical investigations of the Gravity Assisted Inert Gas Injection (GAIGI) process in homogeneous and layered porous media for the recovery of waterflood residual oil.;The experimental investigation of both, the free fall and controlled GAIGI process for the recovery of waterflood residual oil from the water-wet homogeneous and layered porous media resulted in high oil recovery efficiencies. Experimental results obtained with unconsolidated porous media show that the ultimate recovery, before and after gas breakthrough, with the GAIGI process for the recovery of waterflood residual oil at high production rates is the same or better than the recovery at lower rates. The oil recovery at gas breakthrough has been found to correlate very well with the gravity number. The oil production characteristics in unconsolidated columns of glass beads of different permeabilities were found to scale with dimensionless time and gravity number. For positive spreading coefficients of oil over water in the presence of gas, the production data of oil recovery factor versus time were used to calculate the relative permeability to oil in the gas invaded zone.