Gas/oil interfacial tension (IFT) is one of the most important parameters that impact the performance of gas injection in an oil reservoir. The choice or design of the composition of the injection gas for improving the oil recovery is usually affected by the gas/oil IFT. In conventional reservoir simulation, IFT does not explicitly appear in the equations of flow and therefore its effect must be captured by the shape and values of relative permeability of existing phases. A few studies have been previously reported for IFT effects on two-phase flow but very little have been done to investigate gas/oil IFT effect under three-phase flow conditions.Previously, we performed series of core-flood experiments at Heriot-Watt University to investigate the effect of changing gas/oil IFT value (immiscible and near-miscible) on WAG injections. In this paper, we review published laboratory studies on the impact of gas/oil IFT variation on three-phase relative permeability, performance of WAG injections, and in particular reduction of remaining oil saturation. The review shows that in three-phase systems, as IFT varies between gas and oil, the relative permeabilities of all the three phases (gas, oil and water) will be affected. The remaining oil saturation keeps decreasing during WAG injections at very low IFT (near-miscible) conditions and performance of near-miscible WAG is generally better than that of immiscible WAG.
|Journal||Journal of Oil, Gas and Petrochemical Sciences|
|Publication status||Published - 29 Jan 2018|