The Effect of Fluid Saturation Profiles on Three-Phase Oil Relative Permeabilities and Oil Recovery

Abstract

Abstract Network models are often used to predict oil, gas and water relative permeabilities and residual saturations. It was recently shown that most previous network model calculations involving significant numbers of double-displacement events were invalid because of material balance errors1. The current study used a model that conserved oil, gas and water volumes. The model accounted for heterogeneity and the snap-off displacement mechanism. Gas injection followed waterflooding to displace the remaining oil saturation. The remaining saturations were a function of the level of snap-off events that occurred during waterflood imbibition. The model was used to study the effect of the fluid saturation profiles at the end of waterflooding on three-phase oil relative permeabilities and oil recovery from a subsequent gas flood. The level of snap-off events during waterflood imbibition displacement significantly affected the remaining oil and water saturations before gas flooding. This, in turn, affected three-phase oil relative permeabilities and recoveries. Residual oil saturation to gas flood increased with increased remaining oil saturation following waterflood. Introducing spatial and local correlations significantly increased oil, water and gas relative permeabilities and reduced remaining oil and water saturations. Oil relative permeability was found to be a function of both oil saturation and the oil remaining after waterflood. Gas and water relative permeabilities were only functions of their respective saturations.