N=7.758 A,hosi u.s.A N=AhoSoi china where: As surface area of the reservoir,acres/m2. h thickness of the formation,ft/m. porosity,fraction. Soi initial oil saturation,fractionN 758As hSoi  7. where: As = surface area of the reservoir, acres/m2 . h = thickness of the formation, ft/m. Φ = porosity, fraction. Soi = initial oil saturation, fraction. N  As hSoi china U.S.A