A residual oil saturation of a strongly water-wetted sandstone core was determined to

be 0.258 in a routine laboratory waterflood. Initial oil saturation was 0.68. The core was waterflooded by injecting water at a constant pressure drop. At the end of the waterflood, the flood rate was 0.113 cm3/s. Porosity of the core was 0.187 and the diameter was 2.81 cm. IFT between the oil and the water is 53 mN/m and the viscosity of the oil is 6 mPa.s. Calculate the capillary number !" and determine if the residual saturation is representative of the value expected in most sandstone rocks.