Modification and Application of Capillary Number to Oil Displacement in Low Permeability Reservoirs

As concerning the limitations of the classic capillary number theory in the applications to the oil displacement with the ultra low interfacial intension system in low permeability reservoirs, considering the flow velocity of water/oil displacement through pores in low permeability reservoirs and the mechanism of displacement of the remaining oil in the parallel pores, and considering the influences of ultra low interfacial intension on oil/water relative permeability and the influences of non-homogeneity on the recovery, the expression of modification of the capillary number was given. The relation curves of recovery and capillary number were plotted through the displacement experiments with the ultra low interfacial intension system in low permeability cores. Some points on the application of capillary number to the oil displacement with the ultra low interfacial tension system were given, and the reasonable ways of enhancing the recovery of water flooding low permeability reservoirs with ultra low interfacial intension system were shown.