The calculation of drainage rates of filter cakes with a two-phase flow model

We present a theoretical and experimental investigation of the kinetics of the displacement of liquids from filter cakes. The theory, derived from that used in secondary recovery of petroleum, is developed and demonstrates that the forced drainage process occurs in two stages: an initial stage with efficient piston displacement followed by a second stage with inefficient two-phase flow displacement. The effects of the packing structure of the cake, the viscosity of the two phases and the surface tension on the process are taken into account. Experimental results are presented for the air blow displacement of liquids from beds formed from a variety of different types of particle and with different saturating liquids having a range of viscosities and surface tensions. A reasonable agreement is found with the predictions from the theory.