In a previous publication critera were derived for predicting the onset offines release in sandstones. The present paper describes quantitatively thebehavior of the sandstone after the fines have been released. The entrapment offines at pore throats is modelled using a statistical approach and generalpopulation balance equations are written for the various species of interest.The equations are solved for the open pore densities and size distributions,for some special cases. The Effective Medium Theory is used to calculate thepermeability once these are specified. The model therefore providespermeability as a function of time and position i.e. the extent and depth ofdamage. Such information will be valuable in not just predicting formationdamage but also in designing appropriate stimulation jobs once the damage has occurred.