Abstract
We derive a general system of equations accounting for two-phase fines migration with fines mobilization by injected water with different salinity, rock plugging by the migrating fines and consequent permeability damage in the swept reservoir zones. The analytical model derived contains explicit formulae for water-saturation and ion-concentration fronts along with pressure drop and water-cut in production wells. The model developed is applied to the cases of heavy oils, in low consolidated rocks with different clay composition and different injected and formation water compositions.
We show that non-equilibrium effects of the delayed fines release highly affect incremental oil during injection of different-salinity water. The oil-recovery is maximum for fast fines release. For slow fines release, the recovery tends to that of "normal" waterflooding.
The fines-migration-assisted smart waterflood is successful in reservoirs with a high content of fines-generating clays in the rocks (kaolinite, illite, and chlorite).
A novel analytical model presented in the paper allows predicting reservoir behavior and incremental oil for different compositions of injected water and clay contents in the rock. It permits recommending ionic-composition for the injected water.
