Effect of wettability-induced relative permeability change on shock front instability

Adding surfactants, altering salinity, or increasing the temperature of injection water, are among the effective methods of improving oil recovery. All these methods alter the wettability of rock surface towards more water-wet and change the mobility of aqueous and oleic phases. Consequently, the total mobility may be increased upstream of the shock front and lead to fingering. The fingering phenomenonis more recognized for the displacement of a viscous oil by a less viscous fluid. However, changing the wettability of surface rock, reflected in relative permeability, may also increase the total mobility of displacing fluid compared to the displaced fluid that creates fingers. The injection of modified salinity brine, known as advanced waterflooding, might also cause the growth of fingers even with the same viscosity of water and oil. In this work, we examine the impact of relative permeability parameters on the onset of instability due to wettability alteration during advanced waterflooding. Furthermore, we evaluate the performance of flooding with an unstable shock front on the sweep efficiency and its impact on theoil recovery and water-cut. In the absence of capillary pressure, our results show that a substantial shifting of wettability from the non-wetting state towards the wetting state leads to longer fingers and consequently early water breakthrough. Nevertheless, the presence of capillary pressure can significantly suppress wettability-induced fingering