PORE-SCALE INVESTIGATION OF WETTING STRENGTH ON CAPILLARY PRESSURE HYSTERESIS IN A REALISTIC POROUS MEDIA

Abstract

Capillary hysteresis is known as a characteristic of a real porous structure that strongly affects the micromechanism of immiscible fluids displacement so that its understanding provides a better insight from pore-scale studies. This study aims to investigate capillary hysteresis and characterize wetting strength on the capillary pressure-saturation curve using lattice Boltzmann method. After benchmark tests, a comprehensive procedure for recording capillary hysteresis at the pore-scale simulations is presented. Studies have been done in three wetting categories, including nearly neutral wet, moderately wet, and strongly wet. The interesting point is the capillary pressure bump phenomenon in the forced drainage process, so that this model has been able to record it well. Since the capillary pressure plays a resistive role for the displacement of immiscible fluids in the drainage process, the wetting condition controls the flow pattern intensely. Overall, results show that increasing the wetting strength will intensify this phenomenon, despite imbibition and drainage curves shifting toward higher capillary pressures. Indeed, the reason for this is an excessive increase in capillary pressure in some pores. Other interpretations of the results show that increasing the wetting strength will allow more wetting fluid to be trapped in the drainage process, which is a sign of the capillary trapping phenomenon.