Wettability Alteration Induced By Surface Roughening During Low Salinity Waterflooding

Abstrak

Wettability alteration during low salinity waterflooding (LSW) is expected to be one of the prominent reason of incremental oil recovery. However, the underlying mechanisms of improved oil recovery in sandstone during LSW is not entirely clear. Then, we carried out a series of experiments to investigate the conspired underlying mechanisms that drive the wettability alteration. We combined FTIR Spectroscopy and Thermogravimetric analysis to quantify the amount of adsorbed hydrocarbon components on Sandstone with various clay content. Afterward, we observed the time-dependent contact angle on fabricated sandstone substrate (RMS roughness 9.91±1.31μm) with various clay and brine content to monitor the wettability alteration during LSW. The existence of divalent ions (Ca2+ and Mg2+) was found to stabilize sandstone from swelling. Surprisingly, with the presence of divalent ions, our results showed that the rate of contact angle change was insignificant (~1 - 4o/dilution) although the reduction of divalent ion is happening, while the rate of contact angle change with sole presence of NaClwas notably altered (~6°/dilution). Furthermore, the presence of higher clay contents showed an incremental contact angle alteration. We proposed that the phenomena are partially driven by the macroscopic phenomena of clay swelling. It leads to surface roughening that enhance the water wetness.