The impacts of silica nanoparticles coupled with low-salinity water on wettability and interfacial tension: Experiments on a carbonate core

Abstract

Two main reservoir mechanisms that impact oil recovery factors are wettability alteration and interfacial tension (IFT) change. In this study, these two key mechanisms are evaluated experimentally for samples from the Asmari (carbonate) oil reservoir utilizing silica nanoparticles in the presence of low-salinity water. The nanofluid, rock formation and crude oil samples were prepared meticulously to ensure meaningful experimental could be conducted over a range of low-salinity conditions. The results show that across the range of salinities studied, the absolute value of zeta potential of nanofluids decreases with increasing total dissolved solids (TDS) in the water treated with silica nanoparticles interacting with the formation samples. This indicates that increasing the salinity, decreases the stability of the low-concentration (<2000 ppm) silica nanofluids studied. The results of the IFT and wettability alteration experiments for silica-particle nanofluids on this carbonate reservoir suggest that: 1) by increasing the concentration of nano-silica, IFT generally decreases; 2) IFT increases when TDS of the water increases.; 3) contact angle alteration becomes more significant as the concentration of nano silica increases, resulting in significant changes in the reservoir rock’s wettability towards more water-wet conditions; 4) contact angle alteration decreases as TDS of the water increases; and, 5) minimum IFT (about 14.29 dyne/cm) occurred at 5000 ppm nano-silica concentration and salinity of 9000 ppm, whereas the maximum degree of wettability alteration (about 126.2 degree) occurred at 5000 ppm nano-silica concentration and salinity of 1000 ppm.