Studying the effect of various surfactants on the possibility and intensity of fine migration during low-salinity water flooding in clay-rich sandstones

Abstract

In the majority, sandstone reservoirs contain clay particles. When such reservoirs are exposed to low-salinity water, multi-ion exchange (MIE) and electrical double layer (EDL) expansion result in fine migration, which sweeps residual oil in the porous media while imposing damage and permeability reduction. This research investigates the effect of surfactants on the possibility and intensity of fine migration in clay-rich sandstones. First, the impact of these surfactants on the surface charge of quartz and clay particles was investigated. The results showed that both CTAB (CetylTrimethylAmmonium Bromide) and QS (Quillaja Saponin) lower the magnitude of fine particles' zeta potential from −40 mv to 2 and -18 mv, respectively, The zeta potential compensation weakens the repulsive forces. However, SDS (Sodium Dodecyl Sulfate), and TX (Triton X-100) do not change the magnitude of zeta potential. The surfactants were injected at a concentration of 10 g/L into sandpacks containing 5 wt% of kaolin. SDS and TX couldn't prevent fine migration, and sandpack permeability decreased from 65 md to about 8. CTAB completely prevented fine migration (permeability reduction from 66 to 62md). Meanwhile, QS reduced the intensity of fine migration and the permeability decreased to 30 md. Post-flushing diluted surfactant solutions showed that CTAB loses its ability to control fine migration and the magnitude of permeability drops to 8 md. However, QS still controlled the intensity of fine migration. CTAB, QS, SDS, and TX-100 adsorption on oil-aged sandstone rocks lower the contact angle from 1290 to 21.20, 69.50, 52.70, and 62.10, respectively. It should be noted that the aging time for this experiment was 14 days, which was conducted at 60 °C. contact angel studies illustrated that EDL compaction by surfactants can cause wettability alteration toward water wet conditions, through adsorption in the stern layer, which results in oil desorption. BET analysis showed that the kaolinite particles are mesoporous with weak interaction, which are covered by CTAB or QS adsorption. However, after lowering the surfactant concentration in the bulk fluid, CTAB is desorbed, resulting in the revival of pores. In contrast, desorption in QS dilution was negligible. The behavior difference is related to the adsorption mechanism. CTAB is absorbed on the particle surface based on cation exchange and QS due to hydrogen bonding. In QS, the hydrophilic part is adsorbed on the particles, and the hydrophobic part forms the external surface, which prevents water from reaching the hydrophilic part.