Theoretical and Experimental Study of Fine Migration During Low-Salinity Water Flooding: Effect of Brine Composition on Interparticle Forces

The majority of sandstone reservoirs contain clay particles. When clay is exposed to low-salinity water, fine detachment and migration occur due to multi-ion exchange and electrical double layer (EDL) expansion. Fine migration due to low-salinity water enhances oil recovery while damaging injection and production wells. This research investigates the effect of clay particles' weight percentage (wt%), ionic strength, total dissolved solids, and the injection rate of the low-salinity water on fine migration. The interparticle forces of kaolinite-kaolinite and kaolinite-quartz systems in various mediums were determined. Ten quartz sandpacks containing 2, 5, and 10 wt% of kaolinite were made to simulate clay-rich sandstone reservoirs. Afterward, different brines (10 and 50 mM solutions of NaCl, CaCl₂, MgCl₂, and Na₂SO₄ salts as well as seawater and its diluted samples) were injected into these sandpacks with different scenarios. It was observed that the interparticle forces for both systems in the presence of 10 mM solutions of NaCl, Na₂SO₄, and also 50 mM NaCl are repulsive. Therefore, even by injecting the low flow rate of these samples (0.1 cm³/min), the total fine migration was observed leading to intense permeability reduction in high clay-rich sandstones. However, in the case of low clay-containing sandpacks, the magnitude of permeability starts to rise a while after getting imposed to fine migration. In the presence of brines containing 50 mM MgCl₂ and CaCl₂, seawater, and its five-times diluted sample, the interparticle forces were an attraction, and fine migration occurred under no condition. However, using other samples of low-salinity water, the interparticle forces in the kaolin-kaolin system were repulsive and attractive in the kaolin-quartz system. Therefore, the phenomenon of partial fine migration occurs while flooding. So, in low-clay sandpacks, fines migrated only in high rate injection. However, the fine migration was evident for sandpacks containing 10 wt% of clay particles even by low flow rate injection. In general, there is a trade-off between the intensity of fine migration and divalent cations concentration in flooding water. Eliminating these cations or using them at 10 mM concentration may result in total fine migration, which is beneficial for low clay-containing media but damages clay-rich ones strongly. A high concentration of these cations prevents fines from movement, eradicating low-salinity flooding advantages. However, using medium concentrations results in partial fine migration, and the intensity, in this case, depends on clay concentration and flooding rate.