Experimental Study of the Effect of Clay and Oil Polarity on Oil Recovery by Low Salinity Water Flooding Using Glass Micromodel

Low salinity water flooding (LSWF) has been recognized as one of the promising methods for enhanced oil recovery (EOR) in sandstone reservoirs. Both the positive response to LSWF in terms of additional oil recovery and the negative effect of severe permeability impairment due to fines migration have been reported. Therefore, screening of the EOR methods in clay-rich sandstone rocks is required to obtain an optimum EOR design. We examined the effect of kaolinite clay on oil recovery and fines migration due to reducing the injected water salinity using glass micromodels functionalized with clay minerals. Experiments were conducted with both clean (clay-free) and clay-coated porous media using polar (crude oil) and nonpolar oil samples in the presence of connate water. The salinity of the displacing fluid was decreased stepwise in the following order: 30,000 ppm, 4000 ppm, 2000 ppm, and deionized water. Incremental oil recovery was observed for both clay-coated and clay-free systems, polar and nonpolar oil samples in tertiary mode. The redistribution of oil saturation during LSWF in the clay-coated micromodel was more significant compared to that of clay-free micromodel. Image analysis was used to calculate oil recovery and detect fines migration. In addition, single-phase LSWF was performed to evaluate possible fines migration compared to the two-phase flow experiments. Fines migration was observed during both single- and two-phase flow experiments. Low salinity water injection resulted in higher incremental oil recovery from a clay-coated porous media saturated with nonpolar oil compared to a polar crude oil.