Experimental investigation on the complex chemical reactions between clay minerals and brine in low salinity water-flooding.

• Dynamic effect of clay mineral on low salinity water flooding was analyzed by coreflooding experiments. • The chemical reactions between brine and clay minerals were evaluated to figure out the mechanistic reason of incremental oil recovery in LSF. • The incremental oil recovery of kaolinite was higher than that of illite at the same clay content. • Kaolinite content has a strong correlation with MIE, EDL expansion, local pH increase, and oil recovery. This paper presents a dynamic effect of clay types and content on low salinity water-flooding (LSF) based on coreflooding experiments. The EDL (electrical double layer) expansion, MIE (multicomponent ion exchange), local pH increase between clay minerals and brine are investigated to get a better understanding on the complexity of role of clay in LSF. The results of coreflooding experiments using unconsolidated core sample show that the incremental oil recovery of kaolinite is higher than that of illite at the same clay content. Kaolinite and illite have a positive effect on MIE, EDL expansion, and local pH increase. The incremental oil recovery was proportional to the local pH increase in both core samples. Especially, more MIE and EDL expansion occur in kaolinite core samples. Therefore, the wettability is further changed to the water-wet condition in kaolinite sample. The results of correlation coefficient analysis show the kaolinite content has a strong correlation with MIE, EDL expansion, local pH increase, and oil recovery. On the other hand, the correlations between oil recovery and chemical reactions in illite samples are relatively low compared to the kaolinite samples excepting local pH increase. Therefore, the sandstone reservoir containing kaolinite is more suitable for the LSF. [ABSTRACT FROM AUTHOR]