Effects of the presence of fines on the performance of low salinity waterflooding

In recent years, low salinity water flooding, among all enhanced oil recovery (EOR) methods, has received much attention both in academic research and industry. Promising results of increase in ultimate oil recovery with change in salinity of injected brine have been shown through the laboratory and field tests data. Even though there are many published works about this subject, there is still ambiguity regarding unpredictably large variation in responses. So, the fundamental understanding of the underlying mechanisms and the explanation of laboratory experiments need to be addressed. In this study, parallel laboratory core floods including single and two-phase experiments were performed to investigate the effect of brine and low salinity waterflooding on oil recovery, wettability, absolute and relative permeabilities. Single-phase flooding experiments were carried out to understand the behavior of the water/rock system and establish a baseline to interpret multiphase experiments. In two-phase waterflooding, it was observed that the presence of kaolinite clays and silica fine particles along with their mobilization plays a vital role in the sensitivity of oil recovery to salinity. Contrary to some previous studies, in this work oil recovery was obtained in tertiary mode, which reveals that enhanced recovery is related to the combination of fines migration and chemical mechanisms phenomena. However, incremental oil recovery without the presence of kaolinite and multivalent ions was observed. Furthermore, we noticed the reflection of crude oil/brine/rock (COBR) interactions at microscopic scale through the alteration of permeability, potential of hydrogen (pH), conductivity, and the turbidity in the effluent at macroscopic scale.