Effect of barium and strontium on low salinity waterflooding

Abstract

Much work has been done on the subject of low salinity waterflooding (LSWF) as a potential enhanced oil recovery method. It has been shown many times that reducing the salinity of the injected brine could have a positive effect on the oil recovery. Several mechanisms have been proposed to explain why and how LSWF works, but still no mechanism has been able to explain all obtained results. However, in many cases multicomponent ion exchange has been observed to play an important role, and it has been shown to cause effects like changes in the adsorption of polar organic species and altering the wettability of a system. Both of these effects can depend on altering the ionic composition of the formation water and the injected brine. In many laboratory experiments regarding low salinity waterflooding, potentially scale forming ions as Ba and Sr are left out of the synthetic brines to avoid in situ plugging. In this work, the effect of doing so was investigated through simulation and experimental studies, where the concentrations of Ba and Sr in the formation water were varied. The results indicate that leaving out Ba and Sr of the FW used in experimental studies can lead to an unrepresentative initial wettability, as increasing the concentrations causes the system to become more water wet. It was also shown that the variations in Ba and Sr concentrations had an effect on potential low salinity effects. A more systematic concentration variation, evaluating the effects of Ba and Sr alone should be performed, and also effects of Ba and SR in different COBR systems should be tested.