Abstract
Low salinity has been studied extensively, but still the mechanisms for improved oil recovery by lowering brine salinity are unsolved. The target of this paper was to address this problem and make systematic studies that can give insight to the key mechanisms. Given the variety of conditions under which increased recovery by low salinity brine injection may or may not be observed, it is likely that more than one mechanism is contributing to the observed oil recovery. The mechanisms most claimed to be the reason for improved oil recovery are shift in wettability, multi-component ion exchange, and dissolution/fines migration.
In this paper, we have studied low salinity waterflood by systematic changing the rock wettability. The wettability is changed by varying aging with crude oil at elevated temperature. We are investigating how aging time effect affects core analysis properties like; spontaneous imbibition, Amott-Harvey and USBM wettability oil and water indices. The wetting properties were also cross-checked by NMR.
The detailed core analysis is the background for study of oil recovery by seawater injection and subsequent lowering of salinity. In addition to detecting trends of initial wetting and the potential for low salinity, all mechanisms for low salinity recovery are discussed. It is expected from the literature that the clay content in Berea cores favors oil recovery by low salinity waterflooding, however the more oil wet character of the Bentheimer cores in this study, seems more important for improved oil recovery by low salinity waterflood.
