Effect of brine composition on wettability and oil recovery of a Prudhoe Bay crude oil

Waterflood recoveries of a Prudhoe Bay crude oil from Berea Sandstone were determined for two brine compositions used previously in a study of the effect of brine composition on the recovery of Moutray crude oil. These brines will be termed Brine 1 and Brine 2. For standard waterfloods (no difference between the initial and injected brine composition) Brine 1 (4 wt% NaC1 + 0.5 wt% CaCl2) gave 16% higher recovery (% original oil in place) than Brine 2 (0 wt% NaCl + 2 wt% CaCl2). Recovery by injection of Brine 1, with Brine 2 as the initial brine, or vice versa, gave recoveries, even at breakthrough, that were intermediate to the results of standard waterfloods (no Change in brine composition). Standard waterflood recoveries for synthetic reservoir brine were comparable to those obtained with Brine 1,Thr results demonstrate that brine composition can have a large effect on oil recovery and that displacement efficiency is not necessarily dominated by the composition of the initial (connate) brine.