Improved Understanding of Zeta Potentials in Intact Natural Rock Cores and Implications for Controlled Salinity Waterflooding

Summary It is well known that modifying the injection brine composition during waterflooding by controlling the type of ionic species present or the total salinity can lead to improved oil recovery (IOR) however the underlying mechanisms are still not fully understood and there is no accepted method to predict when controlled salinity waterflooding (CSW) will lead to an increase in oil recovery or not. It has been previously determined that IOR responses can be correlated with changes in the zeta potential of the mineral-brine and oil-brine interfaces in carbonate cores. In order to observe IOR the modified salinity brine must change the zeta potential to make the electrostatic forces between the two interfaces more repulsive. Here we present an updated suite of carbonate zeta potential data and coreflood results with several new crude oils tested. This study further includes the first zeta potential measurements on natural intact sandstone cores, over a range of mineralogies, saturated with reservoir relevant brines, along with coreflood results and inferred oil-brine polarities. These results, and the zeta potential model are compared to those previously obtained for carbonates.