MODIFIED SALINITY WATERFLOOD COMPOSITIONS BASED ON MULTI-COMPONENT ION-EXCHANGE

This work computationally studies multi-component ion-exchange process and gives guidelines on modifying salinity of seawater used in waterflooding carbonate reservoirs. The study is restricted to \ce{Ca^2+}/\ce{Na^+} cation ion-exchange and cation (\ce{Ca^2+}) bridging mechanisms of oil binding. We find that injected seawater diluted with low salinity brine or de-ionized water shifts ion-exchange equilibrium toward stronger oil binding and is therefore inefficient strategy for improving incremental oil recovery. Instead, keeping salinity high, increasing sodium and decreasing calcium yields weaker oil binding. This should be the preferred strategy for modified salinity waterflooding.