Hyung T. Kwak

New Insights on the Role of Multivalent Ions in Water-Carbonate Rock Interactions

in the oil industry today. Almost all the conventional reservoirs go through a waterflood cycle to recover a portion of the remaining oil after pressure depletion. A considerable amount of oil still remains trapped underground, however, even after secondary waterfloods. This is attributed to inefficient macroscopic sweep and the microscopic capillary trapping caused by interfacial and surface forces that retain the oil within the pores. Currently, the oil industry is showing great interest in improved enhanced oil recovery (EOR) technologies to either maximize the ultimate oil recovery by waterflooding or recover additional oil from the residual oil left behind after waterflooding. The chemical properties of the injected water initially were not considered in the design of a waterflooding project except for the purpose of preventing formation damage triggered by an incompatibility between injected and formation waters. In recent years, extensive research into both sandstone and carbonate reservoirs has shown that tuning the salinity and ionic composition of the injected water can favorably affect oil/brine/rock interactions, alter rock wettability, enhance microscopic displacement efficiency and eventually improve waterflood oil recovery. As reported in other work, we refer to brine with a designed composition as “SmartWater” and to the waterflooding process governed by increased oil recovery as “SmartWater Flooding.” Unlike conventional EOR, SmartWater Flooding can be implemented at any time during the life cycle of a reservoir, and with minimal investment in current operations it can potentially provide higher