Improvement of Capillary Behavior in Oil-Wet Limestone Reservoirs through Seawater Injection

Capillarity is one of the most important factors, especially in tight reservoir rocks, which controls the fluid flows and entrapment of oil in a porous media. Capillary pressure and relative permeability of oil and brine are greatly affected by the wettability of system. The wettability of the system has had an influence on the distribution of fluids within the pores of the rock. It has been showed that the salinity of the injected water and its constituent ions can lead to change in the wettability of the reservoir rocks or change in the interfacial tension between the oil and brine; therefore, injected water affects the flow of fluids. In this study, the effect of seawater injection, containing acceptable amounts of Ca2+, Mg2+, and SO42- ions, on the capillary behavior of the system has been investigated. For this purpose, Relative permeability and centrifuge were carried out on outcrop limestone. Experimental results showed that Capillarity has been improved due to wettability alteration. Also, injection of seawater modified relative permeability of oil and brine towards more oil production.