Wettability evaluation of a carbonate reservoir rock from core to pore level

Wettability evaluation was performed during stages of as received, cleaned, and restored states on core samples from a Saudi Arabian carbonate reservoir. The wettability behavior from the chemistry of brine-oil-carbonate rock interaction was found to be neutral to slightly oil-wet. The pore size distribution obtained from mercury injection data indicated that about 15-20 percent of the pore volume is not accessible to asphaltene particles in the crude oil. Therefore a mixed-wettability state can exist. The results were confirmed by the evaluation of the wettability of the cores using USBM and Amott techniques.