WETTABILITY AND RELATIVE PERMEABILITY OF PRUDHOE BAY - A CASE-STUDY IN MIXED-WET RESERVOIRS

This paper describes the variation in wettability and relative permeab ility at Prudhoe Bay. We show that measurements are consistent with re cent theories of the relationship between water-saturation, pH, wettab ility and relative permeability.(1) In particular, the wettability of the reservoir changes from water-wet low on structure near the water/o il contact to mixed-wet behavior higher on structure. Increasing oil/w etting character is correlated to decreasing water saturation. Changes in wettability are also accompanied by changes in water-flood recover y efficiency and are optimum at Amott indices approaching zero. Lithol ogy also impacts recovery efficiency, with more clay-rich rocks having higher residual oil saturations.