Wettability and Relative Permeability of Prudhoe Bay: A Case Study in Mixed-Wet Reservoirs

Abstract

Summary This paper describes the variation in wettability and relative permeability at Prudhoe Bay. We show that measurements are consistent with recent theories of the relationship between water-saturation, pH, wettability and relative permeability.1 In particular, the wettability of the reservoir changes from water-wet low on structure near the water/oil contact to mixed-wet behavior higher on structure. Increasing oil-wetting character is correlated to decreasing water saturation. Changes in wettability are also accompanied by changes in water-flood recovery efficiency and are optimum at Amott indices approaching zero. Lithology also impacts recovery efficiency, with more clay-rich rocks having higher residual oil saturations.