Field-Wide Variations in Residual Oil Saturation in a North Sea Sandstone Reservoir

Summary An extensive set of core waterflood data is analyzed to provide a reservoir-wide description of residual oil saturation, Sor. Such core tests are influenced by many parameters, including rock structure, wettability, fluid properties, and experimental procedures. With a data set as large as that used here (more than 200 waterfloods) the effects of these factors can be separated. We investigated rock structure, permeability, porosity, initial water saturation, Swi, and wettability. The data indicated that variations in Sor were caused by trends in Swi and wettability, both of which varied with depth across the transition zone. This implies that a unique Soi/Sor relationship for this reservoir does not exist. The work presented here was used to rescale relative permeability data in regions of the field where spatial variation in Swi exists. The value of the large database for defining trends in reservoir behavior was significant and enabled more accurate reservoir simulation.