Relationship between remaining oil saturation after waterflooding and rock/flow properties at laboratory and reservoir scale

The dependency of waterflood remaining oil saturation (S or ) on initial water saturation (S wi ), wettability and flow rate has been studied in the laboratory at core scale. For both water-wet and mixed-wet cores, S or was found to be inversely proportional to S wi . For mixed-wet cores, S or was also found to be inversely proportional to the number of pore volumes injected. In contrast, water-wet cores showed a dependency between S or and flow rate, indicating that pore structure plays an important role. The oil saturation development in several waterflooded intervals in the Gullfaks Field has been monitored, mainly by saturation logs, over several years. Oil saturation was found to decrease inversely with time after water breakthrough. Also, an oil saturation distribution with depth, which seems to depend on the balance between capillary and gravitational forces, was found.