Modeling the mobilization of connate water while injecting water to displace oil

The presence of connate water in an oil reservoir can significantly affect oil recovery. The mobility of the connate water can have adverse effects on the success of injected water additives designed to increase oil recovery. This research is an effort to characterize the mechanisms involved in the displacement process of connate water. This dissertation is the first attempt to characterize connate water mechanisms by creating a set of relative permeability curves to describe the injected water displacing connate water in a system that contains oil, injected water and connate water. The work in the dissertation is a detailed analysis of the displacement test.

Buckley and Leverett developed the theory and equation to predict the mobility (fractional flow) of oil and water from oil and water relative permeability curves. The Buckley/Leverett equation is the basis of the unsteady-state method of creating relative permeability curves from displacement tests of immiscible fluids.

This dissertation presents a modification of the Buckley/Leverett theory to characterize the miscible displacement of connate water by injected water. Relative permeability curves for connate and injected water were created from fractional flow values determined by using the expanded Buckley/Leverett theory. The relative permeability curves describe the mobility of connate water as the water saturation increases due to water injection.

The combined set of permeability values can be used in a four-component computer simulation routine to predict how the oil recovery was influenced by connate water mobility in a field scale enhanced oil recovery program.