The Role of Capillary Pressure in Compositional Simulation of Heterogeneous Reservoirs

Compositional simulations (neglecting gravity) of a simple reservoir element consisting of regions of high and low permeability reveal imbibition of oil into the low permeability region during depletion, and extraction of the oil from this region during lean gas injection by `capillary pumping', a mechanism driven by variations in interfacial tension. Initial fluid composition is found to have a significant effect. The range of dimensionless capillary numbers for which capillary pressure may be neglected is determined, but evaluation of these numbers is not easy.