A method, a system and a program storage device for predicting a property of a fluid, such as fluid production from a subterranean reservoir containing heavy oil entrained with gas is described. The method includes developing a baseline correlation of gas relative permeability krg versus gas saturation Sg. A capillary number dependent correlation is determined capturing the relationship between at least one of critical gas saturation Sgc and capillary number Nca and gas relative permeability krgro and capillary number Nca phased upon a plurality of depletion rates. Capillary numbers Nc are calculated for a plurality of cells in a reservoir model representative of the subterranean reservoir. The baseline correlation is then adjusted to comport with at least one of Sgc and krgro selected from the capillary number dependent correlation to produce a plurality of corresponding adjusted baseline, correlations. Gas relative permeabilities krg for the plurality of cells are selected from the corresponding adjusted baseline correlations. A reservoir simulation is then run utilizing the selected relative permeabilities krg to predict a property of at least one fluid in a subterranean reservoir containing heavy oil entrained with gas.