Measurement and Modeling of Excess Oil Flow During Tertiary Gas Flood

Relative permeabilities for three-phase flow are commonly predicted from two-phase flow measurements using empirical models. These models are usually tested against available steady state data. However, the oil flow is unsteady state during various production stages such as gas injection after water flood. Accurate measurement of oil permeability (k_ro) during unsteady tertiary gas flood is necessary to study macroscopic oil displacement rate under micro scale events including double drainage, coalescence and reconnection, bulk flow and film drainage.

We conduct several unsteady state three-phase gravity drainage experiments with different initial conditions. We calculate k_ro by using the saturation data measured by a CT scanner. We find that the k_ro data measured during gas flooding to recover waterflood residual oil, are unexpectedly high and weakly depend on oil saturation. In contrast to steady state data, the measured k_ro data here are higher than the two-phase gas/oil limit. We explain how Stone I and saturation-weighted interpolation should be used to predict the permeability of mobilized oil during transient tertiary gasflood.