. For heavy oil systems, it may no longer be safe to assume that the local fluid distribution at a given saturation depends only on the first three factors listed above, and is independent of the viscosity ratio and fluid velocity involved as many people have assumed. Furthermore, while relative permeability of a fluid depends on its own distribution within the pore space of the medium, this may not be the case in heavy oil systems. Assuming that the residual oil is distributed within the porous medium in the form of small globules, if the viscosity of the oil is very high, these globules can behave like solid particles and may plug pore throats more efficiently than globules of a low viscosity of oil
. Also, the use of relative permeability model must also be carefully chosen since most of this model does not take viscosity into account.
More experiments with heavy oil are required to shed more light regarding the effect of each parameter on relative permeability. It cannot be assumed that these parameters will affect relative permeability of oil in the same way described earlier.
 Maini, B. and Okazawa, T., “Effects of temperature on heavy oil/water relative permeability of sand”, Journal of Canadian Petroleum Technology, May-June 1987, 33-41.
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