Effects of non-uniform fluid saturation distribution on pressure transient analysis

Variations of fluid saturation in formation induce unusual trends in pressure transient data, which may cause ambiguities in well test interpretations. Nevertheless, uniform saturation distribution is a common assumption applied in all multiphase well test analysis methods and the effects of fluids saturation changes have not been taken into account in all these approaches. We present a theoretical model which includes non-uniform fluid saturation in pressure transient formulation. The application of the developed model is demonstrated using a simulation of a reservoir containing non-uniform oil and water saturations in the initial condition. This model provides a basis for better interpretation of unusual pressure transient behavior affected by non-uniform saturation distribution.