Pressure – Time data obtained during a pressure transient test include the effect of non-reservoir factors besides the reservoir response. Improper diagnosis to differentiate between reservoir and non-reservoir effects causes misinterpretation of well test data. Phase redistribution is one of the major nonreservoir factors. Even the best available diagnostic techniques fail to detect the phase redistribution effects when they are not obvious from the analysis plots and the data do not match the pressure derivative type curves over the complete time range. One can only suspect the phase redistribution in this case. Verification of anomalous effect due to wellbore phase redistribution is required. In the field of exploration geophysics, there have been established methods for the detection of anomalies in the gravity, magnetic or seismic data. In this paper new analysis techniques besides some of the major techniques from exploration geophysics are applied to transient well test data. And their relative success is discussed for the detection of wellbore phase redistribution effects.

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