This paper considers the influence of wellbore phase segregation effects on pressure buildup test data. Wellbore phase segregation is a phenomenon that occurs in a well that is shut in with gas and liquid in the wellbore leading to an anomalous increase in wellbore pressure. This paper presents the use of pressure derivatives to identify phase segregation distortion and to differentiate this distortion from behavior of dual porosity reservoirs. Practical analysis techniques are presented for such tests. Using an automatic history matching technique, four field examples of buildup tests distorted by wellbore storage and phase segregation are analyzed.

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