Analysis of pressure buildup data influenced by wellbore phase redistribution

Using a theoretical model recently proposed by Fair, this work considers the influence of wellbore phase redistribution effects on the analysis of pressure buildup data. In the first major part of this work, the authors first show that the pressure responses, observed when phase redistribution effects exist, consist of three distinct types, and delineate the conditions under which each of these types exist. Second, they investigate the reliability of using Fair's type curves for analyzing pressure data. Third, for each of the three types of pressure responses, we provide rules for determining when the conventional semilog straight line will begin on a semilog plot of pressure data versus time. In the second major part of this work, they consider general procedures based on Duhamel's principle for analyzing pressure data when sandface flow rates are also available. The application of these methods to analyze pressure data influenced by wellbore storage effects and investigate the effect that errors in the measured sandface rate have on the analysis is discussed.