The analysis of well tests constitutes one of the most powerful tools for the effective description of a petroleum reservoir and its subsequent management. This requires that the well test be placed in the proper context of related disciplines, especially geoscience, production and reservoir engineering. Modern methods of automated data processing can conceal mathematical limitations and overlook the need for realistic physical and geologic models. This book emphasizes the plausible physical contexts and mathematical models and limitations, and also the importance of realistic geologic models in analysis. This book should appeal to students as well as practitioners in industry; many in the latter group may have benefited before from formal exposure to the underlying theory and its limitations in real reservoir environments.