Well testing is the science of measuring pressure changes in wells and interpreting those pressure changes. It is used to provide several types of information that include estimation of permeability, formation damage or stimulation, pressure, length & conductivity of fractures, flow barriers, communication between wells and drainage volume. The three areas addressed by well testing are reservoir evaluation - to determine if the well has sufficient flow capacity to complete and to obtain reservoir information for predicting and analyzing reservoir behavior; reservoir management - to diagnose the condition of production and injection wells to optimize performance, identify candidates for workover and track the movement of fluid fronts in the reservoir; and reservoir description - to identify heterogeneities such as different rock types, stratigraphic interfaces, and faults and barriers.