Schlumberger book:

Well testing applications There are many applications of well testing, but they are grouped into four fundamental classes. Formation pressure measurement This class of application uses the direct static formation pressure measurement. It includes static pressure measurement and depletion determination determination of the inflow performance and productivity index (PI) of the reservoir and, in gas wells, the absolute open flow (AOF) potential of the reservoir determination of reservoir fluid density from gradients determination of reservoir fluid contacts identification of reservoir vertical permeability barriers identification of vertical flow through layered sequences in developed reservoirs numerical reservoir simulation applications. Permeabilityand skin The pressure and associated measurements (e.g., downhole flow) are interpreted to yield reservoir dynamic parameters relevant to fluid flow, such as formation permeability, and any occurrence of skin (e.g., formation damage) that would impair the flow. The measurements will help determine reservoir permeability well deliverability adamaged or stimulated well condition vertical rock permeability the efficiency of stimulation treatments