The Reservoir flow capacity and well productivity index can be derived from pressure transient analysis using data acquired during well testing. In the case of exploratory wells, testing rates as well as bottom hole pressures are acquired under a temporary well completion that consists basically of a production tubing and a separator (no flow lines), which may not be the final production system layout for the well.
A simple production system layout consists of wells, flowlines, production manifold, separator, metering instruments just to mention a few and the study of the pressure-rate relationship throughout the system helps in defining the expected value for the well flow rate for a given values of production parameters. All pressure drops from the reservoir, completion, production manifold and flowlines to the final crude storage vessels need to be known at any production time. Flow rate sensibility to different controlling parameters like pipes ID, gas-oil ratio, wellhead, separator and flowline pressures, PVT fluid parameters, water cut should be carried out to understand the impact on final well production rate.
Although rate transient analysis and decline curve analysis according to the literature is treated almost independently of pressure transient analysis needless to say that well productivity and reservoir performance evaluation is enhanced by combining simultaneously both pressure and rate transient analysis.
