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Abstract

The conventional log-log diagnostic plot with pressure change and derivative with respect to the superposition time function has been applied with tremendous success in diagnosis of reservoir behavior by giving the buildup pressure response a shape similar to that of the drawdown response for a wide variety of different boundary conditions. However, this very success has led in a number of cases to overconfidence in its applicability and interpretation using an inappropriate reservoir model.

This paper discusses the use of a diagnostic plot comprising the pressure change and pressure derivative calculated with respect to, and graphed vs., shutin time. This form of the diagnostic plot requires a catalog of buildup pressure responses for different reservoir geometries and different producing times. This paper provides such a catalog for several common reservoir geometries.

Three field examples illustrating the application of the diagnostic plot using the derivative vs. shutin time are presented.