This paper describes rate derivative curves of constant pressure tests similar to derivative analysis for constant rate tests. Four rate decline derivatives: Cartesian, log-semi, semi-log, and log-log, are constructed, Typically, the rate derivative curves have some special characters. The specific characteristics of these derivative curves are related to the different flow regimes and various boundary effects. The derivative curves and decline curves can be used for well test interpretation and diagnostic in a similar way to the constant rate tests. Therefore, in some cases nonunique problems in well test analysis are eliminated. In this paper, we consider rate declines of an arbitrarily placed well in various shapes such as a circle, a rectangle, a stringer, and an irregular shape.

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