This paper presents the application of the derivative of pressure technique, through a process of pattern recognition, to identify bounded reservoir behaviour under both drawdown and build up conditions. During a well test, the flow and shut in sequence should be carefully selected to optimise the response which will, in turn, enable easier recognition of the outer boundary configuration and reduce the problems of non-uniqueness. With the evolution of high resolution and accuracy pressure gauges, and the introduction of simultaneous downhole flowrate and pressure measurement, convolution techniques should also be utilised to enable the analysis of previously uninterpretable drawdown data.

The pressure derivative technique provides a systematic and global approach to describe the late time features. With this technique, there is no need to resort to specialized analysis methods or correlations for well behaviour in bounded reservoirs, which are available for limited geometries and can yield erroneous results.

Due to the unusual outer boundary features now exhibited by a large number of current well tests, there is a growing need to develop better models to describe their effects. There is an even greater need to incorporate these findings with other sources of data for appropriate dynamic bounded reservoir description.

Three field examples are presented which illustrate the problems associated with interpretation of buildup data when drawdown analysis has not been possible.

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