A Method for the Flow Diagnosis and Interpretation of a Well Test Through the Useof the Pressure Derivative Function

Abstract

This paper presents an alternative technique for transient pressure analysis. The new method is based on the pressure derivative function and the impulse theory. This method uses a mathematical and graphical evaluation of an equation of the type [t,,,~] t"fAp', = m;, where nf is related to the specific flow pattern toward the well and the constant mi with the formation conductivity. This procedure simultaneously allows the diagnosis of the flow pattern through the presence of a horizontal line of a graph of [tc,,.,~] tYLfAp; versus t, and an estimation of the formation conductivity through the value of the constant mi, given by the intersection of this line with the ordinate axis. In the ordinate graphing group, t,,,~ is a correction factor for variable rate producing conditions, approximately equal to unity for long producing times. For constant rate drawdown tests this factor is equal to one. f in this graphing group stands for the type of flow prevailing during a specific period of the test, i.e., spherical, linear, or radial. Variable well flow rates are also considered in the theory of analysis presented in this study. This new method is successfully applied to three field cases published in the literature.