A new analysis procedure for determining aquifer properties from slug test data

Abstract

A new method for determining hydraulic properties from slug test well data in a confined aquifer is presented. The new procedure is based on an exact equation which converts measured slug test head data to equivalent head data that would be obtained due to a constant discharge of a well with well bore storage and skin effects. A related procedure yields equivalent head derivative data (time rate of change of head) that would be obtained for the classical constant discharge with well bore storage and skin problem without applying numerical differentiation. After the constant discharge head data and its derivative data are generated by our procedure, these converted data can be analyzed by using existing well bore storage and skin type curves for the appropriate aquifer/well model. Therefore slug test type curves are no longer needed. For cases in which the relative change in the water level is not significant during the slug test, most of the converted data will fall on the unit slope line of the conventional well bore storage and skin type curves and it will be difficult to obtain a unique type curve match of converted head data. For such cases, it is shown that a discharge normalization procedure can be applied to improve the reliability of the analysis. A field case illustrating the reliability of the new method is presented.