Linear Curve Fitting Methods for Analyzing Slug Tests in Compressible Aquifer

The linear curve fitting methods such as the Hvorslev method and the Bouwer and Rice method provide a rapid and simple means to analyze slug test data for estimating in-situ hydraulic conductivity (k) of geologic material. However, when analyzing a slug test in a relatively compressible aquifer, these methods have difficulties to fit a straight line to the semi-logarithmic plot of the test data that shows a concave-upward curvature because the linear curve fitting methods ignore the role of the compressibility or specific storage (S_s) of an aquifer. The comparison of the Hvorslev method and the Bouwer and Rice method is made for a partially-penetrating well geometry to show analytically that the Hvorslev method estimates higher hydraulic conductivity than the Bouwer and Rice method except that the well intake section locates very close to the bottom of the aquifer. The effect of fitting a straight line to the slug test data is evaluated along with the dimensionless compressibility parameter (α) ranging from 0.001 to 1.