Type Curves for Unsteady Flow to a Large-Diameter Well in Patchy Aquifers

Abstract

This paper analytically considers unsteady flow to a large-diameter well with the well storage in patchy aquifers that is cylindrically composed of two distinctive regions around the well with different hydraulic properties. The solution involves the usage of the independent variable transform. This approach gives, for both regions, the type curves that are dependent on the distance from the pumping well to the interface between two regions and the hydraulic parameter. The parameter is implied as the ratio of the transmissivity and the storage coefficients of two regions. A new well function expression—different from the well-known Theis well function—is defined to evaluate the field data. The function is seen as an approximation and is easily applicable to estimate the transmissivity and the storage coefficients of the patchy aquifers.