A Simple Data Analysis Method for a Pumping Test with Skin and Wellbore Storage Effects

In a pumping test conducted in a confined aquifer in northern Taiwan, drawdown in the observation well was Subject to wellbore storage of its own and the combined effect of wellbore storage and skin of the nearby pumping well. For Such a complicated pumping test condition, the appropriate well hydraulics solutions are complicated in mathematics and involve five unknown a priori parameters; namely, the aquifer transmissivity, the aquifer storage coefficient, the skin factor of the Pumping well, and the wellbore storage coefficients of the pumping and observation wells. The conventional trial-and-error procedure for a simultaneous determination of these five parameters is not easy to apply. Here, a simple data analysis method is developed, which takes advantage of the late-time characteristics of drawdown data and the late-time asymptotic behavior of the appropriate well hydraulics solutions. As a result, some currently available graphic techniques are proven useful for the determination of these parameters. Validity of this approach is verified by the excellent agreement between the calculated drawdown using the appropriate well hydraulics solutions with the parameter estimates obtained from the field drawdown data.