Abstract
As the climate is changing, greater exploitation of groundwater reserves is becoming evident; however, this would have been apparent even without climate change. Therefore, increasing emphasis is given to maintaining well functionality. Wells are susceptible to aging, which reduces their efficiency. Today, there exist several solutions for determining the size of additional resistance (the skin effect), which indicates a well’s current state and that of its close surroundings. The implementation of most of these solutions is often time-consuming. To improve our tools, a goal has been set to accelerate and facilitate the method of determining the size of additional resistance. In this study, we present new software that accelerates this process. It applies an innovative method based upon a partial differential equation describing the radially symmetric flow to a real well, which occurs under an unsteady regime, using the Laplace transform. Stehfest algorithm 368 is used to invert the Laplace transform. Such software can be used to evaluate an additional-resistance well, even when a straight section evaluated using the Cooper–Jacob method is not achieved in the semilogarithmic plot of drawdown vs. log time during the pumping test. This solution is demonstrated in the comprehensive evaluation of 10 wells and 3 synthetic pumping tests.
Highlights
Pumping tests are conducted for the purpose of determining aquifer parameters, and well parameters
Cooper and Jacob [3] built on this work by simplifying the Theis well function, generating a straight section for longer pumping test times when plotting drawdown vs. the logarithm of time and incorporating only the first two elements of the Theis well function, while omitting the others
The obtained parameters are compared with the value that most corresponds to reality. This cross-sectional value for individual runs of pumping tests was obtained by applying the computing method at the core of the software
Summary
Pumping tests are conducted for the purpose of determining aquifer parameters (hydraulic conductivity, transmissivity and storativity), and well parameters (e.g., the coefficient of additional resistance, known as the skin factor, and well storage). Theis used an analog equation describing thermal conduction in a solid environment to describe groundwater flow through a permeable environment [2]. His solution is used to determine an aquifer’s transmissivity and storativity in the case of a well without additional resistances and with a negligibly small radius, and is known as the Theis type-curve method. Pumping tests on actual wells are influenced first by additional resistances (expressed by the skin effect). Mathias and Butler [12]
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