ENGINEERING GEOLOGY WORLD Vol. XV, No. 2/2020
Lekhov M.V.
Lekhov M.V., 2020. Determining aquifer parameters by single-well pumping test. Engineering Geology World, Vol. XV, No. 2, pp. 36–48, https://doi.org/10.25296/1993-5056-2020-15-2-36-48.
Single-well pumpings are still widely used in studying the seepage properties of rocks, since they are much easier and cheaper than multi-well experiments. Determination of transmissivity based on the results of single-well experiments gives an ambiguous result due to the discrepancy between the lack of data and the variety of factors influencing the indicator curve of the water level drawdown in the well, the calculations of the parameters have systematic errors. Parameters obtained by single sampling are not confirmed by multi-well pumpings and the solution of the inverse seepage problem and are not suitable for use in predictive calculations. With regard to the main aquifer types for pumping out, the article discusses the features of the mode of the water level drawdown in a single-well and calculation schemes, summarizes and analyzes data processing methods, the nature and causes of errors. In practice, the usual methods of parameters calculation and experimental data processing remain attractive. The simplest and most understandable techniques follow from the Jacob and Hantush models, which allow to extend the dependencies obtained for a fully penetrating well in a planned-radial flow to the general case of pumping out of an partially penetrating well. Mathematically, the methods are beyond doubt. But almost always there is uncertainty in data processing, which is largely determined by screen skin and technical flaws. There is a contradiction between the analytical solutions developed for ideal conditions and the actual aquifer response, complicated by the effect of well storage, heterogeneity, anisotropy, elastic leakage, near-wellbore resistance, water table movement — factors, which are clearly not enough to characterize the data of a single-well experience. The article notes that a means to increase the reliability of the interpretation of experiments is to solve the direct modeling problem using the 1WELL pumping numerical simulation program.
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MIKHAIL V. LEKHOV
PhD (Geology and Mineralogy); Leading Research Scientist in the
Laboratory of Geological Environment Protection, Relationships Between
Surface and Ground Water, Faculty of Geology, Lomonosov Moscow
State University; Moscow, Russia