Journal Published Online: 17 May 2023
Volume 46, Issue 4

Recent and New Information from the Slug Test Data of Ferris and Knowles (1954)



The slug test theories take into account or not the tested material storativity, S. Ferris and Knowles (1954) proposed a first theory with S, the Ferris-Knowles (FK) theory. A few reasons were given to reject it in the 1970s. New and stronger reasons are given here. The FK test was incomplete because the data started 75 seconds after slugging with a large volume of water. These data are reinterpreted here with recent and correct methods, which have proven that the theories with S are wrong and cannot give an S value. The FK partial data yield a straight velocity plot, typical of all slug tests in aquifers, and a small piezometric error of 1 cm. During the first 75 seconds, 99 % of the water volume left the riser pipe to enter the aquifer. The only data (t > 75 s) were for the last 1 % of the water volume. The article shows that the FK theory yields an elastic S value corresponding to peat, which is nonsense. If the authors tested an aquifer, then their late data described the return to equilibrium of a water mound due to slugging 150 L of water and not the slug test data, which took place in the first 75 seconds. The delay in starting data collection may have been due to long dynamic effects with gas trapping and outgassing after slugging with a huge volume of water, but this was not documented. The correct methods for slug tests show that the FK theory tries to fit an exponential with a hyperbola. The FK theory was the first of weird methods trying to find the S value with confusing math and physics, which have so far delayed the use of physically correct methods in ASTM standards for slug tests.

Author Information

Chapuis, Robert P.
Department of Civil, Geological and Mining Engineering, Polytechnique Montréal, Montréal, Quebec, Canada
Pages: 20
Price: $25.00
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Stock #: GTJ20220167
ISSN: 0149-6115
DOI: 10.1520/GTJ20220167