Numerical analysis of four analytical methods to interpret a pumping test influenced by a neighbouring active well

Simon Weber, Robert P. Chapuis

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Hydrogeology and Groundwater

ABSTRACT: analysis of four analytical methods to interpret a pumping test influenced by a neighbouring active well Simon Weber & Robert P. Chapuis Department of Civil, Geological and Mining Engineering École Polytechnique, Montréal, Québec, Canada ABSTRACT The influence of active neighbouring wells is often neglected when interpreting pumping test data. The authors proposed methods similar to the well-known Cooper-Jacob methods to interpret pumping test data influenced by a neighbouring well, to be used in the simple case of a homogeneous, isotropic, confined aquifer of infinite extension, provided the pumping rate of the interfering well and the time at which it started pumping are both known. Nevertheless, a few methods were previously proposed for the same conditions. This paper briefly sums up the four methods found in the literature to interpret this interference phenomenon and presents an application example of each of them on a numerical data set. These methods are, starting with the oldest, th method. The paper will discuss the pros and cons of these four methods. RÉSUMÉ de auteurs ont proposé des méthodes similaires à celles de Cooper-nterférent et le temps auquel il commence à pomper soient tous deux connus. Néanmoins, quelques méthodes existaient au préalable sous les mêmes conditions. Cet article résume brièvement les quatre méthodes trouvées dans ter ce phénomène Ces méthodes sont, en commençant par la plus ancienne, méthode de Cooper-Jacob généralisée et la méthode de Rushton. Cet article discute également les avantages et inconvénients de ces quatre méthodes. 1 INTRODUCTION Interference between wells during a pumping test is an important issue mentioned by Theis as early as 1935 in his well-known article. However, when interpreting a pumping test in a confined aquifer, neighbouring wells are rarely taken into account (Rushton 1985). The solution of the direct problem is a simple application of the superposition principle thanks to the linearity of the equations in a confined aquifer. The inverse problem, however, has not been much documented. Wenzel and Greenlee (1943) and Corapciolu (1977) have proposed two graphical methods based on the Theis equation. Cooper and Jacob (1946) developed their equations for many wells. These generalized equations were successfully used by Bentley (1979) in the Floridian aquifer. Rushton (1985) quantified the error committed when the interfering well is neglected and used it to correct the drawdown and determine the hydraulic parameters of the aquifer. Weber and Chapuis (2013) proposed new methods, easy to use since similar to the well-known Cooper-Jacob methods without interference to take into account an interfering well while interpreting pumping test data, in the simple case of a homogeneous isotropic confined aquifer, and declinations of these methods for anisotropic aquifers (Weber et al. 2014) or aquifers divided in two areas of different hydraulic properties, but with a similar diffusivity (Weber and Chapuis 2012). Other results on this interference phenomenon may also be found in Weber (2014). The present article sums up the four previously mentioned methods found in the literature during the research on the interference phenomenon. Application examples of these little-known methods are then presented on numerical data sets, before discussing their pros and cons. 2 THEORETICAL ASPECTS This section is meant to briefly sum up the four methods found in the literature as a basis for the following sections. For more theoretical details, the reader is invited to refer to the original papers. All the methods described in this paper were homogenous, isotropic, confined aquifers of infinite extension, with fully penetrating wells of infinitesimal diameter. Note that in the following sections, subscripts p, i and w respectively stand for the tested well, the interfering well(s) and all the active wells (tested and interfering).

RÉSUMÉ: ical analysis of four analytical methods to interpret a pumping test influenced by a neighbouring active well Simon Weber & Robert P. Chapuis Department of Civil, Geological and Mining Engineering

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Simon Weber; Robert P. Chapuis (2014) Numerical analysis of four analytical methods to interpret a pumping test influenced by a neighbouring active well in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper180,author = Simon Weber; Robert P. Chapuis,title = Numerical analysis of four analytical methods to interpret a pumping test influenced by a neighbouring active well,year = 2014}