Slug tests in a confined aquifer: experimental results in a large soil tank and numerical modeling

2002 ◽  
Vol 39 (1) ◽  
pp. 14-21 ◽  
Author(s):  
Robert P Chapuis ◽  
Djaouida Chenaf
Keyword(s):  
Numerical Modeling ◽  
Elastic Solid ◽  
Conservation Equation ◽  
Solid Matrix ◽  
Confined Aquifer ◽  
Slug Test ◽  
Slug Tests ◽  
Variable Head ◽  
Large Tank ◽  
Straight Lines

Variable-head (slug) tests in a confined aquifer can be interpreted using different methods that either consider or neglect the influence of the instantaneous deformation of an elastic solid matrix. This paper defines a unified interpretation for slug tests: it is based on the velocity graph describing the conservation equation underlying all methods. If the storativity S has no influence, the velocity graph is a straight line. If S has an influence, the theory considering this influence predicts the graph should be a curve. Numerous slug tests were performed in a large tank containing a confined aquifer. Other tests were used to determine independently the transmissivity T and S values of the confined aquifer which are compared with those obtained from slug tests. The velocity graphs of the slug tests provided straight lines instead of the smooth curves as predicted by the theory. A numerical analysis of these tests in the sand tank was performed using a finite element method. The analysis gave straight lines instead of curves for any S value and therefore confirmed the experimental observation (in velocity graphs) that slug test results do not depend of S and thus cannot be used to determine the S value.Key words: slug test, hydraulic conductivity, storativity, numerical modeling.

Overdamped slug test in monitoring wells: review of interpretation methods with mathematical, physical, and numerical analysis of storativity influence

1998 ◽  
Vol 35 (5) ◽  
pp. 697-719 ◽  
Author(s):  
Robert P Chapuis
Keyword(s):  
Numerical Analysis ◽  
Classical Solution ◽  
Heat Conduction Problem ◽  
Solid Matrix ◽  
Test Results ◽  
Slug Test ◽  
Slug Tests ◽  
Monitoring Wells ◽  
Pulse Test ◽  
Negligible Influence

Several methods are available to interpret slug tests; however, when applied to the same test data, they usually yield very different results. The methods are classified into three categories depending on their assumptions about the solid matrix deformability during the test. This paper deals with overdamped tests for elastic solids that deform instantaneously. It provides a unified interpretation of transmissivity T and storativity S based on the velocity graph for variable-head tests in monitoring wells or cased boreholes. If S has little influence, the velocity graph is a straight line. If S has some influence, the graph should give a smooth curve. However, smooth curves are exceptions in practice, thereby leading to a reexamination of the influence of S during a slug test. Three independent approaches are used. (1) A mathematical review shows that the overdamped solution, as adapted from a heat conduction problem, did not correctly treat storativity terms and the type of problem: it corresponds to a special pulse test, not a slug test. (2) A physical investigation of deformability shows that the influence of S does not exceed 1% of the initial slug for most compressible materials. Thus, it is almost impossible to detect its influence in test results. (3) Numerical analyses confirm that S has a negligible influence: test results provide straight lines, not curves. The numerical analysis of the special pulse test provides exactly the classical solution, and the correct values of T and S after eliminating the confusion about storativity terms. It is concluded that (1) S has a negligible influence in slug tests, (2) the existing classical solution giving T and S must be abandoned, and (3) the velocity-graph equation and its integral equation (Hvorslev or Bouwer and Rice) which correctly describe the process must be used.Key words: slug test, hydraulic conductivity, storativity, numerical modeling.

scholarly journals Simple methods for quick determination of aquifer parameters using slug tests

2016 ◽  
Vol 48 (2) ◽  
pp. 326-339 ◽  
Author(s):  
A. Ufuk Şahin
Keyword(s):  
Field Data ◽  
Random Noise ◽  
Time Shift ◽  
Real Field ◽  
Hydraulic Parameters ◽  
Arc Length ◽  
Slug Test ◽  
Slug Tests ◽  
Aquifer Parameters ◽  
Heterogeneous Rock

The slug test is still one of the simplest and cost-effective methods to interpret the hydraulic parameters for aquifer analysis. This study introduces two new estimation approaches for the slug test, the time shift method (TSM) and arc-length matching method (AMM), to identify aquifer parameters in a reliable and accurate manner, which was established on the idea that any change in the normalized drawdown or arc-length measurements of the data curve at the predefined drawdown levels is linked with the variation of storativity. These approaches remove the need for superimposition of the type curves and the field data. The proposed methods are straightforward to apply and automatize the parameter estimation process. TSM and AMM were tested with a number of numerical experiments including synthetically generated data augmented with random noise, hypothetical slug tests conducted in a heterogeneous rock-fracture system, and well-known real field data. The skin effect was also implemented to evaluate its impact on the estimation performance of the suggested approaches. The results verified that both proposed methods are able to produce estimates of hydraulic parameters more accurately than existing methods. The proposed methods could serve as a viable supplementary interpretation tool for slug test analysis.

scholarly journals Partially penetrating slug tests in an unweathered till layer

2016 ◽  
Vol 48 (1) ◽  
pp. 117-132
Author(s):  
David W. Ostendorf ◽  
William G. Lukas ◽  
Don J. DeGroot
Keyword(s):  
Laplace Transform ◽  
Spline Function ◽  
Inverse Laplace Transform ◽  
Short Term ◽  
Slug Test ◽  
Slug Tests ◽  
Monitoring Wells ◽  
Exponential Spline ◽  
Eastern Massachusetts

This research improves field based estimates of aquitard compressibility and permeability. A semianalytical model of partially penetrating, overdamped slug tests achieves this objective. The short term solution is an existing fully penetrating model, the long term solution is the polar residue of an inverse Laplace transform, and an exponential spline function patches the solutions together. Large amplitude slug test data from ten pairs of partially penetrating monitoring wells installed in an unweathered till at Scituate Hill in eastern Massachusetts calibrate the model. The deposit is bound by weathered till and the Dedham Granite fracture zone, and both are far more permeable than the unweathered till. The calibrated till permeability of 8.4 × 10–16 m2 is about 25% less than existing model calibrations that include boundary recharge in permeability values. The calibrated till compressibility of 5.1 × 10–10 Pa–1 reflects the proper inclusion of recharge as a long term source of groundwater, rather than the unrealistically large compressibility calibrations required by fully penetrating models.

The Role of Terzaghi Effective Stress in Linearly Elastic Deformation

1983 ◽  
Vol 105 (4) ◽  
pp. 509-511 ◽  
Author(s):  
M. M. Carroll ◽  
N. Katsube
Keyword(s):  
Elastic Deformation ◽  
Effective Stress ◽  
Linear Elasticity ◽  
Simple Form ◽  
Pore Space ◽  
Elastic Solid ◽  
Solid Matrix ◽  
Pore Geometry ◽  
Average Strain

It has been shown that the overall strain of a fluid-filled porous elastic solid is not governed by the Terzaghi effective stress law. We show, in the context of anisotropic linear elasticity, that the overall strain may be resolved into a component which is the average strain of the solid matrix and a component due to change in relative pore geometry, and that the latter is determined by the Terzaghi effective stress. This leads to a simple form of the response laws and, in particular, to effective stress laws for overall strain (obtained previously) and for strain of the pore space.

scholarly journals Comparison of slug test methods to determine conductivity of Holocen aquifer, Dan Phuong area

2020 ◽  
Vol 61 (4) ◽  
pp. 57-66
Author(s):  
Thao Bach Nguyen ◽  
Keyword(s):  
Comparative Analysis ◽  
Real Life ◽  
Method Comparison ◽  
Test Methods ◽  
Field Site ◽  
Slug Test ◽  
Slug Tests ◽  
Well Depth

Two different slug test methods including: i) slug test using the standard slug rod and ii) pneumatic slug test are conducted in different well/depth in Danphuong field site for a comparative analysis. These methods are examined at least 3 times for each well to estimate hydraulic conductivities by using Hvorslev. The results show correlation between two slug test methods is very hight with R2 = 0,93. Slug tests methods have several advantages and also disadvantage compare to each other. Practical considerations of performing the tests in real life settings are also considered in the method comparison. The slug-rod method meets 7/10 criterions while pneumatic slug test satisfy 8/10 criterions.

scholarly journals Smoothing of Slug Tests for Laboratory Scale Aquifer Assessment—A Comparison Among Different Porous Media

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1569 ◽  
Author(s):  
Aristodemo ◽  
Lauria ◽  
Tripepi ◽  
Rivera-Velasquéz
Keyword(s):  
Porous Media ◽  
Wavelet Transform ◽  
Large Scale ◽  
Hydraulic Head ◽  
Frequency Noise ◽  
Confined Aquifer ◽  
Slug Tests ◽  
Experimental Laboratory ◽  
The Fourier Transform ◽  
The University

A filtering analysis of hydraulic head data deduced from slug tests injected in a confined aquifer with different porous media is proposed. Experimental laboratory tests were conducted in a large-scale physical model developed at the University of Calabria. The hydraulic head data were deduced from the records of a pressure sensor arranged in the injection well and subjected to a processing operation to filter the high-frequency noise. The involved smoothing techniques are the Fourier transform and two types of wavelet transform. The performances of the filtered hydraulic heads were examined for different slug volumes and four model layouts in terms of optimal fitting of the Cooper’s analytical solution. The hydraulic head variations in the confined aquifer were analyzed using wavelet transform in order to discover their energy contributions and frequency oscillations. Finally, the raw and smoothed hydraulic heads were adopted to calculate the hydraulic conductivity of the aquifer.

Effects of monitoring and pumping well pipe capacities during pumping tests in confined aquifers

2003 ◽  
Vol 40 (6) ◽  
pp. 1093-1103 ◽  
Author(s):  
Robert P Chapuis ◽  
Djaouida Chenaf
Keyword(s):  
Water Storage ◽  
Pumping Test ◽  
Unconfined Aquifer ◽  
Confined Aquifer ◽  
Pumping Tests ◽  
Constant Flow Rate ◽  
Pumping Wells ◽  
Confined Aquifers ◽  
Large Tank ◽  
Definition Of

This paper establishes how the water stored in the pipes of monitoring and pumping wells influences the drawdown curves of pumping tests in confined aquifers. Experimental and numerical results obtained with a physical model are first studied and then confirmed by field-test data. A large tank was used for fully controlled pumping tests. It contains a lower confined aquifer, an aquitard, and an upper unconfined aquifer. Pumping tests at a constant flow rate in the confined aquifer provided drawdowns that were analyzed for unsteady-state, steady-state, and recovery conditions. For a single monitoring well, the different interpretation methods provided similar values of transmissivity, T, and storativity, S. Drawdown curves gave much too high S values. These S values were equal to those resulting from water storage in the pipes of monitoring and pumping wells, according to the physical definition of storativity. The experimental T and S values were confirmed by two numerical analyses (finite elements) of the pumping test, one considering no water was stored in the pipes and the other considering stored water. Data of real pumping tests in confined aquifers confirmed that the S value calculated from drawdown curves can be influenced by water storage in monitoring and pumping wells for usual pipe diameters.Key words: pumping test, transmissivity, storativity, sandbox, in situ test, pipe capacity.

Hydrodynamic Response — or Slug Tests as a Means to Monitor the Progress of Well Development

1975 ◽  
Vol 12 (1) ◽  
pp. 1-12 ◽  
Author(s):  
J. A. Vonhof
Keyword(s):  
Development Process ◽  
Water Levels ◽  
Clear Water ◽  
Easy Method ◽  
Test Analysis ◽  
Slug Test ◽  
Slug Tests ◽  
Sand Aquifer ◽  
Hydrodynamic Response ◽  
Well Development

Sequential hydrodynamic response—or slug tests in a well during well development—provide an easy method for objective measurement of well development and comparison of the various development techniques that may be employed. Slug-test equipment developed in Saskatchewan permits precise continuous recording of changing water levels for all times except the first few seconds after the introduction of the slug into the well. Three examples of slug-test analysis indicate jetting and air development to be the most successful techniques for well development in a sand aquifer in southeastern Saskatchewan; mechanical surging, on the other hand, actually reversed the development process in the aquifer. The substitution of a bentonite mud for clear water in drilling out the completion zone in one well proved to be highly undesirable because considerably more effort and time were required to develop this well.

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