SINGLE WELL RESPONSE TESTS

a.k.a. Slug Tests     

The previous newsletter discussed some basic concepts of pumping tests, which are used for estimating hydraulic parameters in the large scale.  In this newsletter we will discuss single well response tests, otherwise known as slug tests, which are used for in-situ estimation of hydraulic parameters at an intermediate to small scale. 

Many people consider pumping tests and slug tests to be very similar, if not essentially the same, however, there are inherent differences between the two.  This newsletter will highlight some of the features of slug tests which differentiate it from other aquifer tests.

1.  What is a slug test?

2.  What are the benefits of a slug test?

3.  What are some problems/limitations of slug tests?

4.  What are some types of slug tests analysis methods?

 

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1.  What is a slug test?

A slug test, as mentioned previously, is a test used for estimating hydraulic parameters at intermediate to small scales.  In a slug test a known volume (of water or other material) is rapidly taken out of or put into the monitoring well.  The rate at which the water level falls or rises is measured while the system equilibrates, and then the data is analyzed by an appropriate method to determine hydraulic parameters such as transmissivity and storativity.

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2.  What are the benefits of a slug test?

There are several benefits of slug tests.  Some of them include:

• point values of K can be determined to analyze spatial variability

• can be conducted accurately in low-K (conductivity) materials

• can be used to design full scale pumping tests

• more economical and efficient than a pumping test (only uses one well; cost of disposing of contaminated water is significantly reduced since volume of water pumped is reduced in a slug test; etc.)

   

 

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3.  What are some problems/limitations of slug tests?

While there are benefits to slug tests, there are also problems/limitations.  Some of these include:

• human error in measurement due to a rapid response of the water table

• degree of well development (under developed:  fines brought into the screen and changes the K; over developed: high K region around the well)

• leaks in the casing

• water table fluctuations (especially in low K areas where recovery takes a long time)

• skin effect (side wall alteration from well installation)

 

 

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4.  What are some types of slug tests analysis methods?

There are several different methods of analyzing slug test data.  Some of these methods are discussed below.

1)  Hvorslev Method (1951)

• most commonly used

• developed for a variety of well geometries

• can be applied to various hydrogeologic conditions (confined, unconfined, etc.)

• accounts for anisotropy

• formation storage is ignored

• approximate solution

2)  Bouwer and Rice Method (1976)

• designed for vertical screens only - one shape factor

• can be used for fully or partially penetrating wells in unconfined or confined aquifers

• water levels can enter the screen

• formation storage is ignored

• requires graphical interpretation for select constants

• based on estimated radius of influence of the well over which the perturbation is dissipated

3)  Cooper et al. (1967)

• based on heat flow analogy similar to the Theis equation

• designed to function in confined aquifers with a fully penetrating well

• storage coefficient can be estimated

• graphical curve matching method

There are several other methods of analyzing slug tests.  Many aquifer test analysis programs, such as Aquifer^Win32, include these, and many others.

 

 

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There are many resources available for more information on slug tests.  For this newsletter the following textbooks were used:

Bear, J. (1972).  Dynamics of Fluids in Porous Media.  Published by American Elsevier Publishing Company Inc., New York.

Driscoll, F.G. (1986).  Groundwater and Wells, Second Edition.  Published by Johnson Screens, Minnesota.

Fetter, C.W. (1994).  Applied Hydrogeology, Third Edition.  Published by Prentice-Hall Inc., New Jersey.

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AQUIFER^WIN32

^{Click here to download a demo of AquiferWin32}

^{Click here for the best price on AquiferWin32}

 

AquiferWin32 is capable of analyzing both single well tests and large scale pumping tests.  It contains a large number of solutions for each test type, including those discussed in the technical note on slug tests.  Split into their respective categories, the solutions available are:

Slug Test Analysis:

• Hvorslev (1951)

• Bouwer and Rice (1976)

• Black (1978)

• Cooper, Bredehoeft and Papadopulos (1967)

• KGS Model

• Kipp (1985)

Pumping Test Analysis:

• Cooper and Jacob (1946)

• Theis (1935)

• Theis (unconfined) (1935)

• Theis (recovery) (1946)

• Hantush (1961)

• Papdopulos and Cooper (1967)

• Hantush (1960)

• Hantush and Jacob (1955)

• Hantush (1964)

• Neuman (1972)

• Neuman (1974)

• Moench (1984)

• Moench (1985)

• Moench (1997)

Step Test Analysis:

• Eden and Hazel (1973)

• Birsoy and Summers (1980)

Model Solutions:

• Theis (1935)

• Hantush (1960)

• Hantush and Jacob (1955)

• Neuman (1972)

• WinFlow

• WinTran

What makes Aquifer^Win32 different from other pumping test Analysis Programs?

1.  Ease of Use

2.  Purchase Select Solutions

3.  First order derivative curves

4.  Full Featured Modelling Environment

5.  Presentation of Results

 

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1.  Ease of Use

Aquifer^Win32 has a wide variety of data importing methods to make data entry convenient, and the new import wizard makes data entry even easier.  In addition, Aquifer^Win32 does not require defining wells, you simply need to import or enter the time/drawdown data into the spreadsheet, fill in the radial distance and pumping rate and go!  The units are conveniently displayed in the title of the spreadsheet columns, and Aquifer^Win32 provides a flexible unit conversion calculations.  The tab views employed in Aquifer^Win32 makes it easy to switch across the various graphs and data sets.

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2.  Purchase Select Solutions

One of the things that sets Aquifer^Win32 apart from other aquifer test analysis programs is that you can purchase the solutions you require at that time, and then upgrade later! 

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3.  First Order Derivative Curves

Aquifer^Win32 has a full implementation of derivative analysis, which can significantly improve the analysis of and aquifer test.  Manual curve matching can be done to optimize the match and accurately reduce the data.

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4.  Full Featured Modelling Environment

Aquifer^Win32 includes analytical solutions into a full featured modelling environment that can produce contour maps of hydraulic head and drawdown, color floods of head or drawdown, and particle tracking.  The inclusion of WinFlow and WinTran further expands these capabilities.

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5.  Presentation of Results

Aquifer^Win32 includes a wide variety of choices for editing the presentation of your results to get the effect you want.  You can create a site map to plot well locations over a basemap, and the graphs are customizable with respect to legends, printed headers and footers, symbol control, and other features.  The Object Linking and Embedding (OLE) features allow the graphs created in Aquifer^Win32 to be copied to the Windows clipboard and then imported as pictures and metafiles to documents produced in Microsoft Word and Wordperfect.  The graphs can also be exported to AutoCAD DXF files, Surfer files, etc..

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