Tutorial 3: Single Well Analysis

In this tutorial, you will create a new pumping test for a single pumping well and use the derivative analysis tools to interpret the data and update your analysis to include the effects of storage in the measured drawdown data for the pumping well.

Single Well Pumping Test

To create a new Pumping test project:

[1] If you have not already done so, double-click the AquiferTest icon to start an AquiferTest session.  

[2] At the Welcome page ensure that the "Create Pumping Test" box is checked and choose the "Create a new project" button.  

 
A blank project with the Pumping Test tab active loads automatically. The loaded page should look similar to the one shown below:

[3] Fill in the information required for the new pumping test:

•In the Project Information frame enter the following:

•In the Pumping Test frame enter the following:

•In the Units frame fill in the following:

•In the Aquifer Properties frame enter the following:

•Click the "Click here to create a new well" link under the first well to create a new well. Define the following well parameters for this well:

•Name: PW1 •Type: Pumping Well •X: 0 •Y: 0 •Elevation: 0	•Benchmark: 0 •Penetration: Fully •R: 0.35 •r: 0.35

For this pumping test, only one well (PW1) was used for both pumping and recording drawdown measurements.

[4] Click on the Discharge tab to enter the discharge rate for the pumping well.

[5] In the Discharge frame select the "Constant" option

[6] Enter the following discharge rate: 0.5 L/s.

[7] Click on the Water Levels tab to enter the water level data for the pumping well.

[8] Type 0 in the Static Water Level field.

[9] In this exercise you will import data from an MS-Excel file. From the main menu, select File > Import > Import Data... or Click the Import data... button in the Water Levels toolbar

[10] Navigate to:

         C:\Users\Public\Documents\AquiferTest Pro\Tutorials and select the file PW-1.xls

[11] Click Open. The data should now appear in the time - water levels table.

[12] You will see the calculated drawdown data appear in the Drawdown column and a drawdown graph displayed on the right. (Note, if the graph does not appear, Click on the Refresh button in the main toolbar.

Single Well Analysis - Theis

Now you can create the analysis. First, start with the standard Theis Analysis for a Confined Aquifer (assuming that Well Storage is negligible).

[13] Click on the Analysis tab.

[14] In the Data from window, select PW1. The type curve and data are displayed on the graph.

[15] In the Analysis Name field, type "Theis Analysis"

[16] Select the Apply Graph Settings button in the Analysis toolbar and select the Linear option and click on the button.

AquiferTest will automatically fit the data to the Theis curve by adjusting the estimated values of Transmissivity (T) and Storativity (S), as shown in the image below.

NOTE: The symbols may be different than above - you can adjust your symbols by increasing/decreasing the size of the symbols, you can do so under the Diagram options frame on the right hand side. You can also adjust the default symbol sizes in all new charts by selecting Tools > Options from the Main Menu, selecting the Appearance tab, and adjusting the default symbols.

You can find the calculated values for the aquifer parameters are:

•T: 1.92 E-4 m2/s

•S: 2.93 E-1

Notice that the Theis analytical solution provides a rough fit for the data but underpredicts drawdown during the middle part of the test (approx. 1,000-4,000 minutes) and over-predicts drawdown at the late reasonable fit (>4000 minutes).  In the next section of the Tutorial, you will use derivative analysis and diagnostic plots to facilitate the interpretation of the data to refine the conceptual model of the pumping test system and improve the interpretation of the data.

Interpreting Well Effects with Derivative Analysis

In this section of the Tutorial, you will use the advanced features of AquiferTest Pro to perform a derivative analysis and compare the results to the diagnostic plots to update the analytical based on your findings.

NOTE: The functionality and steps described below are not available in the Standard Edition of AquiferTest. If you are using the Standard Edition of AquiferTest, you may read this section for reference or skip ahead to the next section: Single Well Analysis - Papadopulos-Cooper.

[17] Click on the Diagnostic Graph tab, and the following window will appear

The Diagnostic Graph window contains a plot with the Measured Drawdown data and the calculated Drawdown Derivative. The derivative data is distinguished by an X through the middle of each data symbol (they may be hard to distinguish here, unless you changed the symbol properties in the previous subsection); although the derivative values will typically be lower than the measured drawdown values.

To the right of the graph window, you will see six Diagnostic Plots, with a variety of curves. The plots are called diagnostic, since can be used as references to provide an insight or "diagnosis" of the aquifer type and conditions. Diagnostic plots are available for a variety of aquifer types, well effects, and boundary conditions, which include:

•Confined,

•Leaky aquifer,

•Recharge Boundary,

•Barrier Boundary,

•Unconfined Aquifer or Double Porosity, and

•Well Effects (Wellbore storage)

Each diagnostic graph contains 2 lines:

•Type curve (solid blue line)

•Derivative of type curve (dashed black line).

These plots can be displayed on a log-log or semi-log scale, by selecting the appropriate radio button above the diagnostic graphs.

For this pumping test, the presence of well effects (well bore storage) can be confirmed by comparing the derivative drawdown data (outlined in the image above) to the dashed line in the Well Effects diagnostic plot (circled in the lower right corner of the image above) - the measured data and associated derivatives are very similar in shape to the curves presented in the "Well effects" diagnostic plot. Note that the calculated drawdown derivative values did not stabilize to reach a constant. Therefore, it would have been ideal if the pumping duration had been extended, and there was additional data available for subsequent durations of pumping.

Nevertheless, the drawdown curve is characteristic of well bore storage conditions: at the beginning of the pumping test, there is a delay in drawdown as a result of storage in the pumping well, and the drawdown deviates from the theoretical Theis curve. As pumping durations increase, the drawdown curve becomes more similar to the theoretical Theis curve.

These well effects may be more easily identified in the semi-log plot.

[18] Select the Lin-Log radio button above the diagnostic graphs, and the Diagnostic plots will appear in a new scale

In the Semi-Log plot, you can also compare the observed drawdown curve to the diagnostic plots. In this example, it is evident that the observed drawdown curve displays delayed drawdown (outlined in the image above), then returns to the typical Theis curve as the pumping duration increases. When comparing this to the diagnostic plot for Well Effects on both the log-log and semi-log derivative plots, there is strong evidence indicating the presence of well effects during this pumping test.

Now that you are confident that there is a wellbore storage component to the measured data, you can create a new analysis based on a solution method that includes the effects of wellbore storage (i.e. Papadopulos-Cooper, 1967), and refine your estimates of the aquifer parameters.

[19] Return to the Analysis Graph tab.

Single Well Analysis - Papadopulos-Cooper

In this section of the Tutorial, you will create a new analysis using the Papadopulos-Cooper (1967) method, which accounts for the well storage effects often encountered in larger diameter wells, based on the derivative analysis and interpretation you preformed in the previous section of this tutorial.

[20] From the main menu, select Analysis > Create Pumping well analysis > Create analysis considering well effects.

[21] Click on the button, and the curve will be fit to the data, as shown in the image below

The calculated value for Transmissivity using the Papadopulos & Cooper method is:

•T: 4.63 E-4 m2/s

•S: 1.85 E-3

Compare this to the value calculated using the Theis method (1.92 E-4 m2/s), you can see that the value is greater by a factor of more than 2. Therefore, the Theis solution should not be used, since it assumes there is no storage in the pumping well, and will produce incorrect results.

You may create a report using the instructions provided earlier in this tutorial.

The next tutorial of this tutorial will explore creating and analyzing a slug test.

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