Vertical wells with constant drawdown

<< Click to Display Table of Contents >>

Navigation:  Analytical modeling (AMWELLS) >


Vertical wells with constant drawdown

This module calculates inflow to vertical wells with constant drawdown (or vertical drains). The drawdown is determined in test wells or/and in control points (i.e. observation wells). Inflow can be calculated for all conceptual models that are included in AMWELLS. The tool can also be used to calculate inflows and drawdowns, that are caused by Horizontal Drain Holes (HDH). In this case a slotted HDH can be approximated by a line of vertical wells with screen lengths that are equivalent to the HDH diameter.

The module can be accessed through the button "Drain" that is located under the instrument panel in the AMWELLS dialog box. Pressing the button opens the dialog window "Vertical drains" that enables:

1) selection of vertical drains from the list of input wells;

2) selection of controls for calculations between either a) constant drawdown in vertical drains; or b) constant drawdown at control points;

3) if the (b) option is selected, the user is prompted to choose control points from the list of observation wells;

4) assignment of constant drawdown values either in drains or in control points;

The same dialog window launches calculations through the button "Run".


Dialog window "Vertical drains"


Explanatory table

Frame "Drawdown"

Choice of calculation controls: either drawdowns in drains or drawdowns in control points.

Field "Start"

Start time for applying constant drawdowns after beginning of the analytical model. The drains do not operate before that time.


The table allows selecting drains (or control points) and assigning to them specified drawdowns. Two different tables are used: one - for vertical drains, and another one - for control points.

List under Table

This list becomes active, when calculations are based on drawdowns at control points. The list allows switching between lists of drains and list of control points.


If calculations are based on specified drawdowns at control points, the quantity of points needs to be the same as the quantity of vertical drains, otherwise a warning message appears. Control points needs to be specified in an AMWELLS model as observation wells.

The button "Run" starts calculations of inflows into vertical drains. The Esc button stops simulations. Results of calculations can be viewed by pressing the button "Inflow".

After simulation is complete, an information window comes up showing the total inflow to all wells at the final time and prompting to open the "Inflows to wells" dialog window to review transient results for each well (drain).  As a general rule, inflow to each well will decrease with time. If, for keeping specified drawdowns, water injection is required in some wells, a warning message will appear.



Dialog window "Inflows to wells"


The dialog window "Inflows to wells" is comprised of two tables and one plot. The first table allows selection of wells, for which the sum of inflows is presented in the second table for each time step. Wells that are not specified as drains will be shaded in gray colour. The plot presents an inflow hydrograph based on the second table.

The button "Copy" copies the inflow table on the clipboard.


The following key combinations can be used in this module:

1) copying drawdown from one well to several wells: moving mouse while keeping its left button and SHIFT pressed;

2) check boxes on/off for all wells: double click on the first row of the second column;

3) copying drawdown from the first well to all wells: double click on the title of "Drawdown" column;

4) specifying drawdowns, that are changing at constant increment: mouse selection of input rows that require incremental step in the "Drawdown" column. The program will automatically interpolate drawdown values between the first and the last rows.