catherine ruprecht modeling exercise
TRANSCRIPT
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RECS: TOUGH2ECO2N Numerical Modeling Activity June 8, 2011 Activity Leaders:
Catherine Ruprecht, [email protected]
Ron Falta, [email protected]
Clemson University EE&ES
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Exercise 1: Injection into a Homogeneous Deep Saline Aquifer
This is a basic problem of CO2 injection into a saline aquifer, examining two‐phase flow with CO2
displacing saline water under conditions that may be encountered in brine aquifers at a depth
of approximately 2 km. A CO2 injection well fully penetrates a homogeneous, isotropic, infinite‐
acting aquifer of 100 m thickness, at maximum conditions of 200 bar pressure, 40 ˚C
temperature, and a salinity of 5% by weight. CO2 is injected uniformly at a constant rate of
15.75 kg/s for 20 years. This is the equivalent of the amount of CO2 needed to be captured from
a 50 MWe coal burning power plant. After injection, an 80 year monitoring period is simulated.
1. New Model Set Up Open PetraSim. File>New
Select TOUGH2 and ECO2N, then create a model with bounds such that X Max = 2000, Y
Max=1, and Z Max =100. Press OK.
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2. Edit Layers
Select from the top toolbar. Enter “10” as the number of cells. Press OK.
3. Create a Mesh
Select from the top toolbar.
From the dropdown menu, select “Radial” as the mesh type.
Select “Custom” divisions.
Fill in the values as seen in the table below. Press OK.
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4. Initial Conditions File>Load Initial Conditions. Navigate to the folder titled “Initial Conditions” within the
Exercise 1 folder provided. Select the “SAVE” file and click “Open”.
There is now a pressure gradient equivalent to a bottom depth of 2 km. Formation
temperature of 40 ºC and a salinity of 5% by weight has been initialized. Examine these
properties using the front view button and the “Cell Color” drop down menu.
Note that by selecting a radial mesh, a slice plane of half a cylinder has been produced.
The left side of the figure represents the center of the cylinder and the right side
represents to outer edge. This cylinder represents the Area of Review.
5. Global Properties
Select from the top toolbar. Click on the EOS tab, to edit the equation of state
properties. Choose “Isothermal”, leave all else unchanged. Press OK.
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6. Material Data
Select from the top toolbar.
Edit the existing material “ROCK1” to match the properties given.
Select Additional Material Data…
Under the Relative Perm tab, choose the van Genuchten‐Mualem Model for relative
permeability curves. Enter the appropriate parameters given below.
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Still in the Additional Material Data box, select the Capillary Press tab.
Choose the van Genuchten Function for capillary pressure. Enter the parameters given
below.
Press OK to return to the Material Data box.
Under “Materials” select “New”.
Create a material named “WELL” based on ROCK1.
Press OK.
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Edit the new material “WELL” to match the properties given.
Select Additional Material Data…
Under the Relative Perm tab, choose the van Genuchten‐Mualem Model for relative
permeability curves. Set Slr and Sgr to 2.0E‐02.
Still in the Additional Material Data box, select the Capillary Press tab.
Choose “No Capillary Pressure”. Press OK to return to the Materials box. Select OK again
to return to the PetraSim home screen.
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7. Setting Materials
By using the Zoom Box from the toolbar, drag and release to zoom in on the top left
side of the model. Zoom in until the top grid block of the first column is visible. Press
to select a column from the mesh. Then select the top left grid block (the entire
column will be selected).
Right click on this column and choose to Edit Cells. From the Material drop down menu,
select WELL. Press OK.
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Use the Select Objects tool to left‐click and then right‐click on the top left grid block.
Choose to Edit Cells. In the Sources/Sinks tab, under “Injection” click the CO2 box.
From the drop down menu to the right, choose “Table”.
Select Edit…
Fill the injection rates table in with the following values.
Press OK to return to the Edit Cell Data box, then press OK to return to the PetraSim
home screen.
8. Boundary Conditions
Select for a front view of the model. Again press to select a column from the
mesh. Then select any cell in the right‐most grid block column (the entire column will be
selected). Right click on this column and choose to edit cells.
In the Properties tab, select “Fixed State” from the Type drop‐down menu. Press OK.
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1. Solution Controls
Select from the top toolbar to access solution controls.
In the Times tab, edit the End Time to be “100 years”.
In the drop‐down menu for Max Num Time Steps, allow for “Infinite” time steps.
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In the Weighting tab, select “Harmonic Weighted” under the Permeability at Interface
header.
Press OK.
10. Output Controls
Select from the top toolbar to access Output Controls.
Update the output controls to print and plot every 2000 time steps.
Select Edit… for Additional Print& Plot Times.
Open the Additional_Print_Times.xls file provided in the Exercise 1 folder. Input the given print
and plot times by copying and pasting the column of values into the Additional Print Times box.
Once pasted, they will appear in scientific notation.
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(These values correspond to 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, and 90 years. They are entered in
seconds.)
Press OK to return to the Output Controls. Press OK again to return to the PetraSim home
screen.
11. Run Simulation
To run TOUGH2‐ECO2N, press the tool.
A prompt will appear to name and save the simulation. Navigate to the Exercise 1 folder. Name
it Ex1.sim and press Save. The simulation will then being running.
This simulation will take approximately 6 minutes to run.
12. Examine 3D Results
Select the 3D Results tool .
In the 3D Results window, use the front view tool to rotate the image. On the left‐hand tool
bar, click on “Slice Planes”. Choose “Y” from the first drop down menu and set its coordinate
value to 0.5. Click “Apply” and then close the Slice Planes box.
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A slice plane of pressure contours at 1 year is now visible.
Scroll through the Times box to watch these pressure contours evolve through the simulated
injection and monitoring periods. Note that injection ends at 6.31138e8 seconds.
From the Scalar drop‐down menu, select any variable of interest and scroll through the printed
times. A reference table for this menu is given.
P Pressure (Pa)
T Temperature (ºC)
SG CO2 Gas Saturation
SS Solid Saturation
XNaCl Salt Mass Fraction
YH2OG Water Mass Fraction ‐ Gaseous Phase
XCO2aq CO2 Mass Fraction ‐ Aqueous Phase
PCAP Capillary Pressure (Pa)
k‐red Permeability Reduction
DG Gas Density (kg/m3)
DL Liquid Density (kg/m3)
PER MOD Permeability Modifier
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Useful commands in the 3D Results window: Holding the left click button allows you to rotate the grid.
Holding the Alt key and left click button allows you to zoom in and out of the grid.
Holding the Shift key and left click button allows you to drag the grid.
At any point, press the front view tool to reset the grid view.
Questions for thought:
1. Select solid saturation, SS, from the scalar drop‐down menu. Zoom in on the area near
injection.
a. Describe what is going on during the 20 year injection period (up to 6.31138e8
seconds).
b. Describe what is going on during the 80 year monitoring period.
c. How does the solid saturation relate to the CO2 gas saturation?
2. Select the CO2 gas saturation, SG, from the scalar drop‐down menu. Use the tool to
show the mesh.
a. What is the radial extent of the CO2 plume after 20 years of injection?
b. What is the radial extent of the CO2 plume after 80 years after injection ends?
Hint: Right‐click on an individual grid‐block and choose to edit cells.
Exercise 2: Modeling Hydrogeologic Heterogeneities This exercise builds on Exercise 1. In this case, a three dimensional polygonal grid is implemented. To
examine the effects of hydrogeologic complexities, a random, spatially correlated, heterogeneous
permeability field has been mapped onto the TOUGH2 mesh. Initial conditions, CO2 injection rates, and
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all other hydrogeologic parameters are set the same as Exercise 1. To conserve time, a 20 year CO2
injection period followed by an 80 year monitoring period has already been simulated.
**Do NOT hit the run TOUGH2 button at any point during this exercise.
1. Getting started Open the Ex2.sim from within the Exercise 2 folder.
Notice the polygonal Voronoi grid used to discritize the mesh. This grid has been refined around
the injection point, now found in the center of the Top View .
2. Examine 3D Results Select the 3D Results tool .
From “View”, select “Scale Axes…”
Set the Z Factor to 5.0.
Press OK.
3. Isosurfaces Select CO2 gas saturation, SG, from the Scalar drop‐down menu.
Confirm there is a check mark next to “Show Isosurfaces (Scalar)”.
Use the commands used in Exercise 1 to rotate and zoom in on the CO2 plume. Choose a view
allowing a view in a three dimensions. As seen below.
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Watch the CO2 plume isosurfaces evolve through injection and monitoring periods through the
Time (s) menu.
4. Slice Planes Select “Show Slice Planes” and then select the “Slice Planes…” button.
Set X and Y Axis Coordinates to 2000, and Z Axis Coordinates to 100 as shown below.
Click Close.
Deselect “Show Isosurfaces”. Click on the Show/Hide Wells tool . Slice planes with contours of
supercritical CO2 saturation around the injection point are now visible.
Rotate the image to watch the contours evolve through the injection and monitoring periods.
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Switch back and forth between “Show Isosurfaces” and “Show Slice Planes” with the any other
scalar variables of interest.
Questions for thought:
1. From the 3D Results window: File>Line Plot
Allow the X coordinates to span from 0 to 4000. The Y Coordinates should both be set to
2000 and the Z coordinates should both be set to 100.
Click OK. A window with line plots of primary data will appear. Choose CO2 gas
saturation, SG, from the variable drop‐down menu.
a. Approximately, what is the maximum radial extent of the CO2 plume from the well
after 20 years of injection?
b. After the 80 year monitoring period?
2. How does hydrogeologic heterogeneity affect the flow of CO2?