How to set-up a 28% HCl solution

[mozarg]

Hi

 

I am trying to set up a 28% acid, normally used in acidizing of the carbonate rocks.

for some reason, I come up with the error of :

N-R didn't converge after 999 its., maximum residual = 0.0508, Xi = 0.0000
Largest residual(s):
Resid Resid/Totmol Cbasis
---------------------------------------------------------
HCl -5.45e+04 0.0508 5.149e-05
---------------------------------------------------------

I have attached the script of SpecE8. I appreciate your help.

 

I am using this to simulate acidizing of a medium composed of calcite.

having a porosity of 0.3. I have also attached the X2t file. It shows the same problem.

 

Mohammad

acid.sp8

acid_1.x2t

[Brian Farrell]

Hi,

 

I think there's a problem with SpecE8 when you set the bulk volume of the system. Since this has no effect on the fluid chemistry, just reset the bulk volume and run your model, then check to make sure you get the results you expect.

 

As for the X2t model, your inlet fluid is different from what you've defined in SpecE8. A solution with 28 wt% H+ and 28 wt% Cl- is not the same as one with 28 wt% HCl. A few other things:

• try using X1t before X2t as you develop the model, since a simpler system with fewer nodes will be faster to solve
• there doesn't appear to be any difference between your two reaction intervals, so I might get rid of the second one
• do you know the pH of the initial fluid? It seems strange to set the wt fraction of H+ and Cl-
• the values for the permeability correlation you set don't do anything when you set the discharge directly
• you might not want 0 values for the diffusion coefficient and the dispersivities

Hope this helps,

 

Brian Farrell

Aqueous Solutions

[mozarg]

Hi Brian

 

Thanks. I kind of solved the problems. I am wondering how we can see the wormholes, as Craig said we can.

Please see the attached file.

 

Here are the questions:

 

1- Is there any way to impose the gravity on y axis (for example?)

2- How do we change the scale of the result? (for example y is 100 m and x is 5 meter and we do like to

show more of x more. so we scale the plot)

acid_1.x2t

[mozarg]

At the moment, I have flow from one side to the other. I assume that this will impose the same flow

in all of the blocks in the left and right. Can I impose no-flow boundaries at top and bottom?

[Brian Farrell]

Hi Mohammad,

 

I believe you need some heterogeneity in your domain in order to induce wormhole growth. From Reactive transport modeling: An essential tool and a new research approach for the Earth sciences by Steefel et. al.: "The formation of wormholes, which takes place in carbonate rocks due to the infiltration of fluids undersaturated with respect to the carbonate minerals, is an extreme example of evolving heterogeneity. The wormholes form as a result of a reactive infiltration instability in which the enhancement of permeability resulting from mineral dissolution causes the wormholes to capture progressively increasing amounts of flow, thus accelerating their propagation...slight variations in pore size are needed to form wormholes given the presence of high flow velocities and fast reaction kinetics."

 

Regarding gravity, you prescribe the hydraulic potential drop across the domain, or set the discharge directly, so you don't need to set gravity anywhere. The code currently does not account for buoyancy-driven flow as might arrive where thermal or salinity gradients exist.

 

You set the physical dimensions of your domain on the Domain pane. If you'd like to stretch your plot in one direction or the other, you can do so in Xtplot by going to Edit -> Plot Area... and setting a factor for exaggeration in the x or y direction (the default is 1, indicating no exaggeration).

 

To visualize the flow field, it may be helpful to plot contours of hydraulic potential and velocity arrows. The program uses no-flow boundaries at the top and bottom when calculating the flow field. If you import the flow field from another program, however, the top and bottom boundaries can be open to flow. For more information, see sections 4.3 Calculating the flow field and 4.4 Importing the flow field in the Reactive Transport Modeling Guide.

 

Hope this helps,

Brian