Jump to content
Geochemist's Workbench Support Forum

X2t residuals too large

Recommended Posts

Hello, I am trying to run a X2t model for carbonated brine injection into a reservoir water. It says "residuals too large" when I started to run it. I tried the initial mineral/fluid in Spec8 and there is almost no charge imbalance. I cannot figure out why Cl- residual is too large. Can you help check it? Thanks!

carbonated water injection.x2t

Link to comment
Share on other sites


It seems like your injection fluid has a very high Cl- concentration. Did you also check the charge imbalance on this fluid in SpecE8/React? If I change your model to a zero injection rate for the well, it seems to run to completion just fine. I would suggest starting in React with your fluids and see what might be the issue there. If a fluid has an excess of anions, you should select a cation for charge balancing.

Another suggestion is that for certain basis species, it would help with convergence if you swap in a more abundant species of that form give the conditions (such as pH) of your system.

Another thing to double check is your concentration and units. I noticed that you have set the same concentration (1e-14 mg/l) for certain species. If you have no measurement for certain components, you would want to set the value to an insignificant concentration since the program can't numerically solve equations with zero values but not necessarily too low.

Lastly, you might also be interested in looking into using a virial model for working with brine solutions. For more information regarding datasets available with the GWB installation, please see the Thermo Data page.

Best regards,
Jia Wang
Aqueous Solutions LLC

Link to comment
Share on other sites

I tried to make well injection rate in the domain as zero (no injection), but it still did work, saying residuals too large, 681-th iteration. If I change the charge balance to Na+, then a lot more species will have largest residuals instead of Cl-. 


I checked the initial reservoir fluid and the injection fluid in React. There are some precipitates and the water chemistry changed a little, which is what I expected. I want the injected concentrated water to mix with the reservoir water and see what will happen as a function of time and location. However, it did not work in the X2t model from the very first step. It would be much appreciated if you can help check it again. 


Also what does "free" mean when I set the H2O and mineral volumes%? 

carbonated water injection - 230317.x2t React-injection fluid.rea React-reservoir fluid.rea

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...