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Error message: Newton-Raphson didn't converge after 999 iterations, max residual = 0.000991, Xi = 0.0000 Largest residual(s)


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Hello,

I am having trouble with my model. For start, the reaction model was successful when I reacted CO2 partial pressure with the water analysis data and minerals for one month, then I picked up the fluid and saved them, when I opened the picked-up script, I only swapped the pH to the CO2 partial pressure and increased the time to 30 yrs.

I Keep getting the same error message: Newton-Raphson didn't converge after 999 iterations, max residual =    0.000991, Xi = 0.0000 Largest residual(s).

I tried playing with parameters (CL, HCO3), I have also tried changing the charge balance to Na., But it does not work.

please can you help me figure this out and solve it. 

Capture2.JPG

Capture1.JPG

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Hello,

Could you please attach your input files, the initial one used to create the fluid and the one in the screenshot, so we can troubleshoot directly? Please include any custom thermo or surface datasets used in your runs.

Is the CO2 partial pressure swapped into the second simulation the same partial pressure at the end of the reaction path in your first reaction? Could you explain a little bit of what your simulations are trying to accomplish?

Best regards,
Jia Wang
Aqueous Solutions LLC

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Hi Jia,

Thank you for your reply. 

I am trying to model CO2-Rock-water interaction. I have the basis as the water analysis data and the kinetics are the mineralogy input with their surface area and rate constant. and I reacted 3.5 mol of CO2 and the set the time for 0.2 yr. Then I picked up the fluid to simulate the CO2 for 30yr with the same basis and mineralogy. however, I want the CO2 to be stable in the 30 yrs. so I swapped the H+ to CO2 partial pressure and set to 1100 psi in the basis and fixed the CO2 in the reactant pane to make it stable. 

I am also interested to see the effect on mineral dissolution and precipitation.

I have attached my input files. and I hope what I explain makes sense of what I am trying to model.

The CO2-N1 is the initial successful reaction. The N1 pickup is the one with the error. 

 

Many thanks for your help in advance. 

Nourah

 

 

CO2-N1-supressed-0.2 yr.rea N1-pickup.rea

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Hello Nourah,

Thanks for attaching the files. I think I spot a few places that might be causing you issues.

The first input file CO-N1_suppressed is successful and seems ok.

I am not quite sure that about the second input file. You stated that you picked up the fluid to simulate CO2 for 30 years, but I don't see the composition of the final fluid from the first simulation in the Basis pane.

Maybe you intend to use the fluid in the results from the first simulation as a starting point in your second input file? If so, run the first input file, then go to Run -> Pickup -> System -> Fluid. To keep the same CO2 partial pressure constant, you can then go to the Reactants pane to fix the CO2(g) fugacity for the second simulation. Note that you don't need to specify a partial pressure to fix it. If the necessary components are available, then the program will calculate a partial pressure in equilibrium with your system. I tested if the mass balancing ion was the issue by turning off the balancing ion and a go initial calculation, the script converged with no issue. When I checked the mass imbalance error, it was in the order of magnitudes of 10^-7 %. I returned to the basis pane and chose the Na+ ion as the mass balancing ion, since it was the highest concentration ion analyte, and run the go initial command with no issue either.

At this point, I added in your kinetic mineral reactions from the N1_pickup.rea file. I noticed that the rate constant for Beidellit-Mg is 7.28e+15 mol/cm2/s, which is very large. I think there's a typo here and it should be 7.28e-15, which is what was in the first input file.

Hope this helps,
Jia Wang
Aqueous Solutions

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Hello Nourah,

I would like to follow up with a couple additional comments. I also want to let you know that if you would like to preserve the kinetic mineral reactions in the Reactants pane and the equilibrium minerals at the end of your first simulation, you can do a Run-> Pickup -> System -> Entire command instead of "Fluid". This way, all the minerals in equilibrium with your fluid will be swapped into your Basis pane for you second simulation and your kinetic reactions in the Reactants pane will remain. You will still need to add the command for fixing CO2(g) fugacity on your Reactants pane and adjust the simulation period to the desired length.

I also noticed that you have suppressed all aqueous species besides basis species, which does not seem correct. Perhaps you had intend to only suppress all minerals instead of all species?

Best regards,
Jia

 

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Hi Jia, 

 

Thank you so much for your help and replies. 

I will work on them now and try applying your recommendation. 

I do intend to supress minerals only. thank you for this notice.

Many thanks,

Nourah

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