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lea512

Reacting Both Smectites in Equilibrium in React

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Recently, I have been trying to input both high Fe,Mg-rich smectite and low Fe,Mg-rich smectite into my equilibrium model. When I input the values (in grams) that I want, I get this message at the bottom of the "Run" tab

 

Cutting step size to find phase assemblage

Swapping K+ in for Clinoptil-K

Swapping Hematite in for Nontronit-Mg

Swapping Mg++ in for Clinoptil-Ca

Swapping SiO2(aq) in for Kaolinite

Swapping Fe++ in for Pyrite

Residuals too large, 661-th interation

-- Didn't wake up, abandoning path

 

However, when I change the low-fe-mg-smectite to a smaller value, it seems to work correctly. I would really like to use my value, but if I am doing something incorrectly, please let me know. I have provided my input data below to help in my explanation.

 

 

Input Data:

 

Water Chemistry

H2O = 1 kg

Ca2+ = 63.8

Na+ = 6.5

Mg2+ = 46.9

SO4-- = 100

Cl- = 5

HCO3- = 293 charge balance

H+ = 7.5

Fe2+ = 0.11

Mn2+ = 0.05

K+ = 1.8

O2(aq) = 0.01

SiO2(aq) = 0.01

Al3+ = 0.01

 

Mineral Data

Quartz = 1899.96 g in rxn

K-Feldspar = 112.4 g in rxn

Albite = 18.74 g in rxn

Kaolinite = 89.91 g in rxn

Illite = 1101.84 g in rxn

Hematite = 67.44 g in rxn

Goethite = 67.44 g in rxn

Low Fe,Mg-rich Smectite = 200 g in rxn (I WANT THIS TO = 1035.61g INSTEAD!!)

Fe,Mg-rich Smectite = 498.72 g in rxn

 

Other Data

Temperature = 30C

Time = 0-20 years

Sliding CO2 (g) Fugacity to 53.3 bar

NS4C-1836-1_equil.rea

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Recently, I have been trying to input both high Fe,Mg-rich smectite and low Fe,Mg-rich smectite into my equilibrium model.

 

Hi Lea:

 

Would you mind attaching your React script to this thread, so that I don't have to enter all your data manually?

 

Thanks,

 

Tom Meuzelaar

RockWare, Inc.

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Hi Lea:

 

Would you mind attaching your React script to this thread, so that I don't have to enter all your data manually?

 

Thanks,

 

Tom Meuzelaar

RockWare, Inc.

 

 

I attached the script. Hope it works!!

 

Lea

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I attached the script. Hope it works!!

 

Lea

 

Hi Lea:

 

Are either of these clays observed in the system you are studying? Because in the equilibrium model you've constructed, neither are stable after being titrated. I'm wondering if you need to either consider moving to a kinetic model, or titrating minerals in that have greater long term stability....

 

I hope that helps,

 

Tom Meuzelaar

RockWare, Inc.

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Hi Lea:

 

Are either of these clays observed in the system you are studying? Because in the equilibrium model you've constructed, neither are stable after being titrated. I'm wondering if you need to either consider moving to a kinetic model, or titrating minerals in that have greater long term stability....

 

I hope that helps,

 

Tom Meuzelaar

RockWare, Inc.

 

Actually I have been using both smectites in a kinetic model. Currently, I am working with a carbon sequestration team that is in the planning/researching stages (and writing my thesis) where drilling has yet to begin and we have no data (some mineralogical). Some members on the team believe that we should forget the kinetics and just consider everything in equilibrium. Plus, I was trying to run both kinetic and equilibrium models together to compare how much the concentrations vary from model to model over a period of time. Just a thought. Do you have any suggestions (based on my input data) about how to improve my model for carbon sequestration? Also, I have no actual water chemistry data from the aquifer that we plan to inject into (the water data above is from 200+ miles away). Do you have any suggestions as to how to determine water chemistry data from using only mineralogical data?

 

Thanks again.

Lea

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Actually I have been using both smectites in a kinetic model. Currently, I am working with a carbon sequestration team that is in the planning/researching stages (and writing my thesis) where drilling has yet to begin and we have no data (some mineralogical). Some members on the team believe that we should forget the kinetics and just consider everything in equilibrium. Plus, I was trying to run both kinetic and equilibrium models together to compare how much the concentrations vary from model to model over a period of time. Just a thought. Do you have any suggestions (based on my input data) about how to improve my model for carbon sequestration? Also, I have no actual water chemistry data from the aquifer that we plan to inject into (the water data above is from 200+ miles away). Do you have any suggestions as to how to determine water chemistry data from using only mineralogical data?

 

Thanks again.

Lea

 

The problem will be that the entire suite of minerals you see in the reservoir are not all in equilibrium with the fluid. You can constrain your water chemistry by making assuming that minerals are controlling fluid components, and swapping these minerals in for the components. For instance, modelers commonly assume that quartz in the reservoir controls the silica concentration of the fluid, and thus make the swap Quartz - SiO2(aq).

 

If you're going to go the equilibrium route, you'll need to reduce the number of initial phases (as not all of them can be in equilibrium with the initial fluid). Your other option is to titrate mineral phases in kinetically, provided you have the necessary rate law data.

 

I hope that helps,

 

Tom

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For some ideas about how to improve your database you may want to read this:

 

http://www.netl.doe.gov/publications/proceedings/05/carbon-seq/Tech%20Session%20Paper%20101.pdf

 

Water chemistry can be easily deduced from your mineralogical composition and thermodynamic equilibrium modeling - however, what you get is very likely to be completely different from lab results. With Si, Al, and Fe you run into problems related to colloids leading to much too high analytical concentrations. Another important factor is cation exhange wich cannot be predicted from remote. For a composite methodology about how to determine pore water chemistry you may find the following interesting:

 

Pearson, F. J.; Waber, H. N. (2006): Mont Terri Project, Technical Note 2006-26, Diffusion and Retention (DR) Experiment: Experimental Water Chemistry, Report.

Bradbury, M. H.; Baeyens, B. (1998): A physicochemical characterisation and geochemical modelling approach for determining porewater chemistries in argillaceous rocks, Geochim. Cosmochim. Acta (62,5), 783-795.

Motellier, S.; Ly, J.; Gorgeon, L.; Charles, Y.; Hainos, D.; Meier, P.; Page, J. (2003): Modelling of the ion-exchange properties and indirect determination of the interstitial water composition of an argillaceous rock. Application to the Callovo-Oxfordian low-water-content formation, Appl. Geochem. (18), 1517-1530.

 

Regards,

 

Helge

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For some ideas about how to improve your database you may want to read this..

 

Thank you for the comments and references Helge.

 

Regards,

 

Tom

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