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TOUGHREACT-ECO2N calculation of fugacity of CO2

Hi, I am a new user of TOUGHREACT. I am using ECO2N to simulate diopside dissolution and carbonate mineralization in a temperature range of 6.4˚C - 18.9˚C and a pressure range of 0.1 - 5.1 MPa. I have input constant pCO2 values (bars) that would reflect the maximum solubility of CO2 in water for each P and T condition. In the chemical.inp I have pCO2 values with IGASFIX=1 and in flow.inp I have the corresponding mass fraction of CO2 specified. For the lower T-P range (6.4 -16.4˚C and 0.1 - 4.1 MPa), my estimates of max pCO2 for CO2 solubility match with that calculated by TOUGHREACT, but beyond that, TOUGHREACT calculated higher pCO2 values. Can anyone tell me what equations and steps TOUGHREACT is using to calculate the pCO2 values from the mass fraction of CO2 input in flow.inp? Any help would be very helpful. Below are my P-T conditions. Thanks. 

Temp (˚C)

P_depth (Mpa)

6.4

0.101325

7.65

0.601325

8.9

1.101325

10.15

1.601325

11.4

2.101325

12.65

2.601325

13.9

3.101325

15.15

3.601325

16.4

4.101325

17.65

4.601325

18.9

5.101325

2 replies

null
    • TOUGHREACT Developer
    • Eric_Sonnenthal
    • 4 mths ago
    • Reported - view

    Hi Piyali,

    Did you set a salinity in the INCON? Also, which thermodynamic database are you using? If you send your input files, it will be easier to see why it is higher than you expect. What are you comparing it to?

    regards, 

    Eric

      • Piyali_Chanda
      • 4 mths ago
      • Reported - view

       

      Hi Eric,

       

      Thanks for responding to my queries. I am currently running the model assuming pure water (i.e., salinity = 0). So there is nothing in the INCON and GENER. I am only chemical.inp, flow.inp, and solute.inp to specify the run conditions. I have calculated how much maximum CO2 can be dissolved in each P & T condition and estimated the mole fraction of dissolved CO2. Then, I tried to calculate the fugacity of CO2 (pCO2) that I would need to achieve the maximum mole fraction of dissolved CO2 estimated for each P & T. Based on my estimation, I inserted the pCO2 values in the chemical.inp file and the mass fraction of CO2 in the flow.inp file for each P-T simulation. My estimation of pCO2 (col #6) matches well with TOUGHREACT calculated CO2(g) (col #7)  in kdd_tim.tec file after each simulation for the lower P-T range (6.4 -16.4˚C and 0.1 -4.1 MPa). But at higher P-T conditions there is a significant difference between my pCO2 estimation and TOUGHREACT calculated CO2(g). So, I am trying to find what formulations/equations TOUGHREACT is using to calculate the CO2(g) values in kdd_tim.tec from the input value of the mass fraction of CO2. Following are my run conditions and contents of my chemical.inp, flow.inp, and solute.inp files. I would appreciate it if you could point me to the geochemical equations TOUGHREACT is using to calculate the CO2(g) value from the input CO2 mass fraction.     

       

      Depth (m)

      Temp (˚C)

      P (Mpa)

      mass fraction CO2 at max saturation

      pCO2 at max saturation_calculated (bar)

      pCO2 at max saturation_TOUGH (bar)

      0

      6.4

      0.1

      0.0026

      1.80

      1.8

      50

      7.65

      0.6

      0.0145

      9.90

      9.9

      100

      8.9

      1.1

      0.0245

      16.80

      16.8

      150

      10.15

      1.6

      0.0330

      22.68

      22.7

      200

      11.4

      2.1

      0.0400

      27.65

      27.6

      250

      12.65

      2.6

      0.0459

      31.82

      31.8

      300

      13.9

      3.1

      0.0507

      35.32

      35.3

      350

      15.15

      3.6

      0.0546

      38.21

      38.2

      400

      16.4

      4.1

      0.0577

      40.60

      40.98

      450

      17.65

      4.6

      0.0599

      42.29

      45.98

      500

      18.9

      5.1

      0.0609

      43.19

      50.97

      Chemical.inp 

      #Title

      Diopside dissolution, Chanda, 2024 

       

      #-----------------------------------------------------------------------------

      #DEFINITION OF THE GEOCHEMICAL SYSTEM

      #PRIMARY AQUEOUS SPECIES

      'H2O' 0

      'H+' 0

      'H4SiO4' 0

      'O2(aq)' 0

      'HCO3-'         0

      'Al+3'  0

      'Mg+2' 0

      'Ca+2' 0

      'Fe+2'          0

      'Na+'           0

      'K+'            0

      '*'

       

      # AQUEOUS KINETICS

      '*'

       

      # AQUEOUS COMPLEXES (SECONDARY SPECIES)

      'oh-'

      'co2(aq)'

      'aloh+2'

      'al(oh)2+'

      'halo2'

      'alo2-'

      'feoh+'

      'mgoh+'

      'caoh+'

      'h3sio4-'

      'co3-2'

      '*'

       

      # MINERALS

      # 2:  NAMIN(A)           IKIN(I)  IDISPRE(I)  ISS(I)    M1(I)

      # 2.1:                   RKF(F)    IDEP(I)    CK1(F)    CK2(F)    EA(F)  ACFDISS(F)  BCFDISS(F)  CCFDISS(F)

      # 2.1.2.1                RKDS(F)    EADS(F)     NSPDS(I)  NADIS(A) EXPDSP(F)

       'Calcite'               0          0           0         0

                               0.         0           0.

       'Magnesite(Natur)'      0          0           0         0

                               0.         0           0.

       'Amorphous_silica'      0          0           0         0

                               0.         0           0.

       'Diopside'              1          1           0         0                                                   

                               1.00E-11   2           1.0       1.0      43.9    0.0          0.0         0.0       ! -- neutral mechanism (Hermanska et al., 2022)

                               1                                                                                    ! -- number of additional mechs

                               1.58E-10   32.7        1         'H+'     0.30                                       ! acid base mechanism (+n exp) (Hermanska et al., 2022)

      '*'    

       

      # GASES

      # NAGAS IGASFIX

      'CO2(g)'        1

      '*'

       

      # SURFACE COMPLEXES

      '*'

       

      # SPECIES WITH Kd AND DECAY    decay constant(1/s)

      '*'

       

      # EXCHANGEABLE CATIONS

      '*'

       

      #----------------------------------------------------------------------------

      # INITIAL(NIWTYPE) AND BOUDARY(NBWTYPE) WATER TYPES

      # NIWTYPE(I)  NBWTYPE(I) - # of initial & boundary waters

        1           0

       

      # Initial Waters (Index to match total of NIWTYPE)

         1    25.000     25.0000

      # component  ICON     CGUESS       CTOT     fix log(Q/K)

      h2o              1    1.0000E+00   1.000000E+00   *     0.0

      h+               1    1.0974E-10  -1.346992E-04   *     0.0

      h4sio4           1    2.7480E-05   6.735527E-05   *     0.0

      o2(aq)           1    9.9605E-11   9.960502E-11   *     0.0

      hco3-            1    7.9036E-09   1.152225E-08   *     0.0

      al+3             1    1.1472E-27   9.962092E-11   *     0.0

      mg+2             1    3.3069E-05   3.367769E-05   *     0.0

      ca+2             1    3.3629E-05   3.367769E-05   *     0.0

      fe+2             1    2.6325E-11   9.960502E-11   *     0.0

      na+              1    9.9605E-11   9.960502E-11   *     0.0

      k+               1    9.9605E-11   9.960502E-11   *     0.0

      *

       

      #----------------------------------------------------------------------------

      # INITIAL MINERAL ZONES

      # NMTYPE(I) = number of mineral zones

        1                                  

      # IMTYPE(I) = mineral zone index

        1

      # NAMIN(A)        VOL(F)    IKIN(I)         ! 0=LEA; 1=kinetics; 2=no rxn; VOL(F)=1.0 as mass fraction

      # RAD(F)          AMIN(F)   IMFLG(I)

       'Diopside'        1.00     1

        0.0              2.0E+4    1

      '*'

       

      #----------------------------------------------------------------------------

      # INITIAL GAS ZONES

      # NGTYPE(I)    IBGTYPE(I)

        1            0

      # IGTYPE(I) - Domain

        1

      # NAGAS(A)       VOLG(F)

       'CO2(g)'        50.9              ! VOLG=0 for gas fugacity at equil w/ solution; else partial pressure CO2

      '*'

       

      #----------------------------------------------------------------------------

      # Permeability-Porosity Zones

      '*'

       

      #----------------------------------------------------------------------------

      # INITIAL SURFACE ADSORPTION ZONES

      '*'

       

      #----------------------------------------------------------------------------

      # INITIAL LINEAR EQUILIBRIUM Kd ZONE

      '*'

       

      #---------------------------------------if Sden=0 Kd store retardation factor'

      # INITIAL ZONES OF CATION EXCHANGE'

      '*'

       

      #end

       

      *****************************************************************************************

      !!!!           This file is not read below this point    !!!!!

       

      Flow.inp

      # Diopside dissolution experiment: Chanda, 2024

      ROCKS----1----*----2----*----3----*----4----*----5----*----6----*----7----*----8

      ROK25    1     2650.      0.02  6.51E-12  6.51E-12  6.51E-12       1.6    1000.0

         0.0     

       

      MULTI----1----*----2----*----3----*----4----*----5----*----6----*----7----*----8

          3    4    3    6

      START----1----*----2----*----3----*----4----*----5----*----6----*----7----*----8

      REACT----1MOPR(20)-2----*----3----*----4----*----5----*----6----*----7----*----8

      00021  4

      PARAM----1----*-123456789012345678901234----*----5----*----6----*----7----*----8

         49999    9999000000000000000400005000

                3.1558E+10    1.E-05  8.64E+05           -9.806650

          1.E-05

                  5101325.                 0.0            .060900            18.90000 

       

      TIMES----1----*----2----*----3----*----4----*----5----*----6----*----7----*----8

         7 

      3.1558E+071.5779E+083.1558E+087.8894E+081.5779E+093.1558E+093.1558E+10

      FOFT ----1----*----2----*----3----*----4----*----5----*----6----*----7----*----8

      A0025

       

      ENDCY

       

      Solute.inp

      #Title 

      Diopside dissolution, Chanda P., 2024

       

      # 2:options for reactive chemical transport 

      # ISPIA ITERSFA ISOLVC NGAMM NGAS1 ICHDUMP  KCPL  ICO2H2O  iTDS_REACT

          2      0       5     0     0      0      0       0        0 

       

      # 3:constraints for reactive chemical transport 

      # SL1MIN        rcour     STIMAX    CNFACT(=1 fully implicit)

         1.00e-4      1.000     4.0       1.0      

       

      # 4:Read input and output file names

      database_carbfix.dat           ! thermodynamic database

      iter.out                       ! iteration information

      kdd_conc.tec                   ! aqueous concentrations in tecplot form

      kdd_min.tec                    ! mineral data  in tecplot form

      kdd_gas.tec                    ! gas data  in tecplot form

      kdd_tim.tec                    ! concentrations at specific elements over time

       

      # 5:Weighting space/time, aq. and gas diffusion coeffs

      # ITIME     WUPC   DFFUN     DFFUNG

         1.0      1.0    2.d-08    -1.0

       

      # 6:Convergence and tolerance parameters

      # MAXITPTR  TOLTR    MAXITPCH  TOLCH    NOT-USED  NOT-USED    TOLDC    TOLDR

          1     0.100E-03      300  1.000E-06   00      0.000E-05  0.00E-5  0.00E-5

       

      # 7:Printout control variables:

      # NWTI NWNOD NWCOM NWMIN NWAQ NWADS NWEXC ICONFLAG MINFLAG IGASFLAG

          10   1     0     0   -1    0     0       0       2        0

       

      # 8:Nodes for which to output data in time file (15a5) [must match NWNOD]:

      A0025

       

      # 9:Primary (total) aqueous species for which to output concentrations in time and plot files:

       

      # 10:Minerals for which to output data in time and plot files:

       

      # 11:Individual aqueous species for which to output concentrations in time and plot files:

      CO2(aq)

       

      # Adsorption species for which to output concentrations in time and plot files:

       

      # Exchange species for which to output concentrations in time and plot files:

       

      # Default types of chemical zones

      # Initial  Boundary                                      Porosity/ 

      #  Water    Water   Minerals   Gases Adsorption Exchange  Permeab  Kd zones  Injection Gas Zones

      # IZIWDF   IZBWDF    IZMIDF   IZGSDF   IZADDF   IZEXDF   IZPPDF  IZKDDF     IZBGDF

         1          0        1         1       0       0       0       0          0

       

      # Types of chemical zones for specific nodes (optional)

      # Gridblock  Gridblocks Increment   Water    Water   Minerals   Gases Adsorption Exchange  Permeab  Kd zones 

      # ELEM(a5)   NSEQ         NADD      IZIW     IZBW     IZMI      IZGS    IZAD      IZEX      izpp     IZKD  IZBG

      A0025        1            1         1        0        1         1       0         0         0        0     0

       

      # this "end" record is needed 

      end 

       

      ***************************************************************************

      Inputs are not read below the "end" above

       

      A1106        1            1         2        0        1         1       0         0         0        0     0

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