Diffusive Transport Modeling of Eagle Ford shale with CO2-saturated fluid

[chrisnguen38]

Hello,
I have just started using PhreeqC, and I have been trying to model the reaction between Eagle Ford shale (94.4% calcite) and CO2-saturated fluid at high temperature and pressure. I am mostly interested in determining and plotting different mineral profiles i.e reaction fronts (mineral concentrations as a function of distance).
Specifically, my experiment involved submerging the rock samples in a sodium chloride solution and subsequently inject CO2 until a temperature of 100 degrees Celsius and a pressure of 1700 psia are attained. The experiment is then run for two weeks before samples are taken out for further study.
With PhreeqC, I am trying to emulate the reaction that occurred, investigate and quantify the mineralogy of small scale reaction fronts. So far, this is what I have been able to come up with:
TITLE Example. --
SOLUTION 1  PURE WATER
        pH      7.0
        temp    100
   -water      0.055784   # kg
EQUILIBRIUM_PHASES 1 Define amounts of phases in assemblage.
        Halite          0.0     0.055886379
SAVE SOLUTION 1
END
SOLUTION 0 Acidic water
USE solution 1
EQUILIBRIUM_PHASES 1 Equilibrate rock with carbon dioxide
CO2(g)      2.08807475135
SAVE solution 0
END
SOLUTION 1-20
USE solution 1
EQUILIBRIUM_PHASES 1 Equilibrate rock with pore water
   Kaolinite   0.0    0.000316662
   Quartz      0.0    0.001036349
        Calcite     0.0    0.027175368
   Dolomite    0.0    0.000143937
   K-Feldspar  0.0    0.000259087   
END
PRINT
        -selected_out true
KINETICS 1-20 Kinetic reaction for all cells # 1-20
Calcite
      -m   2.713e-02
      -parms   5.0      0.3
      -tol     1.e-8
TRANSPORT
        -cells                20               
        -length               0.005               
        -shifts               336               
        -time_step            3600             
        -flow_direction       forward
        -boundary_condition   flux flux
        -dispersivity         .05
        -correct_disp         true
        -diffusion_coef       0.0e-9
        -punch_cells          20               
        -punch_frequency      1                 
        -print_cells          20               
        -print_frequency      5                 
END
PRINT
    -selected_out true
USER_GRAPH 1 Plots Ca concentration profile
      -axis_titles "Distance, in m"
              "CO2 concentration, in moles per kilogram water"
       -axis_scale x_axis auto
       -axis_scale y_axis auto
           -connect_simulations true
           -plot_concentration_vs  x
END
I would appreciate any help and advice so as to improve from here.
Thank you in advance!

[dlparkhurst]

I tend to avoid checking or general comments. You know your experiment and results better than I.

[chrisnguen38]

Thank you for your reply. I have been stuck because I have never used PhreeqC before. After running my experiment, I conducted EDS (Energy Dispersive Spectrometry) to identify the various phases of the specimen post-reaction, and tested those phases mechanical properties using nano-indentation. However, the EDS analysis I performed remains very qualitative, and I wanted to confirm those results using PhreeqC. However, I have been stuck for the past couple months, and that is why I sought help on this forum. I hope that makes a bit clearer.

[chrisnguen38]

One of the main questions that I had was how to create a reactive-diffusive transport model for the experiment I described. I thought about the KINETICS and TRANSPORT functions, but I am not sure they are quite adapted to my problem.