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Carbonate acidizing -(Matching ICP result ) - Help to setup initial rock sample and fluid constrains on the system

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Greetings all,

I conducted  HCl ( acid ) core flooding experiments at room temperature on cylindrical limestone rock samples (2.5 cm in diameter 5 cm long) which are mainly composed of ( ~ 97 % calcite from XRD analysis ) and the produced water (effluent) was chemically analyzed for cations using Inductively Coupled Plasma (ICP) spectroscopy to assess the dissolution reaction phenomena.

the chemical equation is as follows : CaCO3 + 2HCl ---> CaCl2 + CO2 + H2O                                                        

My aim is to get the dissolution reaction rate constant and the diffusion coefficient for the conducted experiment by matching laboratory ICP result (Ca++)  with the model (X1t).

I have read transport reactive and other documentation but I am missing something. 

I used X1t app to simulate the acidized core flooding experiments and match the laboratory ICP result.

my concerns are the followings : 

How precisely can I put the constraints on the initial system for the rock sample and the injected acid solution? I am a little bit confused about the input units ( mg/kg, free kg, mmol/kg, ..etc). I am only aware of the limestone rock sample weight ( 50 g) , porosity (22%) and the concentration of the injected acid (pH, wt% ).  how would I put the value of the followings with their units:

  • H2O .... free kg
  • H+ ..... 4 (pH) .. for example !
  • Cl- ...  
  • Ca++ ( mineral ) ...
  • HCO3- ....
  • do I need to equilibrate the fluid and the rock in the initial pane in constraints on the initial system, and if so, how would I equilibrate them?
  • injection rate was 10 cm3/min. how would I mimic the laboratory injection rate within the X1t  the discharge ( injection rate) unit (cm/s, cm3/cm2/s, ..etc)?
  • The laboratory domain was a cylindrical core sample (2.5 cm in diameter 5 cm long) , how would I simulate that domain in the model, I used a spherical domain with r1: 1.25 cm, r2: 1.26 cm and nodes (Nx) = 5, please advise the appropriate way.


Your support in this matter is highly appreciated.




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