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Ross McCartney

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About Ross McCartney

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  1. Problems with custom rate law script

    Tom, Thank you for looking at the script for me - managed to spend a little more time on this and found that the problem was with the quotes on H+ activity (thought it would be obvious!). Anyway, for the benefit of the forum, the attached script now works and so will act as a template for those using the kinetic data in Palandri and Kharaka 2004. albite.rea
  2. Problems with custom rate law script

    Tom, Thank you for the suggestions. I have tried simplifying my script and including it as a script file (attached - note I needed to change fiel extension to .txt as I cannot upload .bas files) but although React now 'runs' it does not appear to be dissolving any albite. I am probably missing something very obvious! Best regards Ross albite kinetic file1.rea albite_kinetic.txt
  3. Modelling injection/recovery in X1t/X2t

    Many thanks for your prompt reply Tom, much appreciated.
  4. I am trying to implement a custom rate law script (see attached)for albite using React but keep getting the error message "could not evaluate rate law". I am using the rate law and rate parameters included in Palandri and Kharaka (2004; A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modelling). I cannot see where the problem is with the script so any advice gratefully received. albite kinetic file.rea
  5. I want to model injection of water into a formation and the subsequent recovery of this fluid (after reaction in the formation) from the same well. Is there a way to do this in X1t or X2t?
  6. Modelling ion exchange with X1t

    I have recently been undertaking some 1-D reactive transport calculations using X1t which include ion exchange reactions. These involve percolation of a fluid into a flow path where it mixes with and displaces the initial fluid. As the mixing zone moves along the path, ion exchange reactions act on the fluid compositions so that under the Gaines-Thomas convention, once a sufficient distance (A) is travelled, the activity ratios of cations affected by ion exchange reactions (e.g. aCa/aNa) in the mixing zone approach those of the initial fluid. In this case, the distance ‘A’ is dependent on several variables that can be measured (CEC, selectivity coefficients, fluid velocity, etc). However, it is also dependent on the number of cells (Nx) contacted by the mixing zone along the flow path. This parameter has to be selected by the modeller. Computing power aside, intuitively, Nx should not be so large that distance A is calculated to only be a few cm where the fluid velocity is high, CEC is low, etc. But equally, where Nx is too low, distance A will not be reached (and numerical dispersion can become an issue if other reactions are of interest). Does anyone know whether the influence of Nx on the modelling of ion exchange reactions has been investigated at all? For example, is there a rule of thumb regarding what value of Nx to use when simulating laboratory/field data affected by ion exchange reactions?
  7. Anion exchange

    Hi, Is there any way to model anion exchange using GWB? Ideally I would like to model Cl-SO4 exchange and I tried modifying the Ionex.dat file but got an error message saying 'Expected a cation as adsorbed species in ion exchange model, found "Cl-"'. If it is not possible at present, is this something that might be included in the next release?
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