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Kyle Horner

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  1. Hi Brian, I have added the kinetic reactants into the mix, and that seems to have sorted out the last of the issues I was having. Thanks again for the help. Cheers, Kyle
  2. Hi Brian, Thanks for the prompt reply. Your comments on the pickup feature have cleared up the issue I was having. The kinetic examples were also useful as our aim is to eventually include kinetics in the model runs. If I modify my approach to add the 'extra' phases through the reactant tab, how will that work with the flush configuration? Won't using 'reactant times >1’ create a titrating effect, slowly adding the 'extra' phase to the system rather than having it present initially? I am happy for that to happen with the flushing fluid, but not for the formation minerals. Ultimately, we are trying to define a unit volume with specified mineralogy (based on XRD/XRF data) that we can flush. The constraints on the basis are understandable as (for example) Feldspars, quartz, and kaolinite cannot be in thermodynamic equilibrium with one another. However, they can coexist in a formation before equilibrium is reached (as is the case in our study area). I would like to define an initial system where the formation water and formation mineralogy are not at steady-state, but I do not see how to in GWB. Given the thermodynamic constraints, is it possible to define our (non-equilibrium) unit volume through the basis tab? Perhaps a Flush model isn't the way to go. I have had a look at X1t, but I think the restrictions on basis swapping to define an initial unit volume are still present. Cheers, Kyle
  3. Hi Brian, Craig I am using GWB 8.012 to simulate the flushing of a formation with variably CO2-saturated groundwater. I am taking a multiple-step approach, described below, and run into hiccups during a few of the steps. I would appreciate your insights into my workflow in GWB, and any tips how to resolve the issues I seem to be having. I have attached a few working files for your reference Workflow: Calculate maximum CO2 solubility in regional groundwater outside of GWB (e.g. Solubility model of Duan et al 2003, 2006). Modify Thermo.dat CO2 ion size to -0.5 to invoke Helgeson's polynomial fit to calculate activity of CO2(aq). Open React w/ modified thermo.dat. Enter regional groundwater concentration into basis. Swap CO2(aq) for H+ in basis and specify CO2(aq) concentration. Balance on bicarbonate. Run React, suppressing all mineral precipitation during this step to simulate rapid equilibration of groundwater with CO2. Pick-up CO2-equilibrated groundwater (the flushing solution) to reactants (Pickup->Reactants->Fluid). Check Flush Configuration option in React. Define mineral assemblage for 1m3 of formation in Initial System tab. Increase mass of H2O to reflect volume of water in porespace of 1m3 of formation. Add additional basis species at nominal concentrations (0.01mg/L) where required so that all ions in flushing solution are in basis. Flush system using varying quantities of reactants ("Reactant Times" > >1) The two issues I have arise in Steps 4 and 6. First, following the pick-up of the CO2-enriched groundwater in Step 4, the reactants tab appears to un-swap H+ and CO2 (that latter of which is absent from reactants). It also assigns an incorrect value to HCO3-. Is GWB incorrectly picking up the solution, or am I misinterpreting the way GWB handles this step? So far, before flushing, I have been adding CO2(aq) to the reactants tab and entering the values for H+, CO2(aq), and HCO3- calculated in Step 3. Second, as the formation mineralogy consists of numerous silicate phases, I often run out of basis species to swap for minerals in Step 6. As a work-around I have been omitting quartz from the formation defined in the basis tab to free up Si to swap for another, more reactive phase. Is there another way to define a complex mineral assemblage in GWB flush models that will allow a greater number of mineral phases to be included? Or is GWB limited to the number of minerals that can be defined by swapping out basis species? Thanks for your help with this. Please let me know if I can explain anything further. Cheers, Kyle CO2_Equilibration.rea Formation_Flushing.rea
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