Kyle Horner Posted June 7, 2013 Share Posted June 7, 2013 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 Quote Link to comment Share on other sites More sharing options...
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.