tylerp

Hi Brian, Thank you very much for your help. I find the GBRM book very useful. Best wishes, Tyler

I think the acidity is not correct because the measured pH (pH 2) was measured a few days prior to titration for acidity. So I used HCO3-/CO2 = 1.2E-07 mol/l (solution in equilibrium with pCO2 = 1% of pCO2 in the atmosphere) and successfully run the reactions of the this solution with some minerals using React. I also used the same solution and minerals to simulate kinetic reactions along surface of fracture with fluid flow using X1t, the simulation ran properly (at 25oC, fixed constants). Now I just need to make some changes to add activation energy and pre-exponential factor so kinetic reactions can be calculated for higher temperatures. Thank you very much for your help, Brian. Tyler

Thanks, Brian. Yes, the measured acidity is total phenolpthalein acidity (titrated o pH 8.3) in which mineral acid (HCl) dominated (I added concentrated HCl to the solution). Apparently, the measured acidity might not be correct (acidity = 1186 mg/L as CaCO3 which is equivalent to ~23.72mmol NaOH). However, I run the React module to titrate this solution (pH 2) with NaOH. It requires about 100 mmol to bring pH to 8.3. In this run, I assume CO2aq is in equilibrium with atmospheric CO2 (during titration) so I used HCO3-/CO2 = 1.2E-05 mol/l, which is calculated from Henry's law. So it comes to this question: (a) The solution is in equilibrium with N2 filled in head space during the experiment. Is it correct (acceptable) to assume the CO2(aq) is in equilibrium with very low PCO2, then calculate CO2aq = KCO2xPCO2 according to Henry's law? this method should give HCO3-/CO2 = <1.2E-05 mol/l. OR ( should I calculate CO2aq from CO2 (aq) + H2O --> H+(aq) + HCO3-(aq), assuming HCO3-= H+ = 0.01 mol/l? this method gives HCO3-/CO2 = 0.01^2/4.45e-7 = 224.7 mol/L (which is too high, is it odd?) Thanks, Tyler

Hi, This is to follow up. I have swapped CO2(aq) for HCO3- and also converted the script to X1t instead as a simple 1D model would work for my application. Unfortunately, there is still error below: Solving for composition of inlet fluid. N-R didn't converge after 999 its., maximum residual = 1.#R, Xi = 0.0000 Largest residual(s): Resid Resid/Totmol Cbasis --------------------------------------------------------- --------------------------------------------------------- Can someone please help? Brian Farrell? The revised script is attached. Thanks, Tyler Brine.x1t

Hi Brian, Thank you very much for your suggestion and quick response. I will try it out. Best regards, Tyler

Hi, Check out this paper. it might have useful info you are looking for. Kinetic modelling of CO2–water–rock interactions Helge Hellevang∗, Van T.H. Pham, Per Aagaard International Journal of Greenhouse Gas Control Cheers,

the concentration of chloride in the solution is very high because of the HCl added. I also tried to set Na+ to be the balance species, but the same error occurred. Thanks!

Hi All, I have trying to use X2t to simulate reactions of brine along fracture. There are errors "Solving for composition of inlet fluid, Residuals too large". I tried to run both 2 solutions using SpecE8, there were no problem with charge balance (error is about 0.5%). The solution is acidic (HCl added), and the acidity was added under HCO3- species. How do I enter HCO3- species using acidity? Can someone please help take a look at the file attached? Thanks, Tyler brine.x2t