Anastasia

Brian, Thank you for getting back to me. Good point about equilibrium with the minerals and kinetic rate laws. I'll change that. I'' double check the concentrations and units too. The conceptual model is to react a sandstone (with initial brine) with the similar brine when it has more CO2 dissolved in it. Do you have a suggestion of what variables can be changed if a reactive flow model runs for a fraction of time (a few years), then crashes with "N-R didn't converge" message shown below? Thank you so much for all your help, I really appreciate it! Anastasia Message: -- Warning: Reactants at node 0 are not charge balanced, z = 0.506328 *N-R didn't converge after 999 its., maximum residual = 19.1, Xi = 0.3137 N-R failed at node 0 Attempting to write last good time step for plotting. -- Can't converge, abandoning simulation. -- Warning, Node 0 has a charge imbalance of -0.2454 faradays

o.k. now it's attached Sandstone.x1t

Of course! Its attached. Thank you so much for all your help, Anastasia

Hello, I'm constructing a 1D reactive transport model where fluid flows through sandstone. I consistently get this (or, similar) message: Solving for composition of inlet fluid. Solving for initial state of each nodal block. Residuals too large, 652-th interation Largest residual(s): Resid Resid/Totmol Cbasis -------------------------------------------------------- Cl- 190.2 1.207e+200 1.031e-196 -------------------------------------------------------- I ran SpecE8 on both initial and inlet fluid compositions, and they both are about charge balanced: * Initial: Charge imbalance = -0.012 meq/kg (-0.001151% error); * inlet: Charge imbalance = -0.005351 meq/kg (-0.0005109% error) I also ran React on the inlet fluid composition reacting with quartz, calcite, K-feldspar, and hematite, and this calculation has converged. Please let me know if you have any ideas of how to set up this 1D reactive flow model. Thank you, Anastasia

Brian, Thank you so much for the solution to this issue! I hope you had nice holidays, Anastasia

Hello Brian, Thank you so much for the reply. I did a quick test and typing in "extrapolate on" in the command does not seem to make any difference in the outcome. I'll e-mail you my files to test. Thank you so much! Anastasia

Hi, I am modeling the chemistry of a Na-Cl brine. For the calculation to be more relevant to my study area I've modified the thermodynamic database to include Al, Si, Cd, N and Si species. Activity correction is h-m-w. As usual, the majority of the Pitzer coefficients are known for 25 C, with some exceptions, therefore the results are most accurate at 25 C. Using the modified database the calculation converges when I use temperatures above 25 C (e.g. 26 C, 59 C). When I try running at 25 C I get the following error: Solving for species distribution. Loaded: 45 aqueous species, 162 minerals, 2 gases, 0 surface species, 12 elements, 0 oxides. Ionic strength out of range. Largest residual(s): Resid Resid/Totmol Cbasis -------------------------------------------------------- O2(aq) 0.002616 1 9e-031 -------------------------------------------------------- The calculation does run if I delete O2(aq) and Fe++ data entries (they are not zeros). I was hoping someone can help me figure out why while using a modified h-m-w thermo database I get an error at 25 C temperature, but at other temperatures the calculation does converge. I've attached a script file with the data. Thanks, Anastasia AGI_test.sp8