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Tom Meuzelaar

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  1. It represents the actual mass and volume of mineral in the system- remember that once a mineral is in equilibrium with a fluid, adding additional mineral mass will not change the concentrations of fluid components constrained by that mineral. I'm not sure I quite understand what your modeling object is- however, if you constrain a mineral mass in the Basis, you are ensuring that the fluid will initially be saturated with respect to that mineral. You could get there with kinetics, but kinetic reactions in GWB, by definition, move towards equilibrium. In other words, in order to model a kinetic mineral precipitation/dissolution reaction, you have to start with a fluid that is either undersaturated or supersaturated with respect to that mineral. I hope that helps, Tom
  2. Hi Thomas: You'll want to refer to the PHRQPITZ documentation for the answer to many of these questions. Here is the reference: Plummer, L.N., D.L. Parkhurst, G.W. Fleming and S.A. Dunkle, 1988, PHRQPTZ - A computer program incorporating Pitzer's equations for calculation of geochemical reactions in brines. U.S. Geological Survey Water-Resources Investigations Report 88-4153, 310 p. thermo_pitzer.dat is outdated, and is included with GWB only for compatibility with early releases. We recommend that you use thermo_hmw.dat or thermo_phrqpitz.dat. Unfortunately, the equations for temperature dependence are not likely to change in the near future, but if you give me a more detailed explanation of what it is you need (email is fine), I'll add it to the wish list. I hope that helps, Tom
  3. Hi ThommyW: I'm not sure what the meaning is of the 4th set of CO2 parameters in the dataset- I'll see what I can find out. However, given that the values are all 0 in every GWB thermo data, I think you're safe to leave this as is. As far as the coefficients for calculating the activity of water, the equation you list is correct (although it's equation 8.8 in the newer text, not 8.6). The parameters are given in figure 8.5 (p. 122), and I see exact agreement between this table and thermo.dat. Make sure you read the data correctly - parameters are only given for 25, 100 and 200C. I hope that helps, Tom
  4. Hi Lea: The Minerals in System section lists minerals in equilibrium with the fluid only- that is, minerals that are defined in the initial Basis tab, or those that precipitate along the way. It does not list minerals that are precipitating or dissolving kinetically. Regards, Tom Meuzelaar RockWare, Inc.
  5. Dear GWB Users: We'll be picking a location for the 2010 GWB workshop by the end of this month. If you have some interest in attending, please send an email to me at gwb@rockware.com and state your preferred location, so that we can gauge interest. Current prospective locations for a 2010 workshop are: Denver, CO, USA Knoxville, TN, USA (coincident with Goldschmidt) a Europe based workshop a South Africa workshop We will consider all locations provided there is sufficient interest. Regards, Tom Meuzelaar RockWare, Inc.
  6. Hi Thomas: The equations used to calculate the activities of electrically neutral species and water are given in chapter 8 of Geochemical and Biogeochemical Reaction Modeling (or chapter 7 if you have the older Geochemical Reaction Modeling). Be sure you also understand the importance of the ion size parameter which is described in the Thermo Datasets Appendix of the GWB Reference manual as follows: Hope that helps, Tom Meuzelaar RockWare, Inc.
  7. Dear Helge: Unfortunately, basis species must be aqueous species. We still await your response to an example of a database with redox reactions formatted according to H2(g) (see forum post: https://www.rockware.com/forum/index.php?showtopic=786) as we would consider implementing this into GWB. Is this forthcoming? Best regards, Tom Meuzelaar RockWare, Inc.
  8. Hi Thomas: Since questions 1 and 4 are the same as posed in your original email, I will post my email reponse first: >>>>>>>> To see temperature dependence for Pitzer models be sure you are using the dataset thermo_phrqpitz.dat. Also- it would be useful to consult the original reference by Plummer et al., 1988. Temperature dependence is calculated by providing up to 4 coefficients (c1, c2, c3, c4) for beta0, beta1, beta2, cphi, theta, lambda or psi, according to the following equation: val = val25 + c1*(Tk-Tr) + c2*(1/Tk - 1/Tr) + c3*ln(Tk/Tr) + c4(Tk^2-Tr^2) Note that there is scant data, and that only beta0, beta1 and cphi for the Na/Cl pair have data for c2, c3 and c4. >>>>>>>> You can find a slight bit of additional information in the Thermo Datasets Appendix of the version 8 GWB Reference manual. With regards to question 5, there is currently no provision in GWB for a user-defined temperature dependence function, nor are there any development plans for this. Regarding the validity range, I again refer you back to Plummer et al., 1988. Regards, Tom Meuzelaar RockWare, Inc.
  9. Hello: In your case, the problem stems from the fact that GWB version 4 is not compliant with Windows 7. Unfortunately, the only solution is to upgrade to GWB version 8. Let me know how I can be of further help. Regards, Tom Meuzelaar RockWare, Inc.
  10. Dear GWB Users: We have released GWB 8.0.8, which addresses the following issues: Support for Windows 7. Resolve all known issues with 8.0 through 8.0.7 All current GWB Essentials, Standard and Pro version 8 users can download the GWB 8.0.8 patch here. Please contact me with any questions. Regards, Tom Meuzelaar RockWare, Inc.
  11. Hi Mathew: Can you provide a script so I can take a look at this? Be sure to include the database if different from the default databases provided with GWB. If you want to keep this private, email them to me at gwb@rockware.com. Regards, Tom
  12. You can calculate partitioning between the dissolved CO2 and CO2 gas using a simple speciation model- but to answer the question I think you are asking- GWB does not track gas phase masses or volumes. Regards, Tom Meuzelaar RockWare, Inc.
  13. Sure- you can do this in the Reactants tab using the slide option. Choose add - Sliding, and then pick either a sliding CO2(g) fugacity or a sliding CO2(aq) activity. Note that you also have options to fix CO2 fugacity or activity. Regards, Tom
  14. Hi Tom: You'll want to distinquish between the CO2(g) and CO2(aq) species in the database. The former simply represents a gas buffer that is modified in response to dissolved CO2 (the latter species) according to Henry's law. To track mass of CO2 released from solution, have a look at the change in the CO2(aq) species. Hope that helps, Tom Meuzelaar RockWare, Inc.
  15. Hello: Gas fugacities are reported in atm (atmosphere) units in GWB. Gas volumes are not tracked by the code. Best regards, Tom Meuzelaar RockWare, Inc.
  16. Hi Lea: There are no 'wrong' minerals - this often becomes more a matter of modeling approach. One strategy is to include just the minerals that you observe in the system you are modeling (or those that do not exist but could be reaction products), as well as those minerals that React needs for Basis swapping to maintain a stable solution matrix. All other minerals are suppressed. Another modeling strategy is to include all minerals, and iteratively remove (Suppress) those that the model predicts which seem unrealistic to you. Generally the decision to include/exclude a mineral is driven by the modeling time frame of interest and the dissolution/precipitation rates (kinetics) of the mineral. In other words, if you are modeling over a very short time scale, minerals that have very slow precipitation/dissolution rates can often be excluded. Regards, Tom
  17. Hi Lea: Part of the problem is that your initial solution is highly supersaturated. Before React can begin the kinetic titration that you've set up, it needs to speciate the initial solution, and bring it to equilibrium. When you leave the precipitation setting in its default state, React swaps in a number of necessary mineral phases to allow the solution to precipitate minor mineral mass and come to equilibrium. Have you considered using the Config - Suppress menu option? This allows you to remove from consideration mineral phases that might interfere with your kinetic titration, yet leave in other mineral phases necessary to allow your initial solution to come to equilibrium, and remain stable during the simulation. Hope that helps, Tom Meuzelaar RockWare, Inc.
  18. Hi Terry: You can add the version stamp on the file via the Run - Suffix command. I didn't realize this existed until a GWB user in the 2nd Canberra workshop pointed it out to me. Try it! Regards, Tom
  19. Hi: You can always stop a simulation via the Run - Kill menu option (or Ctrl-Break). At this point, X1t/X2t will tell you that results are available for plotting- plot output results are stored in the .xtp plotting file created for that simulation in the working directory you've specified. By default, text output for reactive transport models is disabled, because for most models the output files are exceedingly large. You can enable the text output files via the Config - Print Options menu option (check the print dataset box). Once enabled, it functions in the same way as the plot output file- that is, when you stop a model, all output data generated up to that point is saved and available for analysis. It is important to note that when you re-run the X1t/X2t modules, plot and print output from the previous run is over-written- so you should rename both output files if you want to save them for future use. I hope that helps, Tom Meuzelaar RockWare, Inc.
  20. Hi Marty: Have you experimented with the Data - Calculate menu option in GSS? You should be able to speciate your 50 analyses and calculate mineral saturation states within the spreadsheet. You can then plot these directly via the Graphs- XY plot menu option. I hope that helps, Tom Meuzelaar RockWare, Inc.
  21. Thank you for the comments and references Helge. Regards, Tom
  22. The problem will be that the entire suite of minerals you see in the reservoir are not all in equilibrium with the fluid. You can constrain your water chemistry by making assuming that minerals are controlling fluid components, and swapping these minerals in for the components. For instance, modelers commonly assume that quartz in the reservoir controls the silica concentration of the fluid, and thus make the swap Quartz - SiO2(aq). If you're going to go the equilibrium route, you'll need to reduce the number of initial phases (as not all of them can be in equilibrium with the initial fluid). Your other option is to titrate mineral phases in kinetically, provided you have the necessary rate law data. I hope that helps, Tom
  23. Hi Lea: Are either of these clays observed in the system you are studying? Because in the equilibrium model you've constructed, neither are stable after being titrated. I'm wondering if you need to either consider moving to a kinetic model, or titrating minerals in that have greater long term stability.... I hope that helps, Tom Meuzelaar RockWare, Inc.
  24. Hi Thomas: Please email your modified database and React script to me at gwb@rockware.com. Regards, Tom Meuzelaar RockWare, Inc.
  25. Hi Lea: Would you mind attaching your React script to this thread, so that I don't have to enter all your data manually? Thanks, Tom Meuzelaar RockWare, Inc.
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