Geochemist's Workbench Support Forum  # Jubilee

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1. Dear Brian, May i know which of the GWB packages is most suited for carrying out thermodynamic simulations on reservoir rock cores. I am looking to find out the effect of changes in pressure and temperature (reservoir conditions, 3500psi, 130oC) on the concentration of injected fluids during water flooding. The end game is to determine if there is precipitation of the minerals in the injection fluid before they react with the formation. Kindly let me know if GWB is capable of this kind of simulation. Jubilee.
2. Hi Brian, I am still expecting your response to my previous post. Regards, Jubilee
3. Hi Brian, I have yet to come up with a mathematical expression for the equilibrium reaction equation when using the simple reactant in my model. Unfortunately, the geochemical and biogeochemical reaction text does not give sufficient information about this. Although, I had a clue of what is going on with the AsK+(1-Q/k) term of the equation when a simple reactant is chosen, my assumption broke down when I discovered that the dimension analysis (unit) of the dispersion and advection terms of Eq 21.2 is different from that for the reaction term. Is there a reason for this? My understanding is that the dimensions of the RHS of the equation should be equal to that of the LHS, and that all additive terms of the RHS and LHS should have the same dimensions. Regards, Jubilee
4. Hi Brian, Based on your previous response regarding the use of the titration model for simple reactants, i would like to know if this implies that the reaction term will be eliminated from the reactive transport equation. If not, what expression serves as the substitute for the reaction term in the equation. Jubilee.
5. Hi Brian, I am considereing precipitation in X1t using the built in rate law for a kinetically reacting mineral ( r = k+ * A * (1 - Q/K)). Generally, Keq = K+/K- where k+ = dissolution rate constant and k- is the rate constant for precipitation, and Keq is the eqilibrium rate constant. When modeling for precipitation in x1t and i supply a value for the dissolution rate constant (k+), does GWB calculate the k- from the k+ and Keq or precipitation is only determined by the value of Q/K. Regards, Jubilee.
6. Hi Brian Thanks for your constant support. I incorporated the changes you suggested in your previous email and obtained a more accurate result. So far, I have identified the dispersion and mineral specific surface area as key drivers for my model. I still have a couple of questions regarding the reactant plane. On the reactant plane, there are 4 options (simple fixed, kinetic, and sliding). I would like to know the implication of selecting gypsum under “Simple” instead of “Kinetic”. From my observation, “kinetic” gives me a better control as I can specify parameters such as the rate constant, surface area, dissolution or precipitation, and other key parameters that influence my model. However, I can only specify the mineral abundance when using “Simple”. I would like to know the following: 1. Given that I have no control over the aforementioned parameters when using “simple”, what are the defaults for “simple? Is there a document that gives the default parameters of the model? 2. Not much is said in the GWB guides regarding “xaffin”. What does this parameter mean and what is its significance? I look forward to your response. Regards, Jubilee
7. Hi Brian, Thanks for your respo nse. (1) can you expanciate on your previous comment (below). You'll want to actually calculate exactly how much Quartz and Gypsum are in your system. Right now, your input script does not reflect the solid phase mass fractions described in your attachment. Calculating the initial system ("go initial") and checking the mass and volume of the minerals, fluid, etc. should help you verify that your input matches the experimental conditions. How do i set the solid phase mass fractions. My current script is based on script from worked examples in the GWB transport modeling guide (rainwater infiltering a quartz aquifer). please share an example. (2) How do i account for changes in mineral surface area (As) as the reaction proceeds. I did not consider this in my previous script and i believe it will be critical to the accuracy of the model. Please share an example if possible. (3) is it possible to model evaporation in x1t. kindly share an example. Regards, Jubilee
8. Hi Brian, I made the changes you suggested and was able to run the model using the different thermo data sets. However, the experimental values i have obtained in the lab are not well predicted by the model. Also, i have less accurate results using the phriqpitz and HMW datasets, despite the fact that my feed water has very high ionic strength (TDS = 42,000 ppm). kindly let me know if there is a forum whereby i can get some hands on help, regarding the system i am trying to model. Find below my model, in case one or two errors that may affect the accuracy of the model stick out. Also, i have written a brief note to describe the system i am trying to model. Code X1t script, saved Sun May 25 2014 by jadeoye data = "C:\Program Files\Gwb\Gtdata\thermo.com.V8.R6+.dat" verify time start = 0 hr, end = 275 hr delta_x = table {2.5 5 5 5 5 5 5 5 5 5 5 5 5 } cm width = 6.3 cm height = 8 cm Nx = 13 discharge = 25 pore_volumes porosity = .38 dispersivity = .409 cm heat_source = 0 J/cm3/yr, temp_min = 25, temp_max = 25 scope = initial H2O = 1 free kg Ca++ = 1657.27 mg/l Na+ = 14776.9 mg/l Mg++ = 1838.17 mg/l K+ = 649.7 mg/l SO4-- = 5972.32 mg/l Cl- = 22500 mg/l balance on Cl- pH = 7.5 SiO2(aq) = 1e-5 mg/l scope = inlet H2O = 1 free kg Ca++ = 579.3 mg/l Na+ = 14317.6 mg/l Mg++ = 2036 mg/l K+ = 603.05 mg/l SO4-- = 3884.1 mg/l Cl- = 22500 mg/l balance on Cl- pH = 7.75 SiO2(aq) = 1e-5 mg/l TDS = 42000 density = 1.025 kinetic Gypsum 3 volume% rate_con = 4.7e-9 surface = 3000 kinetic Quartz 59 volume% rate_con = 4.2e-18 surface = 1000 Description I have a cylindrical soil column (length = 60 cm, radius = 4 cm). The top 20 cm of the column is filled with sand (97% mass fraction) and gypsum (3% mass fraction).The rest of the column is filled with plain sand. The porosity of the soil column was calculated to be 38%. The column is orientated upside down, so that the 20 cm zone amended with gypsum is at the base. I am flushing the soil column with seawater, from the base, at a rate of 2 mL/min using a peristaltic pump, and maintaining a hydraulic head at the top of the column to ensure that the system is operated under saturated flow. The pore volume will be displaced 25 times. I wish to determine the change in concentration of calcium at different points in the soil column over time. This will help me monitor the dissolution of gypsum in the soil. See the attached file, showing the model and experimental setup. I have also included the graphs in which i compared the model results and experimental results for the three gypsum mass fractions i considered (1%, 2%, 3%). Regards, Jubilee Soil Colum study file.pdf
9. Hi Brian, Thanks for the response. This was helpful. Can you also address my final question, "Also, i would like to find out if any GWB user has complained about unreproducible results in the past. i have battled to reproduce the same result i obtained from a set of codes last month.By this, i mean that, i ran the same codes last month, and now, i am getting results that are totally different from what i got back then." Regards, Jubilee
10. Hi Brian, My i also ask if there is a way to combine two activity coefficient models in GWB. So, i know that at high ionic strength, the thermo.dat will not give me an accurate result. However, it contains the aqueous silicon oxide. On the other hand, PHRQPITZ gives fairly accurate results at high ionic strength, but does not contain aqueous silicon. I need a model that contains aqueous silicon oxide and also gives fairly accurate results at high ionic strength. My inlet water concentration is 42,000 ppm Also, i would like to find out if any gwb user has complained about unreproducible results in the past. By this, i mean that, i ran the same codes a couple of months ago and now i am getting results that are totally different from what i got back then. Regards, Jubilee
11. Thanks Brian for the response. I have gone through all the thermo data sets in the GWB. I tried to run my model making use of each one of them. I was only able to run the model successfully with "thermo.dat and thermo.comV8.R6t.dat. Are these the only two datasets with silica species. May I know if there are alternatives for running the model using the Pitzer activity coefficient model. Also, it is not clearly stated if the thermo.dat is a debye huckle method of Viral method. Kindly clarify. Regards, Jubilee.
12. Hi Brian, I have tried to run the script below several times using the thermo_Phrqpitz. However a couple of errors are displayer when i initiate the run. Find my script below. Regards, Jubilee # X1t script, saved Wed May 14 2014 by jadeoye > data = "C:\Program Files\Gwb\Gtdata\thermo.dat" verify > conductivity = "C:\Program Files\Gwb\Gtdata\conductivity.dat" Reading conductivity data from: C:\Program Files\Gwb\Gtdata\conductivity.dat > time start = 0 day, end = 275 hr > delta_x = table {2.5 5 5 5 5 5 5 5 5 5 5 5 5 } cm > width = 8 cm > height = 8 cm > Nx = 13 > discharge = .000265 cm3/cm2/s > porosity = .38 > dispersivity = 30 cm > heat_source = 0 J/cm3/yr, temp_min = 25, temp_max = 200 > scope = initial > H2O = 1 free kg > Ca++ = 1657.3 mg/l > Mg++ = 1838.3 mg/l > Na+ = 14776.9 mg/l > K+ = 649.7 mg/l > SO4-- = 5972.32 mg/l > Cl- = 22800 mg/l > balance on Cl- > Br- = 101.343 mg/l > pH = 8 > SiO2(aq) = 1e-5 mg/l > TDS = 42000 > density = 1 > scope = inlet > H2O = 1 free kg > Ca++ = 579.3 mg/l > Mg++ = 2036 mg/l > Na+ = 14317.6 mg/l > K+ = 603.05 mg/l > SO4-- = 3834.1 mg/l > Cl- = 22500 mg/l > balance on Cl- > Br- = 95.2 mg/l > pH = 8.25 > SiO2(aq) = 1e-5 mg/l > TDS = 42000 > kinetic Quartz 97 wt% rate_con = 4.2e-18 surface = 1000 > kinetic Gypsum 3 wt% rate_con = 4.7e-9 surface = 3000 > printout on X1t > Regards, Jubilee 0 Quote MultiQuote Edit
13. Hi Brian, I have tried to run the script below several times using the thermo_Phrqpitz. However a couple of errors are displayer when i initiate the run. Find my script below. Regards, Jubilee # X1t script, saved Wed May 14 2014 by jadeoye > data = "C:\Program Files\Gwb\Gtdata\thermo.dat" verify > conductivity = "C:\Program Files\Gwb\Gtdata\conductivity.dat" Reading conductivity data from: C:\Program Files\Gwb\Gtdata\conductivity.dat > time start = 0 day, end = 275 hr > delta_x = table {2.5 5 5 5 5 5 5 5 5 5 5 5 5 } cm > width = 8 cm > height = 8 cm > Nx = 13 > discharge = .000265 cm3/cm2/s > porosity = .38 > dispersivity = 30 cm > heat_source = 0 J/cm3/yr, temp_min = 25, temp_max = 200 > scope = initial > H2O = 1 free kg > Ca++ = 1657.3 mg/l > Mg++ = 1838.3 mg/l > Na+ = 14776.9 mg/l > K+ = 649.7 mg/l > SO4-- = 5972.32 mg/l > Cl- = 22800 mg/l > balance on Cl- > Br- = 101.343 mg/l > pH = 8 > SiO2(aq) = 1e-5 mg/l > TDS = 42000 > density = 1 > scope = inlet > H2O = 1 free kg > Ca++ = 579.3 mg/l > Mg++ = 2036 mg/l > Na+ = 14317.6 mg/l > K+ = 603.05 mg/l > SO4-- = 3834.1 mg/l > Cl- = 22500 mg/l > balance on Cl- > Br- = 95.2 mg/l > pH = 8.25 > SiO2(aq) = 1e-5 mg/l > TDS = 42000 > kinetic Quartz 97 wt% rate_con = 4.2e-18 surface = 1000 > kinetic Gypsum 3 wt% rate_con = 4.7e-9 surface = 3000 > printout on X1t > Regards, Jubilee
14. Thanks Brian, This was helpful. If i want to build a model for sweater infiltrating a porous medium that is composed of Quartz, Gypsum and Bio-char in the first 10-20 cm , and then only Quartz in the next 20 - 40 cm. Is there a way to carry out this kind of model in GWB? I have reviewed the literature on modeling using X1t, but it seems this kind of scenario was not addressed. Thanks, Jubilee
15. Hi Brian, Thanks for the response. Like I told you sometime ago, I am running a laboratory soil column with gypsum amendment of mass percentages varying from 1-5%. I have set up my model to indicate the dissolution rate constants for Quartz and Gypsum ( the two major minerals making up the soil column). The length of the column is 60 cm and I intend to monitor the composition of the pore fluid at intervals namely 5, 10, 15, 20, 30, 40, 50, and 60. However, there seems to be a default setting in GWB that makes the initial reference x position 2.5 cm such that i cannot see what goes on at my preferred x positions. I have tried all methods but it seems i am not able to change this default setting. Find below the code of commands. time start = 0 day, end = 8.403 day delta_x = table {5 5 5 5 10 10 10 10} cm width = 8 cm discharge = 25 pore_volumes porosity = .38 scope = initial H2O = 1 free kg Ca++ = 1570 mg/kg Mg++ = 21.2 mg/kg Na+ = 4 mg/kg K+ = 2 mg/kg SO4-- = 2700 mg/kg Cl- = 100 mg/kg balance on Cl- Br- = .12 mg/kg pH = 7 SiO2(aq) = 1e-5 mg/l scope = inlet H2O = 1 free kg Ca++ = 164.11 mg/l Mg++ = 1639.24 mg/l Na+ = 13133.2 mg/l K+ = 503.26 mg/l SO4-- = 3475.48 mg/l Cl- = 20070.4 mg/l balance on Cl- Br- = 47.18 mg/l pH = 8.25 SiO2(aq) = 1e-5 mg/l kinetic Quartz 61 volume% rate_con = 4.2e-18 surface = 1000 kinetic Gypsum 1 volume% rate_con = 4.7e-9 surface = 1000 printout on go Am I missing out something? Secondly, do i have to input dispersion values into the model of there is a range of default dispersion values in GWB that can be applied in this case. Thanks, Jubilee
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