Neda

Hi Brian, Thank you again for all the help and support. Best regards,

Dear Brian, I am using REACT(version 11.0.04). Recently when I was using the gas transfer option, I received the error "React stopped working". This error only shows up if the gas transfer option is used, and if use sling, simple, etc to enter the gas as reactant, it works perfectly. I appreciate your reply. Best Regards, Neda P.S. Unfortunately I am not able to attach the thermodynamic database that I used, the file seems to be big and the rar file is not allowed to be attached. Pickup fluid-case 14-kinetic-couple-H2-3.5-10-1e-9.rea

Thanks so much Brian. Best,Neda

Hi Brian, Could you please tell if GWB has the capability to simulate geochemical modelling at a fixed pressure. In the output files pressure is always set to 1.013 bars, while temperature can be set to any desired value. If changing the system pressure is not enabled in GWB, is there any trick to apply a fixed pressure in the batch models. Thanks for the reply. Best, Neda

Dear Brian, Thanks so much for the reply. My sincere apologies for not having attached the thermo dataset. Unfortunately my license is expired and I can’t proceed with further modelling. Thank you so much again for all the support. Best, Neda

Hi Brian, Thanks for your reply. Yes I am still working on H2 (g) storage problem. As you might remember we already did some studies (at equilibrium) using GEMS (http://gems.web.psi.ch). I set up the same model in GWB and despite using different thermodynamic database and using different models for gas, at equilibrium I got consistent results with my previous model in GEMS which made me sure that the setup of the model was done correctly. In our previous work we didn’t consider operational condition range in real storage operation and now with GWB and by having kinetic modelling option this study is possible. In the equilibrium model, adding 0.5 mole has really negligible effect on the system. In fact I can define a window for operational condition [0.5 to 10 mole (maximum pressure that can be reached for hydrogen)]. In case of adding 10 mole H2(g), changes in the system are minor but noticeable. In all cases HCO3- and SO4 in the water were reduced to CH4 and HS-. I integrated kinetic rates of minerals to my model as my second study. For the time span of the study that I considered one year, kinetics highly restricts any precipitation or dissolution, but pH is strongly under influence of hydrogen (in comparison with the equilibrium model, kinetic model results to higher H2(aq) concentration, H2(g) fugacity, and pH while changes of mineral abundance is much more less. So in this case knowing the operational window is even more critical. In my third study, I decided to add hydrogen kinetically to limit its dissolution in water and prevent the high increase of pH. In this case I can only work with fugacity as GWB only take fugacity as the input. So I need to properly understand the relation between added H2 and fugacity. If I use the H2 (g) fugacity value that I get after running kinetic model (1e-5 to 1e-3) then adding hydrogen could have almost zero impact on the system while using 3.5 bar fugacity can be considered tricky and at some level problematic for the real operations. I attached some of the plots of the equilibrium and kinetic model (case study of 0.5 mole added H2(g)) for your consideration. Thank you. Best, Neda results_kinetic_ equilibrium_ 0.5 mole H2.compressed.pdf

Dear Brian, Thanks for your reply, I very much appreciate it. The fact is that I am doing geochemical simulations for a gas storage study and my objective is to somehow represent the operational condition in my simulations. Having total size of the reservoir, gas injection rate and duration of injection, total mass of the stored gas which is inside the reservoir is known. The intention of my work is to see how this gas would disturb brine-mineral equilibrium in different conditions. As I mentioned before by downscaling the reservoir scale to the study scale, 0.5 mole gas should provide almost 3.5 bar partial pressure or fugacity for my system. I understand that all introduced gas through simple option doesn’t stay in the gas phase, but to have fugacity of 3.5 bar almost 135 mole of gas is needed (I found this value after plotting fugacity and reactant mass). The results then vary extremely in these cases and I am very confused which one is actually consistent and reliable for my case. I also played with the delxi value but it doesn’t have much influence on the final results. I started to make an equilibrium model in which both minerals and gas are modelled at equilibrium, then I made kinetic model for minerals and in the end I introduced gas kinetically. In all simulations, operational range (either gas mass or fugacity) is crucial for my results and conclusions. I would appreciate your advice and recommendations for this case study to find the most consistent way to represent the stated operational condition. Thanks so much in advance for your reply. Best regards, Neda

Hello, I am struggling with the meaning of fugacity and the way it is defined in GWB and I appreciate if you could help me to clarify my confusion. I am simulating gas injection into a closed system (minerals and brine) that is initially at equilibrium. I found I can add the gas as a reactant substance to my system either using simple or sliding (fugacity) option. The partial pressure of the gas is needed to reach to a certain value. By doing simple calculations for my system, to have a partial pressure of 3.5 bar, I need 0.5 mole of the gas. Fugacity coefficient in my case is 1.02, so fugacity is almost equal to the partial pressure. I created two models using different reaction paths for an identical system. In the first model I added 0.5 of gas using simple option and in the second model I used sliding and set the fugacity to 3.5, the value that should be reached by adding 0.5 mole gas. Results I got from these simulations are hugely different. When I plotted the result from the first simulation I found 0.5 mole injected gas creates fugacity of order of 1e-6 in the gas phase while I was expecting a value of 3.5. I really need to understand the meaning of fugacity in GWB to be able to have a realistic model to represent operational condition for my system. It seems setting small value for fugacity through sliding modelling acts as if I added huge amount of gas (in terms of mole) and I don't understand the reason. I would greatly appreciate your help. Thanks. Best, Neda

Hi Brian, Thank you for clarifying fugacity unit. Since there is no unit written in front of this parameter, it a bit confusing to understand the exact meaning of it. Best regards, Neda

Hi again, In regards to my previous question, I'd like to make sure the entered value for kinetic gas is a fugacity coefficient. Is it correct or it is an effective pressure of gas so it needs to have a unit such as atm or bar. Thanks. Best, Neda

Hi, I am trying to set up a kinetic geochemical model that simulates injection of gas (H2) into a system composed of brine and minerals. I'd like to model the injected gas kinetically through Reactants-->Kinetic--> Gas transfer option. After reading the Gas transfer kinetics description in the Reaction Modeling Guide tutorial of GWB and doing quite a bit of research, I could not find any information about rate constant or specific contact area of the gases. I am wondering if anyone has an idea of the order of magnitude reaction rates for gases as well as specific contact area. I would greatly appreciate any comments. Thank you. Best regards, Neda

After seeing the example in that section I realized when and how TEdit recalculates the log K for a new minerals. Thanks. Cheers, Neda

Hi Brian, Thanks for the explanations, really appreciate it. I don'e have any information about the oxidation state of the real system. I had to add O2(aq) since React needed it for smectite to get involved in the reactions so I just added small concentration of it. In fact I don't have enough knowledge of making a proper assumption and I am not willing to disturb the Basis which is made based on the water sample analysis I have. I added some CO2 to my system to account for degassing that most probably occurred during water sampling and to get a pH of 6.8 in the end which I am expecting for the studied reservoir and now reaction path can be completed. I am going to read the materials you mentioned to get better insight on what React is doing. Thanks again. Best, Neda

Hi, I am wondering if there is any option to fix the quantity of a mineral in React. I am trying to set up an equilibrium model in React to calculate initial chemical composition status of a system composed of brine and host rock minerals. I introduced minerals quantities in the Reactant pane, and I'd like to have a fixed quantity of Quartz in the end (equal to the initial value that is entered in the reactant tab for Quartz). I tried to use "fix" keyword in the command tab but it seems it doesn't work for minerals. Could anyone please advise me if there is another keyword that can be used in the command section to do this? Thanks in advance. Best, Neda

Thanks Brian. I calculated and added the log K values for the principle temperatures for Ankerite. Values seems fine to me. I still don't know how TEdit automatically recalculates the log K since I don't see any option for it but I assume this is done internally in the program. Thanks so much again for your help. Best, Neda

Hi Brian, Thanks for your reply. As you said I found a balanced reaction for Ankerite and I included it into the database using basis species. Please find the attached file which includes Ankerite for more details. The problem is that the program doesn't recalculate the log K automatically according to my reaction. I have noticed it only re-balance the equation and it gives warning if Mole Weight is entered incorrectly. I am not sure if I missing any step and would appreciate if you could take a look at the attached file. Thanks again. Regards, Neda thermo-Ankerite.tdat

Hi, I'd like to integrate the a new mineral (Ankerite) into the thermodynamic database. My question is how and from which formula, equilibrium constants corresponding to the reaction could be generated at principle temperatures? I have seen in thermoddem database (http://thermoddem.brgm.fr/data/mineraux.php), these log K values are provided for many minerals but not for Ankerite. I used Van t'Hoff equation to check if I can generate the Log K values, but it seems there is another equation for equilibrium constants. Could anyone please advise on how a new mineral can be integrated into the database only by knowing its thermodynamic properties such as Molar volume, Standard Gibbs energy and Standard enthalpy? Thank you. Neda

Hello, I have been trying to set up an equilibrium model in React to calculate initial chemical composition status of a system composing of brine and host rock minerals. I added water components in the Basis pane and minerals quantities in the Reactant pane. During the course of modelling I suppressed couple of minerals which I think should not present at initial equilibrium state. I'd like to use "Pick up" option later and add some gases to study evolution of the system in presence of them. When I suppressed the minerals I faced the convergence problem and I get the following error. -- Can't converge, abandoning path. -- Xi step is too small If I don't use the suppress option there will be no problem and I can use " Pickup->system->entire". Could you please advise on how this suppress option may be causing this problem and how I can fix it without neglecting this option? I have attached the the React file for more details. Thank you. Minerals-initial status-supress minerals.rea Regards, Neda