How do I conduct a batch modeling of NaCl-water with primary minerals
Hello everyone,
I am trying to conduct a batch modelling of NaCl-water with primary minerals in a rock sample over 10-year period to determine the brine composition and primary species in the rock. How can I use Toughreact or PhreeqC for the batch modelling and transfer the cations and anions concentration for reactive transport modelling in Toughreact? How will I determine the salinity and pH after the batch modeling? I will be glad to get an advice on this .
Thanks.
Nicholas
8 replies
-
Hi Efenwengbe,
I am by no means an expert in TR so take my word with lots of salt.
In the TOUGHREACT manual, you can change MOPR(1) in REACT depending on what kind of simulation you are running.
REACT
Reactive transport flags (MOPR - Methods Or Parameters Reactive Transport): Format 25I1
1234567890123456789012345
MOPR(1) = 0 Reactive transport (flow, transport, reaction).
= 1 Flow, no reactive transport, chemical input files read.
= 2 Flow, no reactive transport, no chemical input files read. Equivalent to running TOUGH2.
= 3 Flow and transport without chemical reactions.
= 4 Transport and chemical reactions using velocity field from first time step.
= 5 Transport (no chemical reactions) using velocity field from first time step.Define your primary aqueous species and minerals in chemical.inp. Run a simulation with MOPR(1) = 0 (I think, I am not 100% sure). Set your TIMAX to 10 years and run the simulation.
As for salinity and pH, there will be a file named cdhump.out and chemical.out that should answer your question. Check co2d_conc too. If not, try looking at every single output file and check them for the variables you are looking for.
Hope this helps.
Majid
-
Hi Efenwengbe,
Pitzer sample problems 1 & 2 in the distribution package (Problem1-BlackSea-evap-eos1 & Problem2-Williston12-evap-eos1) in the Sample_Problems_Pitzer folder are single grid block brine evaporation problems. These can be easily modified by replacing some of the salt minerals with primary minerals, modifying the water composition, and removing the GENER file so it does not remove water and evaporate the solution.
Eric
-
Thanks Eric Sonnenthal
Thanks Majid Trf
I think I didn't present the question clearly. I am trying to determine the total concentration of primary species in a reservoir (for initial water/brine). For instance, I have distilled water (with a known pH) needed to equilibrate with some primary minerals (say, albite, calcite, quartz, anorthite, etc.). I believe that it is based on these primary minerals-water equilibration that I can determine the primary species and their total concentration for reactive transport simulation (I am not 100% sure). My problem is how to determine the total concentration/molality (composition) of the primary species to fill the initial water section of Toughreact chemical.inp file. Can I use Toughreact to determine the total concentration (to represent when the primary minerals have equilibrated with water)? Or is there another way to determine total concentration to fill the initial water section of Toughreact chemical.inp file?
Please advise!
Thanks.
Efenwengbe Nicholas Aminaho -
Hi Efengwengbe,
Yes, you could put a small concentration (eg., 1e-10) for the initial and the guess concentration and then use icon=2, followed by the mineral (or gas) you want the solution to equilibrate with, to determine the concentration of a single species in equilibrium. However, with multiple minerals ,it will be very difficult to do it that way, since the solution could be impossible given the minerals you choose. If you want to start with a completely blank solution, then set all the concentrations to 1.e-10 (maybe less for Al+3), and then put some amount of each mineral in as an equilibrium mineral and the solution will equilibrate in one time step. Again this is unlikely to work for a large number of minerals. So I would first equilibrate the solution with quartz, and then use that concentration as the input to the next simulation where you equilibrate the solution with calcite, etc. Basically do it one by one. However, some of the minerals may never be possible in equilibrium (anorthite) because that is a magmatic or metamorphic mineral. The mineral in the reservoir may only have plagioclase that has a small amount of the anorthite endmember. If this becomes very difficult to converge then you can make each of the minerals a kinetic mineral with a small rate, and let the system approach equilibrium by running for a long enough time till the solution stops changing. However, just pure water is not so likely, because there would usually some NaCl. Of course you can do a combination, where you fix the silica concentration with quartz, as well as calcium with calcite, and then make the other more complex minerals kinetic phases. Every system is a little different, and if there is redox it can be more challenging, but there are a lot of ways to approach it.
Eric
-
Hi Efengwenbe,
The last part of your question was "is there another way?" The way I solve these problems is to set up single grid block or 1-D problem with the observed mineralogy, some potential secondary minerals, and observed water chemistry and using kinetics for the minerals run it for thousands of years or longer. The concept is that the fluid is probably only in near-equilibrium with some of the alteration minerals but not all the minerals. If the system can run for a long time and the solution stays roughly similar in composition as the reservoir composition then you know that you have chosen a good initial mineral assemblage and reactive surface areas. It often takes some tweaking to get right. But reaching some rough steady-state in fluid composition that is reasonably similar to the "native-state" reservoir composition is the best validation of the mineral assemblage and parameters you have chosen.
Eric