TR-V3-OMP: Composition of gas zone / VOLG
Hello everybody,
I am using the new Toughreact Version 3.0 OMP with ECO2N EOS. I took the Sample problem no. 5 (1D radial model for CO2 Sequestration) and tried to add some SO2 as tracer gas in the injecting CO2. I intended to simulate 99% CO2 and 1% SO2. As the initial pressure of the reservoir is 200 bar, the SO2 partial pressure should be something like 2 bar.
As far as I understood, the composition of the (injection) gas zone is specified in record Igas.6 of chemical.inp file via the parameter VOLG. According to p. 54 of the V3 manual, the VOLG parameter is the partial pressure of the gaseous species in bars. Thus I first tried this inputfile version:
But this yielded unrealistic high dissolved SO2(aq) in the mass balance file and the partial pressure output looked like this:
I tried to change the output specification of the gaseous species via IGASFLAG at record_7 of solute.inp, but this did not influence the crude calculation (as expected), but simply resulted in a printout of molfractions of 1 and 2 for CO2 and SO2, respectively (i.e. with the sum = 3, which of course should not exceed 1.0). Hence I tried to use VOLG rather as a molfraction of gaseous compounds instead of partial pressure and applied the following inputfile (the VOLG value for CO2 as 0.0 or 0.99 did not change anything):
and it yielded fine and reasonable results:
Hence my question is: Am I doing something totally wrong or is the description of VOLG parameter in the manual on p. 54 simply incorrect, maybe due to the earlier description from V2?
Thanks in advance for any help!
3 replies
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Hi Lennard,
Yes, you are right that it should say "volume fraction". The manual and sample problem headers need to be updated. I don't think the description for VOLG was correct in the V2 manual, either. I will update the manual and the sample problem headers for the next minor bug-fix release that is coming out fairly soon. Thanks for letting us know.
Eric
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Hi Lennard,
After talking with Nic Spycher, and looking at your problem again, I need to modify my previous answer. The initial gas concentration is still partial pressure for all modules (as in V2), but the injected trace gas is mole fraction.The issue with gas injection is that there is no pressure associated with an injected gas, since it is an external flux of a gas composition different from the block it is injected into. We still need to update the manual for that distinction.
However, for ECO2n you cannot inject CO2 as a trace gas, as in your sample problem, because it is the main carrier gas in the flow simulation, and is not a trace gas. Now the code accepted your input, but just skipped it because it skips transport of CO2 and H2O for ECO2n problems. So you just need to define SO2 as a trace gas in chemical.inp but set CO2 = 0.99 * (total pressure) in INCON. However, then 0.01* total pressure will be H2O. If you want SO2 transported in pure CO2 then CO2 will be 1.0*total pressure in INCON and SO2 is just assumed to be a trace gas in the transport.
I hope that clarifies things.
Eric
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Hello Eric,
thank you for your quick response. Yes, it did clarify my problem in total.
I already assumed that the entry for CO2 in the injection block has no effect as CO2 is the main gas phase component / carrier gas. For water it is explicitly mentioned in the manual not to specify the partial pressure or something similar, for CO2 this hint is missing yet (although it is quite obvious).
In fact, I wanted to simulated a CO2 plume spreading in a reservoir with initially Sg=0, i.e. with the CO2 partial pressure equal 0 in the INCON block. I will define my incoming gas phase by setting the rate in the GENER block and specifying the SO2 0.01 fraction for injection gases. I am confidently expecting, this will work pretty well.
Lennard