I have been a =n user of the open source version of Tochnog for since 2004. I have been one of the maintainers and have contributed to the capabilities of the progrm. I have started using the Professional version of Tochnog and was converting the open source version of some transient groundflow problem that I have been modeling but realized that I cannot get the groundflow velocities to print. I have written to Dennis Roddemann about this current issue but he must be very busy because he has not responded yet.

I have been trying to model a transient salt water disposal problem. This involves high pressure salt water injection into a deep well reservoir. The salt water is produced when Oil is produced and environmental regulations require that the salt water must be recovered and reinjected.

I was able to model the problem using the open source using

groundflow_pressure
groundflow_velocity
materi_velocity

in the header, and specifying

group_type 0 -groundflow -materi
groundflow_density 0.0378 (lb/in^3)
group_groundflow_capacity 0 7.0427e-07 (density x gravity x porosity x Compressibility [1/in])
group_groundflow_materidivergence 0 -yes
group_groundflow_permeability 0 3.76639E-05 3.76639E-05 3.76639E-05 (in/s)
group_groundflow_porosity 0 0.15
group_materi_density 0 0.0378 (lb/in^3)
group_materi_viscosity 0 3.6086e-05

the GiD post processing files contained both the pressure and the velocity distribution for the time intervals specified.
I wanted to calculate the flow into the reservoir by using the groundflow velocities and was able to get flowrates in line with actual measurements. However, when I converted the problem to the professional version using

groundflow_pressure
groundflow_pressure_gradient
groundflow_velocity
materi_velocity

and

group_type 0 -groundflow -materi
groundflow_density 0.0378 (lb/in^3)
group_groundflow_capacity 0 2.9187E-05 (density x gravity x porosity x Compressibility [1/in])
group_groundflow_permeability 0 6.52149E-05 6.52149E-05 6.52149E-05 (in/s)
group_materi_density_groundflow 0 0.0378 0.0378
group_materi_viscosity 0 3.6086e-05
group_porosity 0 0.15
inertia_apply -yes
groundflow_consolidation_apply -yes

However, I cannot get the grounflow or materi velocities to print, that is. The GiD *.res file does not holds anything for groundflow velocities. I even tried adding groundflow_pressure_gradient to the file header but still Tochnog Professional did not printed or calculated the groundflow velocities.

Any ideas as to what I may be doing wrong?

I am including the two input files for Tochnog Professional (test2TP.dat)

Your help is always appreciated.

All the best, Fernando Lorenzo

Pressure.png

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3 Comments
  1. Maciej Ochmański
    Maciej Ochmański 9 months ago

    Hi Fernando,

    I don’t see your input file. Could you please upload it again? (or send it straight to my e-mail ochmaskm@natur.cuni.cz).

    From your description, it seems that your setup is correct. You may try to use command “control_groundflow_consolidation_apply -yes”, however, it should have the same effect as “groundflow_consolidation_apply” thus I don’t expect that it will solve your issue.

    Anyway, if you send me your input file I will run it and debug for you.

    Maciej

  2. Maciej Ochmański
    Maciej Ochmański 9 months ago

    Hi Fernando,

    Going through your input file, I’ve realized that sign for pressure should be negative (it was somewhere in the manual, but now I’m not able to find it). With the positive one, you have suction. Required tochnog command “post_calcul -groundflow_pressure -total_pressure” for groundflow is used to calculated pore pressure, thus when it’s equal to 0 it means that element is not filled with water. For this reason, you will not have any flow. In the manual, it’s in section 6.634 “To determine if an element is filled with water, tochnog does not the following: If post_calcul -groundflow_pressure -total_pressure is put in the input file then total pressures (pore pressures) are calculated”.

    This is also consistent with the simulation of dam filtration which you’ve indicated (example ground5.inp). If you turn off van Genuchten law for non-saturated flow (‘groundflow_saturation’ and ‘group_groundflow_nonsaturated_vangenuchten’) and plot pore pressures (‘groundflow pressure total pressure to pres’), you will notice that in the zone were pressure is equal to 0 there is no flow (values are equal to absolut 0 and not to a very small value like 1e-10) as voids are indicated as empty.

    Hope you find this informative.

    Maciej

  3. Fernando Lorenzo Author
    Fernando Lorenzo 9 months ago

    Maciej,

    One more time, thank you very much for pointing out the required pressure sign. I tested my sample input file as well as others and everything works as expected.

    Thanks again!

    Fernando

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