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EOS7C-running problem

Hi everyone,

I am doing a simulation with EOS7C in the heterogeneous coal seam aquifer with water and gas extraction from the well located in the middle of the model.

The model is running correctly without defining the GENER part into the model. However, by adding the GENER and extracting the gas and water from the coal seam, the model crashed after 0.5 days (the total time is close to 12 days).

I have attached my input file, INCON and MESH files.

I appreciate if anyone can provide some suggestions as to why this is occurring, and if anyone can help overcome this issue.

Best regards,

Sara

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  • Sara,

    What is the error message?

    Stefan

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  • Hi Stefan,

    I don't have any error as such. It has crashed after [KCYC,ITER] = [  75,  2]..

    I have attached my output file here.

    I also have attached the plotted pressure against time in the well location element.

    Thanks

    Sara

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  • Hi Sara,

    I'm sure there was an error message on your screen.

    But anyway, your pressure plot and the output file clearly show what is going on. You are pumping too much, pressure goes down, reaches the saturated vapor pressure at 20 degrees, all the liquid evaporates, the pressure keeps decreasing as you enforce production at a constant mass rate, and finally, pressure reaches absolute zero in element B1540.

    TOUGH2 gives you the  physically correct result for the specified boundary conditions - but it does not go into the physically impossible realm of negative pressures!

    Cheers,

    Stefan

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  • Thanks Stefan, the problem was solved by increasing the pressure in INCON file.

    Best Regards

    Sara

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  • Hi Sara,

    I'm glad it works now.

    I suggest you consider which of the parameters affecting the pressure drawdown is most uncertain. I presume you know the pressure (which is the parameter you changed) much better than, for example, absolute permeability or any of the (gas) relative permeability parameters. Slightly increasing permeability would also prevent the pressure from reaching absolute zero for the given production rate. Also note that changing the initial pressure changes the thermophysical properties of fluids.

    While I don't know what your application is about, make sure you honor what you know relatively well (presumably the pressure), and take the liberty to adjust parameters that you don't know that well.

    Regards,

    Stefan

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