Declining steam cap pressure

Dear TOUGH community,

I am modeling a liquid-dominated geothermal reservoir underlying a  steam cap. In the natural state I was able to match the cap pressure providing mass by means of several sources dislocated along the permeable part of the modeling domain. However, once removed them, the cap pressure declines up to an undesired value despite the domain is closed to flows of both heat and mass.

How can I solve ? It is possible that the cap rock material, despite having a very low permeability, is unable to mantain the desired cap pressure ?

1 reply

    • Finsterle GeoConsulting
    • Stefan_Finsterle
    • 1 yr ago
    • Reported - view

    Hi Mirco,

    I obviously don't know where exactly you put your natural-state mass sources, but once you turn them off, it is only natural that the pressure increase around these sources dissipates, i.e., fluid is redistributed within the model domain, potentially leading to a pressure decline in the steam cap, even if the model domain is closed. You should also check whether you have substantial (!) flows into the low permeability caprock. 

    Regarding your conceptual model: What is your explanation that the mass sources acting during the natural-state period disappear during the exploitation period? It seems that you either did not run the natural-state simulation to steady state, or you have an outflow boundary (probably specified by a Dirichlet boundary condition), which - according to your description - was changed for the production run. Justify such changes and/or account for them when interpreting the simulation results.

    Good luck!


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