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  • 1.  What is the surface density of a component

    Posted 05-20-2024 03:17 AM

    Dear All,

    Sorry of this looks like a naive question.

    in the quantities to be reported as spatial map for performance assessment, there is a reference to σi defined as "the surface density of a component". How exactly is this quantity defined, as this is not clear to me ?



  • 2.  RE: What is the surface density of a component

    Posted 05-21-2024 02:58 AM

    I'm not sure if this answers your question, but 'surface density' in reservoir engineering is used to describe the density at surface conditions. It is usually best to define the reference conditions as they vary between unit system, but I assume here they will be SI. You might find that it is an output from the simulator you are using (or an input as found in a black oil model).

    However, I note that there is another quantity in other areas of science called the same thing, but that is essentially a 2-dimensional density and I don't think is relevant here. 


    Adam Turner
    Reservoir Engineer
    RPS Energy

  • 3.  RE: What is the surface density of a component

    Posted 05-22-2024 02:59 AM

    Thanks Adam,

    I think you're right. A density is needed to make the quantity adimensional, and it looks like it's constant along the surface.

    If I understand correctly, what is computed are the phase densities, and they need to be converted to component densities (easy)



  • 4.  RE: What is the surface density of a component

    Posted 05-23-2024 01:48 AM


    The surface density is used to define the two reporting quantities, 'max_res_norm' and 'mb_error', which are meant to be the equivalent of the CNV and MB convergence measures used in certain commercial black-oil simulators. In a black-oil model, the chemical species are lumped together to form two pseudo-components at surface conditions, a heavy hydrocarbon component called "oil" and a light hydrocarbon component called "gas." At reservoir conditions, the two components can be partially or completely dissolved in each other depending on pressure and temperature, forming either one or two phases: a liquid oleic phase and a gaseous phase.  The surface density is then the density of the oil and gas pseudo-components at surface conditions.

    When applying a black-oil type simulator to a CO2-brine system, it is common to model CO2 as the "gas" component and brine as the "oil" component since this is the simplest way to model CO2 dissolving into brine. In this setting, the surface density would then refer to the density of CO2 and H2O at surface conditions, i.e., at 1 atm pressure and 20°C.

    I hope that this helps.

    Best regards,