ppor

    • Group 1 - IPOROS
    • Group 2 - JA, JB, JC, POR1, POR2, POR3, POR4
    Input Variable Format Description
    IPOROS integer
    Model type:
    IPOROS = 1, aquifer compressibility model
    IPOROS = -1, specific storage model (use
    only for isothermal conditions)
    IPOROS = -2, Gangi model (not available for
    air-water-heat conditions)
    Model (1): IPOROS = 1,  
    Aquifer compressibility \(\phi = \phi_0 + \alpha_a(P-P_0)\) where
    \(\alpha_a\) = aquifer compressibility (MPa-1),
    \(\phi_0\) = initial porosity,
    \(P_0\) = initial pressure (MPa)
    POR1 real Aquifer compressibility \(\alpha (MPa^{-1})\)
    Model (-1): IPOROS = -1,  
    Specific storage \(S_s = \rho(\alpha_a + \phi \beta)\) where
    \(\rho\) = liquid density (kg/m3),
    \(g\) = gravity,
    \(\alpha_a\) = aquifer compressibility (MPa-1),
    \(\phi\) = porosity,
    \(\beta\) = liquid compressibility (MPa-1)
    POR1 real Specific storage \(S_S (m^{-1})\)
    Model (-2): IPOROS = -2,  
    Gangi model with calculation of initial permeability and porosity.
    \(\phi = \phi_0 \left[ 1 - \left(\frac{P_c}{P_x}\right)^m \right]\) and \(P_c = \sigma - P - \alpha E(T-T_0)\)
    where
    \(\phi_0\) = initial porosity,
    \(m\) = Gangi exponent,
    \(P_x\) = fitted parameter (MPa)

    Note: for the Gangi model the permeability is varied by \(k = k_0 \left(\frac{\phi}{\phi_0}\right)^3\)
    POR1 real Exponent \(m\) in Gangi bed of nails model.
    POR2 real \(P_x\) parameter (MPa) in Gangi equation.
    POR3 real \(\sigma\) in-situ stress (MPa).
    POR4 real
    \((\sigma E)\) The product of the coefficient of thermal expansion for the rock and the Young’s modulus (MPa/C).

    Note: For isothermal simulations the thermal term does not apply.

    In the following example of ppor, aquifer compressibility is modeled. All nodes in the model are assigned a compressibility of 1.e-2 MPa-1.

    ppor      
    1      
    1 0 0 1.e-2
           

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