def gassmann_dry2sat(Kdry, Kmin, Kfl, phi):
    """
    Gassman substitution from Dry Rock moduli to saturated moduli
    """

    a = 1.0 - Kdry/Kmin
    b = phi/Kfl + (1.0-phi)/Kmin - Kdry/(Kmin**2.0)

    Ksat = Kdry + (a**2.0)/b

    return Ksat