def saturated_density(rhog, rhofl, phi):
    """Saturated bulk density

    Args:
        rhog (array-like): dry frame grain density
        rhofl (array-like): fluid density
        phi (array-like): porosity (frac)

    Returns:
        (array-like): saturated rock bulk density (rhob)
    """
    return rhog * (1 - phi) + rhofl * phi