  The fixed-stress splitting scheme is a popular method for iteratively solving
the Biot equations. The method successively solves the flow and mechanic
subproblems while adding a stabilizing term to the flow equation, which
includes a parameter that can be chosen freely. However, the convergence
properties of the scheme depend significantly on this parameter and choosing it
carelessly might lead to a very slow, or even diverging, method. In this paper,
we present a way to exploit the matrix structure arizing from discretizing the
equations in the regime of impermeable porous media in order to obtain a priori
knowledge of the optimal choice of this tuning/stabilization parameter.
