        , [g_fine.cells.num, 1]);
    
    % use the cubic assumption for the fracture permeability
    % with unit porosity
    kf = g_fine.faces.apertures.^2/12;
    for i = 2:-1:1 % note that hybrid cells with tag 3
        % i.e the Cartesian grid is omitted from the loop)
        [fcells,ncells] = getFractureCells(g_fine,i);
        rock.perm(fcells) = kf(g_fine.cells.tags(fcells));
        rock.perm(ncells) = max(kf(g_fine.cells.tags(fcells)));
        rock.poro(fcells) = 1;
        rock.poro(ncells) 