A method of injecting fluid into a formation, comprises exerting a mechanical force on a wall of a bore extending through a formation to modify the permeability of the formation; and injecting fluid into the modified formation. The mechanical force may be exerted through inflation of at least one pressure deformable member mounted on a base member. The base member may be a base pipe. The pressure deformable member may be a hollow or tubular member mounted externally of the base pipe.