Packing element back-up system incorporating iris mechanism

摘要

An annular sealing assembly and method are disclosed. The assembly includes a mandrel and an expandable element disposed around the mandrel which expands to seal against the inner diameter of a tubing or casing string. The expandable element seals the mandrel from the annulus between the mandrel and the tubing string. The assembly includes at least one back¬up element having a plurality of pivoting blades circumferentially secured in a ring around the mandrel. The back-up element is capable of radially expanding and contracting upon longitudinal movement along, and engagement with, a generally ring-shaped ramp. A guide ring guides the back-up element along the guide ramp. The method is directed to expanding the expandable element to seal the annulus and the back-up element so the blades come in contact with the inner diameter of the tubing string preventing the expandable element from extruding outward into the annulus beyond the back-up element.