US Patent 8393388 Retractable petal collet backup for a subterranean seal

A high expansion plug has multiple sealing elements and an extrusion barrier system that uses overlapping petals in a stack of rings. When setting the plug, the petals are elastically moved toward a surrounding tubular wall in an elastic deformation between a housing that surrounds the mandrel and a tapered ring on the mandrel. That sandwich controls the amount of deformation and allows a potential energy force to be stored in the petals that allows them to return toward their initial position when the set of the plug is released and the seals are allowed to relax and extend axially as they shrink radially. The plug can then be removed without milling. Expansions in the order of 25% of the initial seal dimension are contemplated.