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Helical No-Gap Anti-Extrusion Backup System

IP.com Disclosure Number: IPCOM000239600D
Publication Date: 2014-Nov-18
Document File: 6 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Abstract

A seal back-up system is usually adapted for use in preventing the extrusion of the packing element. Conventional back up system (Fig. 1) is made of swage cones, an assembly of cone rings and packer rings with rail system and cuts that are oriented to be opposite to each other, and seal rings that allow assembly of cone and packer ring to ramp up and expanded radially out to touch firmly against casing to prevent element from extruding as shown in Fig. 2. This design has achieved tremendous success over past decades for the reservoir pressure less than 10,000psi. The reasons for limiting this design to be applicable in the field with pressure above 10,000psiare stated as follows: 1. When the backup rings are set in position, the open cut are getting much wider comparing to the gap width before setting (Fig.3). The packing element will be squeezed into this open spaces causing non-uniform contact pressure in circumferential direction, and the sharp edges of the open rings will break the packing element into pieces under increased pressure. 2. The clearance between cone ring and packer ring at rail area forms a leaking path for packing element if pressure is elevated to high level. This invention discloses a new design of back up ring which will forms a no gap barrier in circumferential direction and better conformability to both casing ID and seal ring after right amount of setting force is applied. It eliminates the possibility of breaking packing element into pieces while it is energized. This proposed helical backup ring designs which replaces the assembly of cone ring and packer ring are made of one piece so it eliminates the unavoidable escape path created by clearance due to assembly requirement. This new backup system is tasked to boost the packer or bride plug pressure rating above 10,000 psi and especially it is designed for as-rolled casing or casing with grooves. The proposed back up system is shown in Fig 4. The backup ring system is made of swage cone, helical backup ring with bevel cut, and seal ring that allows backup ring to ramp up. This helical backup ring could be made of metallic material like ductile steel, aluminum, bronze copper alloy, etc., or thermal plastic material like PEEK. The backup ring is engineering designed so that the OD perimeter of backup ring is little more than the perimeter of the maximum casing ID, where the packer is going to set. In this way, the bevel cut in the helical backup ring will be fully closed in circumferential direction (Fig.5) when right amount of setting force is applied. The sides of backup rings touching packing element when packer is in setting position is continuous and smooth, therefore, it won’t cut into packing element. To enhance the conformability of the backup ring to the irregular casing ID (either as-rolled casing or casing with groove caused by work over operation), a design shown in Fig.6 is proposed to add collapsible protrusion teeth on the OD of the backup ring. This protruded teeth dimension could be between 0.030”and 0.075”, and can be manufactured by machining. The protruded teeth are designed to easily plastically deformed, therefore; conform to the irregular Casing ID for form a extrusion barrier for packing element. This backup ring could be made of metallic material like ductile steel, aluminum, bronze copper alloy, etc., or thermal plastic material like PEEK. Fig. 7 shows the backup system with collapsible teeth feature in setting position.

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Helical No-Gap Anti-Extrusion Backup System

A seal back-up system is usually adapted for use in preventing the extrusion of the packing element.  Conventional back up system (Fig.  1) is made of swage cones, an assembly of cone rings and packer rings with rail system and cuts that are oriented to be opposite to each other, and seal rings that allow assembly of cone and packer ring to ramp up and expanded radially out to touch firmly against casing to prevent element from extruding as shown in Fig.  2.  This design has achieved tremendous success over past decades for the reservoir pressure less than 10,000psi.  The reasons for limiting this design to be applicable in the field with pressure above 10,000psiare stated as follows:

1.       When the backup rings are set in position, the open cut are getting much wider comparing to the gap width before setting (Fig.3).  The packing element will be squeezed into this open spaces causing non-uniform contact pressure in circumferential direction, and the sharp edges of the open rings will break the packing element into pieces under increased pressure.

2.       The clearance between cone ring and packer ring at rail area forms a leaking path for packing element if pressure is elevated to high level. 

This invention discloses a new design of back up ring which will forms a no gap barrier in circumferential direction and better conformability to both casing ID and seal ring after right amount of setting force is applied.  It eliminates the possibility of breaking packing element into pieces while it is energized.  This proposed helical backup ring designs which replaces the assembly of cone ring and packer ring are made of one piece so it eliminates the unavoidable escape path created by clearance due to assembly requirement.  This new backup system is tasked to boost the packer...