Angled Segmented Backup Ring Axial Extrusion
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Solution Overview
Problem
Traditional downhole sealing element anti-extrusion backup designs, such as split rings, metal petal rings, and segmented rings, face limitations in maintaining sealing ability under high pressure and temperature due to extrusion gaps that compromise the containment of the sealing element.
Innovation Solution
An angled segmented backup ring design featuring radially inward slots and overlapping segments that expand axially, minimizing axial gaps and preventing extrusion, is used in conjunction with a radially expandable tubular seal element to enhance sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional segmented backup rings are used, then the sealing element is protected from radial extrusion, but axial gaps are created that compromise sealing ability under high pressure
Solution Approach 1:
The slots in the segmented backup ring are positioned asymmetrically at non-180-degree intervals (e.g., 120-degree intervals for three slots), creating overlapping segments when the ring expands radially. This asymmetric configuration eliminates continuous axial extrusion paths while maintaining radial expansion capability, preventing both radial and axial extrusion of the sealing element.
Solution Approach 2:
The backup ring is divided into multiple segments by radial slots, allowing each segment to expand independently when radial pressure is applied. This segmentation enables the ring to conform to the casing inner diameter while the overlapping arrangement of segments blocks axial extrusion paths, resolving the contradiction between radial expansion and axial gap prevention.
2Ease of operation
If split rings with opposed scarf cuts are used, then the rings can expand radially to contact the casing, but the width between ring ends creates significant extrusion volume that decreases rubber pressure
Solution Approach 1:
The solution transitions from considering only radial expansion to incorporating axial overlap in the segment arrangement. By positioning slots at asymmetric angles, the segments overlap in the axial dimension when radially expanded, creating a three-dimensional barrier that blocks extrusion paths without compromising radial expansion capability or sealing pressure.
3Reliability
If metal petal rings are used, then the petals flex outward to contact the casing wall and trap rubber, but gaps between petals during expansion become extrusion paths
Solution Approach 1:
The segmented backup ring combines the radial expansion capability of flexible rings with the extrusion-blocking effectiveness of overlapping segments. The asymmetric slot configuration creates a composite structure where the rigid segment boundaries and overlapping geometry work together to eliminate extrusion paths, achieving effective containment without requiring multiple stacked components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The angled segmented backup ring effectively reduces the need for secondary backup rings by eliminating axial gaps during expansion, thereby improving the resistance to element extrusion and maintaining sealing integrity under high pressure and temperature conditions.
Implementation Method 1
Once the element setting pressure is applied, the rings expand radially outward and contact the casing inner diameter
Implementation Method 2
The petals trap the element rubber from extruding outwards past the clearance between the packer outer diameter and the casing inner diameter, due to the outward pressure on the petals from the element rubber and the friction between the petals and the casing inner diameter
Data Source
AI summary
An angled segmented backup ring includes a plurality of slots extending radially inward from an outer surface and extending axially parallel to one another and non-parallel to a longitudinal axis and a plurality of the segments defined by the plurality of slots. The adjacent segments may overlap one another in the axial direction.