Segmented Composite Backup Ring for Subterranean Plug
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Solution Overview
Problem
Existing composite plugs with metallic backup rings face challenges in withstanding high pressure differentials and are difficult to drill out due to the rigidity of metallic materials, which hinders their removal and repositioning in constricted tubular strings.
Innovation Solution
A composite plug design featuring backup rings made of non-metallic materials with connected segments that break into gaps when set, allowing for rotational locking and easy drilling by overlapping segment gaps between adjacent rings, ensuring no extrusion gaps and facilitating rapid milling out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic backup rings are used to contain the sealing element, then the seal can withstand high pressure differentials, but the rings become difficult to drill out and remove
Solution Approach 1:
The backup rings are divided into multiple segments that can break apart during drilling operations. Each segment is separated by gaps that allow drill bits to penetrate easily, while the segments themselves maintain structural integrity to contain the sealing element under pressure differentials.
Solution Approach 2:
The backup rings are constructed from composite materials that combine the strength needed to resist pressure differentials with properties that facilitate drilling removal. The composite structure allows the rings to maintain their containing function during operation while enabling easy extraction after use.
2Adaptability or versatility
If the plug needs to pass through constricted tubular strings, then the sealing element must radially extend, but this requires backup rings that can tolerate high degree of expansion
Solution Approach 1:
The backup rings are designed with dynamic characteristics that allow them to expand and contract as needed. The segmented structure with gaps between segments enables the rings to flex and accommodate radial extension of the sealing element when passing through constrictions, while still maintaining their containing function when expanded.
3Strength
If stacked thin metal rings are used as backup rings, then the sealing element is contained, but the rings are difficult to mill out
Solution Approach 1:
The backup rings are segmented with gaps between segments, which dramatically reduces the material that needs to be milled or drilled. The gaps allow cutting tools to pass through easily, transforming a continuous milling operation into a much faster process where only small segment portions need to be removed.
Solution Approach 2:
The backup rings have different properties in different locations - the segments maintain full strength and continuity for extrusion barrier function, while the gaps between segments provide easy access for drilling and milling tools, optimizing both containing capability and removal efficiency.
Data Source
AI summary
A composite plug that can be used in fracturing has backup rings for the seal that are preferably made of a composite material. The backup rings are essentially connected segments that allow the connections to break when the plug is set and the cones are brought closer together. When the rings break to form gaps between segments in a specific ring, the adjacent ring has offset gaps so that as a whole there are no extrusion gaps that would allow the seal element to pass. The rings can be rotationally locked to each other initially at the adjacent segments that are formed when the plug is set to maintain their relative positions so that gaps between segments adjacent the seal are overlapped with segments from the adjacent ring. The segmenting backup rings can be used on one or on both sides of a sealing element.