Expandable Centralizer Sliding Link Design
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Solution Overview
Problem
Conventional expandable bow spring centralizers suffer from plastic deformation at collar and bow spring connections during expansion, leading to instability and potential twisting of the bow springs out of alignment, and existing methods for deploying and restraining bow springs are costly, complex, or introduce unwanted materials into the borehole.
Innovation Solution
The design features a close-tolerance expandable centralizer with slidably coupled links and sacrificial connections that expand primarily through sliding, minimizing plastic deformation, and uses in-situ formed restraining bands to collapse and deploy the bow springs without introducing extra materials, allowing for a smaller diameter and stable collar/bow spring connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional expandable centralizers are expanded within the borehole, then the pipe string can be centered to provide uniform annulus, but the collar and bow spring connections undergo substantial plastic deformation leading to instability and potential twisting
Solution Approach 1:
The centralizer employs a dynamic expansion mechanism where the collar expands by sliding links relative to each other rather than through plastic deformation. The links are arranged to slide apart radially as the centralizer expands, maintaining structural integrity and preventing deformation at critical connection points while achieving the required expansion ratio
Solution Approach 2:
The collar is segmented into multiple links that can slide relative to one another during expansion. This segmentation allows the collar to increase in diameter through controlled movement of discrete components rather than uniform plastic deformation, preserving the strength and alignment of bow spring connections
2Ease of operation
If restraining bands are used to collapse bow springs for installation, then the centralizer can be installed through restrictions, but expensive or complex deployment systems are required that introduce unwanted materials into the borehole
Solution Approach 1:
The centralizer includes self-contained collapsing mechanisms that allow the bow springs to be restrained without external deployment equipment. The collar structure itself provides the means to collapse and expand the bow springs through simple operational actions, eliminating the need for complex hydraulic systems, acid treatments, or other external materials
Solution Approach 2:
The collar acts as an intermediary mechanism between the bow springs and the external environment. It provides built-in restraining features that can hold the bow springs in a collapsed state during installation, then release them to expand without requiring separate deployment tools or materials to be introduced into the borehole
3Force
If the collapsed diameter is reduced to minimize installation forces, then the centralizer can be installed more easily, but the collar thickness must be minimized which increases susceptibility to failure
Solution Approach 1:
The collar transitions from a thin-walled structure in the collapsed state to a thick-walled structure in the expanded state through sliding link movement. During installation, the collar maintains minimal diameter to reduce installation forces, but once expanded, the links lock into position providing substantial thickness and strength to resist failure at connection points
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
This solution enables the expandable centralizer to maintain stable and twist-resistant connections, ensuring reliable deployment and centering of the pipe string within the borehole without substantial plastic deformation, and reduces installation forces by minimizing the collapsed diameter of the centralizer.
Implementation Method 1
The flexible bow springs can be biased toward a deployed configuration to bow radially outwardly and away from the axis of the bore through the centralizer to engage the wall of the borehole and can center a pipe string received through the bores of the collars
Implementation Method 2
The bow springs can flex or collapse radially inwardly to accommodate restrictions and/or irregularities in the wall of the borehole
Data Source
AI summary
A close-tolerance expandable bow spring centralizer 8 having a first expandable collar 10A coupled to and spaced apart from a second expandable collar 10B through a plurality of bow springs 30 wherein expandable collars 10A, 10B comprise a plurality of slidably coupled links 16 that separate to expand the diameter of the collars 10A, 10B, e.g., upon expansion of an expandable pipe string 80 on which the centralizer 8 is received. Expandable bow spring centralizer 8 may grip the expandable pipe string 80 when in the collapsed configuration to eliminate the need for a stop collar. Additionally or alternatively, a fin 32 may be connected to each bow spring 30, and then connected to one or more adjacent fins 32 upon collapse of the bow springs 30 to form a restraining band 39 that may be ruptured, e.g., upon expansion of the expandable pipe string 80.