Expandable Bow Spring Centralizer with Sliding Collar Links
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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 failure, and existing methods for restraining and deploying bow springs are costly and complex, often requiring additional materials or systems that increase the diameter of the collapsed centralizer, making it difficult to install in narrow boreholes.
Innovation Solution
The design features a close-tolerance expandable centralizer with slidably coupled links that expand without substantial plastic deformation, using sacrificial link connections and a restraining band formed by bow spring fins to minimize the collapsed diameter and facilitate deployment without introducing unwanted materials into the borehole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional expandable bow spring centralizers are used, then the centralizer can provide stand-off from the borehole wall, but plastic deformation occurs at collar and bow spring connections during expansion leading to instability and potential failure
Solution Approach 1:
The collar is divided into multiple slidable links that can move relative to each other during expansion. This segmentation allows the collar to expand through controlled link movement rather than plastic deformation of the entire collar structure, maintaining connection stability between the bow springs and collar segments.
Solution Approach 2:
The collar transitions from a static structure to a dynamic one where links can slide relative to each other. This dynamic capability allows the collar to adapt its shape during expansion while maintaining structural integrity and connection stability, preventing plastic deformation at critical connection points.
2Reliability
If external restraining bands are used to restrain bow springs in collapsed configuration, then the bow springs can be deployed reliably, but the diameter of the collapsed centralizer increases making it difficult to install in narrow boreholes
Solution Approach 1:
The restraining band is integrated with the bow spring structure itself rather than being a separate external component. The fins are attached to the bow springs and form the restraining band when the springs are collapsed, eliminating the need for additional external restraining structures and reducing the overall collapsed diameter.
Solution Approach 2:
The bow spring fins serve multiple functions: they provide structural support to the bow springs, form the restraining band to hold the springs in collapsed configuration during installation, and can be used to secure the centralizer to the pipe string. This multi-functionality eliminates the need for separate restraining bands.
3Reliability
If sacrificial link connections are used to restrain links in collapsed configuration, then the links can be deployed reliably, but the collar structure becomes more complex
Solution Approach 1:
The link connections are designed as sacrificial elements that are intended to fail in a controlled manner during expansion. These connections are simpler in design but are replaced or sacrificed during the expansion process, allowing reliable deployment without requiring complex permanent restraining mechanisms.
4Volume of moving object
If conventional end collars are expanded, then the pipe string capacity is increased, but substantial plastic deformation of the collar material occurs which may result in instability
Solution Approach 1:
The collar is segmented into multiple links that expand by sliding relative to each other rather than through plastic deformation. This segmentation allows the collar to increase in diameter to provide greater pipe string capacity while maintaining structural stability through controlled mechanical movement of the link segments.
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 maintains stable and twist-resistant collar and bow spring connections, allowing for reliable deployment and centering of the pipe string within the borehole while reducing installation forces and costs by minimizing the collapsed diameter and eliminating the need for external restraining bands.
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
Implementation Method 2
The how springs may fully collapse to lie generally flat along a portion of the pipe string to facilitate installation of the centralizer into 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.