Stepped Composite Centralizer Blade Stress Distribution
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Solution Overview
Problem
Traditional composite centralizer blades and stop collars used in wellbore tubulars are prone to cracking and de-bonding in low temperature, high pressure environments due to stress concentration at the edges, which affects their performance and durability.
Innovation Solution
The use of centralizer blades and stop collars with a stepped profile design, featuring a first layer bonded directly to the tubular and a second layer extending outward with thin edges, reduces stress concentration by decreasing the attack angle and distributing stresses to the more robust body portion, thereby enhancing engagement and reducing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional composite centralizer blades with uniform thickness are used, then material usage is sufficient for structural integrity, but stress concentration occurs at the edges leading to cracking and de-bonding in low temperature high pressure environments
Solution Approach 1:
The centralizer blade employs varying thickness across its structure, with the root portion having greater thickness than the distal portion. This local quality variation concentrates material where stress is highest (at the bonding interface with the tubular) while reducing material at the distal end, thereby eliminating stress concentration at edges without compromising overall structural integrity.
Solution Approach 2:
The transition between different thickness portions of the centralizer blade is achieved through curved surfaces rather than sharp edges. This curvature eliminates stress concentration points by creating smooth stress flow paths, preventing the edge-related cracking and de-bonding that occurs in uniform thickness designs under low temperature high pressure conditions.
2Ease of operation
If composite material is bonded directly to the tubular for centralizer blades, then centralizer functionality is achieved, but the composite material cracks or de-bonds in extreme low temperature high pressure conditions
Solution Approach 1:
The centralizer blade is designed with a root portion that has greater thickness and is positioned at the bonding interface with the tubular. This localized concentration of material at the critical bonding region enhances the durability and resistance to de-bonding in extreme environments, while maintaining ease of installation through the overall centralizer design.
Solution Approach 2:
The patent utilizes composite material construction for the centralizer blade, optimizing the material distribution through varying thickness. The composite structure provides both the necessary bonding capability for installation and the enhanced durability required for extreme low temperature high pressure service conditions when properly designed with the varying thickness profile.
3Ease of manufacture
If uniform thickness composite blades are used, then manufacturing is simple, but the blades require more material and weight than necessary
Solution Approach 1:
The varying thickness design concentrates composite material at the root portion where it is most needed for structural integrity and bonding, while reducing material at the distal portion where less strength is required. This eliminates unnecessary weight while maintaining manufacturability through conventional composite forming processes.
Solution Approach 2:
The centralizer blade design changes the geometric parameter of thickness along its length, transitioning from a uniform thickness design to a varying thickness design. This parameter change optimizes the weight-to-strength ratio by placing material strategically at the root portion while reducing overall material consumption and weight.
Data Source
AI summary
In accordance with embodiments of the present disclosure, a centralizer for aligning a tubular in a wellbore includes a stepped centralizer feature. The stepped centralizer feature includes a composite material with a stepped profile. That is, the stepped centralizer feature includes a first layer of the composite material having a convex rounded side for interfacing with the tubular, and a second layer of the composite material extending from the first layer. The first layer is wider than the second layer. The stepped centralizer feature may be a centralizer blade bonded to an outer surface of the tubular, or a stop collar used to hold a centralizer spring in place on the tubular. The stepped centralizer feature helps to distribute stress through the centralizer feature so that the centralizer feature does not crack or de-bond from the tubular in low temperature, high pressure environments.