Polymeric Centralizing Assembly for Sucker Rod Wear
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Solution Overview
Problem
Sucker rod strings in oil wells experience frequent failures due to abrasion and rod pullouts, leading to costly repairs and reduced pumping efficiency, with existing end fittings and centralizing devices not adequately addressing these issues.
Innovation Solution
A centralizing assembly with an elongate, annular guide body made of a non-fibre reinforced copolymer matrix, featuring longitudinally directed fins that abut the tubular portion to provide sacrificial wear surfaces and fluid passages, is used to center downhole devices and reduce wear, while a coupling device with a centralizing assembly ensures reliable connection between downhole devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional steel connectors and end fittings are used to join sucker rods, then the rod string can be assembled, but frequent rod pullouts and connector failures occur due to abrasion and improper centering
Solution Approach 1:
A polymeric centralizing assembly is introduced as an intermediary component between the sucker rod and the tubing wall. This centralizing assembly includes a body with an inner surface that contacts the rod and an outer surface with fins that contact the tubing, providing sacrificial wear surfaces that maintain proper rod centering and prevent connector failures
Solution Approach 2:
The polymeric centralizing assembly is designed as a sacrificial component that wears instead of the expensive rod connectors. The polymeric material provides a cost-effective solution that can be replaced rather than replacing entire rod strings or connectors when wear occurs
2Strength
If fiber reinforced composite materials are used for the guide body, then strength and abrasion resistance are improved, but fluid flow is restricted and manufacturing complexity increases
Solution Approach 1:
The polymeric material composition is optimized for local requirements - the centralizing assembly body provides structural strength where needed, while the fin surfaces provide sacrificial wear characteristics. The material formulation balances mechanical properties with fluid flow characteristics without requiring fiber reinforcement
Solution Approach 2:
The polymeric material properties are specifically selected to provide appropriate friction characteristics and wear resistance while maintaining fluid flow capacity. The material parameters are tuned to achieve the desired balance between strength and fluid passage capability
3Ease of manufacture
If the centralizing assembly uses a solid monolithic structure, then manufacturing is simplified, but fluid flow passages must be separately formed adding complexity
Solution Approach 1:
The fluid flow passages are merged into the fin structure itself - the spaces between the fins naturally form the flow passages. This eliminates the need for separate passage formation operations while maintaining a simple monolithic body structure that is easy to manufacture
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 centralizing assembly effectively reduces wear and maintenance needs, enhances the durability of sucker rod strings, and improves the efficiency of fluid lifting by minimizing friction and abrasion, allowing for longer-lasting and more reliable downhole operations.
Implementation Method 1
the guide body comprising a non-fibre reinforced copolymer matrix and having at least two generally longitudinally directed fins on the guide body of the centralising assembly and defining passages therebetween for the passage of fluid, the fins abutting the interior surface of a tubular portion into which the downhole device is located in use and defining sacrificial wear surfaces against the tubular portion
Data Source
AI summary
A centralising assembly for a downhole device in the mining or oil well field, a method of manufacture therefor and to a coupling device including a centralising device.