Expandable Downhole Centralizer Resolving Plastic Shrinkage Stress
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Solution Overview
Problem
Existing downhole centralizers, such as those described in GB 2385342, can break under certain conditions due to stress caused by shrinkage of plastics materials on rigid reinforcing apparatus, leading to inadequate standoff and cement bond formation.
Innovation Solution
A downhole apparatus with a reinforcing apparatus configured to contract and expand, allowing the plastics material to set without inducing stresses, featuring a mesh or fibrous structure that can expand and contract, and using thermoplastic materials like Nylon for increased strength and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid reinforcing apparatus is used to reinforce the plastics material, then the structural strength is improved, but the plastics material shrinks and induces stresses leading to breakage
Solution Approach 1:
The reinforcing apparatus is designed with expandable and contractible members that can dynamically adjust their configuration. During setting, the apparatus contracts to accommodate plastics material shrinkage without inducing stresses. During operation, it expands to provide necessary structural reinforcement, thus resolving the contradiction between strength and breakage resistance.
Solution Approach 2:
The reinforcing apparatus changes its physical parameters (size, shape, volume) between contracted and expanded states. This parameter change allows the apparatus to adapt to the plastics material during setting while maintaining structural integrity during operation, preventing breakage while ensuring strength.
2Strength
If the reinforcing apparatus is rigid and allows for no give, then the structural support is improved, but stresses arise during plastics material setting
Solution Approach 1:
The expandable and contractible members are designed beforehand to accommodate shrinkage movements. This beforehand cushioning allows the reinforcing apparatus to absorb the shrinkage of plastics material without generating harmful stresses, while still providing structural support.
3Strength
If the reinforcing apparatus is made of sheet metal, then the reinforcement is improved, but the apparatus cannot accommodate plastics material shrinkage
Solution Approach 1:
The reinforcing apparatus transitions from a rigid sheet metal structure to a dynamic structure with expandable and contractible members. This allows the apparatus to adapt its shape and volume during plastics material setting while maintaining reinforcement capabilities during operation.
Solution Approach 2:
The reinforcing apparatus incorporates flexible elements that can deform and adapt to the plastics material shrinkage. These flexible members maintain reinforcement functionality while accommodating dimensional changes during setting.
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 solution minimizes stress in the downhole apparatus, providing reliable standoff and enhanced mechanical properties, including increased hoop strength and resistance to impacts, while maintaining performance at elevated temperatures.
Implementation Method 1
the plastics material normally shrinks as it sets
Implementation Method 2
the reinforcing apparatus is configured to at least one of contract and expand
Data Source
AI summary
The present invention relates to a method of forming downhole apparatus. The method comprises disposing a plastics material (26) on a reinforcing apparatus (24) to form a body (12) having a bore extending through the body. The reinforcing apparatus (24) provides reinforcement of the plastics material (26) and the thus formed body (12) is configured to provide, when in use, standoff between downhole components, with the reinforcing apparatus being configured to at least one of contract and expand.