Retrievable Pre-Tension Packing Assembly for Wellbore Sealing
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Solution Overview
Problem
Existing packing assemblies in wells face issues with poor sealing performance and retrievability due to high stress and strain on seal elements when expanding to contact the inner surface of the tubing string, often resulting in neutral configurations that are not optimally loaded axially.
Innovation Solution
A retrievable pre-tension packing assembly that applies tension to the seal element before deployment, allowing it to expand radially upon axial compression, reducing stress and enhancing sealing performance while facilitating easy retrieval by maintaining low stress levels during expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the seal element is run downhole in a neutral configuration and then expanded to contact the inner surface of the tubing string, then the seal element can be easily deployed, but high stress and strain are applied to the seal element resulting in poor sealing performance and retrievability issues
Solution Approach 1:
The seal element is pre-tensioned before deployment by winding it around a mandrel with a smaller diameter than its neutral configuration. This preliminary action stores elastic energy in the seal element, so that when deployed in the tubing string, the pre-stored tension automatically expands the seal element to contact the inner surface, achieving both easy deployment and reliable sealing without applying excessive stress during the expansion process.
2Reliability
If the seal element is expanded to contact the inner surface of the tubing string, then sealing is achieved, but high compression forces are applied making retrieval difficult
Solution Approach 1:
The seal element is pre-tensioned before deployment by winding it around a mandrel with a smaller diameter than its neutral configuration. This preliminary action stores elastic energy in the seal element, so that when deployed in the tubing string, the pre-stored tension automatically expands the seal element to contact the inner surface, achieving both easy deployment and reliable sealing without applying excessive stress during the expansion process.
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 achieves improved sealing performance and ease of retrieval by applying pre-tension to the seal element, reducing stress during expansion and ensuring the seal element engages the inner surface effectively without excessive compression, thereby addressing the limitations of existing technologies.
Implementation Method 1
a seal element disposed on the base pipe and defining a first outer diameter while in the first configuration; applying a tensile axial force to the seal element to move the plug assembly to a second configuration, the seal element defining a second outer diameter while in the second configuration
Data Source
AI summary
A method includes providing a retrievable plug assembly at a surface of an oil or gas well, the plug assembly having a seal element that has an original outer diameter. The method also includes stretching the seal element so that the outer diameter is less than the original outer diameter and then placing the plug assembly between first and second zones formed within the tubing string. The method also includes removing any tensile axial load on the seal element so that it shrinks back towards its original outer diameter while positioned between the first and second zones. The method also includes compressing the seal element so that the seal element sealingly engages an inner surface of the tubing string to isolate the first zone from the second zone.