Stepped Energizing Ring for Wellhead Metal-to-Metal Sealing
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Solution Overview
Problem
Conventional metal-to-metal seals in wellhead assemblies are prone to leakage due to thermal growth and axial displacement, which reduces sealing forces and causes leaks, as the sealing and locking features are not separately configurable.
Innovation Solution
A wellhead seal assembly with a stepped energizing ring that includes wickers for locking and a sealing surface with indentations, allowing the locking and sealing features to be independently configured, minimizing axial movement and maintaining sealing performance despite thermal transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional metal-to-metal seal uses a single integrated seal ring with wedging action, then the seal can be set by axial displacement of the energizing ring, but thermal growth and axial displacement reduce sealing forces and cause leakage
Solution Approach 1:
The seal ring is divided into two distinct functional portions: a sealing portion with a sealing surface for forming the metal-to-metal seal, and a locking portion with locking features (such as teeth or lugs) for preventing axial movement. This segmentation allows each portion to be optimized independently for its specific function, resolving the contradiction between ease of operation and reliability by ensuring the sealing function maintains adequate sealing forces even when axial displacement occurs.
2Force
If the seal relies on radial loading between the seal and mating surfaces, then sealing forces are generated, but thermal transients cause axial movement that reduces radial loading and causes leakage
Solution Approach 1:
The locking features (such as teeth or lugs) are integrated into the seal ring structure itself, merging the locking function with the seal body. This integration ensures that axial position stability is maintained through mechanical interlocking, which in turn preserves the radial loading and sealing forces even during thermal transients, resolving the contradiction between force generation and positional stability.
3Device complexity
If the sealing and locking features are integrated in a single seal ring, then the structure is simplified, but the performance of each feature cannot be tuned separately
Solution Approach 1:
The seal ring is segmented into distinct sealing and locking portions, each with specialized features optimized for its function. The sealing portion includes a sealing surface with specific geometry for metal-to-metal contact, while the locking portion includes teeth or lugs with specific engagement characteristics. This segmentation provides adaptability and versatility by allowing independent optimization and tuning of each feature's performance while maintaining a relatively simple integrated structure.
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 effectively separates locking and sealing functions, enabling independent tuning of their performance and reducing leakage by maintaining radial loading and axial stability, even under thermal and pressure changes.
Implementation Method 1
An energizing ring is pushed into the slot to deform the inner and outer walls apart into sealing engagement with the inner and outer wellhead members.
Implementation Method 2
the nose of the energizing ring engages the lower portion of the slot to form a lock against the walls of the inner and outer wellhead members
Implementation Method 3
the upper end portion of the energizing ring engages the upper portion of the slot to form a seal against the walls of the inner and outer wellhead members
Implementation Method 4
The well fluid flowing upward through the tubing heats the string of tubing, and to a lesser degree the surrounding casing. The temperature increase may cause the tubing hanger and/or casing hanger to move axially a slight amount relative to the outer wellhead member or each other.
Data Source
AI summary
A wellhead seal assembly that forms a metal-to-metal seal between inner and outer wellhead members. A seal member has inner and outer walls separated by a slot, where the slot has an upper portion that is wider than a lower portion of the slot. An energizing ring having an upper end portion and a nose is moved into the slot, where the upper end portion has a greater cross-sectional thickness than the nose. As the energizing ring is moved into the slot, the nose of the energizing ring engages the lower portion of the slot to form a lock against the walls of the inner and outer wellhead members, and the upper end portion of the energizing ring engages the upper portion of the slot to form a seal against the walls of the inner and outer wellhead members.