Bellows Nose Ring Seal for Wellhead Thermal Expansion
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Solution Overview
Problem
Existing wellhead seal systems face leakage issues due to thermal growth and axial displacement, which reduce sealing forces and lead to leaks, particularly in surface wellheads where temperature differences cause movement between casing and tubing hangers and wellhead members.
Innovation Solution
A metal-to-metal seal assembly with a nose ring featuring bellows that increase lockdown capacity by collapsing and expanding to provide additional radial force and friction, enhancing the seal's locking mechanism without the need for additional trips or equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal-to-metal seal with energizing ring is used, then sealing capability is improved, but sealing forces are reduced due to thermal growth and axial displacement
Solution Approach 1:
The bellows structure transforms the rigid nose ring into a dynamic component that can expand and collapse axially. This dynamic capability allows the bellows to accommodate thermal expansion and axial displacement while maintaining constant radial sealing forces on the hanger, resolving the contradiction between sealing capability and force maintenance under thermal conditions.
Solution Approach 2:
The bellows changes its geometric parameters (axial length, radial expansion) in response to thermal growth. As temperature increases and the hanger expands axially, the bellows collapses axially and expands radially, maintaining the same radial sealing force. This parameter transformation resolves the force reduction problem caused by thermal displacement.
2Reliability
If lockdown C-rings or lockdown style hanger are used to prevent movement, then seal leakage is prevented, but device complexity and additional trips are required
Solution Approach 1:
The bellows structure merges the sealing function and lockdown function into a single integrated component. The same bellows that provides radial sealing force also provides axial lockdown by friction engagement with the hanger, eliminating the need for separate lockdown C-rings or lockdown style hangers and reducing overall device complexity.
Solution Approach 2:
The bellows serves multiple functions simultaneously: it provides radial sealing force on the hanger, accommodates thermal expansion, and provides axial lockdown through friction engagement. This multi-functionality eliminates the need for additional dedicated lockdown components and trips.
3Reliability
If additional lockdown capacity is provided through separate mechanisms, then seal performance is improved, but installation time and cost increase
Solution Approach 1:
The bellows merges the sealing and lockdown functions into a single component that is installed in one trip. The integrated design provides both radial sealing and axial lockdown capacity simultaneously, eliminating the need for separate lockdown component installation and reducing installation time and cost.
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 bellows on the nose ring enhance lockdown capacity, preventing leaks by sharing upward forces and accommodating thermal expansion, thus improving the seal's performance and reducing the need for re-tripping to install a lockdown hanger, while also saving time and money.
Implementation Method 1
Thermal growth between the casing or tubing and the wellhead may occur, particularly with wellheads located at the surface, rather than subsea. 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.
Implementation Method 2
The bellows may be formed in a helical shape and have an inner surface that faces an outer profile of the hanger, and an outer surface on the bellows that faces the bore of the housing. Each of the bellows may have legs that form a 'V' or 'U' shape with gaps formed between the outer surfaces of the bellows. Similarly, gaps are formed between the inner surfaces of the bellows. When the seal assembly is set, the bellows will collapse, reducing a width of the gaps as the bellows expand inward and outward into the outer profile of the hanger and the bore of the housing.
Data Source
AI summary
A seal assembly between a wellhead housing having a bore and a casing hanger, has an inner seal leg for sealing against hanger and an outer seal leg for sealing against housing. An extension extends downward from outer seal leg and has a downward facing shoulder that rests on an upward facing shoulder formed on a nose ring. Connection connects seal ring to the nose ring with a lower portion of the nose ring resting on the upward facing shoulder of the casing hanger. Bellows are formed on the nose ring to increase lockdown capacity. Bellows have an inner surface that faces an outer profile of the hanger, and an outer surface on the bellow that faces the bore of the housing. When the bellows are axially collapsed, they expand radially outward and contract radially inward into the bore of the housing and the outer profile of the hanger.