Wellhead Annular Seal Assembly With Rigid-Flexible Load Decoupling

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Solution Overview

Problem

Existing wellhead annular seal systems face challenges in maintaining integrity under pressure due to relative movement between the lockdown ring and wellhead housing, leading to seal degradation, especially when axial loads are applied.

Innovation Solution

The introduction of an actuator ring with both rigid and flexible components, where a rigid load path ensures the seal's axial position is locked, and a flexible load path allows variability in the lockdown ring's position relative to the wellhead housing, reducing play and maintaining seal integrity by decoupling axial loads through a compliant loading path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the seal assembly is rigidly fixed to prevent movement, then sealing integrity is improved, but the system cannot accommodate axial load variations and component play

Engineering Contradiction:

Improveseal integrityVSAvoidaccommodation of axial load variations

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The actuator ring is divided into two distinct segments: a rigid portion that maintains fixed positioning and a flexible portion that accommodates movement. This segmentation allows the system to simultaneously achieve seal integrity through the rigid portion while adapting to axial load variations through the flexible portion that allows the lockdown ring to move independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the actuator ring are given different mechanical properties - the rigid portion maintains structural stability for positioning, while the flexible portion provides compliance for absorbing play and load variations. This local differentiation of material properties resolves the contradiction between needing rigidity for sealing and flexibility for adaptation.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the lockdown ring is rigidly engaged with the wellhead housing, then positioning accuracy is improved, but seal degradation occurs due to relative movement under pressure

Engineering Contradiction:

Improveplacement accuracyVSAvoidseal durability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The flexible portion of the actuator ring serves as an intermediary element between the rigid lockdown ring and the wellhead housing. It allows the lockdown ring to be precisely positioned during installation while accommodating subsequent movements under pressure, thereby preventing seal degradation without compromising initial placement accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system transitions from a static rigid connection to a dynamic connection where the flexible portion allows controlled movement. This dynamic capability enables the lockdown ring to maintain accurate positioning initially while adapting to pressure-induced movements, preventing seal degradation.

Inventive Principle:

Principle #15Dynamics

3Strength

If axial loads are directly transferred to the seal assembly, then structural support is improved, but seal performance degrades under pressure

Engineering Contradiction:

Improvestructural supportVSAvoidseal performance under pressure

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The flexible portion of the actuator ring extracts or isolates the seal assembly from direct exposure to axial loads. By providing a compliant load path, it absorbs and mitigates the transmission of axial forces to the seal, allowing the seal to maintain performance under pressure while the supporting structure still provides necessary structural support.

Inventive Principle:

Principle #2Taking out (Extraction)

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

This solution effectively maintains the seal's integrity by reducing play between components and absorbing or limiting the transfer of axial loads, thereby enhancing the sealing system's performance under pressure.

Implementation Method 1

the flexible portion of the actuator ring adapted to axially compress to allow positional variation between the lockdown ring and the wellhead housing

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 2

the rigid portion of the actuator ring contacts a surface of the casing hanger

Methodology Applied

Scientific EffectMechanical contact: Mechanical Force

Data Source

PatentUS11492865B2Annular seal assembly with axial load decoupling feature

Publication Date: 2022.11.08 BAKER HUGHES OILFIELD OPERATIONS LLC

AI summary

An annular seal system for sealing between a casing hanger and a wellhead housing, the system including an actuator ring having a rigid portion and a flexible portion, and a lockdown ring positioned adjacent the actuator ring. The annular seal system further includes a seal assembly capable of moving from a de-energized position to an energized position, wherein when the seal assembly is in the de-energized position there is defined a space between the seal assembly and the rigid portion of the actuator ring, and when the seal assembly is in the energized position the space is closed, the rigid portion of the actuator ring contacts a surface of the casing hanger, and the flexible portion of the actuator ring pushes the lockdown ring into engagement with the wellhead, the flexible portion of the actuator ring adapted to axially compress to allow positional variation between the lockdown ring and the wellhead housing.