Wellhead Isolation Tool Mandrel Sealing and Locking
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Solution Overview
Problem
Wellhead isolation tools face challenges during oilfield operations due to extreme pressures and flow rates, leading to packoff assembly 'lift-off' and leakage, and require support against external forces to prevent damage.
Innovation Solution
A wellhead isolation assembly comprising a hydraulic cylinder, valve stack, lock assembly, anchor assembly, and adapter, which secures a mandrel within the wellhead, using self-energizing annular seals and threaded connections to maintain sealing engagement and prevent force transfer, thereby reducing leakage and protecting the packoff assembly from external forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the packoff assembly is used to isolate the wellhead from fluid flow, then sealing effectiveness is improved, but the packoff assembly is susceptible to lift-off and leakage under high pressure
Solution Approach 1:
The patent applies counterbalancing forces through the lock assembly and anchor assembly to counteract the high fluid pressures that cause packoff assembly lift-off. The lock assembly secures the mandrel in position while the anchor assembly provides additional anchoring, creating opposing forces that prevent the packoff assembly from lifting off the sealing surface under extreme pressure conditions.
2Reliability
If the mandrel is secured within the wellhead to prevent leakage, then sealing reliability is improved, but the device becomes more complex with additional lock and anchor assemblies
Solution Approach 1:
The patent combines the lock assembly and anchor assembly into an integrated system that works together to secure the mandrel. The lock assembly and anchor assembly are structurally merged to provide both locking and anchoring functions through a coordinated mechanism, reducing the number of separate components while maintaining sealing reliability.
3Strength
If support is provided against external forces to protect the packoff assembly, then protection from damage is improved, but the device complexity increases
Solution Approach 1:
The lock assembly and anchor assembly serve multiple functions: they provide support against external forces, prevent mandrel displacement, and maintain sealing pressure. This multi-functionality allows a single structural system to protect the packoff assembly from damage while avoiding the need for separate dedicated support components.
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 isolates the wellhead from fluid flow, reduces the risk of packoff assembly 'lift-off', and supports the mandrel and packoff assembly against external forces, enhancing operational reliability and preventing damage during high-pressure operations.
Implementation Method 1
using self-energizing annular seals to maintain sealing engagement
Implementation Method 2
threaded connections to maintain sealing engagement and prevent force transfer
Data Source
AI summary
An isolation tool and related methods for protecting a wellhead to which a casing string is operably coupled. In an exemplary embodiment, the isolation tool includes an anchor assembly adapted to be connected to the wellhead; a mandrel adapted to sealingly engage an interior portion of at least one of the wellhead and the casing string; and a lock assembly including a mandrel head connected to the mandrel and adapted to be displaced, relative to the anchor assembly and the wellhead, to sealingly engage the mandrel with the interior portion; a landing sleeve connected to the mandrel head and adapted to be displaced, relative to the mandrel head, the mandrel, the anchor assembly, and the wellhead, to engage the anchor assembly; and a connector adapted to secure the landing sleeve to the anchor assembly when the mandrel sealingly engages the interior portion and the landing sleeve engages the anchor assembly.