Liner Packoff Sealing and Locking Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for hanging a liner string from a tubular string cemented in a wellbore lack an efficient and reliable mechanism for secure sealing and locking, which can lead to instability and leakage during hydrocarbon extraction processes.
Innovation Solution
A packoff system comprising a tubular body with inner and outer grooves, seal assemblies, a cap, dogs, and a lock sleeve with collet fingers and cam profile, allowing for secure engagement and longitudinal movement to ensure proper sealing and locking of the liner string.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a packoff system is used to hang a liner string from a tubular string, then sealing integrity is improved, but device complexity increases due to multiple seal assemblies and locking mechanisms
Solution Approach 1:
The packoff system employs nested seal assemblies where an inner seal assembly is positioned within an outer seal assembly. Both seal assemblies are housed within the packoff body, with the inner seal assembly containing its own piston, seals, and retention members. This nested configuration provides multiple sealing zones (inner and outer seals) to ensure reliable sealing integrity while organizing complex components in a compact, hierarchical structure that manages device complexity.
2Reliability
If a lock sleeve with collet fingers and cam profile is used to secure the liner string, then locking reliability is improved, but ease of operation deteriorates due to complex engagement mechanisms
Solution Approach 1:
The lock sleeve is designed as a dynamic component that can move longitudinally within the packoff body. The collet fingers are configured to radially expand and contract as the lock sleeve moves, enabling automatic engagement and disengagement of the dogs. The cam profile on the lock sleeve converts longitudinal movement into radial expansion of the collet fingers, creating a mechanical advantage that secures the dogs in place during liner string deployment while allowing controlled release when needed.
3Strength
If dogs are used to engage with the liner string, then mechanical strength of connection is improved, but difficulty of detecting and measuring increases
Solution Approach 1:
The dogs are equipped with visual indicators that change appearance or position to indicate their engagement status. When the dogs are properly engaged with the liner string and secured by the lock sleeve, the visual indicators display a specific configuration or color state that can be easily observed through the packoff body or on the exterior. This allows operators to visually confirm proper engagement and connection strength without complex measurement instruments.
Data Source
Figure 1A
Figure 1B~1C
Figure 2A~2D
AI summary
A packoff for hanging a liner string from a tubular string cemented in a wellbore includes: a tubular body having an outer groove and an inner groove; an inner seal assembly disposed in the inner groove; an outer seal assembly disposed in the outer groove; a cap connected to an upper end of the body for retaining the seal assemblies; a plurality dogs disposed in respective openings formed through a wall of the body; and a lock sleeve. The lock sleeve is: disposed in the body, longitudinally movable relative to the body, and has a cam profile formed in an outer surface thereof for extending the dogs.