Wellhead Hanger Assemblies with Locking Dogs for Torque Transmission
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Solution Overview
Problem
Current wellhead systems face challenges in efficiently rotating casing strings during cementing operations, which can lead to uneven cement distribution and increased risk of cavities or fissures, and also struggle with easy removal of running tools without damaging the hanger components.
Innovation Solution
The implementation of a wellhead hanger system that includes locking dogs in a running tool, which engage with angled recesses on the casing hanger to transmit torque for synchronous rotation and allow easy disengagement, reducing the risk of thread sticking and facilitating tool removal without break-out torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If locking dogs are used to transmit torque for rotation, then synchronous rotation of casing hanger is achieved, but difficulty in removing running tool increases due to thread sticking
Solution Approach 1:
The running tool is segmented into modular components including locking dogs, biasing springs, and shearable shear components. This segmentation allows the locking mechanism to be independently controlled and disassembled, facilitating easy removal after rotation is complete.
Solution Approach 2:
Shearable shear components are pre-installed in a loaded state to automatically restrain the locking dogs during rotation. After rotation is complete, these shear components can be easily broken or sheared off, automatically releasing the locking dogs and enabling tool removal without break-out torque.
2Ease of operation
If conventional running tools are used without locking mechanisms, then tool removal is easy, but torque transmission and synchronous rotation cannot be achieved
Solution Approach 1:
Locking dogs act as intermediary elements between the running tool and casing hanger, transmitting torque during rotation while allowing easy removal afterward. The locking dogs engage with recesses in the casing hanger to provide reliable torque transmission, then can be automatically released through shearable components.
Solution Approach 2:
The system changes the mechanical state of the locking mechanism from engaged to disengaged by breaking or shearing the shear components. This parameter change from a locked state to an unlocked state enables transition from torque transmission mode to easy removal mode.
3Ease of operation
If running tool is rotated in opposite direction to unthread, then tool removal is possible, but locking dogs may interfere and cause damage
Solution Approach 1:
The shearable shear components are pre-positioned to automatically release the locking dogs when subjected to reverse rotation or break-out torque. This preliminary arrangement prevents the locking dogs from interfering with tool removal and protects sealing surfaces from damage.
Solution Approach 2:
The locking dogs are extracted or removed from the engagement path by breaking the shear components, allowing the running tool to be freely unthreaded in the opposite direction without interference from the locking mechanism.
Data Source
AI summary
Rotating wellhead hanger assemblies are provided. In one embodiment, a wellhead hanger assembly includes a casing hanger and a casing hanger running tool coupled to the casing hanger. An exterior surface of the casing hanger includes a recess and the casing hanger running tool includes a dog that extends inward from the casing hanger running tool into the recess of the exterior surface of the casing hanger. Engagement of the dog with the recess of the casing hanger facilitates synchronous rotation of the casing hanger and its running tool. Additional systems, devices, and methods are also disclosed.