Mandrel Casing Hanger Torque Transmission via Spring-Loaded Dogs
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Solution Overview
Problem
Existing mandrel casing hanger and running tool systems are limited in their ability to rotate the casing string due to concerns about applying excessive torque, which restricts clockwise rotation and prevents efficient installation in deviated boreholes.
Innovation Solution
A mandrel casing hanger and running tool system with a selectively engageable connection that allows clockwise rotation without substantial tightening of the threaded connection, utilizing retractable spring-loaded dogs and milled slots to transmit torque directly to the casing hanger, bypassing the threaded connection between the running tool and the casing hanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the casing string is rotated clockwise during installation, then the installation efficiency in deviated boreholes is improved, but excessive torque is applied to the threaded connection between the running tool and casing hanger
Solution Approach 1:
The patent introduces an intermediary mechanism (dogs and slots) between the running tool and casing hanger that transmits rotational force without engaging the threaded connection. The dogs engage with the slots to provide a direct mechanical link for torque transmission, bypassing the threaded interface and preventing damage while enabling rotation during installation.
2Device complexity
If the threaded connection between running tool and casing hanger is used to transmit torque, then the connection is simple, but the torque causes substantial tightening that complicates subsequent disassembly
Solution Approach 1:
The patent segments the torque transmission function from the threaded connection by introducing a separate dog-and-slot mechanism. This segmentation allows the threaded connection to remain simple for assembly while the dogs handle torque transmission, preventing excessive tightening and facilitating easy disassembly by simply unscrewing the threads without overcoming tightened conditions.
3Reliability
If rotation of the casing string is limited to prevent over-backing off connections, then the threaded connections are protected, but the ability to install in deviated boreholes is restricted
Solution Approach 1:
The dog-and-slot mechanism serves as an intermediary that enables rotation for navigating deviated boreholes while protecting the threaded connections from excessive torque. The dogs transmit rotational force directly to the casing hanger body, bypassing the threaded interface and preventing over-backing off, thus maintaining connection reliability while enabling adaptability to complex well geometries.
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
Enables efficient clockwise rotation of the casing string during installation in deviated boreholes without excessive torque on the threaded connection, facilitating easier disassembly and full installation of the casing string in the well.
Implementation Method 1
utilizing retractable spring-loaded dogs and milled slots to transmit torque directly to the casing hanger
Implementation Method 2
retractable spring-loaded dogs and milled slots to transmit torque directly
Data Source
AI summary
A method for rotating a casing string in a borehole and a mandrel casing hanger and running tool system, include a selectively engageable connection between a mandrel casing hanger and a running tool; and a rotational force may be applied to the mandrel casing hanger, running tool, and casing string, without substantially tightening a threaded connection between the running tool and the mandrel casing hanger, by transmitting the rotational force through the selectively engageable connection.