Torque Limiting Mechanism for Drill String Stall Prevention
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Solution Overview
Problem
Conventional drilling systems face issues with torque overload, leading to stall conditions and stick-slip phenomena, which result in damage to drill strings and bottom hole assemblies, and are often over-designed to compensate for peak torque, resulting in larger and more expensive components.
Innovation Solution
The implementation of a torque limiting system that disengages before reaching peak torque, allowing for full torque transmission during normal operating conditions while slipping at a predetermined torque threshold, thereby reducing the likelihood of stall or stick-slip and enabling smaller component designs or increased operating torque without exceeding peak torque limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drilling components are designed to withstand peak torque, then reliability is improved, but component size and cost increase
Solution Approach 1:
The torque limiting mechanism performs preliminary action by disengaging before peak torque is reached, preventing the stall condition from occurring in the first place. This proactive approach eliminates the need to design components for peak torque loads, allowing for smaller, more cost-effective components while maintaining reliability.
Solution Approach 2:
The torque limiting mechanism acts as an intermediary between the drive shaft and torsion rod, controlling torque transmission. It mediates the torque flow by slipping at a predetermined threshold, protecting downstream components from excessive torque without requiring those components to be oversized.
2Reliability
If shaft sizes are increased to reduce torque overload damage, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The torque limiting mechanism performs preliminary protection by disengaging before peak torque damages the drill string. This prevents the need for complex, oversized drill string components, maintaining simplicity while improving reliability.
3Productivity
If operating torque is increased for higher drilling efficiency, then productivity is improved, but the risk of reaching peak torque and causing damage increases
Solution Approach 1:
The torque limiting mechanism provides feedback control by automatically slipping when torque reaches the predetermined threshold. This creates a self-regulating system that maintains safe operating levels without requiring external intervention, allowing for aggressive drilling operations with built-in safety protection.
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 approach allows for increased drilling efficiency and speed while maintaining component sizes below peak torque levels, reducing the risk of damage and enabling additional space for instrumentation within the drill string, and allows for higher operating torques without the need for oversized components.
Implementation Method 1
The clutch plates are engaged and compressed against each other by the loading of the springs, and are configured to slip relative to one another at a desired torque threshold, providing torque relief
Implementation Method 2
The clutch plates are engaged and compressed against each other by the loading of the springs
Data Source
AI summary
A drill string for drilling a subterranean wellbore includes a shaft connectable to a first drill string portion and a housing connectable to a second drill string portion. A torque relief section is disposed between the shaft and housing. The torque relief section includes a slip section operable to slip and release torque buildup when torque applied between the shaft and housing exceeds a threshold torque. The threshold torque of the torque relief section is selected to be within the range of about 110% and 150% of the operating torque and below the peak operating torque for the drill string.