Locking Clutch for Downhole Motor Stuck-Bit Prevention
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Solution Overview
Problem
Downhole motors, particularly turbine mud motors, face challenges in preventing drill bits from becoming stuck and efficiently freeing stuck bits due to low torque output, which can lead to costly fishing operations and increased risk of drill string sticking in the borehole.
Innovation Solution
A locking clutch mechanism with locking pawls that biases into an engaged position to transmit torque from the stator to the rotor when the drill bit becomes stuck, disengaging when the rotor speed exceeds a certain threshold to prevent wear and allow normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a mud motor is used to drive the drill bit, then drilling efficiency is improved, but the drill bit may become stuck due to low torque output
Solution Approach 1:
The locking pawl is designed to dynamically switch between engaged and disengaged states based on rotational speed conditions. At low speeds below a threshold, the pawl engages to provide mechanical locking and prevent sticking. At high speeds above the threshold, the pawl disengages to allow free rotation and normal mud motor operation. This dynamic state change resolves the contradiction by providing torque assistance only when needed.
Solution Approach 2:
The locking mechanism operates autonomously based on the rotational speed of the drill bit. The system self-regulates by engaging the locking pawl when the drill bit slows down (indicating potential sticking) and disengaging when rotation speed is sufficient. This eliminates the need for external control systems or surface intervention, allowing the system to self-correct sticking conditions.
2Reliability
If torque is continuously applied from the drill string to prevent sticking, then drill bit sticking is prevented, but wear increases during normal operation
Solution Approach 1:
The locking pawl transitions from a continuously engaged state to a dynamically controlled state that engages only when rotational speed drops below the threshold. This dynamic engagement eliminates continuous contact and wear during normal high-speed operation, while providing protective torque transmission only when the drill bit slows down and sticking risk increases.
Solution Approach 2:
The locking mechanism operates in periodic cycles rather than continuously. The locking pawl engages intermittently only during low-speed conditions when sticking is likely, and disengages during normal high-speed operation. This periodic action pattern reduces cumulative wear while maintaining reliability during critical low-speed periods.
3Reliability
If a locking mechanism is added to prevent sticking, then reliability is improved, but device complexity increases
Solution Approach 1:
The locking mechanism uses the rotational speed of the drill bit itself as the control signal for engagement and disengagement. The kinetic energy and centrifugal forces generated during rotation automatically actuate the locking pawl without requiring external sensors, actuators, or control systems. This self-service approach minimizes added complexity while achieving reliable automatic protection against sticking.
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 locking clutch effectively prevents drill bits from becoming stuck and facilitates their freeing by applying torque from the drill string to the stator and rotor, reducing the risk of drill string sticking and eliminating the need for surface intervention during stuck-bit situations.
Implementation Method 1
centrifugal force urges the at least one locking pawl into a disengaged position when the rotor is rotated above a disengagement speed
Implementation Method 2
the at least one locking pawl is biased into an engaged position by a biasing mechanism
Data Source
AI summary
A locking clutch to selectively transmit torque from a stator of a downhole tool to a rotor of the downhole tool includes at least one locking pawl disposed upon the rotor, wherein the at least one locking pawl comprises a load path, at least one pivot axis, and a mass center, wherein the at least one locking pawl is biased into an engaged position by a biasing mechanism, wherein the at least one locking pawl transmits force from the stator to the rotor along the load path when in the engaged position, and wherein centrifugal force urges the at least one locking pawl into a disengaged position when the rotor is rotated above a disengagement speed.