Hydraulically Actuated Safety Sub With Inverted Threads
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Solution Overview
Problem
In deep-water or highly deviated wells, the counter-clockwise torque required to disconnect the lower portion of a drill pipe at a safety joint can exceed the breakup torque of other threaded connections, leading to unintended unscrewing at non-desired locations due to friction with the wellbore wall.
Innovation Solution
A safety joint with an upper sub and a middle sub, featuring threads of opposite handedness, and a piston sleeve that transmits rotation in one position and not in another, allowing for controlled disconnection by hydraulic actuation, reducing the torque needed to overcome friction and preventing unintended unscrewing of other connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard right-handed threaded connection is used at the safety joint, then the connection can be made up by applying clockwise torque, but the counter-clockwise torque required to disconnect it exceeds the breakup torque of other threaded connections due to friction with the wellbore wall, causing unintended unscrewing at non-desired locations
Solution Approach 1:
The patent applies a left-handed thread configuration at the safety joint instead of the conventional right-handed thread. This inversion allows the safety joint to be disconnected by applying clockwise torque (same direction as making up the connection) while other right-handed threaded connections in the drill string require counter-clockwise torque for disconnection. This resolves the technical contradiction by enabling selective disconnection at the safety joint without accidentally unscrewing other connections, even when high torques are applied during drilling operations in deep-water or highly deviated wells.
2Ease of operation
If friction between the drill pipe and wellbore wall is present, then the drill pipe can be held in position, but the friction increases the counter-clockwise torque needed to overcome the breakup torque of the safety joint, potentially exceeding it and causing disconnection at non-desired locations
Solution Approach 1:
By inverting the thread handedness at the safety joint to left-handed while keeping other connections right-handed, the patent enables controlled disconnection by applying clockwise torque. This approach allows operators to disconnect the safety joint even in the presence of significant friction forces from wellbore contact, without risking unintended disconnection at other locations where higher torques would be required.
Solution Approach 2:
The patent applies a unique local quality (left-handed thread) specifically at the safety joint location, while all other threaded connections in the drill string maintain the standard right-handed configuration. This localized differentiation allows the safety joint to have distinct disconnection characteristics, enabling controlled release at this specific location while maintaining secure connections elsewhere, even under high friction conditions.
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 selective release of the safety joint without disrupting other threaded connections, ensuring that the drill pipe disconnects at the intended location by minimizing the torque required to overcome friction and wellbore wall contact.
Implementation Method 1
a spline protruding radially from a body of the piston sleeve. For rotation transmission, the spline may further engage a first internal groove of the upper sub and a second internal groove of the middle sub
Implementation Method 2
Moving the piston sleeve to the second position may be performed using hydraulic pressure of a fluid flowing in the upper central passageway
Implementation Method 3
The upper portion of the drill pipe located between the drilling rig and the safety joint may contact the wellbore wall and generate friction
Data Source
AI summary
A safety joint having threads with a first handedness, for example right-handed threads, to connect the safety joint to an upper drill pipe portion and a lower drill pipe portion. The safety joint includes a releasable threaded connection having a second handedness inverse of the first handedness. The safety joint also includes a hydraulically actuated piston sleeve that locks rotation across the releasable threaded connection. Disconnecting the upper drill pipe portion from the lower drill pipe portion is achieved by moving the piston sleeve to a position wherein the piston sleeve does not transmit rotation across the releasable threaded connection, and rotating the upper drill pipe portion in the first handedness direction to unscrew the releasable threaded connection.