Flush Self-Locking Threaded Connection for High-Torque Sealing
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Solution Overview
Problem
Existing threaded connections for shale gas operations face challenges in achieving high torque capacity, seal performance, and cost efficiency, particularly for small pipe diameters, while maintaining flush connections and withstanding high tension, compression, and complex well configurations.
Innovation Solution
A semi-premium flush connection with self-locking threads, featuring partially made-up male and female threaded zones with varying thread widths and roots, allowing for a locking region that provides sufficient sealing and torque capacity without requiring complex torque charts, and can be manufactured at reasonable costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional abutment surfaces are used to achieve high torque capacity, then torque transmission is improved, but the critical plastication threshold is rapidly reached especially for small diameter pipes
Solution Approach 1:
The threaded zone is divided into multiple segments along the axial direction, with each segment having different thread geometries. The first segment has threads with larger dimensions for high torque capacity, while the second segment has threads with smaller dimensions for flush connection, effectively segmenting the functional requirements along the axial direction
Solution Approach 2:
Different regions of the threaded connection are given different local qualities: the first threaded zone has larger thread dimensions and is positioned to handle high torque loads, while the second threaded zone has smaller thread dimensions optimized for flush connection appearance. This local differentiation allows each region to optimize for its specific function
2Shape
If threaded zones are formed in the wall thickness of pipes to achieve flush connection, then outer diameter is maintained, but connection efficiency is reduced due to limited thickness
Solution Approach 1:
The solution moves from a two-dimensional constraint (thread depth limited by wall thickness) to a three-dimensional solution by utilizing the axial dimension. Multiple threaded zones are arranged axially, with the first zone providing strength and the second zone providing flush connection, effectively using the axial direction to resolve the contradiction between strength and shape
3Reliability
If self-locking threaded zones are used to provide seal performance, then sealing is improved, but manufacturing complexity increases
Solution Approach 1:
The thread geometry parameters are changed along the axial direction, with the first threaded zone having different thread dimensions, pitch, or profile compared to the second threaded zone. This parameter variation enables self-locking behavior for sealing while maintaining manufacturability through systematic geometric progression rather than complex mechanisms
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 connection achieves high torque capacity, efficient sealing, and reduced manufacturing costs, with improved make-up efficiency and reduced risk of handling damage, suitable for shale gas operations and complex well configurations.
Implementation Method 1
self-locking threaded zones with varying thread widths and roots
Implementation Method 2
partially made-up male and female threaded zones with varying thread widths and roots, allowing for a locking region
Data Source
AI summary
A flush self-locking threaded connection partially in a non-locking engagement comprises a first and a second tubular component provided respectively with male and female threaded zone at their respective ends. First portions of the male and female threaded zones with varying thread width and root cooperate along a self-locking tightening arrangement. A locking region within the threaded connection is located in the middle of non-locking regions, and radially centered to the pipe body API tolerances in order to withstand high torque and seal performances.