Threaded connection
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Solution Overview
Problem
Existing threaded connections for oil well pipes face challenges in maintaining sealability when subjected to varying torque levels, particularly in shale wells where high torque is required, and can lead to disengagement of male and female threads.
Innovation Solution
A threaded connection design featuring a wedge male thread with a varying-thread-width portion and a wedge female thread, where a shoulder on the pin contacts another member only after the threads have engaged, allowing for a wider torque range without compromising sealability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a threaded connection is designed for high torque performance, then torque capacity is improved, but sealability deteriorates when torque exceeds the appropriate range
Solution Approach 1:
The patent changes the geometric parameters of the thread profile by introducing a varying thread width along the thread length. The thread width transitions from a larger value at the root to a smaller value at the crest, creating a wedge-shaped profile. This parameter variation allows the thread to distribute contact stresses more effectively, maintaining sealability while accommodating high torque loads without exceeding the torque range that compromises sealing performance.
2Power
If a trapezoidal thread form is used to increase torque, then torque capacity is improved, but thread engagement stability deteriorates due to separation forces
Solution Approach 1:
The patent employs an asymmetric thread profile where the thread width varies along its length, being larger at the root and smaller at the crest. This asymmetric geometry creates a wedge effect that generates axial compressive forces to counteract the separation forces inherent in trapezoidal thread forms. The varying width distribution optimizes the balance between torque transmission and maintaining thread engagement stability under load.
3Ease of manufacture
If a constant thread width is used, then manufacturing simplicity is maintained, but torque range and performance adaptability are limited
Solution Approach 1:
The patent applies local quality by varying the thread width at different locations along the thread length. The larger thread width at the root provides enhanced strength and torque capacity where the load is highest, while the smaller width at the crest reduces stress concentration and improves sealing surface contact. This localized variation in thread geometry optimizes performance across different torque conditions while remaining manufacturable using conventional threading processes.
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 design enhances sealability and torque range, preventing disengagement and improving the connection's performance across a broader torque spectrum, suitable for high-torque applications in oil well pipes.
Implementation Method 1
The male thread engages the female thread. The threaded connection is constructed such that a shoulder provided on the pin is not in contact with a shoulder provided on another member when a stab flank and a load flank of the male thread contact a stab flank and a load flank, respectively, of the female thread
Data Source
AI summary
A threaded connection includes a pin including a wedge male thread having a varying-thread-width portion and a box including a wedge female thread having a varying-thread-width portion. The threaded connection is constructed such that, when both stab flanks and load flanks of the male thread of the pin contact the box, the shoulder on the pin is not in contact with the shoulder on the pin, and, with a further rotation in the make-up direction, the shoulder on the pin is capable of contacting the shoulder on the pin before the threads (i.e. male and female threads) yield.