Tubular Goods Coupling With Wedge Threads for Over-Torque Control
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Solution Overview
Problem
Existing tubular goods connections face challenges in maintaining optimal make-up torque and over-torque capacity, leading to issues such as axial interference, stress corrosion cracking, and galling, especially in unconventional drilling applications like deviated wellbores and shale formations.
Innovation Solution
A made-up tubular goods connection featuring continuous internal and external wedge threads with a wedge coefficient between 1.3 and 1.9, allowing for a distance of 0 to 10 millimeters between pin end faces at optimal torque, and an over-torque capacity of 150%-250% of the optimum make-up torque, which activates interference contact to transmit axial load and withstand additional torque without increasing hoop stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threaded connections are used to couple tubular members, then the connection can be made, but axial interference and stress occur leading to galling and stress corrosion cracking
Solution Approach 1:
The patent changes the geometric parameters of the thread profile by introducing a non-zero clearance wedge thread design with specific wedge coefficients (1.05-1.80). This parameter modification allows the threads to engage without axial interference, eliminating galling and stress corrosion cracking while maintaining connection reliability.
Solution Approach 2:
The patent introduces a coupling element as an intermediary component between two tubular members. This coupling with internally threaded bores provides a controlled interface that prevents direct axial interference between the tubular members, thereby eliminating harmful stresses and galling while maintaining reliable connection.
2Manufacturing precision
If high make-up torque is applied to ensure proper thread engagement, then thread engagement is improved, but over-torque causes axial interference and increases hoop stresses
Solution Approach 1:
The patent modifies the thread geometry parameters, specifically the wedge coefficient and clearance design, to achieve optimal thread engagement at reduced torque levels. This prevents over-torque application and the resulting excessive hoop stresses while maintaining precise thread engagement.
Solution Approach 2:
The patent designs the thread profile with built-in geometric features that prevent over-torque application. The non-zero clearance and specific wedge coefficients create a self-limiting engagement mechanism that stops thread advancement before excessive hoop stresses develop, providing preliminary protection against over-torque damage.
3Strength
If traditional wedge threads with high wedge coefficients are used, then thread strength is improved, but galling occurs due to excessive friction
Solution Approach 1:
The patent optimizes the wedge coefficient parameter to a specific range (1.05-1.80) that balances thread strength with friction reduction. This parameter optimization maintains adequate thread strength while minimizing the friction that causes galling, solving the contradiction between strength and surface damage.
Solution Approach 2:
The patent applies different local characteristics to different parts of the thread profile. The non-zero clearance region reduces friction and prevents galling, while the engaged thread portions maintain sufficient strength. This local differentiation of thread properties resolves the contradiction between overall strength and local surface damage.
4Reliability
If tight thread engagement is achieved to prevent leakage, then connection integrity is improved, but axial interference occurs leading to stress corrosion cracking
Solution Approach 1:
The coupling acts as an intermediary that provides a controlled engagement interface. The internally threaded bores of the coupling engage with the externally threaded pins without creating axial interference, thereby maintaining connection integrity while preventing stress corrosion cracking.
Solution Approach 2:
The patent changes the engagement parameters by using non-zero clearance wedge threads with specific wedge coefficients. This allows tight engagement for leakage prevention while maintaining zero axial interference, eliminating the conditions that lead to stress corrosion cracking.
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 maintains optimal make-up torque within operator ranges, reduces galling, and enhances resistance to stress corrosion cracking, enabling reliable performance in challenging environments like deviated wellbores and shale formations.
Implementation Method 1
a wedge coefficient WC of the continuous first internal wedge thread, the continuous second internal wedge thread, the continuous first mating external wedge thread, and the continuous second mating external wedge thread is less than 2.0
Implementation Method 2
a made-up tubular goods connection featuring continuous internal and external wedge threads with a wedge coefficient between 1.3 and 1.9, allowing for a distance of 0 to 10 millimeters between pin end faces at optimal torque, and an over-torque capacity of 150%-250% of the optimum make-up torque
Data Source
AI summary
A tubular goods connection for releasably coupling tubular members includes: a coupling having a first internal wedge dove-tail thread formed within a longitudinal bore of the coupling and a second internal dove-tail wedge thread; a first tubular member having a first mating external vanishing dove-tail wedge thread extending from a first proximal pin end face; and a second tubular member substantially identical to the first tubular member; wherein when the first and second tubular members are made-up into the coupling using a predetermined recommended optimum torque, a distance D between the first pin end face and the second pin end face is in the range of 0 to 10 millimeters and when the distance D is equal to 0 there is contact between the first pin end face and a second pin end face of the second tubular good but there is no axial interference.