Tubular Goods Connection With Wedge Threads for Over-Torque Capacity
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Solution Overview
Problem
Existing tubular connections for oil and gas drilling face issues with high stress states, galling, and stress corrosion cracking due to high torque and interference fits, especially in deviated wellbores and shale formations, limiting their operational effectiveness.
Innovation Solution
A tubular connection design with a wedge coefficient WC less than 2.0, featuring continuous internal and external dovetail or vanishing wedge threads, allowing for a 0-10mm pin end face gap at optimal torque, which activates over-torque capacity through pin-to-pin interference contact when needed, reducing hoop stresses and enhancing stress corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high torque and interference fits are used in existing tubular connections, then connection strength is improved, but stress corrosion cracking and galling occur
Solution Approach 1:
The patent changes the geometric parameters of the thread profile by introducing a wedge coefficient WC less than 2.0 (specifically 1.3-1.9), which modifies the stress distribution and reduces peak stresses that lead to stress corrosion cracking while maintaining connection strength
Solution Approach 2:
The patent creates different functional zones within the threaded connection: a make-up zone with optimal torque characteristics and a running torque zone with reduced stress, allowing different local qualities in different regions of the thread engagement
2Strength
If high torque and interference fits are used in existing tubular connections, then connection strength is improved, but galling occurs
Solution Approach 1:
The patent modifies the thread geometry parameters including the wedge coefficient and lead angle to reduce friction and contact pressure, thereby preventing galling while maintaining adequate connection strength through optimized stress distribution
3Reliability
If continuous wedge threads with WC < 2.0 are used, then stress corrosion resistance is improved, but over-torque capacity needs to be activated
Solution Approach 1:
The patent creates a dynamic system where the pin end faces remain separated during normal operation (providing stress corrosion resistance) but can come into contact under over-torque conditions (activating additional strength capacity), allowing the connection to adapt to different loading conditions
4Strength
If pin end faces are in contact at optimal torque, then over-torque capacity is activated, but axial interference occurs
Solution Approach 1:
The patent designs a dynamic gap system where the pin end faces are separated under normal optimal torque conditions (avoiding axial interference) but can contact under over-torque conditions (activating additional strength), allowing conditional activation of over-torque capacity without permanent interference
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 maintains optimal make-up torque while increasing over-torque capacity, reducing galling and stress corrosion cracking, ensuring reliable performance in challenging drilling environments.
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
continuous first internal wedge thread formed within the longitudinal coupling bore and extending from the first box end face to a mid-point of the longitudinal coupling bore
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.