Two-Step Wedge Threaded Tubular Connection for Seal Positioning
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Solution Overview
Problem
Wedge thread connections in tubular connections for hydrocarbon wells lack a final make-up stop shoulder, leading to indeterminate positioning of sealing surfaces and potential seal stand-off issues due to the wedging effect between threads, which complicates the make-up process and affects the accuracy of contact pressures required for a radial metal-to-metal seal.
Innovation Solution
A threaded tubular connection with a tapered two-step wedge thread configuration, featuring small and large diameter thread steps with external and internal dovetail wedge threads, where one set has a first axial clearance and the other a second axial clearance, ensuring the wedge thread set with the second axial clearance governs the make-up process, allowing for accurate positioning of sealing surfaces by selecting it as the reference thread set during rotational make-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wedge threads are used without a final make-up stop shoulder, then the make-up process is simpler and more flexible, but the positioning of sealing surfaces becomes indeterminate and seal reliability deteriorates
Solution Approach 1:
The thread connection is divided into two distinct thread sets: a first thread set that engages first during make-up and a second thread set that engages second. This segmentation allows each thread set to perform a specific function - the first thread set controls the positioning of sealing surfaces while the second thread set provides additional structural support, thereby resolving the contradiction between operational flexibility and seal reliability.
Solution Approach 2:
The first thread set is designed to engage and establish the correct positioning of sealing surfaces before the second thread set engages. This preliminary action ensures that sealing surfaces are properly positioned early in the make-up process, preventing seal stand-off while maintaining the flexibility of the wedge thread design without a final make-up stop shoulder.
2Adaptability or versatility
If wedge threads with varying width are used, then the connection can accommodate positioning variations, but the make-up becomes indeterminate and sealing surface positioning accuracy deteriorates
Solution Approach 1:
By segmenting the thread connection into two distinct thread sets with different engagement sequences, the invention allows the first thread set to control positioning accuracy while the second thread set provides adaptability. This segmentation resolves the contradiction by assigning different functional roles to each thread set.
Solution Approach 2:
The first thread set is specifically designed with local quality features that prioritize positioning accuracy of sealing surfaces, while the second thread set is designed with features that prioritize structural support and adaptability. This differentiation of local qualities across the two thread sets resolves the contradiction between adaptability and positioning accuracy.
3Reliability
If a radial metal-to-metal seal is used, then sealing effectiveness is improved, but the requirement for accurate sealing surface positioning increases device complexity
Solution Approach 1:
The first thread set performs the preliminary action of positioning sealing surfaces correctly before the second thread set engages. This preliminary positioning action ensures that the radial metal-to-metal seal functions effectively without requiring complex positioning control mechanisms, as the correct positioning is achieved through the sequential engagement design itself.
Solution Approach 2:
The two-step wedge thread connection design allows the connection itself to automatically position the sealing surfaces correctly through the sequential engagement of the two thread sets. This self-service mechanism eliminates the need for additional complex positioning control devices, thereby maintaining sealing effectiveness while avoiding increased device complexity.
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
This configuration ensures accurate positioning of sealing surfaces relative to each other, preventing seal stand-off and ensuring proper contact pressures by governing the make-up process with the wedge thread set energized first, maintaining stability up to 80% of the optimum make-up torque, thereby ensuring a reliable radial metal-to-metal seal.
Implementation Method 1
The wedge threads typically do not have such a final make-up stop shoulder. This makes their make-up 'indeterminate' and, as a result, the position of the pin member relative to the box member may vary more during make-up
Data Source
AI summary
A threaded tubular connection for drilling or operating hydrocarbon wells comprising a longitudinal axis, a metal pin member having a tapered two-step wedge pin thread with dovetail wedge threads and a pin sealing surface located between the small and large diameter pin thread steps, and a metal box member having a tapered two-step wedge box thread with dovetail wedge threads and a box sealing surface located between the small and large diameter box thread steps, wherein the tubular connection is free from any final make-up stop shoulder defining a final make-up position for the pin member relative to the box member, the small diameter wedge thread set and the large diameter wedge thread set are dimensioned to have a first axial clearance and a second axial clearance.