Scalloped Wedge Threads for Tubular Seal Integrity
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Solution Overview
Problem
Wedge-threaded connections in oilfield tubulars face challenges with thread seal integrity due to indeterminate make-up, increased stress from higher torque, and pipe dope-related issues like stand-off and galling, especially in large diameter connections and high-temperature environments, which can lead to premature failure and loss of seal integrity.
Innovation Solution
The introduction of thread interruptions along the helical length of either the pin or box member, specifically scalloped or interrupted thread crests, to create voids for pipe dope escape and reduce pressure build-up, allowing for effective thread sealing without the need for alternative pipe dope compounds, and accommodating eccentric cross-sections and long thread lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher torque is applied to achieve better thread sealing, then seal integrity is improved, but stress on the connection increases leading to premature failure
Solution Approach 1:
The continuous thread structure is segmented into multiple sections by introducing thread interruptions (scallops) at specific locations. This segmentation allows the thread to better distribute and manage stress during make-up, enabling adequate sealing without concentrating excessive stress that would lead to premature failure.
2Reliability
If more pipe dope is applied to ensure thread sealing, then seal robustness is improved, but pressure build-up causes stand-off and galling
Solution Approach 1:
Thread interruptions (scallops) are introduced to extract or remove excess pipe dope from the thread interface during make-up. These interruptions create escape paths that allow pipe dope to be pushed out rather than trapped, preventing dangerous pressure build-up while still maintaining adequate sealing.
Solution Approach 2:
The potential harm of excess pipe dope causing pressure build-up is converted into a benefit by using thread interruptions to deliberately push the pipe dope out. The same make-up pressure that would cause harm is instead used to expel excess dope through the scalloped interruptions, preventing stand-off and galling while maintaining seal robustness.
3Object-affected harmful factors
If thread interruptions are added to manage pipe dope pressure, then pressure build-up is reduced, but thread seal complexity increases
Solution Approach 1:
Thread interruptions (scallops) are introduced at specific local positions along the thread rather than modifying the entire thread structure. This localized modification allows effective pipe dope management while minimizing overall structural complexity and maintaining the majority of the thread's original simple geometry.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A threaded connection between adjacent tubular members includes a pin member providing an external wedge thread and a box member providing an internal wedge thread, wherein the internal wedge thread corresponds with the external wedge thread. Further, the threaded connection includes at least one interruption along a helical thread length of one of the external wedge thread and the internal wedge thread and at least two regions along an axial length of the threaded connection where the external wedge thread and the internal wedge thread form a thread seal.