Drill Pipe Threaded Connection Lubricant Evacuation
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Solution Overview
Problem
Conventional threaded connections for drilling and operating hydrocarbon wells face issues with lubricant evacuation during make-up, leading to false torque readings and potential connection failure due to trapped lubricant, and existing solutions compromise fatigue strength or complicate inspection.
Innovation Solution
The design features threaded zones with varying lead angles between stabbing and load flanks, allowing for efficient lubricant evacuation by altering the contact points and pressure distribution, while maintaining self-locking capabilities and fatigue strength through dovetail profiles and tapered orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If self-locking threadings with variable thread widths are used to relieve abutment surfaces, then the contact surface area increases and torque transmission improves, but the make-up operation becomes complex due to lubricant trapping
Solution Approach 1:
The threaded zone is segmented into multiple sections with different lead angles. The first section has a first lead angle optimized for lubricant evacuation, while the second section has a second lead angle optimized for torque transmission. This segmentation allows each section to perform its specific function without compromising the other.
Solution Approach 2:
Different sections of the threaded zone are assigned different local qualities (lead angles) to perform different functions. The first section has a larger lead angle for lubricant evacuation, while the second section has a smaller lead angle for torque transmission. This local differentiation resolves the contradiction by allowing each region to be optimized for its specific purpose.
2Reliability
If a lubricating film is applied to threaded zones before assembly, then friction and wear are reduced, but excess lubricant becomes trapped under pressure causing false torque readings
Solution Approach 1:
The threaded zone is divided into sections with different lead angles. The first section's larger lead angle creates a self-evacuation effect that removes excess lubricant during make-up, preventing trapping and ensuring accurate torque readings while maintaining connection reliability.
Solution Approach 2:
Instead of trying to retain all lubricant for lubrication purposes, the design inverts the approach by using the first section to actively evacuate excess lubricant. This inversion prevents the harmful effect of trapped lubricant while maintaining sufficient lubrication in the second section for reliable connection.
3Measurement precision
If grooves are introduced onto threads to evacuate lubricant, then lubricant evacuation improves and torque readings become accurate, but fatigue strength and sealing are compromised
Solution Approach 1:
Instead of introducing grooves that compromise strength, the invention changes the geometric parameter (lead angle) of the threaded zone sections. The first section has a larger lead angle that naturally evacuates lubricant through geometric progression, achieving accurate torque readings without compromising fatigue strength or sealing.
Solution Approach 2:
The threaded zone functions as a composite structure with two distinct sections, each having different lead angle characteristics. This composite approach combines the lubricant evacuation function of the first section with the torque transmission and sealing functions of the second section, achieving multiple benefits without the drawbacks of groove-based solutions.
4Ease of operation
If perturbation is created in threaded zones to allow lubricant movement, then lubricant evacuation is improved, but inspection of threaded zones becomes complex and galling risks increase
Solution Approach 1:
The invention uses a systematic parameter change (lead angle differentiation between sections) rather than arbitrary perturbations. This creates a regular, predictable geometric progression that is easy to inspect and verify, while still achieving effective lubricant evacuation and reducing galling risks through controlled contact pressure distribution.
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
Facilitates accurate make-up torque measurement and enhanced fatigue strength by effectively evacuating excess lubricant and optimizing contact pressures, reducing the risk of connection failure and maintaining structural integrity.
Implementation Method 1
altering the contact points and pressure distribution... effectively evacuating excess lubricant
Implementation Method 2
the threads (also termed teeth) of the male end and the threads (also termed teeth) of the female end have a constant lead but the thread widths are variable... the flanks of the male threads (or teeth) lock against the flanks of the corresponding female threads (or teeth)
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention concerns a set for producing a threaded connection, comprising a first and a second tubular component with an axis of revolution (10), one of their ends (1, 2) being provided with a threaded zone (3; 4) formed on the external or internal peripheral surface of the component depending on whether the threaded end is of the male or female type, said ends (1, 2) finishing in a terminal surface (7, 8) which is orientated radially with respect to the axis of revolution (10) of the tubular components, said threaded zones (3; 4) comprising threads (32; 42) comprising, viewed in longitudinal section passing through the axis of revolution (10) of the tubular components, a thread crest (35, 45), a thread root (36, 46), a load flank (30; 40) and a stabbing flank (31; 41), the width of the thread crests (35, 45) of each tubular component reducing in the direction of the terminal surface (7; 8) of the tubular component under consideration, while the width of the thread roots (36, 46) increases, characterized in that the lead of the male stabbing flanks and/or load flanks is different from the lead of the female stabbing flanks and/or load flanks. The invention also pertains to a threaded connection.