Asymmetrical Threaded Well Connection for Pressure-Cycle Resistance
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Solution Overview
Problem
Current threaded connections for oil and gas wells, particularly in deep wells, face challenges in machining and assembly due to complex geometries and require improved resistance to internal and external pressures, as well as better tolerance of handling variations during grease application.
Innovation Solution
A threaded tubular connection design featuring male and female tool joints with specific helix pitch and tooth width ratios, along with unique thread profiles and sealing surfaces, allowing for efficient assembly and enhanced resistance to pressures while minimizing machining complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a self-locking wedge thread with different pitch values for load flank and stabbing flank is used, then resistance to internal and external pressures is improved, but machining difficulty increases significantly
Solution Approach 1:
The patent applies asymmetry by defining different pitch values for the load flank (LFLp) and stabbing flank (SFLp) of the threaded portions. Specifically, the pitch of the load flank differs from the pitch of the stabbing flank, creating an asymmetric helical profile that provides self-locking capability and enhanced pressure resistance while maintaining manufacturability through standardized machining processes
2Strength
If complex threading geometries with different pitch values are implemented, then connection strength under pressure is improved, but assembly tolerance sensitivity increases
Solution Approach 1:
The patent utilizes parameter changes by establishing specific mathematical relationships between the pitch of the load flank (LFLp) and the pitch of the stabbing flank (SFLp). The pitches are designed to satisfy particular ratio conditions that optimize both connection strength and tolerance robustness, allowing the threaded connection to maintain performance across varying assembly conditions
3Device complexity
If integral connections without couplings are used for deep wells, then assembly complexity is reduced, but resistance to pressure cycles decreases
Solution Approach 1:
The patent employs parameter changes by modifying the helical profile parameters of the threaded portions, specifically the pitch values and tooth width ratios, to compensate for the absence of couplings. The asymmetric pitch design creates mechanical interference and friction that enhance pressure cycle resistance in integral connections
4Ease of manufacture
If conventional symmetrical threading is used, then machining is easier, but adhesion and pressure resistance are insufficient
Solution Approach 1:
The patent implements asymmetry in the threading geometry by defining different pitch values for the load-bearing flank and the stabbing flank. This asymmetric helical profile increases adhesion through mechanical interference and friction, while maintaining compatibility with standard machining operations through appropriate parameter selection
Data Source
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AI summary
Threaded tubular connection for the casing of hydrocarbon wells obtained by makeup of a male tool joint with a female tool joint, the connection comprising a threaded portion (16a, 18a), such that the male and respectively female threaded portions each comprise a helix provided with a load flank, a thread crest, a stabbing flank, a thread root, such that a pitch of the load flank (LFLp, LFLb) and a pitch of the stabbing flank (SFLp, SFLb) fulfils the following condition: [Math 22] SFL b = LFL b = SFL p = LFL p = k, A tooth width (Wtp) of the male helix and a tooth width of the female helix (Wtb) are such that [Math 23] or [Math 24] and [Math 25] Wtp + Wtb < k