Oil Well Casing Threaded Connection With Dual Metal Seals
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Solution Overview
Problem
Existing threaded connections for oil and gas wells, particularly in deep wells, face challenges in machining and assembly due to high internal and external pressure resistance requirements, as well as tolerances under traction and compression, and require improved sealing and adhesion to handle variations in grease application effectively.
Innovation Solution
A threaded tubular connection design featuring a male tool joint with a male inner sealing surface, male abutment shoulder, and male intermediate sealing surface, paired with a female tool joint having a female inner sealing surface and intermediate sealing surface, where the helix pitches of the threaded portions are constant, and the connection includes a semi-flush configuration with a non-zero axial distance and specific taper angles to enhance sealing and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If 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 changes the geometric parameters of the threading by making the pitch values equal for both load flank and stabbing flank, while maintaining different angles. This simplifies machining operations while still achieving the required pressure resistance through the optimized angle configuration and intermediate abutment design.
Solution Approach 2:
The patent applies different properties to different parts of the threading system: the load flank and stabbing flank have different angles relative to the axis, with the load flank angle being greater than the stabbing flank angle. This local differentiation optimizes pressure resistance while the equal pitch simplifies manufacturing.
2Device complexity
If integral connection without coupling is used for deep wells, then assembly complexity is reduced, but machining precision requirements increase
Solution Approach 1:
The intermediate abutment is designed to automatically position and align the male and female tool joints during assembly. The abutment surfaces provide self-aligning features that reduce the impact of machining tolerances, allowing the integral connection to achieve proper alignment without requiring extremely high machining precision.
Solution Approach 2:
The design incorporates intermediate abutment surfaces that compensate for potential misalignments before the final threaded connection is made. This pre-positioning mechanism cushions against machining tolerance variations and facilitates easier assembly of the integral connection.
3Ease of manufacture
If constant pitch threading is used, then machining ease is improved, but adhesion under pressure variations deteriorates
Solution Approach 1:
The patent introduces asymmetry through different angles for the load flank and stabbing flank relative to the axis, while maintaining equal pitch values. The load flank angle is greater than the stabbing flank angle, creating an asymmetric configuration that enhances adhesion and pressure resistance while keeping the threading manufacturable with constant pitch.
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 connection achieves 96% effectiveness of the tube, providing improved resistance to internal and external pressures, and tolerances, while facilitating easier assembly and handling variations in grease application, making it suitable for large-diameter tubes used in deep well drilling and exploitation.
Implementation Method 1
positive interferences that can be created between male threading and female threading
Implementation Method 2
sealing zones by radial interference between conical surfaces
Data Source
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 includes in order from a free edge of the male tool joint: an inner metal-metal seal, a first threaded portion, an intermediate abutment, an intermediate metal-metal seal and a second threaded portion, the free edge being at a non-zero axial distance from the female tool joint, the threaded portions each comprising a helix equipped with a load flank, a thread crest, a stabbing flank, a thread root, such that a pitch of the load flank and a pitch of the stabbing flank of the first threaded portion, and respectively a pitch of the load flank and a pitch of the stabbing flank of the second threaded portion fulfil the following condition: SFLb1=LFLb1=SFLb2=LFLb2=SFLp1=SLFLp2=LFLp2.