Offset Shoulder Threaded Tubular Connection for Compressive Load
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Solution Overview
Problem
Existing threaded tubular connections for hydrocarbon transport in oil wells face challenges in maintaining mechanical strength and tightness under fluctuating stresses, particularly axial and compressive loads, while ensuring compatibility with borehole dimensions and fluid flow.
Innovation Solution
A threaded tubular connection design featuring offset inner and outer threaded portions with tapered teeth and shoulder surfaces, optimized to provide a mated shoulder contact area ratio between 15% and 25% of the nominal cross-section, enhancing compressive load resistance without compromising fluid flow or borehole compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the diameter at the female threaded end is expanded and the diameter at the male threaded end is reduced, then sufficient material thickness is achieved to ensure geometric and mechanical strength, but the assembly becomes more complex and requires additional processing steps
Solution Approach 1:
The threaded connection is divided into two distinct components: a female threaded portion with expanded diameter and a male threaded portion with reduced diameter. This segmentation allows each component to be optimized independently for strength while maintaining a manageable assembly process.
Solution Approach 2:
Different diameter characteristics are applied locally to different ends of the tubular component. The female end has an expanded diameter to provide material thickness for strength, while the male end has a reduced diameter to facilitate assembly and threading operations.
2Force
If the mated shoulder contact area ratio is increased to improve compressive load resistance, then axial load capacity improves, but the available space for threaded portions and fluid flow is reduced
Solution Approach 1:
The mated shoulder contact area ratio is optimized to a specific range (15-25% of nominal cross-section) to achieve the best balance between compressive load resistance and available space for threaded portions and fluid flow.
Solution Approach 2:
Instead of maximizing the shoulder contact area, a partial action approach is used where the contact area is set to an optimal intermediate value that provides sufficient compressive load resistance without overly constraining the threaded portions and fluid flow space.
3Reliability
If the tapering angle of threaded portions is reduced to 6% or less, then thread engagement and tightness improve, but the length of threaded portions must be increased
Solution Approach 1:
The tapering angle of the threaded portions is precisely controlled to be 6% or less, which optimizes thread engagement and tightness while minimizing the required length of threaded portions.
Solution Approach 2:
The traditional larger taper angle mechanical thread design is replaced with a shallow taper angle (≤6%) thread design that achieves equivalent or superior tightness through improved thread engagement geometry rather than increased mechanical interference.
Data Source
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AI summary
A threaded tubular connection comprises a first tubular component and a second tubular component. The first tubular component includes a female portion defined on an interior surface of the first tubular component. The female portion includes an inner threaded portion and an outer threaded portion which are offset radially with respect to a longitudinal axis of the first tubular component by a first shoulder. The second tubular component includes a male portion defined on an exterior surface of the second tubular component. The male portion is to be inserted into the female portion, and includes an inner threaded portion and an outer threaded portion which are offset radially with respect to a longitudinal axis of the second tubular component by a second shoulder. The second shoulder is to abut the first shoulder once the male portion is connected to the female portion.