Balanced Thread Form for Tubulars
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Solution Overview
Problem
Existing threaded connections for downhole tubulars in oil and gas drilling lack optimal balance between bearing and shear strength, leading to reduced torsional strength and potential failure under service loads.
Innovation Solution
The development of threaded connections with pin and box connectors featuring threads that taper at 1.0 to 1.5 inches per foot, with specific thread geometry and density configurations to balance bearing and shear strength, ensuring a product of 2 * H * TPI falls within 0.95 to 1.05, optimizing torsional strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional thread geometries are used, then manufacturing is simpler, but bearing and shear strength are not optimally balanced leading to reduced torsional strength
Solution Approach 1:
The patent applies parameter changes by optimizing specific geometric parameters of the thread form including the taper angle (1.0 to 1.5 inches per foot), thread height, root radius, and crest geometry. These parameter adjustments balance the bearing strength and shear strength to maximize torsional strength while maintaining manufacturability through precise control of thread dimensions.
Solution Approach 2:
The patent implements local quality by creating different geometric characteristics at different locations of the thread. The thread form includes a tapered section with specific angle, a root region with optimized radius for stress distribution, and a crest region with specific geometry. This localized optimization of geometric properties ensures balanced bearing and shear strength distribution along the thread engagement length.
Data Source
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AI summary
A tubular member (50) having a longitudinal axis (55), a first end (60), and a second end (80) is disclosed. The tubular member includes a pin connector including an external shoulder (62), an internal shoulder (64) axially spaced from the external shoulder, and a plurality of threads (68) in a region between the external shoulder and the internal shoulder that taper relative to the longitudinal axis at 1.0 to 1.5 inches per foot. The threads include an axial density measured in a number of threads per inch (TPI), and when the pin connector is threadably engaged with a box connector, each of the threads contacts a corresponding box thread on the box connector along a projected radial distance Hc. In addition, the threads are configured such that the product of 2(√3)(H c )(TPI) is greater than or equal to 0.95 and less than or equal to 1.05.