Threaded Casing Coupling With Reduced End Threads for Torque Capacity
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Solution Overview
Problem
Existing casing couplings in the oil and gas industry have low torque capacity, leading to mechanical integrity issues, particularly during hydraulic fracturing completions, and are prone to failures in connections.
Innovation Solution
A threaded coupling design featuring a first and second thread profile with the latter's threads reduced in height by an extra machining angle, providing higher make-up torque and distributing axial and torsional loads effectively, while maintaining economic manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If API standardized couplings are used, then ease of manufacture is improved, but torque capacity is insufficient
Solution Approach 1:
The coupling applies local quality by implementing different thread profiles at different locations. The mill end features a first thread profile with higher torque capacity, while the field end uses a second thread profile optimized for connection. This allows the coupling to have enhanced torque capacity where needed while maintaining ease of manufacture through standardized field end connections.
Solution Approach 2:
The coupling is segmented into two distinct thread profile sections: a mill end with a first thread profile and a field end with a second thread profile. This segmentation allows each end to be optimized for its specific function—the mill end for high torque capacity during manufacturing and the field end for standardized field connections—thereby resolving the contradiction between ease of manufacture and torque capacity.
2Reliability
If coupling strength is increased to prevent failures, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The invention applies local quality by concentrating the enhanced thread profile with higher torque capacity at the mill end, while keeping the field end with a standardized second thread profile. This localized enhancement improves reliability where it is most needed (during manufacturing and handling) without unnecessarily complicating the overall coupling design or field installation procedures.
Data Source
AI summary
A threaded coupling suitable for drilling oil and gas wells is provided. The threaded coupling having a first end and a second end. A first portion of the threaded coupling proximal to the first end can have a first thread profile, and a second portion of the threaded coupling proximal to the second end can have a second thread profile that is different from the first thread profile. In particular, at least two threads of the second thread profile proximate to the second end are reduced in height according to an extra machining angle. The first thread profile and the second thread profile can further be tapered according to a taper angle.