Threaded Joint with Concave Profile for Well Drilling Torque
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Solution Overview
Problem
Existing threaded connections for hydrocarbon well drilling and operation face challenges in accommodating high torque without compromising seal integrity and fatigue strength, particularly due to issues with lubricant management and complex machining processes.
Innovation Solution
The design features self-locking threaded zones with a continuous concave profile over at least 10% of the engaged threads, allowing for efficient lubricant movement and maintaining seal integrity, including optional features like metal/metal sealing surfaces and tapered profiles to enhance sealing and radial rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If self-locking threadings with interfering contact are used to accommodate high makeup torque, then torque transmission capability is improved, but lubricant becomes trapped under pressure causing counter-pressure that tends to disconnect the threads
Solution Approach 1:
The threading is segmented into multiple zones with different contact characteristics. The first threaded zone has interfering contact between crests and roots to generate sealing pressure, while the second threaded zone has non-interfering contact to avoid trapping lubricant. This segmentation allows the connection to simultaneously achieve both sealing capability and lubricant evacuation.
Solution Approach 2:
Different portions of the threading have different geometric properties. The first threaded zone features interfering contact geometry for sealing, while the second threaded zone features non-interfering contact geometry for lubricant flow. This local differentiation of quality allows each zone to perform its specific function optimally.
2Ease of operation
If a lubricating film is applied to the threaded zones before assembly, then friction is reduced during makeup, but surplus lubricant flows through and may be trapped generating counter-pressure
Solution Approach 1:
The harmful effect of trapped lubricant is eliminated by providing a second threaded zone with non-interfering contact that acts as an evacuation path. The lubricant that flows through during makeup is continuously removed through this second zone, preventing pressure buildup that would compromise seal integrity.
3Reliability
If interfering contact between thread crests and roots is provided to seal the threaded zones, then sealing capability is improved, but the threads are weakened and fatigue strength is reduced
Solution Approach 1:
The threading is divided into two separate zones: the first zone provides interfering contact for sealing, while the second zone provides non-interfering contact that maintains thread strength. This segmentation allows the connection to achieve sealing without compromising the overall structural integrity and fatigue resistance of the threads.
4Force
If the width of threads increases progressively from the end to accommodate high torque, then torque transmission is improved, but the makeup operation becomes complex when lubricant is used
Solution Approach 1:
The progressive width increase is applied only to the first threaded zone to maintain torque transmission capability, while the second threaded zone has constant thread width to simplify lubricant flow and evacuation. This segmentation reduces makeup operation complexity while preserving the necessary torque transmission properties.
Data Source
AI summary
An assembly for production of a threaded connection, including a first and a second tubular component with an axis of revolution and each including at one of its ends at least one first threaded zone produced on an external or internal peripheral surface of the component depending on whether the threaded end is male or female in type, and capable of cooperating together on makeup, the ends finishing in a terminal surface. At least one of the threaded zones has, in longitudinal section passing through the axis, a profile that follows a continuous and concave portion of a curve over at least 10% of the length of engaged threads of the threaded zone.