Production Tubing Threaded Joint With Spherical Sealing Surfaces
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Solution Overview
Problem
Existing thread connections for tubings in oil, gas, and gas-condensate fields fail to withstand multiple cycles of make-up/break-out without damage to contact surfaces, leading to loss of tightness under high mechanical loads due to jamming and galling.
Innovation Solution
The thread connection employs tapered trapezoidal threads with specific slope angles and additional features like concave and convex spherical surfaces between sealing and shoulder end face surfaces, preventing damage and ensuring reliable centering and sealing, thereby enhancing make-up characteristics and resistance to multidirectional mechanical loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thread connections are used, then assembly is straightforward, but the connection cannot withstand multiple cycles of make-up/break-out without damage to contact surfaces
Solution Approach 1:
The invention introduces spherical seating surfaces at the ends of thread turns, where the outer surface of the male element and inner surface of the female element are formed with spherical geometries. This curvature allows for gradual contact and distribution of mechanical loads during make-up and break-out cycles, preventing stress concentration and surface damage while maintaining connection reliability.
Solution Approach 2:
The spherical seating surfaces are pre-formed during manufacturing to establish optimal contact geometry before the connection is assembled. This preliminary preparation ensures that during subsequent make-up and break-out cycles, the contact surfaces engage smoothly without sudden impact or misalignment that could cause galling or damage.
2Ease of operation
If conventional thread profiles are used, then manufacturing is simple, but jamming occurs at the initial stage of make-up
Solution Approach 1:
The thread profile incorporates spherical seating surfaces that provide a gradual, curved transition zone at the entry of the thread connection. This curvature guides the mating elements into proper alignment during the initial stages of make-up, preventing sudden engagement and jamming while maintaining relatively simple manufacturing processes.
3Reliability
If standard sealing surfaces are used, then sealing is adequate, but tightness is lost under high multidirectional mechanical loads
Solution Approach 1:
The invention optimizes the angular parameters of sealing surfaces, specifying precise angle ranges (17-19° for sealing surfaces to the thread axis, and specific angles for shoulder end face surfaces). These parameter changes are designed to distribute multidirectional mechanical loads more effectively across the sealing interface, maintaining tightness under complex loading conditions while remaining achievable with standard manufacturing tolerances.
Data Source
AI summary
A threaded joint for production of tubing includes a male element and female elements, having outer surface and inner surfaces, respectively, whose ends are configured with a trapezoidal tapered thread and with sealing surfaces, auxiliary surfaces and abutting end surfaces, which form an inner sealing assembly. The threads have characteristics described in the present disclosure. Auxiliary surfaces are provided between the sealing surfaces and the abutting end surfaces. The junction between the sealing surfaces and the auxiliary surfaces is configured in the form of a concave spherical surface on the male element and a convex spherical surface on the female element. This provides for the formation of a tight joint under high mechanical loads by virtue of improved coupling characteristics and the prevention of damage to the surfaces.