Threaded Pipe Collar Connection With Pressure-Energized Metal Seal
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Solution Overview
Problem
Wellbore strings often experience fluid leakage through connections due to mechanical issues, leading to costly damage and operational problems during drilling, production, and wellbore operations.
Innovation Solution
A pipe assembly with a collar that forms a double taper threaded connection, featuring annular lips with external and internal seal surfaces and beveled surfaces, which create a metal-to-metal seal energized under fluid pressure, preventing fluid leakage across the connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threaded connections are used in wellbore strings, then the device complexity is reduced and ease of manufacture is improved, but fluid leakage occurs due to mechanical issues under high-pressure conditions
Solution Approach 1:
The connection structure is segmented into multiple functional zones: external seal surfaces on annular lips, internal seal surfaces, beveled surfaces for pressure distribution, and dope pockets for lubrication. This segmentation allows each zone to perform its specific sealing function independently, improving overall reliability without requiring a completely new complex design
Solution Approach 2:
The collar acts as an intermediary component between two pipes, providing both external and internal sealing surfaces. The dope pockets serve as intermediaries that retain lubricating material between thread crests, mediating the interaction between threaded surfaces to prevent galling and enhance sealability under high pressure
2Reliability
If threaded connections are designed with multiple seal surfaces and dope pockets, then sealability under high pressure is improved, but manufacturing precision requirements increase
Solution Approach 1:
Dope pockets are designed to retain lubricating material beforehand, cushioning the interaction between threaded surfaces during assembly and under pressure. This pre-positioned lubrication compensates for minor manufacturing variations in thread tolerances, allowing effective sealing without extremely tight precision requirements
Solution Approach 2:
The connection design utilizes pressure-activated sealing where fluid pressure causes deformation of the annular lips against external seal surfaces, and energizes the seal at beveled surfaces. This pressure-dependent sealing mechanism adapts to manufacturing variations, maintaining reliability without requiring ultra-precise dimensional control
3Reliability
If metal-to-metal seals are energized under fluid pressure, then leak-tightness is improved, but the risk of galling between threaded surfaces increases
Solution Approach 1:
Dope pockets positioned between thread crests serve as intermediaries that retain and distribute lubricating material along the threaded engagement. This lubrication intermediary prevents direct metal-to-metal contact and galling during assembly and under high-pressure operation, while the separate seal surfaces maintain leak-tightness
Solution Approach 2:
The connection structure segments sealing functions from threading functions. External seal surfaces on annular lips handle the sealing function, while dope pockets between thread crests handle the lubrication function. This segmentation allows optimization of each function independently, achieving leak-tightness without compromising galling resistance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The pipe assembly significantly enhances connection sealability during high-pressure operations, reducing the risk of seal failure and the need for costly workover operations, while also increasing the galling resistance and torsional capacity of the connection.
Implementation Method 1
a metal-to-metal seal that is energized under fluid pressure at the first and second internal annular beveled surfaces
Implementation Method 2
contact, with the coupling connection formed, the first external seal surface and the second external seal surface to form a metal-to-metal seal
Data Source
AI summary
A pipe assembly includes a first pipe, a second pipe, and a collar. The first pipe has a first external thread and a first annular lip that has a first external seal surface and a first internal annular beveled surface. The second pipe has a second external thread and a second annular lip with a second external seal surface and a second internal annular beveled surface. The collar is threadedly coupled to the first pipe and the second pipe to form a coupling connection. The collar has a first internal thread threadedly coupled to the first external thread and a second internal thread threadedly coupled to the second internal thread. The collar has a bore that contacts the first external seal surface and the second external seal surface to form a metal-to-metal seal that is energized under fluid pressure at the first and second internal annular beveled surfaces.