Threaded Pipe Connection With Coined Seal for Fracturing Stress
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Solution Overview
Problem
Leakage in threaded pipe connections used in high-pressure fluid applications, such as hydraulic fracturing, occurs due to extreme shear and tensile stresses, leading to damage and interruption of the fracturing process.
Innovation Solution
A leak-resistant threaded pipe connection design featuring a pin end with an annular seal bulge and a box end with a tapered seal area, where initial make-up to a recommended torque causes plastic deformation, creating a metal-to-metal seal resistant to elevated fluid pressures and stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threaded connections are used in high-pressure hydraulic fracturing applications, then the connection structure is simple and easy to manufacture, but leakage occurs under extreme shear and tensile stresses at elevated fluid pressures
Solution Approach 1:
The connection is segmented into distinct functional zones: a seal area with an annular seal bulge on the pin end and a corresponding tapered seal area in the box end, separated from the threaded connection area. This segmentation allows the seal function to be independently optimized with the annular seal bulge geometry, while the threaded portion maintains structural simplicity for easy manufacturing.
Solution Approach 2:
The annular seal bulge is pre-formed on the pin end before assembly, and during initial make-up to recommended torque, it automatically deforms plastically against the tapered seal area to create a metal-to-metal seal. This preliminary sealing action occurs before the connection is subjected to high-pressure hydraulic fracturing operations, ensuring leak resistance is established in advance.
2Reliability
If threaded connections are designed for high-pressure containment, then leakage is prevented, but the connections fail under extreme shear and tensile stresses due to pipe wash
Solution Approach 1:
The annular seal bulge provides localized enhanced sealing quality at the seal interface, while the overall connection structure maintains adequate strength through the threaded engagement between pin and box ends. The seal bulge geometry is specifically optimized for pressure containment, while the threaded portion is designed for stress resistance, allowing each zone to perform its specialized function.
3Reliability
If plastic deformation is used to create a metal-to-metal seal, then leak resistance is achieved, but the manufacturing precision requirements increase
Solution Approach 1:
The annular seal bulge is designed with specific geometric parameters (outer diameter, inner diameter, height, and taper angle) that are optimized to achieve reliable sealing through plastic deformation during assembly. The bulge geometry parameters are selected to ensure that under recommended make-up torque, the material yields plastically to form a conformal seal against the tapered seal area, balancing seal integrity with manufacturability.
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 connection effectively prevents leakage even under extreme conditions, maintaining integrity during hydraulic fracturing processes with pressures up to 15,000 psi and significant stress, as demonstrated by testing under 22,500 psi and 80,000 pounds of tensile load without fluid leakage.
Implementation Method 1
initial make-up of the leak-resistant threaded pipe connection to a recommended make-up torque causes a plastic deformation of the annular seal bulge against the tapered seal area of the box end to provide a leak-resistant metal-to-metal seal
Data Source
AI summary
A leak-resistant pipe connection has an annular seal bulge on a pin end of the connection and a tapered seal area adjacent a secondary box shoulder of a box end of the connection. The annular seal bulge is coined on contact with the tapered seal area on initial make-up of the connection which provides a metal-to-metal seal that is very resistant to high-pressure fluid leakage even after the connection is subjected to extreme shear and tensile stresses.