Session: 13-03-03: General: Mechanics of Solids, Structures and Fluids III

Paper Number: 168204

High-Fidelity 3d Finite Element Modeling for Threaded Shear Plug Metal-to-Metal Sealing 

Metal-to-metal sealing is of paramount importance for preventing leaks in the high-pressure, high-temperature environment of oil and gas extraction. The threaded connection hydraulic chamber housing and the shear plug are critical components in safety valves that ensure the containment of hydraulic and gas pressure. By employing precise make-up torque, a tight contact is established at the sealing shoulder, offering a robust and dependable solution for containing high-pressure fluids in extreme conditions. However, the inherent stiffness of metal means that metal-to-metal sealing components lack the flexibility like elastomer seals, which can better align with each other under pressure. The possible relative deformation between metal-to-metal sealing components can lead to non-uniform contact pressure distribution at the sealing surface, potentially causing leaks.

 

To reduce computational costs, engineers often utilize 2D axisymmetric finite element analysis (FEA) models to assess the effectiveness of the sealing by examining the contact pressure at the sealing shoulder. The required make-up torque is restored by applying an interference fit at the contact shoulder, necessitating multiple iterations to achieve the desired make-up torque. The most significant drawback of 2D axisymmetric models is their failure to account for asymmetric geometries and loads, making them unsuitable for hydraulic systems with complex geometries, including hydraulic and gas tunnels. Consequently, 2D axisymmetric models can overlook potential leakage risks.

 

To address this issue, a high-fidelity 3D model was developed in Abaqus/Explicit. This model considers asymmetric geometries and loads, and allows for interactions with other components in the hydraulic system. By incorporating the helical structure of the threads into the sealing components, the shear plug is explicitly screwed inside the hydraulic chamber housing. The total reaction rotating moment at the threads region and contact shoulder is directly outputted, eliminating the need for multiple trial-and-error iterations to restore the required make-up torque, as is necessary with 2D methods. By employing the mass scaling technique for explicit solver, computing costs are kept to a minimum while still ensuring a quasi-static response.

 

The 3D simulation revealed a non-uniform contact pressure distribution at the sealing shoulder, attributed to the elliptical shape of the components after the application of hydraulic and gas pressure. Certain regions of the annulus sealing shoulder showed a noticeable decrease in contact pressure compared to other areas. This non-uniform contact distribution indicates potential leakage concerns, which align with the result of in-house lifecycle test of the shear plug under working hydraulic and gas pressure.

 

This investigation highlights the limitations of 2D axisymmetric models and underscores the importance of employing 3D models for accurately capturing the precise deformation behavior and non-uniform contact distribution at the metal-to-metal sealing surface of the threaded shear plug.

 

Keywords: Metal-to-metal sealing, threads connection, finite element analysis, 2D axisymmetric model, 3D modeling, non-uniform contact distribution, hydraulic systems

Presenting Author: Yuqing Zhao SLB

Presenting Author Biography: Yuqing Zhao is currently employed as a Modeling and Simulation Engineer at ETD Modeling & Simulation CPE within SLB. She earned her doctoral degree in Mechanics from Tongji University. Before joining SLB, she worked as a research scientist at Baylor University. Her primary research interests include structural analysis and damage/failure analysis of solid structures with method of finite element modeling.

Authors:

Yuqing Zhao SLB
Ben Ren SLB
Lei Xu SLB