Self-Energizing Annular Seal for Dynamic Wellhead Pressure
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Solution Overview
Problem
Horizontal tree systems in oil and gas wells face challenges in maintaining a consistent seal due to pressure and thermal expansion, as well as external forces, which can lead to asymmetric deflections and reduced contact pressures, compromising the seal's effectiveness.
Innovation Solution
A seal assembly with a cylindrical base and tapered rims that store elastic energy, providing an interference fit and self-energizing capability to maintain contact pressure and accommodate movement, combined with optional elastomeric elements and pressure relief ports for enhanced sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional seal assembly is used in a horizontal tree system, then the seal can initially contact the surfaces, but under pressure and thermal expansion conditions the contact pressure decreases and the seal effectiveness is compromised
Solution Approach 1:
The seal assembly incorporates a compliant body with tapered rims that can dynamically adjust their shape and position in response to changing conditions. The tapered rims are designed to deflect asymmetrically under load, allowing the seal to adapt to asymmetric deflections of the tree bore and tubing hanger while maintaining contact pressure. This dynamic compliance resolves the contradiction by enabling the seal to maintain effectiveness despite changes in contact pressure due to thermal expansion and external forces.
Solution Approach 2:
The seal assembly utilizes changes in physical parameters of the compliant body material, specifically its elasticity and compliance. The compliant body is made of a material that can undergo elastic deformation to accommodate movements and maintain seal contact. By leveraging parameter changes in the material properties (elastic modulus, compliance), the seal maintains its sealing function under varying pressure and temperature conditions without requiring rigid geometric precision.
2Adaptability or versatility
If the annular space between tree bore and tubing hanger varies due to pressure and thermal expansion, then the seal surfaces move relative to each other, but a conventional rigid seal cannot accommodate these movements while maintaining sufficient contact pressure
Solution Approach 1:
The seal assembly is designed with dynamic compliance through the compliant body and tapered rims that can deflect and adjust to relative movements between the tree bore and tubing hanger. The tapered rims are specifically designed to deflect asymmetrically, allowing the seal to accommodate asymmetric deflections while maintaining contact pressure. This dynamic adaptation resolves the contradiction between compliance and contact pressure maintenance.
Solution Approach 2:
The seal assembly employs a compliant body that acts as a flexible element capable of deforming to accommodate movements of the seal surfaces. The compliant body's flexibility allows it to conform to the changing geometry of the annular space while maintaining sufficient contact pressure through its elastic recovery. This flexible structure resolves the contradiction by providing both compliance and contact pressure maintenance simultaneously.
3Adaptability or versatility
If asymmetric geometry of the tree bore or mandrel is present, then asymmetric deflections occur under applied loads, but a symmetric conventional seal cannot accommodate these asymmetric deflections effectively
Solution Approach 1:
The seal assembly incorporates asymmetric tapered rims that are specifically designed to deflect asymmetrically under load. This asymmetric geometry matches and accommodates the asymmetric deflections caused by the asymmetric tree bore or mandrel geometry. By introducing controlled asymmetry into the seal design, it can effectively adapt to the asymmetric conditions in the wellhead system while maintaining consistent sealing performance.
Solution Approach 2:
The compliant body with tapered rims provides dynamic adaptation to asymmetric deflections. The tapered rims can deflect in different directions and by different amounts depending on the asymmetric geometry and applied loads. This dynamic asymmetric deflection capability allows the seal to maintain contact with both the tree bore and tubing hanger surfaces despite asymmetric geometric conditions, resolving the contradiction between adaptability and seal consistency.
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 seal assembly effectively maintains a reliable seal under dynamic conditions, accommodating changes in the annular space and resisting deformation, ensuring consistent contact pressures and sealing performance despite pressure and thermal variations.
Implementation Method 1
A seal assembly with a cylindrical base and tapered rims that store elastic energy, providing an interference fit and self-energizing capability to maintain contact pressure
Implementation Method 2
The seal assembly effectively maintains a reliable seal under dynamic conditions, accommodating changes in the annular space and resisting deformation
Data Source
AI summary
An annular seal assembly for forming a seal between two annular surfaces. The seal assembly includes an annular base including a sealing surface. The seal assembly also includes a pair of spaced apart rims extending from the annular base opposite the base sealing surface and in opposite directions, the rims also including sealing surfaces. The base is elastically deformable and the rims are elastically deformable relative to the base to effect a self-energized seal between the two annular surfaces.