HPHT Sealing Ring Compression for Stable Contact Stress
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Solution Overview
Problem
Chevron seals used in oil and gas operations face performance issues due to elevated pressures and temperatures, leading to volume reduction and compromised sealing integrity, as the contact stress between the seal and concentrically disposed members falls below fluid pressure.
Innovation Solution
A sealing apparatus comprising a sealing ring with frusto-conical surfaces, a compression ring, and back-up rings that expand radially to exert contact stress exceeding fluid pressure, ensuring effective sealing in high-pressure high-temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional chevron seals are used under HPHT conditions, then the seal structure remains simple and design is straightforward, but the contact stress falls below fluid pressure causing seal failure
Solution Approach 1:
The seal is divided into multiple chevron elements (typically 3-5 V-shaped segments) arranged concentrically, where each element independently contributes to the contact stress. This segmentation allows the seal to maintain reliability under HPHT conditions while managing structural complexity through modular design
Solution Approach 2:
The seal combines elastomeric material with a reinforcing filler (such as carbon black or silica) to create a composite material that maintains higher contact stress under HPHT conditions. The composite structure provides both the flexibility needed for sealing and the strength required to resist crushing at elevated temperatures and pressures
2Strength
If elastomeric material volume is reduced under hydrostatic loading, then the seal cross-section decreases, but this leads to insufficient contact stress and seal compromise
Solution Approach 1:
The seal design changes the physical parameters of the elastomeric material by incorporating fillers and adjusting the compound formulation to increase bulk modulus and reduce compressibility. This allows the seal to maintain its volume and contact stress under hydrostatic loading, preventing the cross-section reduction that would lead to seal failure
Solution Approach 2:
The chevron elements are designed with specific curvature radii and V-angle geometries that optimize the distribution of contact stress. The curved surfaces allow the seal to conform to the concentric members while maintaining adequate contact stress, compensating for any volume reduction under pressure
3Adaptability or versatility
If chevron seals are subjected to elevated temperatures and pressures, then the bulk modulus becomes temperature dependent, but this causes volume crush and cross-section reduction
Solution Approach 1:
The elastomeric composite is formulated with heat-resistant fillers and stabilizers that maintain the material's bulk modulus and volume stability across a wide temperature range. This composite structure allows the seal to adapt to HPHT conditions while resisting the temperature-dependent volume crush that would otherwise occur
Solution Approach 2:
The seal design incorporates regions with different material properties or geometries to address local stress concentrations. The chevron elements are positioned and dimensioned to provide enhanced support in areas most susceptible to temperature-induced volume changes, maintaining overall volume stability under HPHT conditions
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 sealing apparatus maintains contact stress above fluid pressure, preventing seal failure and extrusion, even under extreme conditions, outperforming traditional chevron seals.
Implementation Method 1
the interior and exterior surfaces thereof expand radially to exert contact stress on each of the concentrically disposed members
Implementation Method 2
a compression ring, and back-up rings that expand radially to exert contact stress exceeding fluid pressure
Data Source
AI summary
A sealing apparatus and related method for sealing an annular space between concentrically disposed members. In an exemplary embodiment, the method includes providing a sealing ring within the annular space, the sealing ring defining oppositely inclined interior and exterior surfaces each having a generally frusto-conical shape and defining opposing first and second edges, a nose adjoining the respective first edges of the interior and exterior surfaces, and a first convex surface adjoining the respective second edges of the interior and exterior surfaces opposite the nose; and forming a seal against a fluid pressure in the annular space, comprising depressing the first convex surface of the sealing ring so that the interior and exterior surfaces thereof expand radially to exert contact stress on each of the concentrically disposed members.