VDF-Graphite Pipe Sheath Composition for Sour Gas Barrier
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Solution Overview
Problem
Offshore pipelines used for hydrocarbon extraction face challenges with corrosion due to permeation of acid gases like CO2 and H2S, which reduces mechanical performance and service life, and current solutions using sour steel grades are expensive and have poor mechanical properties.
Innovation Solution
A polymeric composition comprising vinylidene fluoride (VDF) polymer and selected graphite particles with specific particle size and BET specific surface ranges, which reduces gas permeation and enhances mechanical properties, allowing for improved durability and manufacturing ease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sour steel grades are used for pressure armour layers and tensile armour layers to prevent corrosion from CO2 and H2S permeation, then corrosion resistance is improved, but manufacturing cost increases and mechanical properties deteriorate
Solution Approach 1:
The patent introduces a polymeric internal sealing sheath as an intermediary barrier between the hydrocarbon stream and the metal armour layers. This sheath, formulated with specific polymers and additives, actively reduces the permeation of CO2 and H2S gases to the metal layers, thereby protecting them from corrosion without requiring the use of expensive sour steel grades. The intermediary layer solves the corrosion problem while maintaining cost-effectiveness and mechanical properties of standard steel materials.
2Ease of operation
If polymeric internal sealing sheath is used to seal the pipe and prevent material migration, then flexibility and sealing are improved, but permeation of acid gases through the sheath causes corrosion of metal reinforcements
Solution Approach 1:
The patent modifies the chemical and physical parameters of the polymeric internal sealing sheath by incorporating specific additives and formulations. These parameter changes include adding corrosion inhibitors, permeation reducers, and optimizing polymer composition to reduce the permeation coefficient of CO2 and H2S gases. The modified sheath maintains its flexibility and sealing properties while significantly reducing gas permeation to protect the metal armour layers.
3Ease of manufacture
If graphite particles with very low or very high BET specific surface are used, then manufacturing simplicity is improved, but permeation reduction effectiveness deteriorates
Solution Approach 1:
The patent optimizes the particle size parameter of graphite additives to achieve a specific BET specific surface area range that balances manufacturing ease with permeation reduction effectiveness. By controlling the graphite particle size within defined parameters, the formulation achieves optimal gas permeation reduction while maintaining manufacturability. This parameter optimization ensures that the graphite particles effectively reduce CO2 and H2S permeation without requiring overly complex manufacturing processes.
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 composition significantly reduces sour gas permeation and maintains excellent mechanical properties, extending the service life of pipes in harsh environments while being cost-effective and easier to manufacture.
Implementation Method 1
Under operating temperatures and pressures, carbon dioxide (CO2) and hydrogen sulphide (H2S) contained in the hydrocarbons permeate through the polymeric internal sealing sheath into the tensile armour layers
Data Source
AI summary
The present invention relates to a polymeric composition comprising: one or more vinylidene fluoride (VDF) polymers, from 1 to 100 parts, preferably from 2 to 50 parts, more preferably from 2 to 30 parts, even more preferably from 3 to 20 parts by weight for 100 parts of VDF polymer of a plurality of particles of graphite, wherein said particles of graphite have an D90 particle size as measured with laser scattering of less than 50 μm, preferably from 2 to 30 μm more preferably from 2 to 20 μm, even more preferably from 2 to 10 μm and a BET specific surface of from 10 to 50 m2/g, preferably 15 to 35 m2/g. The invention also relates to tubular articles comprising the composition and to their use in oil and gas operations.