VDF-Graphite Pipe Sheath for Acid Gas Permeation Resistance
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Solution Overview
Problem
Offshore pipelines used for hydrocarbon extraction face challenges with acid gas permeation, leading to corrosion of metallic layers, and existing polymeric compositions with improved mechanical properties are costly and heavy due to the use of sour steel grades, which reduces their service life.
Innovation Solution
A polymeric composition comprising a vinylidene fluoride (VDF) polymer and selected graphite particles with specific particle size and BET specific surface ranges, which reduces acid gas permeation and maintains mechanical properties, allowing for the use of lighter and less expensive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sour steel grades are used in pressure armour layers and tensile armour layers to prevent corrosion from CO2 and H2S permeation, then corrosion resistance is improved, but cost and weight increase significantly
Solution Approach 1:
A polymeric internal sealing sheath comprising a VDF polymer and graphite particles is introduced as an intermediary barrier between the hydrocarbon stream and the metallic armour layers. This sealing sheath mediates the permeation process by providing a low-permeability barrier to CO2 and H2S, preventing these acid gases from reaching the metal layers and causing corrosion, thereby eliminating the need for expensive sour steel grades while maintaining corrosion protection
Solution Approach 2:
The polymeric internal sealing sheath is formulated as a composite material combining VDF polymer with graphite particles (0.1-10 wt%). This composite structure leverages the chemical resistance and low permeability of VDF polymer along with the barrier properties of graphite particles to create a highly effective anti-permeation barrier that protects against sour gas corrosion without requiring heavy sour steel grades
2Ease of operation
If polymeric internal sealing sheath is used to seal the pipe and prevent material migration, then flexibility is improved, but permeation resistance to acid gases deteriorates
Solution Approach 1:
The polymeric internal sealing sheath is formulated as a composite material combining VDF polymer with graphite particles (0.1-10 wt%). This composite structure leverages the chemical resistance and low permeability of VDF polymer along with the barrier properties of graphite particles to create a highly effective anti-permeation barrier that protects against sour gas corrosion without requiring heavy sour steel grades
Solution Approach 2:
The permeability parameters of the polymeric internal sealing sheath are modified by incorporating graphite particles with specific surface area characteristics (BET specific surface area of 0.5-5.0 m²/g). This parameter change in the composite structure significantly reduces CO2 and H2S permeation while preserving the flexibility and sealing properties of the VDF polymer matrix
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 effectively reduces CO2 and H2S permeation, enhances mechanical properties like elongation at break and yield strain, and extends the service life of pipes in harsh environments, making it suitable for repeated mechanical deformation and harsh conditions.
Implementation Method 1
carbon dioxide (CO2) and hydrogen sulphide (H2S) contained in the hydrocarbons permeate through the polymeric internal sealing sheath
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 50µm, 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.