Spoolable Composite Tubing for Deepwater Pressure and Corrosion
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Solution Overview
Problem
The oil industry faces challenges with conventional steel tubing, which is heavy and limited to shallow water due to high weight and corrosion issues, while seeking lighter, corrosion-resistant, and high-strength tubing for deep ocean applications that can withstand chemical exposure and varying pressure levels.
Innovation Solution
A spoolable composite tubing design featuring an inner thermoplastic liner and a reinforcing laminate with at least two layers: one layer of vinylidene fluoride polymer without fibers and another with continuous vinylidene fluoride polymer fibers, providing enhanced strength-to-weight ratio, resistance to fatigue, and ability to handle corrosive fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If steel tubing is used for spoolable applications, then the tubing can be spooled and transported, but the weight becomes extremely high and limits use to shallow water
Solution Approach 1:
The patent applies composite materials by combining a thermoplastic inner liner with a reinforcing laminate consisting of multiple fiber layers (glass or carbon fibers) in a polymeric matrix. This composite structure achieves the necessary strength-to-weight ratio to reduce tubing weight for deep ocean applications while maintaining spoolability through controlled flexibility.
2Strength
If steel tubing is used to provide structural strength, then the tubing can withstand pressure, but corrosion resistance is poor in chemical environments
Solution Approach 1:
The composite tubing uses a thermoplastic inner liner that provides corrosion resistance to chemical environments, while the outer reinforcing laminate with glass or carbon fibers provides the necessary structural strength. This combination eliminates the corrosion issues of steel tubing while maintaining pressure withstanding capability.
Solution Approach 2:
Different layers of the tubing are assigned different functions: the inner liner specifically addresses corrosion resistance where it contacts chemicals, while the outer reinforcing laminate addresses structural strength where it bears mechanical loads. Each layer is optimized for its specific role.
3Strength
If composite tubing with thermoset matrix is used, then strength is improved, but spoolability and flexibility are reduced
Solution Approach 1:
The patent changes the material parameter from thermoset to thermoplastic polymer matrix. Thermoplastics offer greater flexibility and ductility compared to thermosets, enabling the tubing to be spooled and bent repeatedly while maintaining sufficient strength through the fiber reinforcement.
Solution Approach 2:
The tubing design incorporates dynamic flexibility through the thermoplastic matrix that allows repeated bending and spooling operations. The material can deform elastically during spooling and return to its original shape, enabling repeated operational cycles.
4Strength
If fiber reinforcement is added to composite tubing, then strength increases, but fatigue resistance during repeated spooling decreases
Solution Approach 1:
The patent uses a multi-layer composite structure with fiber reinforcement embedded in a thermoplastic matrix. The thermoplastic matrix provides ductility and fatigue resistance, allowing the fibers to be properly supported and stress distributed, preventing fiber breakage during repeated spooling and bending operations.
Solution Approach 2:
The thermoplastic matrix locally surrounds and protects the fiber reinforcement, providing a flexible medium that accommodates repeated deformation. This local flexibility at the matrix-fiber interface prevents stress concentration and fiber failure during cyclic loading.
Data Source
AI summary
Spoolable tubing suitable for use in the oil industry, and more particularly spoolable composite tubing with the ability to withstand high stress and high cracking resistance.