CFRP in sea oil fields has become an important application and research direction. Oil exploration and extraction have gradually extended from land to sea, and from shallow to deep waters to meet market demands. The land and sea environments are vastly different, increasing production costs.
Land-based extraction equipment is mostly steel, but using steel for deep-sea extraction faces many technical challenges, such as seawater corrosion. Engineers use carbon fiber reinforced polymers (CFRP) to solve these problems.
Advantages of CFRP in Sea Oil Fields
| Lightweight: Carbon fiber density is about 1.76-1.80g/cm³; the resulting composite material density is 1.50-1.60g/cm³, while steel is about 7.87g/cm³. CFRP is much lighter than steel.
| High specific strength and modulus: CFRP’s specific strength is about 7-12 times that of steel, and its particular modulus is about 3-5 times higher. Therefore, CFRP can manufacture various light, strong, and rigid products.
| High fatigue strength: CFRP has high fatigue strength, is significantly better than steel, and has a longer service life. This is especially important for sucker rods’ reciprocating motion, where the imbalance between external seawater pressure and internal pressure can cause material fatigue and fatigue fracture. Using CFRP sucker rods can solve this problem.
| Corrosion resistance: CFRP is highly resistant to acids and alkalis, various environmental corrosion, and doesn’t rust. It has a much longer service life in seawater compared to steel parts.
| Excellent thermal properties: CFRP has a low thermal expansion coefficient, with an axial thermal expansion coefficient of about -0.1×10-6/℃ and a perpendicular thermal expansion coefficient of about +35×10-6/℃. It doesn’t become brittle in cold environments and maintains dimensional stability in hot environments. CFRP’s heat resistance largely depends on the matrix resin. Carbon fiber itself can be used long-term in air below 300℃.
The Application of CFRP in Shallow-sea Oil Fields
CFRP applications in offshore oil fields mainly include Tension Leg Platforms (TLP), Mobile Offshore Drilling Units (MODU), and Floating Production Systems (FPS). Specific component applications include:
| Risers: These extend from the seabed to the drilling platform deck, mostly using 266mm diameter tubular structures. Oil and gas flow from the seabed to storage tanks through internal piping. For offshore oil fields, steel risers can be used but have a short lifespan; CFRP risers can greatly extend the service life. Steel pipes typically last 2-3 years, while CFRP risers can last 20-25 years. The former is easily corroded by seawater, leading to leaks and requiring repairs or replacement.
| Buoyancy modules: Carbon fiber is used in manufacturing reinforced small-diameter hollow spheres for composite foam bodies. These buoyancy modules can be used in 1200m deep water. They show many advantages for oil and gas extraction in 1500-3000m deep water, with increasing usage becoming a new growth point for the carbon fiber market. For example, CFRP-made buoyancy lift components can provide 8.6t of buoyancy, lifting anchors from 390m underwater.
| Flexible pipes and umbilicals: CFRP is used to manufacture flexible pipes and umbilicals, using pultrusion to create concentric circular shapes with reinforced metal spiral layers (circumferential reinforcement layers) on polymer resin pipes, forming two relatively thin layers. The outer layer maintains strength, while the inner layer provides corrosion resistance. These transport various fluids under varying working conditions.
| Tanks and pressure vessels: CFRP-made tanks and pressure vessels are notably lightweight, with increasingly mature manufacturing technology. CFRP geological exploration samplers made by winding can withstand high temperatures (149℃) and high pressure in wells over 3000m deep. Additionally, aluminum-lined CFRP pressure vessels and gas filters used in refineries also have good application prospects. Although CFRP pressure vessels perform excellently, cost issues hinder their widespread use in subsea oil fields. With improved carbon fiber quality, increased production, and reduced costs, this situation is improving.
The Application of CFRP in Deep-sea Oil Fields
As offshore oil fields move to deep-sea locations, usage is increasing daily. Deep-sea oil field development will be one of the major potential markets for carbon fiber applications.
| Tethers: For deep-sea oil fields, tethers anchoring platforms to the seabed and risers connecting wellheads to platforms are important components. If made of steel, their weight requires larger floating platform sizes, increasing investment. Using CFRP reduces both self-weight and associated weight effects significantly. For example, a 1500m deep-sea operation platform would require about 6500t of steel cables, but only 1000t of CFRP cables. Moreover, the former can only reach depths of about 1500m, while the latter can be used in 3000m deep-sea oil fields.
| Tension-Leg Platforms: CFRP applications in deep-sea (900-3000m) oil fields are receiving much attention, with hopes to replace steel products with high-strength, high-modulus, and lightweight CFRP to reduce the self-weight of tension leg platforms and the load on tension leg support structures. For example, elevators used in 1200m deep-sea oil fields in the Gulf of Mexico use hybrid composite materials for lifting lightweight pipes. Compared to steel pipes, they reduce weight by 45kg/m, saving 54t over 1200m, significantly reducing investment costs.
| Sucker rods: Sucker rods are one of the core components of oil extraction systems, and their performance directly affects extraction efficiency and costs. Traditional steel sucker rods in deep-sea oil extraction often lead to increased energy consumption and maintenance costs due to their heavy weight and susceptibility to corrosion. The emergence of carbon fiber sucker rods has effectively solved these problems. They are lightweight, significantly reducing suspended point loads and energy consumption, and highly corrosion-resistant, extending service life and reducing replacement frequency.
CFRP Provider: Tengye
At Tengye, we’re thrilled to be early participants in your new projects. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects.
Image Source: Cortlandcompany & Mdpi & Offshore-technology & Rockwestcomposites & Researchgate & Sciencedirect & Quora
