At present, oil exploitation is dominated by land and supplemented by the sea. With the gradual decrease of land oil, the exploitation of offshore oil fields has attracted great attention from all countries. The facilities for oil extraction on land use steel as the main material, but the environment for mining offshore oilfields is very different from that on land. The weight and corrosion of steel are no longer suitable for the marine environment. Advanced composite materials based on carbon fiber composite materials are popular. Obviously, the free breaking length of steel wire is the shortest, while carbon fiber and aramid show excellent self-weight drapability. This means that when steel parts are used in deep-sea oil fields, a large amount of buoyancy foam is needed to provide buoyancy, while carbon fiber composite parts can save this part of the cost. In addition, steel parts are easily corroded by seawater and have a short service life, about 3 to 5 years; while CFRP is resistant to seawater corrosion and has a long service life, about 20 to 25 years.
Carbon fiber composite materials can be used to manufacture components of tension leg platforms (TLP), drilling units (MODU) and floating production systems (FPS). Specific application examples are as follows.
(1) Production well pipe. The production well pipe is a component that extends from the seabed to the deck of the drilling platform. Most of the pipes are 10.5in (266mm) in diameter. Through the supporting device installed therein, the oil and gas flow from the seabed to the storage tank (tank). In the elevator used in the 1220m deep-sea oil field in the Gulf of Mexico, when the elevator's elevator pipe adopts carbon fiber and glass fiber hybrid composite material, when compared with stainless steel pipe, the effective weight per meter is 45kg lighter, and the weight of 1200m can be reduced by 54t, which greatly reduces The cost of the buoyancy body required.
(2) Pipes, storage tanks and decks. Glass fiber reinforced plastic (GFRP) can be used to make seawater pipelines, fire-proof water pipes, low-pressure water delivery buoyancy water pipes, storage tanks and other structures. However, GFRP is an insulator, which may cause static fire or explosion due to fluid flow friction. If carbon black or chopped carbon fiber is added to the matrix resin, the occurrence of static electricity can be prevented. If carbon fiber and glass fiber hybrid reinforcement (CF/GFRP) is used, the development of static electricity accidents can be effectively prevented, and production costs can be reduced.
(3) Ropes (tethers). The rope is used to tie the TLP to the seabed. The deepest steel rope is used in the 4000 (1ft=0.3048m) deep TLP in the Gulf of Mexico; if the TLP exceeds 500 (1500m) deep, the cost of the steel rope becomes very large and needs to be replaced by carbon fiber composite ropes (comptethers). At the same time, comptethers can be coiled on a shaft with a diameter of 4.4m, which is very convenient for storage, transportation and use, which can reduce engineering costs.
(4) Flexible pipes and connecting pipes. Flexible pipes and connecting pipes used in the deep sea are one of the largest potential markets for carbon fiber. The flexible tube is an extruded concentric circular tube, and a metal spiral layer (reinforced in the circumferential direction) is applied to the top of the resin polymer tube. It forms two relatively thin layers, the surface layer maintains strength, and the inner layer has corrosion resistance such as alkali resistance. These two levels are not joined together, but remain flexible. It can be used to transport various fluids under large changes.
Umbilicals (umbilicals) are used to bind hydraulic control pipelines, methanol transmission pipelines, thermoplastic resin hoses, electrical cables, etc. that extend from the platform to the seabed. It plays an important role in controlling the production and maintenance under the sea.
(5) Secondary structural materials for offshore platforms. The secondary structural parts of offshore platforms include grille frames, escalators, auxiliary platforms, cable trays and cable trays. FRP grille frame has been widely used. Shell uses FRP grille frame structures in four TLPs in the Gulf of Mexico. The hybrid composite beam uses carbon fiber on its head and tail flanges.
(6) Buoyancy modules (buoyancy modules). Carbon fiber can be used in the manufacture of composite foams that reinforce small-diameter hollow spheres. This buoyancy component can be used under the sea surface of 4000t. In order to exploit the 5000~10000f deep sea petroleum and petroleum gas, the demand for this kind of buoyancy components and boxes is increasing, and a large amount of carbon fiber is needed. In addition, carbon fiber composite materials can also be used to make tanks and pressure vessels. In summary, carbon fiber composite materials are used in drilling pipes, production well pipes, flexible pipes, connecting pipes, TLP tethers and high-pressure vessels. With the opening of offshore oilfields to deep-sea oilfields, the usage is increasing day by day. Obviously, the development of deep-sea oil fields will be one of the largest potential markets for carbon fiber applications.