1. In the petrochemical industry
In recent years, for the development of the ocean, some companies have developed many high-performance FRP equipment, such as offshore oil extraction equipment (sucker rods, etc.), buoys and oil separators, etc., which take advantage of the seawater corrosion resistance, light weight and high strength of composite materials .
The development of the upper-layer lightweight structure of offshore platforms, composite material tethers, pipelines, and pontoons is one of the development directions. In the perspective of tidal energy power generation, the composite material can also exert its inherent advantages of insulation, corrosion resistance, light weight and other materials.
1.1 Carbon fiber continuous sucker rod
Domestic oil exploration has been searching for new oil fields in the western Tarim since the 1990s. The proven reserves have surpassed the Daqing oil field and become the largest oil field in the country. For ultra-deep wells, the depth of general oil wells exceeds 3,000 meters, and some oil wells are close to 5,000 meters.
Due to its own limitations, metal sucker rods cannot meet the needs of domestic oil mining. Continuous sucker rods based on carbon fiber composite materials have a huge potential market due to their excellent performance and long service life. Carbon fiber pultrusion composite The material sucker rod may be the only material that meets the actual needs of oil mining.
Rod pumping is currently the most widely used mechanical oil recovery technology at home and abroad. At present, the number of mechanical oil production wells in the world has exceeded 90% of the total number of production wells. About 80% of the mechanical oil production wells adopt the rod pumping mode. With the secondary development of old oilfields such as Shengli Oilfield and Daqing Oilfield, as well as the development of Western Tarim Oilfield and offshore oilfields, the well and mining environment is getting worse and worse, and the mining difficulty is becoming more and more difficult. Reservoirs and hard-to-use reservoirs are also gradually being developed, and this proportion will also increase.
In the rod pumping system, the sucker rod is one of the key components. Although a variety of high-strength and ultra-high-strength metal sucker rods have been developed in China and the related process technology has been continuously improved, the service life of the sucker rod has been greatly improved. However, due to the structural characteristics of the metal sucker rod itself, It has the following insurmountable weaknesses:
1) Conventional sucker rods must connect multiple sucker rods by joints and couplings to achieve downhole pumping. The deeper the lower pump, the more couplings. These couplings often experience failure behaviors such as tripping, fracture, and bending fatigue breakage of the rod under long-term working conditions of alternating, impact and vibration loads. More than 50% of the total number of sucker rod string failures;
2) Due to the multi-stage piston effect of the coupling, when the sucker rod string moves in the oil, a large additional frictional resistance will be generated;
3) Since the lifting and lowering operations of the conventional sucker rod are carried out intermittently, the operation time is longer;
4) In inclined wells, the friction between the sucker rod and the tubing is mainly concentrated on the coupling, and the maximum load is on the upstroke, which aggravates the wear between the coupling and the tubing. Add a centralizer on the rod, but this will increase the load of the pumping unit by more than 20%;
5) In deep well oil extraction (pump hanging depth 2500 ~ 5000 meters), the weight of the steel sucker rod itself has accounted for more than 60% of the lifting weight, resulting in a significant decrease in system benefits and increased costs;
6) The steel sucker rod is constrained by its own density and tensile strength, and the depth of the lower pump is limited;
In view of the above, the development of continuous sucker rods with anti-vibration loosening, impact fracture resistance, fatigue fracture resistance, wear resistance, corrosion resistance, low density, high tensile strength, and no (or less) joints has become a hot research field. In recent years, oil extraction systems using continuous sucker rods have begun to appear at home and abroad (see the table below). Carbon fiber composite material continuous sucker rods (hereinafter referred to as carbon fiber rods) oil extraction system is one of them.
With the increase of well depth, traditional metal sucker rods have become a bottleneck restricting the development and growth of this oil recovery method. According to statistics, the number of oil well accidents caused by the failure of metal sucker rods accounts for 60 to 70% of oil well accidents in China. It is urgent to research and develop new sucker rods to overcome this bottleneck. The development of ultra-high strength and corrosion-resistant continuous rods in China is the development direction of sucker rod technology. During the Tenth Five-Year Plan period, the development of supporting technologies for oil recovery engineering suitable for ultra-deep wells of 4000 to 6000 meters and offshore oil wells of 1,000 to 2000 meters has begun. The bottleneck problem, along with its promotion and application, will bring a real revolution in technical equipment to mechanical oil recovery.
The carbon fiber sucker rod is made of high-strength polypropylene-based (PAN) -based carbon fiber filament as the reinforcing material, and epoxy (or modified epoxy) resin or vinyl cool resin as the matrix material, which is prepared by the pultrusion process . Compared with the steel sucker rod, the carbon fiber sucker rod can be made into a flat strip-shaped continuous rod with a smaller cross-section. It has the following characteristics:
1) The specific gravity is light, the mass per kilometer is only 210Kg, and the steel sucker rod (in the form of 7 / 8in for example) has a mass per kilometer of 2980Kg, so it can reduce the lifting energy consumption, reduce the pumping unit model, reduce One-time investment for ground equipment. According to preliminary statistics, the energy consumption is reduced by about 50%, and the pumping unit model is reduced by 1 or 2 models;
2) Due to its light weight and high strength, it solves the problem of mechanical oil recovery in deep and ultra-deep wells;
3) No need to use conventional metal joints, more than 110 conventional metal joints can be saved per kilometer, which can reduce the piston effect and reduce the breakage / off accident rate of the joints;
4) The elastic modulus of the carbon fiber / resin composite material is about 120GPa, the elastic modulus of the ordinary metal sucker rod is 210GPa, and the elastic modulus of the steel wire flexible sucker rod is 160GPa, so the carbon fiber sucker rod can realize super-stroke oil recovery It can increase the effective stroke of the plunger of the oil pump and increase the amount of liquid produced;
5) Good corrosion resistance, suitable for wells with severe corrosion conditions;
6) The cross section of the carbon fiber sucker rod is rectangular and flat, and can be wound on a certain diameter wheel disk. It is extremely convenient to transport, simple to operate, and improves the operating efficiency;
7) The carbon fiber / resin composite material has high fatigue strength, so the carbon fiber sucker rod has a long service life. Even after 107 times of alternating action, its strength is still 90% of the original value.