OCTG tubing is a pipeline which transports crude oil and nature gas from hydrocarbon reservoir to the surface after the completion of drilling. It’s one of the main products of OCTG and it can withstand the pressure generated in the process of mining. While Coiled tubing technology is the current international advanced operation technology. Coiled tubing is made of low carbon alloy steel pipe and has good flexibility. A roll of coiled tubing is thousands of meters long, which can be used to replace conventional tubing for a lot of work. Coiled tubing operation equipment has the characteristics of pressure operation and continuous up and down.
In 1962, the United States California oil companies and Bowen Oil Tools Company jointly developed the first coiled tubing light workover device. The coiled tubing diameter was 33.4 mm, which mainly used for sand flushing operation of oil and gas wells in the Gulf of Mexico. 30 years after the birth of the coiled tubing, its value was really understood, to the 1990s, coiled tubing technology has been the development by leaps and bounds. Coiled tubing device has been known as the "universal operating machine", widely used in the oil and gas well workover, drilling, completion, well logging throughout the whole process of the exploitation of oil and gas.
The development of the number of coiled tubing equipment is as follows: 1962, the first coiled tubing equipment was born; in the mid-1970s, approximately more than 200; in 1993, about 561; at the beginning of 2001, about 850; at the beginning of 2004, about 1050 units, mainly distributed in North America, South America and Europe; At the beginning of 2011, about 1881, China has 61.
Coiled tubing is a new type of oil pipe which can up to several kilometers and can be repeatedly bent to realize multiple plastic deformation. The core technology for the manufacture of this particular tubing is:
Due to the harsh environment service, coiled tubing mechanical properties and corrosion resistance have high requirements. The chemical composition of the material to be optimized design must reduce the content of inclusions and S, P and other harmful elements.
Since dislocation multiplication and other factors can cause hardening and Bauschinger effect, the conversion rules of the pipe body strength should be controlled.
By tube heat treatment to achieve optimum control of properties, especially high strength and high ductility and low residual stress.
For low carbon micro alloyed steel, HFW welding technology is adopted at present. The optimum welding parameters (such as current, voltage, frequency, welding speed, welding speed, forming angle, extrusion, etc.) should be studied.
In order to realize the continuous production of HFW welded pipe, it is necessary to lengthen the plate. The current methods of TIG, MAG and plasma welding are mainly used in the plate butt welding, and the method of friction stir welding is being studied.
Coiled tubing may cause local damage in the use process, which must be cut off or defect, and by welding to connect the pipe. Traditional docking methods generally use the manual TIG welding, but welding quality is difficult to control. At present, automatic welding technology has been adopted.
Such as CVR technology. Using the same specifications of the coiled tube to heat 940°C by induction, then hot rolling, on the one hand to achieve seamless or HFW weld optimization, on the other hand to change wall thickness or diameter. In addition, there are special stainless steel coiled tube excitation light welding technologies and so on.
