In the process of coiled tubing running in, due to the influence of the gravity of the string itself and the friction between the string and the well wall, the string changes from the initial approximate linear state to the curve state when it is under pressure, which is the buckling of the string.
Under the condition of under balanced pressure, coiled tubing drilling has shown great advantages, the main advantages are as follows:
The diameter of coiled tubing is increasing, the manufacturing materials are developing from carbon steel to quenched and tempered alloy steel, titanium alloy and other alloy materials and composite materials,
Many coiled tubing drilling operations can use the conventional coiled tubing equipment used in workover operations.
According to the types of drilling, there are two kinds of common coiled tubing: directional re drilling and vertical well drilling. According to the process, there are under balanced drilling, balanced drilling and over balanced drilling.
Coiled tubing has good flexibility and can drill horizontal wells with short bending radius. There are few ground equipment, low noise, less waste overflow and little impact on the environment.
Coiled tubing originated during World War II and has been used in the oil industry since the 1960s. In 1962, the first coiled tubing operation equipment in the world. In the mid-1970s, there were more than 200 sets, and in 1993, there were about 561 sets. In February 2001, there were about 850 sets.
Coiled tubing workover technology has represented the development direction of the current world workover technology, and will be widely used as a common and efficient operation technology in the world.
The development and application of coiled tubing drilling technology began in the early 1990s, and it is still in the primary stage of research and development. In 1991, the United States, Canada and France successively successfully tested and applied CT drilling technology. In recent years, the number of wells drilled with coiled tubing in the world has increased dramatically.
It is difficult to process the high quality tubing thread only by CNC lathe. It can only be realized by controlling the quality of raw materials from the source and implementing total quality control in the upsetting process of tube blank.