Coiled oil tubing initially gained a foothold in the market as a cost-effective wellbore cleanup tool. The economic income of workover and completion operations accounts for more than 75% of the total income of coiled oil tubing operations, and the application range of coiled oil tubing in various oil and gas fields in the world continues to expand. The advantages and application value of coiled oil tubings, such as under-balanced operation under pressure, fast and efficient operation, low damage to the formation, low cost (from the simplification of the process), etc., are the last 30 years after the birth of coiled oil tubing. It was not until the 1990s that people became aware of it. Since then, coiled oil tubing has been widely used in oil and gas field workover, drilling, well completion, well logging, and other operations, playing an increasingly important role in oil and gas field exploration and development.
After the 1990s, coiled oil tubing fracturing technology and coiled oil tubing drilling technology have developed rapidly in terms of technology and practical application. The introduction and utilization of coiled oil tubing operation technology in my country began in the 1970s. In 1977, my country introduced the coiled oil tubing operation machine produced by other companies. In Sichuan Oilfield, coiled oil tubing began to be used for small-scale acidification of gas wells, nitrogen injection and residual acid removal, and gas lift. Some simple operations such as downdraft, sand washing, paraffin removal, drilling, grinding, etc. have been applied in hundreds of wells and have achieved remarkable results. After accumulating preliminary experience, they have been popularized and applied in various oilfields.
According to incomplete statistics, there are about 30 imported coiled oil tubing units in China, mainly distributed in oil fields such as Sichuan, Daqing, Changqing, Shengli, North China, Central Plains, Jilin, Xinjiang, Liaohe, Tuha, Dagang, Henan, and Karamay. Since the introduction of coiled oil tubing in Sichuan, Liaohe, and North China, the accumulative number of operating wells has exceeded 1,000. Since the introduction of coiled oil tubing equipment in Daqing Oilfield in 1985, various downhole operations such as workover have been carried out in more than 100 wells, mainly for gas lift, wax removal, well washing, sand washing, cement extrusion, and cement drilling. Plug and so on. Since the introduction of coiled oil tubing machines in Turpan-Hami Oilfield in 1993, the number of operating wells has reached 40 to 60 wells, and the well depth for logging with coiled oil tubing has reached 4300m.
Generally speaking, domestic coiled oil tubing machines are mainly used in the following aspects: sand flushing, well drilling, bridge plugging, gas lift, liquid nitrogen injection, wax removal, liquid drainage, acid squeezing, and coordination testing. Sand washing and plugging, gas lift drainage, and wax removal are more frequently used, accounting for more than 95%. Coiled oil tubing operations are generally welcomed in my country's oilfields.
