Coiled tubing is a kind of continuous synthetic tubing which can be wound on the drum by the manufacturer according to the required length. The outer diameter of the tubing is usually 0.75′-5′, and the yield strength of the steel used ranges from 55000Psi to 120000Psi. At present, the longest tubing that can be wound by a single drum in commercial use is more than 9000 meters.
The main components of coiled tubing equipment are drum, injection head, operating room, power unit and well control device. The drum is the storage and transmission of coiled tubing, the injection head is the power supply for starting and descending coiled tubing, the operating room is the equipment operator to monitor and control coiled tubing here, the power unit is the hydraulic power source required for operating coiled tubing equipment, and the well control device is the wellhead safety device for coiled tubing under pressure operation.
The well control device is another key part of coiled tubing operation. Typical coiled tubing well control devices include BOP and BOP box. All these devices must take into account their pressure level and suitable temperature range when operating in the field. Blowout preventive box is equipped with sealing elements, which are used to isolate the pressure system in the well. It is usually installed between BOP and injection head. There are two kinds of sealing: dynamic sealing and static sealing. The blowout preventive box is designed as a side-type device to facilitate the replacement of the sealing elements of the coiled tubing in the well.
The coiled tubing operation can fix the tubing string in the well, protect the production tubing, complete some operations which can not be carried out by conventional methods, and replace some conventional operations, with higher efficiency and quality of operation. It is not only simple, time-saving, safe and reliable but also save costs. The coiled tubing has a wide range of uses.
Coiled tubing technology has been widely used in workover, well completion, drilling, logging and so on. Especially from the shale gas development project in 2014, coiled tubing fracturing has been more widely used.