The coiled tubing drilling system has many advantages:
The coiled tubing system has a strong ability of controlling pressure and can drill safely and efficiently under the condition of under balance. It is suitable for deep drilling and sidetracking of existing wells. Compared with conventional drilling equipment or workover equipment, it can save 25% – 40% by using coiled tubing. It is easy to improve the automation level of drilling technology, with fewer operators. The equipment has good mobility, easy installation and disassembly, and saves time. Coiled tubing has the advantages of fast tripping and running in, fast drilling speed and short drilling cycle. The ground equipment covers a small area and is suitable for operation in areas with limited ground conditions or offshore platforms. 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.
The coiled tubing system also has its disadvantages.
The diameter of coiled tubing is small, which limits the borehole size and mud flow. The coiled tubing can’t rotate like the conventional drill pipe, and the bit’s rotating power can only come from the downhole motor, which limits its horizontal displacement. The life of coiled tubing is shorter than that of conventional drill pipe. It is impossible to complete all operations from spudding to completion by using common coiled tubing device. It is necessary to make preparations before drilling with the help of conventional drilling machine or workover rig, such as pulling out production tubing and packer, cleaning well bore, etc., and entering long section casing or liner string.