Casing drilling is the drilling method of using the casing as a drill string. It can be drilled with a drillable drill bit or a recyclable drill. After reaching the target layer, the drill bit is left in the wellbore or the bottom hole is drilled with a wire rope. When the combination is taken out and the casing string is placed in the well, the cementing operation can be performed, thereby omitting the drilling and casing process, saving the cost of the expensive drilling rig, shortening the drilling time, and reducing the construction cost.
The casing drilling wellbore always has casing support. The fluid flow velocity of the annulus is high, and there is no suction phenomenon caused by the drilling. Therefore, drilling accidents such as formation expansion, well wall collapse, wellbore keyway steps and well control failure can be reduced. Improve drilling efficiency and save drilling costs.