CT drilling has a number of undisputable advantages, which provided for its rapid development. In the first place, this is an opportunity of underbalanced drilling of the whole well or some certain sections of the borehole.

 

At the same time the peculiarities of CT drilling hydraulics should be taken into account: low hole clearance, low ascending flow velocity in the annular space; high loss for flow resistance in CT; more limited, as compared to traditional drilling, possibilities for achieving an effective mode of bottomhole rock breaking due to low load on rock-breaking tool, low torque and high rotation speed of the downhole motor; limited drilling mud injection in CT and surface equipment.

Besides, it is necessary to point to limitations imposed on CT drilling by geological factors: its safe use is possible only in consolidated rock sections (dolomites, limestone, cemented sandstone, etc).