The impactor is the key to the whole eccentricity. The selection of the impactor generally has the following principles: a. It can generate enough impact energy to make the casing follow smoothly. b. The impact energy should not be too large. Excessive impact energy will make the casing easy to break. The choice of special process in the actual drilling process, because the drilling depth is required to be deeper, the diameter of the hole is the same as that of the pipe, and the power of the rig and the impactor is not enough. Second, even if the casing can withstand, when pulling out The casing is broken due to too much friction. In order to facilitate drilling and extubation, we can use the "big pipe small tube process". The large tube sleeve can be used as follows: φ146 with φ108, φ168 with φ127, φ178 with φ146.