External insertion cementing is typically applied into large-sized shallow well, where collapse and loss happens frequently and circulation is difficult to establish.
Technical Features:
Little error in calculation of cement volume for saving purpose.
Low flow resistance with little loss.
Less mixture of cement slurry and drilling fluid.
Shortened rig time.
Only suitable for shallow wells; generally applied into large cased holes and where circulation can not be established; sometimes, it can contribute to the upper annular cementing for wells with low flow-back so as to improve the support to the casing.
In oil/gas cemented wells with technical casing, when there is gas communication due to negative sealing effect, external insertion cementation can also be adopted as a method for annular isolating.