On the basis of research for alloy W and many experiment in well site, we select a new type of alloy W, and make the structure of mill - tool better, get a set of high efficient mill - tool, they are flat - base milling bit, concave - base milling bit, cone mill bit, tube mill bit and multiple cone mill bit.

The milling bit rotates during the bit drilling cement plug and the milling head cuts the edge of the plug to form cement column.

For removal and change of casing in oil layer section, the cementing quality can not be ensured,the oil layer protection technique is not perfect,the mill efficiency is low,and the air bleeder treatment technique is not qualified.

Risk analysis and measurements optimization for two casing milling modes of permanent packer in deep deviated well;

8mm casing was analyzed, the measures including washovering and fishing were put forward, the trouble was successfully relea sed.