Construction Company of Jixi Mining Group adopting short digging and building combined work can fully make the ability of mechanization collecation equipment,extend new technology of umbellar borer holing and deep hole blasting and sinking by double center rotating grab,continuously breach 100 m in 2005 and accumulate experience in rapid construction in big diameter and deep vertical well.

At the same time , hole enlargement is a disadvantage of underbalanced drilling, it has a greater adverse impact on Cementing and completion of the well .