Analysis on Borehole Diameter Shortening and Drilfing Tool Jamming Accident in Yilan Coalfield

Abstract:

According to the borehole diameter shortening and drilling tool jamming accident in Yilan, the basic reason was thought to be rapidly - thickening mud cake on the wall of borehole in crack development in some rock stratum with high permeability and absorbency, but not to be rock expanding. Concrete measures for the accident prevention were put forward.