Hydraulic hammer drilling technology: Developments and capabilities

Percussion drilling technology was considered many years ago as one of the best approaches for hard rock drilling. Unfortunately, the efficiency of mo st hydraulic hammer (HH) designs was very low (8 percent maximum), so they were successfully used in shallow boreholes only. Thirty years of research and field drilling experience,vith HH application in former Soviet Union (F SU) countries led to the development of a new generation of HH designs with a proven efficiency of 40 percent. That advance achieved good operational results in hard rock at depths up to 2000 m and more. The most recent resea rch has shown that there are opportunities to increase HH efficiency up to 70 percent. This paper presents HH basic design principles and operational features. The advantages of HH technology for coiled-tubing drilling is sho wn on the basis of test results recently conducted in the USA. [S0195-0738( 00)00101-1].