Abstract:By analyzing the efficiency of transmission of impact energy in down-hole hammers and its affecting factors, it has been revealed that the percussive action of down-hole hammers can greatly increase the rate of penetration in shallow well drilling, but its efficiency will be deeply decreased in very deep well drilling. Further analysis showed that there exists a reasonable mass matching of the piston to the bit for different formations. Meanwhile, in an effort to effectively transmit the impact energy from rotary-percussive drilling, it is suggested that the roller-conical bits widely used in petroleum industry and the recently developed flat-fixed PDC bits should be changed into parabolic-fixed diamond enhanced bits.

Key words: down-hole hammer; bit design; impact energy; efficiency