Directional drilling system for hard rock

摘要

A bottom hole assembly having a bent housing (4), and a reciprocating hammer (2) driving a bit (1) for forming a borehole in rock. A motor (14) operating through a gear reduction device (13) rotates the reciprocating hammer (2) and thus the bit (1). The drill bit (1) can thus bore a directional hole in the hard rock without rotating the drill string. The rotary drive motion of the motor (14) can be coupled to the reciprocating hammer (2) through shock absorber (10) and flexible couplings (9). The bent housing (4) is supported in the borehole during directional drilling by a frontal thrust pad stabilizer (18) and a rear stabilizer (19).