| 摘要 |
<p>A down-hole drilling assembly (12,16) and control system (120) therefor, for directional drilling including a bent housing of a bottom hole assembly (18), utilising a gearbox (102) to derive a higher speed (about 600 r.p.m.) rotational drive (104) from the drill string (10) to drive a drilling bit (20) via an electromagnetic clutch (110,112) controlled by the control system (120) such that the clutch balances reaction torque when the orientation angle of the bent housing is correct.</p> |
