| 摘要 |
<p>A directional drilling apparatus and method in which the drill bit is coupled to the lower end of a drill string through a universal joint (20, 40) which allows the bit to pivot relative to the string axis. The bit is contra-nutated in an orbit of fixed radius and at a rate equal to string rotation but in the opposite direction. This speed-controlled and phase-controlled bit nutation keeps the bit heading off-axis in a fixed direction. The invention enables directional drilling while the drill string rotates normally.</p> |
