| 摘要 |
A method for directional drilling of a borehole in a formation, the method comprising the steps of: - rotating a drill string (16) having a central fluid passage (202) for the passage of drilling fluid and a rotatable drill bit (10) connected to an end of the drill string (16) in the borehole (3), the drill bit comprising mechanical cutting means forming a bit face (26) for extending the borehole (3) upon rotation of the drill bit, an intermediate space (32) for receiving the drilling fluid from the drill string, at least two nozzles (35, 38) for ejecting the drilling fluid, each nozzle being in fluid communication with the intermediate space (32); - pumping drilling fluid through the internal fluid passage (202) of the drill string; - the drilling fluid directly driving and rotating a first rotor section (210) arranged within the central fluid passage (202) of the drill string (16) with respect to the drill string in a first direction and at a first rotational speed (( 0211), the first rotor section being provided with a flow diverter (45) connected to a downhole end of the first rotor section (214) for diverting the drilling fluid with respect to an axis of the drill string; - the drilling fluid directly driving and rotating a second rotor section (212) with respect to the first rotor section in a second direction opposite to the first direction and at a second rotational speed (W3/2); and - controlling the second rotational speed (W3/2) of the second rotor section (212) with respect to the first rotor section to thereby control the first rotational speed (W2/1) of the first rotor section (210) with respect to the drill string. |
