| 摘要 |
<p>A method is provided for creating a borehole in an earth formation using a drilling assembly comprising a drill string (5) extending into the borehole, a downhole motor (6) including a housing (7) and a drive shaft (8) for rotating a drill bit (9), which drive shaft has an inclined orientation relative to a longitudinal axis of the lower part of the drill string. The motor housing is connected to the lower part of the drill string in a manner so as to allow rotation of the motor housing about said longitudinal axis. The drilling assembly further comprises an electric motor (23) for rotation of the motor housing about said longitudinal axis and relative to the drill string. The method comprises drilling a substantially straight section of said borehole by inducing said electric motor to rotate the motor housing continuously about said longitudinal axis and relative to the drill string while the downhole motor is operated to rotate the drill bit.</p> |
