Method for controlling drilling directions of a drill bit by a rotary steerable drilling tool

Abstract

A rotary steerable drilling tool with an electromagnetic steering system can include a drill collar, a bit shaft, an orientation control module, a mud tube, a mud tube coupler, a universal joint, a mud sealing device, and a drill bit. The bit shaft can be mechanically coupled to the drill collar through the universal joint and the orientation control module and rotate about the universal joint. The orientation and the inclination angle of the bit shaft against the drill collar can be controlled by the orientation control module with the electromagnetic steering system. The orientation control module can include a guide track mounted on the inside wall of the drill collar, arrays of electromagnets mounted on the guide track, a positioning frame, a permanent magnet mounted on the positioning frame, a coupling tube, and at least two bearing wheels. A corresponding electromagnetic steering method is also provided.

What is claimed is: 
     
         1 . A method of controlling drilling directions of a drill bit by a rotary steerable drilling tool having a bit shaft mechanically coupled to an orientation control module including a first and a second arrays of electromagnets and an array of permanent magnets, comprising the steps of:
 a) determining a geo-stationary orientation of the drill bit;   b) determining a relative position between the permanent magnets and the electromagnets;   c) calculating the voltage to be applied to the electromagnets;   d) generating magnetic flux in the first and the second arrays of the electromagnets; and,   e) controlling the orientation of the bit shaft.