Downhole drilling device

1. A downhole drilling device ( 1 ) comprising:

a rotating bit shaft ( 2 ) rotatable via a drill string ( 11 );

a guiding device ( 4 ) provided between said rotating bit shaft ( 2 ) and said drill string ( 11 ), said guiding device ( 4 ) being connected to and operable independently from said drill string ( 11 ), the guiding device ( 4 ) being a tubular nonrotating near bit stabilizer ( 41 ), the nonrotating near bit stabilizer ( 41 ) being radially displaceable from said drill string ( 11 ); and

a power source ( 5 ) for powering said guiding device ( 4 ), characterized in that the downhole drilling device ( 1 ) further includes:

an inductive coupler ( 6 , 6 ′) having a primary side ( 61 ) and a secondary side ( 63 ), said inductive coupler ( 6 , 6 ′) being adapted to transfer power from said power source ( 5 ), connected to the primary side ( 61 ) of said inductive coupler ( 6 , 6 ′), to said guiding device ( 4 ), connected to the secondary side ( 63 ) of said inductive coupler ( 6 , 6 ′).

2. The downhole drilling device ( 1 ) according to claim 1 , wherein the power source ( 5 ) is a downhole power source.

3. The downhole drilling device ( 1 ) according to claim 2 , wherein the power source ( 5 ) is a mud turbine generator.

4. The downhole drilling device ( 1 ) according to claim 1 , wherein the power source ( 5 ) is a remote power system.

5. The downhole drilling device ( 1 ) of claim 1 , wherein the downhole power source ( 5 ) is connected to the primary side ( 61 ) of said inductive coupler ( 6 , 6 ′) via a rectifier and a power inverter.

6. The downhole drilling device ( 1 ) of claim 1 , wherein the power source ( 5 ) is an alternating current power source directly connected to the primary side ( 61 ) of said inductive coupler ( 5 ).

7. The downhole drilling device ( 1 ) of claim 1 , wherein said guiding device includes:

a first electric actuator ( 42 ) for controlling the radial displacement of said guiding device ( 4 ) relative to said drill string ( 11 ); and

a second electric actuator ( 43 ) for controlling the direction of a radial displacement of said guiding device ( 4 ) relative to said drill string.

8. The downhole drilling device ( 1 ) of claim 1 , wherein said inductive coupler ( 6 , 6 ′) is further adapted for bi-directional data transfer.

9. The downhole drilling device ( 1 ) according to claim 8 , wherein one or more coils ( 66 b , 68 b ) for bi-directional data transfer are isolated from one or more coils ( 66 a , 68 a ) for power transfer.

10. The downhole drilling device ( 1 ) according to claim 9 , wherein said one or more coils ( 66 b , 68 b ) for bi-directional data transfer are provided without magnetic means ( 62 a , 64 a ) of coils for power transfer.

11. The downhole drilling device ( 1 ) of claim 1 , wherein said inductive coupler ( 6 , 6 ′), on the secondary side ( 63 ), includes a feedback transmit coil for coupling a signal proportional to an output voltage in a power coil on the secondary side ( 63 ) to the primary side ( 61 ).

12. The downhole drilling device ( 1 ) of claim 1 , wherein said inductive coupler includes ( 6 , 6 ′) magnetic means ( 62 a , 62 b , 64 a , 64 b ) formed with anomalies for the determination of relative position and speed of the primary and secondary sides ( 61 , 63 ).

13. The downhole drilling device ( 1 ) of claim 1 , wherein one or more coils of said inductive coupler include U-shaped magnetic means ( 62 a , 62 b , 64 a , 64 b ).

14. The downhole drilling device ( 1 ) of claim 1 , wherein at least a part of said inductive coupler ( 6 , 6 ′) device is potted in a resin-based material.

15. The downhole drilling device ( 1 ) of claim 1 , wherein a gap between the primary side ( 61 ) and the secondary side ( 63 ) of said inductive coupler is less 1 millimeter and preferably less than 0.5 millimeters.

16. The downhole drilling device ( 1 ) of claim 1 , wherein the primary side ( 61 ) and the secondary side ( 63 ) of said inductive coupler ( 6 ) are arranged in a radial configuration.

17. The downhole drilling device ( 1 ) of claim 1 wherein the primary side ( 61 ) and the secondary side ( 63 ) of said inductive coupler ( 6 ′) are arranged in an axial configuration.

18. The downhole drilling device ( 1 ) of claim 1 wherein said guiding device ( 4 ) is radially displaceable relative to said drill string ( 11 ).

19. A method for transferring power and/or data between two parts of a downhole drilling device comprising:

providing the downhole drilling device, the downhole drilling device including:

a rotating bit shaft ( 2 ) rotatable via a drill string ( 11 );

a guiding device ( 4 ) provided between said rotating bit shaft ( 2 ) and said drill string ( 11 ), said guiding device ( 4 ) being connected to and operable independently from said drill string ( 11 ), the guiding device ( 4 ) being a tubular nonrotating near bit stabilizer ( 41 ), the nonrotating near bit stabilizer ( 41 ) being radially displaceable from said drill string ( 11 ); and

a power source ( 5 ) for powering said guiding device ( 4 ), and

an inductive coupler ( 6 , 6 ′) having a primary side ( 61 ) and a secondary side ( 63 ), said inductive coupler ( 6 , 6 ′) being adapted to transfer power from said power source ( 5 ), connected to the primary side ( 61 ) of said inductive coupler ( 6 , 6 ′), to said guiding device ( 4 ), connected to the secondary side ( 63 ) of said inductive coupler ( 6 , 6 ′); and

transmitting, using the inductive coupler, the power and/or data between a rotating part and a non-rotating part of the downhole drilling device.