Directional drilling control

1. A method of using a quill to steer a hydraulic motor when elongating a wellbore in a direction having a horizontal component, wherein the quill and the hydraulic motor are coupled to opposing ends of a drill string, the method comprising:

monitoring an actual toolface orientation of a tool driven by the hydraulic motor by monitoring a plurality of drilling operation parameters each indicative of a difference between the actual toolface orientation and a desired toolface orientation; and

adjusting a position of the quill by an amount that is dependent upon each of the plurality of the monitored drilling operation parameters.

2. The method of claim 1 wherein the amount of quill position adjustment is sufficient to compensate for the difference between the actual and desired toolface orientations.

3. The method of claim 1 wherein adjusting the quill position comprises adjusting a rotational position of the quill relative to the wellbore.

4. The method of claim 1 wherein adjusting the quill position comprises adjusting a vertical position of the quill relative to the wellbore.

5. The method of claim 1 wherein adjusting the quill position comprises:

adjusting a rotational position of the quill relative to the wellbore; and

adjusting a vertical position of the quill relative to the wellbore.

6. The method of claim 1 wherein monitoring the drilling operation parameter comprises monitoring data received from a toolface orientation sensor, and wherein the amount of quill position adjustment is dependent upon the toolface orientation sensor data.

7. The method of claim 6 wherein the toolface sensor comprises at least one of a gravity toolface sensor and a magnetic toolface sensor.

8. The method of claim 1 wherein one of the plurality of the drilling operation parameters comprises a weight applied to the tool (WOB).

9. The method of claim 1 wherein one of the plurality of the drilling operation parameters comprises a depth of the tool within the wellbore.

10. The method of claim 1 wherein one of the plurality of the drilling operation parameters comprises a rate of penetration of the tool into the wellbore (ROP).

11. The method of claim 1 wherein one of the plurality of the drilling operation parameters comprises a hydraulic pressure differential across the hydraulic motor (ΔP).

12. The method of claim 11 wherein the ΔP is a corrected ΔP based on monitored pressure of fluid existing in an annulus defined between the wellbore and the drill string.

13. The method of claim 1 wherein monitoring the plurality of drilling operation parameters indicative of the difference between the actual and desired toolface orientations comprises:

monitoring data received from a toolface orientation sensor;

monitoring a weight applied to the tool (WOB);

monitoring a depth of the tool within the wellbore;

monitoring a rate of penetration of the tool into the wellbore (ROP); and

monitoring a hydraulic pressure differential across the hydraulic motor (ΔP).

14. The method of claim 13 wherein adjusting the quill position comprises adjusting the quill position by an amount that is dependent upon the monitored toolface orientation sensor data, the monitored WOB, the monitored depth of the tool within the wellbore, the monitored ROP, and the monitored ΔP.

15. The method of claim 14 wherein monitoring the plurality of drilling operation parameters and adjusting the quill position are performed simultaneously with operating the hydraulic motor.

16. The method of claim 1 wherein adjusting the quill position comprises causing a drawworks to adjust a weight applied to the tool (WOB) by an amount dependent upon the monitored drilling operation parameter.

17. A method of using a quill to steer a hydraulic motor when elongating a wellbore in a direction having a horizontal component, wherein the quill and the hydraulic motor are coupled to opposing ends of a drill string, the method comprising:

monitoring an actual toolface orientation of a tool driven by the hydraulic motor by monitoring a drilling operation parameter indicative of a difference between the actual toolface orientation and a desired toolface orientation; and

adjusting a position of the quill by an amount that is dependent upon the monitored drilling operation parameter, wherein adjusting the quill position comprises adjusting a neutral rotational position of the quill, and wherein the method further comprises oscillating the quill by rotating the quill through a predetermined angle past the neutral position in clockwise and counterclockwise directions.

18. A system for using a quill to steer a hydraulic motor when elongating a wellbore in a direction having a horizontal component, wherein the quill and the hydraulic motor are coupled to opposing ends of a drill string, the system comprising:

means for monitoring an actual toolface orientation of a tool driven by the hydraulic motor, including means for monitoring a plurality of drilling operation parameters indicative of a difference between the actual toolface orientation and a desired toolface orientation; and

means for adjusting a position of the quill by an amount that is dependent upon the plurality of monitored drilling operation parameters.

19. An apparatus for using a quill to steer a hydraulic motor when elongating a wellbore in a direction having a horizontal component, wherein the quill and the hydraulic motor are coupled to opposing ends of a drill string, the apparatus comprising:

at least one sensor configured to detect a plurality of drilling operation parameters indicative of a difference between an actual toolface orientation of a tool driven by the hydraulic motor and a desired toolface orientation of the tool; and

a toolface controller configured to adjust the actual toolface orientation by generating a quill drive control signal directing a quill drive to adjust a rotational position of the quill based on the plurality of monitored drilling operation parameters.

20. The method of claim 1 , wherein the adjusting comprises integrating information from the plurality of monitored drilling operation parameters.