System and method for deflection compensation in power drive system for connection of tubulars

1. A method of connecting threaded tubular members for use in a wellbore or a riser system, comprising:

operating a power drive unit, thereby rotating a first threaded tubular member relative to a second threaded tubular member;

measuring the rotation of the first threaded tubular member; and

compensating the rotation measurement by subtracting a deflection of at least one of:

the power drive unit, and

one of the tubular members.

2. The method of claim 1 , further comprising measuring torque applied by the power drive unit.

3. The method of claim 1 , wherein the rotation measurement is compensated by subtracting the deflection of the power drive unit.

4. The method of claim 3 , further comprising:

measuring torque applied by the power drive unit; and

calculating a deflection of the power drive unit.

5. The method of claim 4 , wherein the deflection is calculated by referencing a database of torques and deflections of the power drive unit.

6. The method of claim 1 , wherein the rotation measurement is compensated by subtracting the deflection of the power drive unit and the one of the threaded members.

7. The method of claim 6 , further comprising:

measuring torque applied by the power drive unit; and

calculating a deflection of the power drive unit by referencing a database of torques and deflections of the power drive unit and the one of the tubulars.

8. The method of claim 1 , further comprising:

detecting an event during rotation of the first threaded tubular member; and

stopping rotation of the first threaded tubular member when reaching a predefined value from the detected event.

9. The method of claim 8 , wherein:

each of the two threaded members comprises a shoulder,

the event is a shoulder condition, and

the predefined value is a rotation value.

10. The method of claim 9 , wherein the shoulder condition is detected by calculating and monitoring a rate of change of torque with respect to the compensated rotation measurement.

11. The method of claim 10 , further comprising determining acceptability of the threaded connection.

12. The method of claim 1 , wherein the power drive unit is a power tongs unit.

13. The method of claim 1 , wherein the power drive unit is a top drive unit.

14. The method of claim 13 , wherein:

the top drive unit comprises a gripping member, and

the gripping member is engaged to an inner surface of the first tubular.

15. The method of claim 13 , wherein:

the top drive unit comprises a gripping member, and

the gripping member is engaged to an outer surface of the first tubular.

16. The method of claim 1 , wherein the rotation measurement is compensated by subtracting the deflection of the one of the tubular members.

17. A system for connecting threaded tubular members for use in a wellbore or a riser system, comprising:

a power drive unit operable to rotate a first threaded tubular member relative to a second threaded tubular member;

a power drive control system operably connected to the power drive unit, and comprising:

a torque detector;

a turns detector; and

a computer receiving torque measurements taken by the torque detector and rotation measurements taken by the turns detector; wherein the computer is configured to perform an operation, comprising:

operating the power drive unit, thereby rotating the first threaded tubular member relative to the second threaded tubular member; and

measuring torque applied by the power drive unit;

measuring the rotation of the first threaded tubular member; and

compensating the relative rotation measurement by subtracting a deflection of at least one of:

the power drive unit, and

one of the tubular members.

18. The system of claim 17 , wherein the rotation measurement is compensated by subtracting the deflection of the power drive unit.

19. The system of claim 18 , wherein the computer further comprises a database of torques and deflections of the power drive unit and the operation further comprises calculating the deflection of the power drive unit by referencing the database of torques and deflections of the power drive unit.

20. The system of claim 17 , wherein the rotation measurement is compensated by subtracting the deflection of the power drive unit and the one of the threaded members.

21. The system of claim 20 , wherein:

the computer further comprises a database of torques and deflections of the power drive unit and the one of the tubular members, and

the operation further comprises calculating the deflection of the power drive unit and the one of the tubular members by referencing the database of torques and deflections of the power drive unit and the one of the tubular members.

22. The system of claim 17 , wherein the power drive unit is a power tongs unit.

23. The system of claim 17 , wherein the power drive unit is a top drive unit.

24. The system of claim 23 , wherein: the top drive unit comprises a gripping member, and the gripping member is configured to engage an inner surface of the first tubular.

25. The system of claim 23 , wherein:

the top drive unit comprises a gripping member, and

the gripping member is configured to engage an outer surface of the first tubular.

26. The system of claim 17 , wherein the operation further comprises:

detecting an event during rotation of the first threaded tubular member; and

stopping rotation of the first threaded tubular member when reaching a predefined value from the detected event.

27. The system of claim 26 , wherein:

each of the two threaded members comprises a shoulder,

the event is a shoulder condition, and

the predefined value is a rotation value.

28. The system of claim 27 , wherein the operation further comprises determining acceptability of the threaded connection.

29. The system of claim 27 , wherein the shoulder condition is detected by monitoring a rate of change of torque with respect to the compensated rotation measurement.