System and method for defining permissible borehole curvature

1. A method for defining a permissible borehole curvature, comprising:

determining curvature characteristics of at least one of a downhole assembly and a borehole;

calculating, by a processor of a computer, an envelope of permissible borehole curvatures from a predetermined location in the borehole based on the curvature characteristics, a direction of the borehole at the predetermined location in the borehole, and a turning angle of the borehole relative to the direction of the borehole at the predetermined location; and

automatically controlling the downhole assembly in real time based on the calculated envelope of permissible borehole curvatures.

2. The method of claim 1 , further comprising:

generating a representation of the envelope of permissible borehole curvatures on a display element of the computer.

3. The method of claim 2 , wherein the representation of the envelope of permissible borehole curvatures includes a plurality of concentric shapes, each representing a degree of borehole curvature.

4. The method of claim 2 , wherein the representation of the envelope of permissible borehole curvatures includes a plurality of concentric shapes, each representing a bending load of the downhole assembly.

5. The method of claim 1 , wherein the envelope of permissible borehole curvatures is calculated based on the curvature characteristics of the borehole.

6. The method of claim 1 , wherein the envelope of permissible borehole curvatures is calculated based on the curvature characteristics of the downhole assembly.

7. The method of claim 6 , wherein determining the curvature characteristics includes calculating drag on a drill string.

8. The method of claim 7 , wherein calculating the drag on the drill string includes calculating the drag on the drill string of a subsequent operation in the borehole.

9. The method of claim 1 , further comprising:

selecting a borehole curvature to be drilled by a drilling tool based on the calculated envelope of permissible borehole curvatures.

10. The method of claim 9 , further comprising:

drilling, by a drilling tool, the borehole having the selected borehole curvature.

11. The method of claim 1 , further comprising:

drilling, by a drilling tool, the borehole;

during drilling, monitoring a curvature of the borehole; and

generating an alert based on the curvature exceeding the envelope of permissible borehole curvatures.

12. The method of claim 11 , further comprising:

taking corrective action to adjust a path of the drilling tool based on the alert.

13. The method of claim 1 , wherein calculating the envelope of permissible borehole curvatures includes taking into account a criticality of different curvature characteristics, such that less critical curvature characteristics have less of an effect on the envelope of permissible borehole curvatures than more critical curvature characteristics.

14. A borehole system, comprising:

memory configured to store curvature characteristics of at least one of a downhole assembly and a borehole configured to be inserted in a borehole;

a processor configured to calculate an envelope of permissible borehole curvatures downhole from a predetermined location in the borehole based on the curvature characteristics, a direction of the borehole at the predetermined location in the borehole, and a turning angle of the borehole relative to the direction at the predetermined location, and to automatically control a downhole assembly in real time based on the calculated envelope of permissible borehole curvatures.

15. The borehole system of claim 14 , further comprising:

a display apparatus configured to receive display data from the processor,

wherein the processor is configured to generate the display data to generate a graphical representation on the display apparatus in polar coordinates of one of a bending load at a bending load sensor of the downhole assembly and the turning angle of the borehole relative to the direction at the predetermined location.

16. The borehole system of claim 14 , further comprising:

a display apparatus configured to receive display data from the processor,

wherein the processor is configured to generate the display data to generate a graphical representation of the envelope of permissible borehole curvatures.

17. The borehole system of claim 16 , wherein the processor is configured to generate the display data to generate on the display apparatus a plurality of envelopes of permissible borehole curvatures corresponding to a plurality of inclination angles of the borehole.

18. The borehole system of claim 16 , wherein the processor is configured to generate display data for displaying on the display apparatus a graphical representation of a plurality of envelopes of permissible borehole curvatures corresponding to a plurality of different curvature characteristics.

19. The borehole system of claim 14 , the processor is configured to calculate the envelope of permissible borehole curvatures downhole based on the curvature characteristics of the borehole.

20. The borehole system of claim 14 , the processor is configured to calculate the envelope of permissible borehole curvatures downhole based on the curvature characteristics of the downhole assembly.

21. The borehole system of claim 14 , wherein the display data includes an indication of a criticality of the different curvature characteristics relative to each other.

22. The borehole system of claim 14 , wherein the envelope of permissible borehole curvatures is based on a determination of a level of criticality of one or more components of the downhole assembly.

23. A borehole system, comprising:

a downhole assembly located in a borehole;

a borehole analysis computer configured to generate an envelope of permissible borehole curvatures downhole from a predetermined location in the borehole based on curvature characteristics of at least one of the downhole assembly, a subsequent downhole assembly, and a borehole, and further based on a direction of the borehole at the predetermined location in the borehole and a turning angle of the borehole relative to the direction at the predetermined location, and to automatically control a downhole assembly in real time based on the calculated envelope of permissible borehole curvatures.

24. The borehole system of claim 23 , wherein the downhole assembly includes a drilling assembly at a downhole end of the downhole assembly, and

the borehole analysis computer is configured to control the drilling assembly to drill the borehole to have a curvature within the envelope of permissible curvatures.

25. The borehole system of claim 23 , wherein the borehole analysis computer includes a user interface to receive a user selection of at least one of a borehole curvature and a curvature direction to be drilled by the drilling assembly based on a display of a graphical representation of the envelope of permissible borehole curvatures.