Detecting wellpath tortuosity variability and controlling wellbore operations

1. A method for determining well path tortuosity comprising:

determining a tortuosity of a borehole segment;

determining a tortuosity of a casing associated with the borehole segment, wherein the tortuosity of the casing is determined based, at least in part, on the tortuosity of the borehole segment and a path conformity characteristic of the casing; and

generating a tortuosity variation factor based on a value of the tortuosity of the casing relative to a value of the tortuosity of the borehole segment.

2. The method of claim 1 , further comprising determining a friction factor for a wellpath corresponding to the borehole segment based, at least in part, on the determined tortuosity of the casing.

3. The method of claim 1 , wherein said determining a tortuosity of the casing includes calculating a position of a casing tubular within the borehole segment using a stiff-string model that models the casing within the borehole segment including modeling flexure of the casing based on a contour of the borehole segment and a flexure property of the casing.

4. The method of claim 3 , wherein said determining a tortuosity of the borehole segment includes determining an inclination angle within the borehole segment, and wherein the stiff-string model applies the determined inclination angle.

5. The method of claim 3 , wherein the path conformity characteristic includes at least one of a bending stiffness of the casing tubular and a torsion stiffness of the casing tubular, and wherein the stiff-string model applies at least one of the bending stiffness of the casing tubular and the torsion stiffness of the casing tubular.

6. The method of claim 3 , wherein the path conformity characteristic includes at least one of an elastic deformation property of the casing tubular and a plastic deformation property of the casing tubular, and wherein the stiff-string model applies at least one of the elastic deformation property of the casing tubular and the plastic deformation property of the casing tubular.

7. The method of claim 3 , wherein said determining a tortuosity of the borehole segment includes determining a curvature and a torsion of the borehole segment, and wherein the stiff-string model applies the determined curvature and torsion.

8. The method of claim 1 , wherein said generating a tortuosity variation factor includes:

comparing a value of the tortuosity of the casing and a value of the tortuosity of the borehole segment to generate a tortuosity variation value;

determining an increasing or decreasing wellpath tortuosity based, at least in part, on the tortuosity variation value; and

adjusting a downhole operation in response to determining an increasing wellpath tortuosity.

9. The method of claim 8 , wherein said adjusting the downhole operation in response to determining an increasing wellpath tortuosity includes:

determining whether the tortuosity variation value exceeds a threshold value; and

adjusting the downhole operation in response to determining that the tortuosity variation value exceeds the threshold value.

10. The method of claim 9 , wherein the downhole operation comprises a drilling steering operation, said adjusting the downhole operation comprising:

adjusting a borehole trajectory in response to determining an increasing wellpath tortuosity; and

modifying a drill string steering operation parameter based, at least in part, on the adjusted borehole trajectory.

11. The method of claim 9 , wherein the downhole operation comprises a casing installation operation, said adjusting the downhole operation comprising adjusting installation of casing tubulars within the borehole segment in response to determining an increasing wellpath tortuosity.

12. The method of claim 9 , wherein said comparing the value of the tortuosity of the casing and the value of the tortuosity of the borehole segment includes:

determining a ratio between the tortuosity of the casing and the tortuosity of the borehole segment; and

determining an increasing or decreasing wellpath tortuosity based, at least in part, on the determined ratio.

13. An apparatus comprising:

a processor; and

a machine-readable medium having program code executable by the processor to cause the apparatus to,

determine a tortuosity of a borehole segment;

determine a tortuosity of a casing associated with the borehole segment, wherein the tortuosity of the casing is determined based, at least in part, on the tortuosity of the borehole segment and a path conformity characteristic of the casing; and

generate a tortuosity variation factor based on a value of the tortuosity of the casing relative to a value of the tortuosity of the borehole segment.

14. The apparatus of claim 13 , wherein the program code includes program code to determine a friction factor for a wellpath corresponding to the borehole segment based, at least in part, on the determined tortuosity of the casing.

15. The apparatus of claim 13 , wherein said determining a tortuosity of the casing includes calculating a position of a casing tubular within the borehole segment using a stiff-string model that models the casing within the borehole segment including modeling flexure of the casing based on a contour of the borehole segment and a flexure property of the casing.

16. The apparatus of claim 15 , wherein said determining a tortuosity of the borehole segment includes determining an inclination angle within the borehole segment, and wherein the stiff-string model applies the determined inclination angle.

17. The apparatus of claim 15 , wherein the path conformity characteristic includes at least one of a bending stiffness of the casing tubular and a torsion stiffness of the casing tubular, and wherein the stiff-string model applies at least one of the bending stiffness of the casing tubular and the torsion stiffness of the casing tubular.

18. The apparatus of claim 15 , wherein the path conformity characteristic includes at least one of an elastic deformation property of the casing tubular and a plastic deformation property of the casing tubular, and wherein the stiff-string model applies at least one of the elastic deformation property of the casing tubular and the plastic deformation property of the casing tubular.

19. The apparatus of claim 15 , wherein said determining a tortuosity of the borehole segment includes determining a curvature and a torsion of the borehole segment, and wherein the stiff-string model applies the determined curvature and torsion.

20. The apparatus of claim 13 , wherein said generating a tortuosity variation factor includes:

comparing a value of the tortuosity of the casing and a value of the tortuosity of the borehole segment to generate a tortuosity variation value;

determining an increasing or decreasing wellpath tortuosity based, at least in part, on the tortuosity variation value; and

adjusting a downhole operation in response to determining an increasing wellpath tortuosity.

21. The apparatus of claim 20 , wherein said adjusting the downhole operation in response to determining an increasing wellpath tortuosity includes:

determining whether the tortuosity variation value exceeds a threshold value; and

adjusting the downhole operation in response to determining that the tortuosity variation value exceeds the threshold value.

22. The apparatus of claim 21 , wherein the downhole operation comprises a drilling steering operation, said adjusting the downhole operation comprising:

adjusting a borehole trajectory in response to determining an increasing wellpath tortuosity; and

modifying a drill string steering operation parameter based, at least in part, on the adjusted borehole trajectory.

23. The apparatus of claim 21 , wherein the downhole operation comprises a casing installation operation, said adjusting the downhole operation comprising adjusting installation of casing tubulars within the borehole segment in response to determining an increasing wellpath tortuosity.

24. The apparatus of claim 21 , wherein said comparing the value of the tortuosity of the casing and the value of the tortuosity of the borehole segment includes:

determining a ratio between the tortuosity of the casing and the tortuosity of the borehole segment; and

determining an increasing or decreasing wellpath tortuosity based, at least in part, on the determined ratio.