Claims
- 1. A system for riserless drilling of a subsea borehole from a platform and through a cased borehole, the system comprising:
a lightweight drill string suspending a bottomhole assembly and extending from said platform downwardly through a depth of water and into said cased borehole; a first limiter limiting the range of motion of said drill string adjacent said platform; and a second limiter limiting the range of motion of said drill string adjacent said cased borehole.
- 2. The system of claim 1 wherein said first limiter is a bellmouth.
- 3. The system of claim 2 wherein said bellmouth includes a low friction internal coating.
- 4. The system of claim 1 wherein said first limiter is a segmented bend restrictor.
- 5. The system of claim 4 wherein said segmented bend restrictor includes a flexible tube disposed therethrough.
- 6. The system of claim 4 wherein said segmented bend restrictor has rollers mounted therein.
- 7. The system of claim 1 wherein said first limiter is a sheave.
- 8. The system of claim 1 wherein said first limiter is a pivotal support means for an injector suspending the drill string.
- 9. The system of claim 1 wherein said second limiter is a bellmouth.
- 10. The system of claim 1 wherein said second limiter is a segmented bend restrictor.
- 11. The system of claim 1 further comprising an inclination measurement means for measuring the entry angle of said drill string adjacent said cased borehole.
- 12. The system of claim 1 wherein said drill string comprises composite coiled tubing.
- 13. The system of claim 1 wherein said bottomhole assembly enables drilling of a slim borehole.
- 14. The system of claim 1 wherein said bottomhole assembly further comprises a tension/compression sensor.
- 15. The system of claim 14 further comprising an injector that adjusts tension in said drill string in response to measurements made by said tension/compression sensor.
- 16. The system of claim 1 wherein said bottomhole assembly includes means for maintaining the bottomhole assembly in said cased and subsea boreholes.
- 17. The system of claim 1 wherein said first limiter comprises an extension member.
- 18. A method of drilling a subsea borehole from a platform and through a cased borehole, the method comprising:
lowering a bottomhole assembly suspended on a lightweight drill string from the platform through a depth of water; limiting the bend radius of the drill string adjacent the platform; guiding the bottomhole assembly into the cased borehole; limiting the bend radius of the drill string adjacent the cased borehole; maintaining the bottomhole assembly in the cased borehole; and drilling the subsea borehole.
- 19. The method of claim 18 further comprising:
measuring tension in the drill string; and adjusting the tension in the drill string at the platform in response to the measured tension.
- 20. The method of claim 18 wherein limiting the bend radius of the drill string adjacent the platform comprises disposing the drill string through a bellmouth.
- 21. The method of claim 18 wherein limiting the bend radius of the drill string adjacent the platform comprises disposing the drill string through a bend restrictor.
- 22. The method of claim 18 wherein limiting the bend radius of the drill string adjacent the platform comprises disposing the drill string around a sheave.
- 23. The method of claim 18 wherein limiting the bend radius of the drill string adjacent the platform comprises pivotally supporting an injector that suspends the drill string.
- 24. The method of claim 18 wherein limiting the bend radius of the drill string adjacent the cased borehole comprises disposing the drill string through a bellmouth.
- 25. The method of claim 18 wherein limiting the bend radius of the drill string adjacent the cased borehole comprises disposing the drill string through a bend restrictor.
- 26. The method of claim 18 wherein the platform is a floating platform.
- 27. The method of claim 18 wherein the lightweight drill string is composite coiled tubing.
- 28. The method of claim 18 wherein guiding the bottomhole assembly into the cased borehole comprises the use of remotely operated vehicles.
- 29. The method of claim 18 wherein drilling the subsea borehole comprises drilling a slim borehole.
- 30. The method of claim 18 further comprising maintaining the bottomhole assembly in the subsea borehole.
- 31. The method of claim 18 further comprising:
measuring an entry angle of the drill string adjacent the cased borehole; and adjusting the platform position in response to the entry angle measurement.
- 32. The method of claim 18 further comprising:
measuring an entry angle of the drill string adjacent the cased borehole; and adjusting the drill string tension in response to the entry angle measurement.
- 33. A system for drilling a subsea borehole from a platform and through a cased borehole, the system comprising:
an injector suspending a lightweight drill string; maintenance means on a lower end of said lightweight drill string; and at least one tension sensor that measures tension in said lightweight drill string; wherein said injector adjusts the tension in said lightweight drill string in response to the measured tension.
- 34. The system of claim 33 wherein said maintenance means comprises a tractor.
- 35. The system of claim 33 wherein said maintenance means comprises a weight.
- 36. The system of claim 33 wherein said injector further adjusts the weight on bit of a bottomhole assembly in response to the measured tension.
- 37. The system of claim 34 further comprising a compression sensor below said tractor that measures compression in a bottomhole assembly.
- 38. The system of claim 37 wherein said tractor further adjusts the weight on bit of the bottomhole assembly in response to the measured compression.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is related to application Ser. No. ______, filed Oct. 4, 2002 and entitled Methods and Apparatus for Open Hole Drilling, Attorney Docket No. 1391-35000, hereby incorporated herein by reference in its entirety.