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The present invention generally relates to methods for drilling a subsea wellbore and landing a casing mandrel in a subsea wellhead. In one aspect, a method of drilling a subsea wellbore with casing is provided. The method includes placing a string of casing with a drill bit at the lower end thereof

The present invention generally relates to methods for drilling a subsea wellbore and landing a casing mandrel in a subsea wellhead. In one aspect, a method of drilling a subsea wellbore with casing is provided. The method includes placing a string of casing with a drill bit at the lower end thereof in a riser system and urging the string of casing axially downward. The method further includes reducing the axial length of the string of casing to land a wellbore component in a subsea wellhead. In this manner, the wellbore is formed and lined with the string of casing in a single run. In another aspect, a method of forming and lining a subsea wellbore is provided. In yet another aspect, a method of landing a casing mandrel in a casing hanger disposed in a subsea wellhead is provided.

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1. A method of drilling a subsea wellbore with casing, comprising:placing a string of casing with a drill bit at the lower end thereof in a riser system; urging the string of casing axially downward; and reducing the axial length of the string of casing through telescopic movement between a larger d

1. A method of drilling a subsea wellbore with casing, comprising:placing a string of casing with a drill bit at the lower end thereof in a riser system; urging the string of casing axially downward; and reducing the axial length of the string of casing through telescopic movement between a larger diameter portion and a smaller diameter portion of the string of casing to land a wellbore component in a subsea wellhead. 2. The method of claim 1, further including rotating the string of casing as the string of casing is urged axially downward.3. The method of claim 2, wherein the wellbore component lands in the subsea wellhead without rotation of the wellbore component in the subsea wellhead.4. The method of claim 1, wherein the wellbore component is a casing mandrel disposed at the upper end of the string of casing.5. The method of claim 1, wherein reducing the axial length of the string of casing aligns pre-milled windows in the string of casing.6. The method of claim 5, further including positioning a diverter adjacent the pre-milled windows.7. The method of claim 6, wherein the diverter includes a flow bypass for communicating drilling fluid to the drill bit.8. The method of claim 7, further including forming a lateral wellbore by diverting a drilling assembly through the pre-milled windows.9. The method of claim 1, further including disposing a diverter in the string of casing at a predetermined location.10. The method of claim 9, wherein the diverter includes a flow bypass for communicating drilling fluid to the drill bit.11. The method of claim 10, further including diverting a drilling assembly away from an axis of the subsea wellbore to form a lateral wellbore.12. The method of claim 1, wherein reducing the axial length of the string of casing displaces an outer drilling section of a drilling shoe to allow the drilling shoe to be drilled therethrough.13. The method of claim 1, wherein reducing the axial length of the string of casing moves a sleeve in a float apparatus from a first position to a second position, thereby activating the float apparatus.14. The method of claim 1, further including applying an axial force to the string of casing.15. The method of claim 14, wherein the axial force is generated by a wireline apparatus disposed in the string of casing.16. The method of claim 1 wherein the axial length of the string of casing is reduced by a collapsible apparatus disposed above the drill bit.17. The method of claim 16, wherein the collapsible apparatus includes a locking mechanism that is constructed and arranged to deactivate upon receipt of a signal from the surface.18. The method of claim 16, wherein the collapsible apparatus includes a torque assembly for transmitting a rotational force from the string of casing to the drill bit.19. The method of claim 18, wherein the collapsible apparatus includes a locking mechanism that is constructed and arranged to fail at a predetermined axial force.20. The method of claim 19, wherein the locking mechanism comprises a shear pin.21. The method of claim 19, wherein the locking mechanism allows the collapsible apparatus to shift between a first and a second position.22. The method of claim 21, wherein the collapsible apparatus in the second position reduces the axial length of the string of casing.23. The method of claim 1, further including permitting a weight of the string of casing to compress a portion of the string of casing to reduce the axial length thereof.24. A method of forming and lining a subsea wellbore, comprising:disposing a run-in string with a casing string at the lower end thereof in a riser system, the casing string having a casing mandrel disposed at an upper end thereof and a collapsible apparatus and a drill bit disposed at a lower end thereof; rotating the casing string while urging the casing string axially downward to a predetermined depth, whereby the casing mandrel is a predetermined height above a casing hanger; and reducing the length of the casing string thereby seating the casing mandrel in the casing hanger. 25. The method of claim 24, further including applying a downward axial force to the casing string.26. The method of claim 24, wherein the length of the casing string is reduced by the collapsible apparatus disposed above the drill bit.27. The method of claim 26, wherein the collapsible apparatus includes at least one torque assembly for transmitting a rotational force from the string of casing to the drill bit.28. The method of claim 26, wherein the collapsible apparatus includes a locking mechanism that is constructed and arranged to fail at a predetermined axial force.29. The method of claim 26, wherein the locking mechanism allows the collapsible apparatus to shift between a first and a second position, whereby in the second position the collapsible apparatus reduces the length of the casing string.30. The method of claim 24, further including placing the casing string in compression.31. The method of claim 24, further including cementing the casing string in the wellbore.32. A method of landing a casing mandrel in a casing hanger disposed in a subsea wellhead, comprising:placing a casing string with the casing mandrel disposed at the upper end thereof into a riser system: drilling the casing string into the subsea wellhead to form a wellbore; positioning the casing mandrel at a predetermined height above the casing hanger; and reducing the axial length of the casing string through sliding movement between a larger diameter portion and a smaller diameter portion of the string of casing to seat the casing mandrel in the casing hanger. 33. The method of claim 32, wherein a collapsible apparatus disposed above a drill bit reduces the axial length of the casing string.34. The method of claim 33, wherein the collapsible apparatus includes a locking mechanism that is constructed and arranged to fail at a predetermined axial force.35. The method of claim 34, further including applying a downward axial force to the casing string causing the locking mechanism to fail.36. The method of claim 32, further including permitting a weight of the string of casing to compress a portion of the string of casing to reduce the axial length thereof.37. A method of drilling with casing, comprising:providing a string of casing with a drill bit at the lower end thereof; rotating the string of casing while urging the string of casing axially downward; and reducing the axial length of the string of casing through axial movement between a first portion and a second portion of the string of casing to land a wellbore component in a wellhead, wherein the second portion has a smaller diameter than the first portion. 38. A method of drilling a subsea wellbore with casing, comprising:placing a string of casing with a drill bit at the lower end thereof in a riser system; rotating the string of casing while urging the string of casing axially downward; reducing the axial length of the string of casing through movement between a first and a second section of the string of casing to land a wellbore component in a wellhead, wherein the second section has a larger diameter than the first section. 39. A method of drilling a subsea wellbore with casing, comprising:placing a string of casing with a drill bit at the lower end thereof in a riser system; urging the string of casing axially downward; and reducing the axial length of the string of casing to land a wellbore component in a subsea wellhead by permitting a weight of the string of casing to compress a portion of the string of casing to reduce the axial length thereof. 40. A method of landing a casing mandrel in a casing hanger disposed in a subsea wellhead, comprising;placing a casing string with the casing mandrel disposed at the upper end thereof into a riser system; drilling the casing string into the subsea wellhead to form a wellbore; positioning the casing mandrel at a predetermined height above the casing hanger; and reducing the axial length of the casing string to seat the casing mandrel in the casing hanger by permitting a weight of the casing string to compress a portion of the casing string to reduce the axial length thereof.