Method and device for liner system

1. A method for drilling and lining a subsea well, comprising in sequence:

drilling a first bore hole section at a subsea bore site, riserlessly;

pre-positioning below a well head and within a surface casing at the subsea bore site, at least one liner with a larger external diameter than a drilling riser not yet installed;

installing the drilling riser by coupling the riser to the well head, said riser extending to the sea surface so as to connect a drilling rig to said bore site;

lowering a drill string through the riser and the at least one liner;

drilling a subsequent bore hole section with a diameter exceeding the diameter of the at least one liner, the subsequent bore hole section having a larger diameter than the at least one liner; and

installing the at least one liner into the subsequent bore hole section.

2. A method for drilling and lining a subsea well, comprising in sequence:

drilling a first bore hole section at a subsea bore site, riserlessly;

pre-positioning, below a well head and within a surface casing at the subsea bore site, at least one liner with a larger external diameter than a drilling riser not yet installed, and a drill bit below the at least one liner, said drill bit having a larger diameter than the external diameter of the at least one liner;

installing the drilling riser by coupling the riser to the well head above the bore site, said riser extending to the sea surface so as to connect a drilling rig to said bore site;

lowering a drill string through the riser and operatively coupling said drill string to said drill bit;

drilling a subsequent bore hole section having a larger diameter than the at least one liner; and

installing the at least one liner into the subsequent bore hole section.

3. A method according to claim 1 , said pre-positioning of the at least one liner comprising positioning the at least one liner within the surface casing while the surface casing is above the sea surface, and lowering the surface casing and the at least one liner into the first bore hole section as a unit.

4. A method according to claim 3 , wherein the well head is coupled to the surface casing while the surface casing is above the sea surface before lowering the unit into the first bore hole.

5. A drilling and liner system for drilling a subsea well, comprising;

a subsea well bore site;

a subsea well head;

a subsea surface casing;

a drill string;

a drill bit;

a drilling riser; and

at least one liner with a larger external diameter than the drilling riser;

the liner being pre-positioned below the well head and within the surface casing at the bore site;

the drill bit being adapted for insertion into the bore hole by means of the drill string through the riser, the well head and the at least one liner, and for drilling of a bore hole section of a diameter sufficient to receive the at least one liner.

6. A drilling and liner system for drilling a subsea well, comprising:

a subsea well bore site;

a subsea well head;

a surface casing;

a drill string;

a drill bit;

a drilling riser not yet coupled to said subsea well head; and

at least one liner with a larger external diameter than the drilling riser, said liner being pre-positioned below the well head and within the surface casing at the bore site; the drill bit having a diameter larger than the at least one liner and being pre-positioned below the at least one liner, the drill bit being adapted for operatively coupling to the lower end of the drill string for drilling of a bore hole section of a diameter sufficient to receive the at least one liner.

7. A drilling and liner system according to claim 5 , said at least one liner comprising at least two liners, wherein a first liner with a larger diameter is receiving a second liner with a smaller diameter in its interior.

8. A drilling and liner system according to claim 5 , comprising a temporary sealing between the at least one liner and the surface casing at or near the lower end of the liner.

9. A drilling and liner system according to claim 5 , wherein said at least one liner comprises an expandable liner and an expanding cone, said cone comprising a part shaped as a conical ring with a maximum outer diameter corresponding to the internal diameter of the expandable liner when expanded.

10. A drilling and liner system according to claim 5 , having an expanding cone comprising a part shaped as a conical ring with a maximum outer diameter corresponding to the internal diameter of an expandable liner hanger when expanded, and an internal diameter which is equal to or larger than the external diameter of any parts that have to pass through to the sections of the well below the cone.

11. The method according to claim 1 , said lowering a drill string through the riser and the at least one liner comprising:

lowering an expandable drill bit through the least one liner and expanding the expandable drill bit below the least one liner.

12. The method according to claim 1 , comprising:

pre-positioning at least one drill bit with a larger diameter than the external diameter of the least one liner below the least one liner.

13. The system according to claim 7 , having temporary sealing between said first liner and the surface casing at or near the lower end of the liner and between said first liner and said second liner.

14. The system according to claim 6 , said at least one liner comprising a first liner with a larger diameter receiving a second liner with a smaller diameter in its interior.

15. The system according to claim 14 , having temporary sealing between said first liner and the surface casing at or near the lower end of the liner and between said first liner and said second liner.

16. The system according to claim 6 , comprising a temporary sealing between the at least one liner and the surface casing at or near the lower end of the liner.

17. The system according to claim 6 , said at least one liner comprising an an expandable liner and an expanding cone, said cone comprising a part shaped as a conical ring with a maximum outer diameter corresponding to the internal diameter of the expandable liner when expanded.

18. The system according to claim 6 , having an expanding cone comprising a part shaped as a conical ring with a maximum outer diameter corresponding to the internal diameter of an expandable liner hanger when expanded, and an internal diameter which is equal to or larger than the external diameter of any parts that have to pass through to the sections of the well below the cone.

19. The drilling and liner system of claim 5 , said liner being pre-positioned within the surface casing.

20. The drilling and liner system of claim 6 , said liner being pre-positioned within the surface casing.