Semi-submersible vessel and operating method

Patent metadata

Field	Value
Publication number	US-9352809-B2
Application number	US-201113808778-A
Country	US
Kind code	B2
Filing date	Jul 7, 2011
Priority date	Jul 8, 2010
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

A semi-submersible vessel for offshore operations is suitable to be operated in icy waters and in ice-free waters. The vessel includes an operating deck, at least one lower hull, an essentially vertical connecting structure between the at least one lower hull and the operating deck, and a ballast system. The connecting structure has a water portion and an icebreaking portion arranged on top of each other. The vessel is configured to have an icebreaking draft for icy waters, and a water draft for ice-free waters in which the waterline is substantially level with the water portion. The icebreaking portion has a closed tapered contour. During the water draft, the collective area of the water portion of the connecting structure intersecting the water surface is smaller than the collective area of the icebreaking portion of the connecting structure intersecting the water surface during the icebreaking draft.

First claim

The invention claimed is:

1. A semi-submersible vessel for offshore operations which is suitable to be operated in icy waters and in ice-free waters, said vessel comprising:
an operating deck to accommodate equipment;
at least one lower hull;
an essentially vertical connecting structure between the at least one lower hull and the operating deck; and
a ballast system to ballast or deballast the vessel,
wherein the connecting structure has a water portion and an icebreaking portion being arranged on top of each other,
wherein the water portion of the connecting structure is formed by multiple columns,
wherein the vessel is configured to have an icebreaking draft for icy waters in which the water- or iceline is substantially level with the icebreaking portion, and a water draft for ice-free waters in which the waterline is substantially level with the multiple columns of the water portion,
wherein the icebreaking portion has a single closed tapered contour, and
wherein during the water draft the collective area of the water portion of the connecting structure intersecting the water surface is smaller than the collective area of the icebreaking portion of the connecting structure intersecting the water surface during the icebreaking draft.

2. The semi-submersible vessel according to claim 1 , wherein the icebreaking portion is located between the water portion and the operating deck.

3. The semi-submersible vessel according to claim 2 , wherein the icebreaking portion is essentially circular.

4. The semi-submersible vessel according to claim 1 , wherein the water portion is located between the icebreaking portion and the at least one lower hull.

5. The semi-submersible vessel according to claim 1 , wherein the icebreaking portion is essentially circular.

6. The semi-submersible vessel according to claim 1 , wherein the vessel comprises at least one lower deck below the operating deck which at least one lower deck is integrated in the icebreaking portion.

7. The semi-submersible vessel according to claim 1 , comprising a subsea drilling installation and a moonpool through the one or more decks through which drilling operations can be performed.

8. The semi-submersible vessel according to claim 7 , further comprising a protective wall extending downwards from the vessel in a central space around the moonpool as protection of the drilling equipment extending through the moonpool against ice that has entered the central space.

9. The semi-submersible vessel according to claim 8 , wherein the protective wall extends to below the water draft.

10. The semi-submersible vessel according to claim 1 , wherein the columns extend from the lower hull obliquely inwards towards a centre of the vessel.

11. The semi-submersible vessel according to claim 1 , wherein the water portion has one or more openings provided with a net or mesh structure to prevent ice from entering a central space in the water portion via the one or more openings.

12. The semi-submersible vessel according to claim 11 , wherein the net or mesh structure is configured to be used as heating and/or cooling element.

13. The semi-submersible vessel according to claim 1 , wherein additional openings or through holes extend through the operating deck up until a central space below the operating deck, so that air is able to flow between the central space and the surroundings of the vessel via the openings or through holes.

14. The semi-submersible vessel according to claim 13 , wherein the openings or through holes are provided with respective valves to allow the controlled opening or closing of the openings or through holes.

15. The semi-submersible vessel according to claim 1 , wherein the area of the connecting structure being intersected by the water surface during the water draft in water draft conditions comprises multiple separate cross-sections corresponding to the respective multiple columns, wherein the multiple separate cross-sections are placed in a circular manner to define a circumscribed circle and in inscribed circle together forming a ring shape, wherein the collective area of the multiple separate cross-sections being intersected by the water surface in water draft is between 50% and 70% of the total area of the ring shape.

16. The semi-submersible vessel according to claim 15 , wherein the collective area of the multiple separate cross-sections being intersected by the water surface in water draft is 60% of the total area of the ring shape.

17. The semi-submersible vessel according to claim 15 , wherein the water portion comprises eight columns.

18. The semi-submersible vessel according to claim 1 , wherein the lower hull is ring-shaped with an opening, and wherein the opening in the lower hull and/or openings in between the multiple columns are adjustable during operation.

19. The semi-submersible vessel according to claim 1 , wherein the connecting structure further includes an intermediate portion arranged between the water portion and the icebreaking portion, the intermediate portion having a closed vertically extending contour.

20. A method for operating the semi-submersible vessel according to claim 1 , wherein the ballast system is operated to change the draft of the semi-submersible vessel to the water draft when the semi-submersible vessel is in ice-free waters, and wherein the ballast system is operated to change the draft of the semi-submersible vessel to the icebreaking draft when the semi-submersible vessel is in icy waters.

Assignees

• Roodenburg Joop
• Brinkman Marc Louis
• Bereznitski Alexei
• Itrec Bv

Inventors

• Roodenburg Joop
• Brinkman Marc Louis
• Bereznitski Alexei

Classifications

• E21B19/143

  specially adapted for underwater drilling · CPC title

• B63B35/4413 Primary

  Floating drilling platforms, e.g. carrying water-oil separating devices · CPC title

• B63B1/04

  with single hull · CPC title

• B63B35/08

  Ice-breakers {or other vessels or floating structures for operation in ice-infested waters; Ice-breakers, or other vessels or floating structures having equipment specially adapted therefor} · CPC title

• B63B2241/12

  annular or toroidal · CPC title