Floating Deep Draft Semi-Submersible Offshore Platforms and Methods for Assembling and Deploying Same

Patent metadata

Field	Value
Publication number	US-2016201285-A1
Application number	US-201514824795-A
Country	US
Kind code	A1
Filing date	Aug 12, 2015
Priority date	Jan 12, 2015
Publication date	Jul 14, 2016
Grant date	—

Abstract

A semi-submersible platform for offshore operations includes a buoyant hull including an adjustably buoyant base and a plurality of adjustably buoyant columns extending vertically from the base. In addition, the platform includes a deck moveably coupled to the columns. The deck is configured to move vertically up and down relative to the hull.

First claim

What is claimed is:

1 . A semi-submersible platform for offshore operations, the platform comprising:
a buoyant hull including an adjustably buoyant base and a plurality of adjustably buoyant columns extending vertically from the base; a deck moveably coupled to the columns of the hull, wherein the deck is configured to move vertically up and down relative to the hull.

2 . The platform of claim 1 , further comprising a plurality of jack-up assemblies moveably coupling the deck to the columns, wherein each jack-up assembly moveably couples the deck to one of the columns

3 . The platform of claim 2 , further comprising a deck sub-structure moveably coupled to the columns, wherein the deck is seated on the deck-substructure and each jack-up assembly moveably couples the deck sub-structure to one of the columns.

4 . The platform of claim 3 , wherein each jack-up assembly comprises:
a toothed rack fixably secured to the corresponding column; and a powered pinion gear coupled to the deck sub-structure, wherein the powered pinion gear mates and engages the corresponding toothed rack.

5 . The platform of claim 4 , wherein each toothed rack is oriented parallel to the corresponding column and has an upper end proximal an upper end of the corresponding column and a lower end disposed between the upper end and a lower end of the corresponding column.

6 . The platform of claim 3 , wherein each jack-up assembly comprises a hydraulic jacking system or a strand jack system.

7 . The platform of claim 1 , wherein the hull has a vertical height H h measured from a lower end of the hull to an upper end of the hull, wherein the vertical height H h is greater than 150 ft.

8 . The platform of claim 7 , wherein the deck is configured to move relative to the hull between an uppermost position and a lowermost position;
wherein the deck is disposed at a vertical height H u measured from the lower end of the hull at the uppermost position; wherein the deck is disposed at a vertical H l measured from the lower end of the hull at the lowermost position; wherein the vertical height H u is greater than 150 ft. and the vertical height H l is less than 150 ft.

9 . The platform of claim 8 , wherein the vertical height H l is less than 120 ft.

10 . The platform of claim 8 , wherein the uppermost position of the deck is vertically spaced from the lowermost position of deck by a vertical distance D d greater than 25 ft.

11 . The platform of claim 1 , wherein the deck is not buoyant and is not adjustably buoyant.

12 . The platform of claim 1 , wherein the deck is configured to move relative to the hull between an uppermost position and a lowermost position;
wherein a portion of each column extending below the lowermost position of the deck has an outer surface comprising strakes.

13 . A method comprising:
(a) floating a buoyant hull in water at a dockside location, wherein the buoyant hull has a draft less than 40 ft. at the dockside location; (b) moveably coupling a deck to the hull during (a) to form the semi-submersible offshore platform, wherein the deck is configured to move vertically relative to the hull.

14 . The method of claim 13 , further comprising:
(c) floating the semi-submersible platform from the dockside location to an operating site in the water after (b); (d) adjusting the draft of the semi-submersible hull to maintain stability during (c) or during installation at the operating site; and (e) raising the deck vertically relative to the hull at the operating site.

15 . The method of claim 14 , wherein (e) is performed simultaneous with (d).

16 . The method of claim 14 , wherein (c) comprises:
(c 1 ) floating the semi-submersible platform from the dockside location to a second location; (c 2 ) increasing the draft of the hull at the second location; and (c 3 ) floating the semi-submersible platform from the second location to the operating site after (c 2 ).

17 . The method of claim 14 , wherein (d) comprises increasing the draft of the hull to a predetermined depth of at least 150 ft.

18 . The method of claim 17 , wherein (e) comprises raising the deck to a predetermined height above the waterline.

19 . The method of claim 18 , wherein (e) comprises raising the deck between 25 ft. and 75 ft. relative to the hull.

20 . The method of 13 , wherein the hull includes an adjustably buoyant base and a plurality of columns extending vertically from the base;
wherein (b) comprises:
(b 1 ) moving the deck horizontally between a pair of adjacent columns;
(b 2 ) raising the deck with a lifting crane at the dockside location; and
(b 3 ) coupling the deck to the hull at a height less than a maximum lifting height of the lifting crane.

21 . The method of claim 20 , wherein the maximum lifting height of the lifting crane is less than 200 ft.

22 . The method of claim 13 , wherein the deck is non-buoyant.

23 . A method comprising:
(a) floating the semi-submersible platform to the operating site, wherein the platform comprises a buoyant hull and a non-buoyant deck moveably coupled to the hull, wherein the hull is disposed at a draft D during (a); (b) ballasting the hull at the operating site after (a) to increase the draft D of the hull at the operating site; and (c) raising the deck vertically relative to the hull at the operating site.

24 . The method of claim 23 , wherein (c) is performed simultaneous with (b).

25 . The method of claim 23 , wherein (b) comprises increasing the draft of the hull to a predetermined depth; and
wherein (c) comprises raising the deck to a predetermined height to set an airgap between the deck and the waterline.

26 . The method of claim 23 , wherein (c) comprises jacking the deck upward relative to the hull with a plurality of jack-up assemblies that moveably couple the deck to a plurality of vertical columns of the hull.

Assignees

• Bp Corp North America Inc

Inventors

• Murray John James

Classifications

• B63B75/00

  Building or assembling floating offshore structures, e.g. semi-submersible platforms, SPAR platforms or wind turbine platforms · CPC title

• B63B35/44

  Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices {(construction methods for floating offshore platforms B63B75/00)} · CPC title

• E02B17/06

  for immobilising, e.g. using wedges or clamping rings {(as elements of the raising or lowering means E02B17/08)} · CPC title

• B63B2035/442

  Spar-type semi-submersible structures, i.e. shaped as single slender, e.g. substantially cylindrical or trussed vertical bodies · CPC title

• B63B35/4413

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