Tension Leg Platform With Improved Hydrodynamic Performance

• US 20110206466A1
• Filed: 02/25/2010
• Published: 08/25/2011
• Est. Priority Date: 02/25/2010
• Status: Abandoned Application

• Current Assignee: Modec International Incorporated (Mitsui E&S Holdings Co., Ltd.)
• Original Assignee: Modec International Incorporated (Mitsui E&S Holdings Co., Ltd.)
• Inventors: Kyriakides, Andrew C., Miao, Gang, Li, Sheng-Chyi, Ling, Qi, Rawles, William S. II
• Application Number:
  US12/712,543
• Publication Number:
  US 20110206466A1
• Time in Patent Office: Days
• US Class Current: 405/223.1
• CPC Class Codes: B63B 1/107 Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH
• CPC Class Codes: B63B 2001/128 comprising underwater connectors between the hulls
• CPC Class Codes: B63B 21/502 by means of tension legs
• CPC Class Codes: B63B 35/4413 Floating drilling platforms, e.g. carrying water-oil separating devices
• CPC Class Codes: E02D 27/52 Submerged foundations , i.e. submerged in open water E02D27/12 - E02D27/24 take precedence

Abstract

A tension leg platform that is stable with a quayside-integrated deck without the use of temporary stability modules or specialized installation techniques. The hull preferably consists of four radially-oriented vertical corner columns connected with four central ring pontoon segments. The vertical columns are fixed to the outer periphery of the central pontoon. The columns are characterized by a major radial axis and a minor transverse axis. The mooring system includes tendons supported at tendon porches directly at the four column outboard lower corners, without additional radially-extending tendon support structures.

Claims

1. A tension leg platform (10) comprising:

a hull (11, 11a, 11b) including a plurality of vertical columns (12, 112), a pontoon structure (14, 114) disposed inboard of said columns and adjoined to said columns at lower ends (12a, 112a) thereof, each of said columns having a horizontal cross-sectional shape that defines a major axis A₁) that is oriented radially outward from a center point (C) of said hull;

a deck (13) supported at upper ends (12b, 112b) of said columns; and

a plurality of tendons (17) connected under tension between said columns and the seabed for maintaining said tension leg platform above a desired subsea location and substantially restraining said tension leg platform from vertical heave motions.

2. The tension leg platform (10) according to claim 1 wherein:

said columns (12, 112) and said pontoon structure (14, 114) are constructed substantially of flat plate.

3. The tension leg platform (10) according to claim 1 wherein:

each of said plurality of columns (12, 112) has a polygonal transverse cross-section.

4. The tension leg platform (10) according to claim 1 wherein:

each of said plurality of columns (12, 112) has a quadrilateral transverse cross-section.

5. The tension leg platform according to claim 4 wherein:

each of said plurality of columns (112) has a generally trapezoidal transverse cross-section defined by an inboard side wall (112d) and an outboard side wall (112e) interconnected in parallel spaced relation by two nonparallel laterally spaced side walls (112c), said outboard side wall (112e) being wider than said inboard side wall (112d), whereby said major axis (A₁) extends between said inboard and outboard side walls.

6. The tension leg platform (10) according to claim 4 wherein:

each of said plurality of columns (12) has a generally rectangular horizontal cross-section defined by an inboard side wall (12d) and an outboard side wall (12e) of substantially equal width interconnected in parallel spaced relation by two parallel laterally spaced side walls (12c) of greater width than said inboard and outboard side walls (12d, 12e), whereby said major axis (A₁) extends between said inboard and outboard side walls.

7. The tension leg platform (10) according to claim 1 wherein:

said pontoon structure (14, 114) is octagonal-shaped.

8. The tension leg platform (10) according to claim 7 wherein:

each of said columns (12, 112) is adjoined to a corner portion (14b, 114b of said pontoon structure (14, 114) by an extension member (15).

9. The tension leg platform (10) according to claim 1 wherein:

said pontoon structure (14) includes a central moonpool opening (14c) formed vertically therethrough.

10. The tension leg platform (10) according to claim 9 wherein:

said pontoon structure (14) includes four orthogonally-oriented side segments (14a) interconnected with four diagonally-oriented corner segments (14b); and

each of said side segments and corner segments (14a, 14b) are generally rectangular in transverse cross section and define horizontal axes (HC).

11. The tension leg platform (10) according to claim 9 wherein:

each of said columns (12, 112) is adjoined to one of said corner segments (14b) of said pontoon structure (14) by an extension member (15).

12. A tension leg platform (10) comprising:

a hull (11, 11a, 11b) including a pontoon structure (14, 114) having an outer periphery surrounding a central vertical axis (C), vertical columns (12, 112) each adjoined at a lower end (12a, 112a) to said pontoon structure outer periphery, said pontoon structure disposed inboard of said columns, each of said columns defining a vertical column axis (VC) located radially outward from said central vertical axis (C) a first non-zero distance (D₁) from said outer periphery of said pontoon structure;

a deck (13) supported by upper ends (12b, 112b) of said columns; and

tendons (17) under tension connected at upper ends to said columns by tendon porches (18) mounted directly to said columns (12, 112) and at lower ends to the seabed for maintaining said tension leg platform above a desired subsea location and substantially restraining said tension leg platform from vertical heave motions.

13. The tension leg platform (10) according to claim 12 wherein:

each of said columns (12, 112) has a transverse cross-sectional shape with a horizontal major axis (A₁) oriented radially outward from said central vertical axis (C).

14. The tension leg platform (10) according to claim 13 wherein:

said pontoon structure (14) includes a vertical central opening (14c) formed therethrough;

said pontoon structure (14) includes four orthogonally-oriented side segments (14a) intervaled with four diagonally-oriented corner segments (14b);

each of said side segments and corner segments (14a, 14b) have a polygonal vertical cross-section and define horizontal longitudinal axes (HC) therethrough; and

each vertical column axis (VC) of each column (12, 112) is located a second non-zero distance (D₂) radially outward from the horizontal longitudinal axis (HC) of an adjacent corner segment (14b) of said pontoon structure (14).

15. The tension leg platform (10) according to claim 13 wherein:

each of said columns (12, 112) has a polygonal transverse cross section.

16. The tension leg platform (10) according to claim 15 wherein:

each of said columns (112) has a generally trapezoidal transverse cross section formed of D an inboard side wall (112d) and a outboard side wall (112c) that is narrower than said inboard side wall, which are interconnected in parallel spaced relation by two nonparallel laterally spaced side walls (112c).

17. The tension leg platform (10) according to claim 15 wherein:

each of said columns (12) has a generally rectangular transverse cross section formed of an inboard side wall (12d) and an outboard side wall (12e) of substantially equal width interconnected in parallel spaced relation by two parallel laterally spaced side walls (12c) of greater width than said inboard and outboard side walls.

18. The tension leg platform (10) according to claim 12 wherein:

an imaginary line (S) extending between the vertical column axes (VC) of two adjacent columns (12, 112) lies outboard of said pontoon structure outer periphery.

19. The tension leg platform (10) according to claim 14 wherein:

an imaginary line (S) extending between the vertical column axes (VC) of two adjacent columns (12, 112) lies outboard of the horizontal longitudinal axis (HC) of the side segment (14a) located generally between said two adjacent columns.

20. A tension leg platform (10) comprising:

a ring pontoon structure (14) surrounding a central opening (14c) and formed by a plurality of segments (14a, 14b) which in transverse cross section define a horizontal center line (HC);

vertical columns (12, 112) each adjoined at a lower end (12a, 112a) to an outboard side of said pontoon structure (14) so that said pontoon structure is disposed inboard of said columns, each of said columns defining a central vertical longitudinal axis (VC) disposed radially outward from a platform center (C) a distance (D₂) from said horizontal axial center line (HC) so as not to intersect therewith; and

vertical mooring tendons (17) connected between said columns and the seabed.