Offshore Buoyant Drilling, Production, Storage and Offloading Structure

• US 20110107951A1
• Filed: 10/28/2010
• Published: 05/12/2011
• Est. Priority Date: 11/08/2009
• Status: Active Grant

• Current Assignee: Jurong Shipyard Pte. Limited
• Original Assignee: SSP Offshore Inc.
• Inventors: Vandenworm, Nicolaas J.
• Granted Patent: US 8,251,003 B2
• Time in Patent Office: Days
• US Class Current: 114/125
• CPC Class Codes: B63B 1/041 with disk-shaped hull
• CPC Class Codes: B63B 2001/044 with a small waterline area compared to total displacement, e.g. of semi-submersible type
• CPC Class Codes: B63B 2035/446 for converting wind energy into electric energy
• CPC Class Codes: B63B 2039/067 effecting motion dampening by means of fixed or movable resistance bodies, e.g. by bilge keels
• CPC Class Codes: B63B 22/021 and for transferring fluids, e.g. liquids container type buoys having means to selectively release contents, not adapted for mooring a vessel B63B22/26
• CPC Class Codes: B63B 2211/06 Operation in ice-infested waters
• CPC Class Codes: B63B 2241/06 circular
• CPC Class Codes: B63B 35/44 Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices construction methods for floating offshore platforms B63B75/00
• CPC Class Codes: B63B 35/4413 Floating drilling platforms, e.g. carrying water-oil separating devices
• CPC Class Codes: B63B 39/00 Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude for amphibious vehicles B60F3/0038

Abstract

An offshore structure having a vertically symmetric hull, an upper vertical wall, an upper inwardly-tapered wall disposed below the upper vertical wall, a lower outwardly-tapered wall disposed below the upper sloped wall, and a lower vertical wall disposed below the lower sloped wall. The upper and lower sloped walls produce significant heave damping in response to heavy wave action. The addition of a heavy slurry of hematite and water ballast is added to the lower and outermost portions of the hull to lower the center of gravity below the center of buoyancy. The offshore structure provides one or more movable hawser connections that allow a tanker vessel to moor directly to the offshore structure during offloading rather than mooring to a separate buoy at some distance from the offshore storage structure. The movable hawser connection includes an arcuate rail with a movable trolley that provides a hawser connection point that allows vessel weathervaning.

Claims

1. A buoyant structure (10) for petroleum drilling, production, storage and offloading, comprising:

a hull (12) characterized by an upper cylindrical portion (12b),

an upper frustoconical portion (12c) directly connected to the bottom of said upper cylindrical portion (12b) so as to have inward-sloping walls,

a lower frustoconical portion (12d) disposed below said upper frustoconical portion (12c) and having outward-sloping walls, and

a lower cylindrical portion (12e) directly connected to the bottom of said lower frustoconical portion (12d),

wherein the bottom of said lower cylindrical portion (12e) defines a keel (12f) of said hull (12) with the top of said upper cylindrical portion (12b) defining a main deck (12a) of said hull (12),

said hull (12) defining a vertical axis (100) whereby said hull (12) is characterized by circular horizontal cross-sections at all elevations.

2. The structure (10) of claim 1 wherein:

said lower frustoconical portion (12d) is directly connected to the bottom of said upper frustoconical portion (12c), and said bottom of said upper frustoconical portion (12c) defines a hull neck diameter D₃.

3. The structure (10) of claim 1 wherein:

the height (h) of said hull (12), defined from said keel (12f) to said main deck (12a), is less than a largest diameter (D₁) of said hull.

4. The structure (10) of claim 2 wherein:

the height (h) of said hull (12), defined from said keel (12f) to said main deck (12a), is less than the smallest diameter (D₃) of said hull.

5. The structure (10) of claim 1 wherein:

said inward-sloping walls of said upper frustoconical portion (12c) of said hull (12) slope at an angle (α

) with respect to said vertical axis (100) between 10 and 15 degrees.

6. The structure (10) of claim 1 wherein:

said outward-sloping walls of said lower frustoconical portion (12d) of said hull (12) slope at an angle (γ

) with respect to said vertical axis between 55 and 65 degrees.

7. The structure (10) of claim 1 wherein:

said upper cylindrical portion (12b) defines an upper hull diameter (D₂);

said lower cylindrical portion (12e) defines a lower hull diameter (D₁);

an intersection of said upper and lower frustoconical portions (12c, 12d) defines a hull neck diameter (D₃);

said hull neck diameter (D₃) is between 75 and 90 percent of said upper hull diameter (D₂); and

said lower hull diameter (D₁) is between 115 and 130 percent of said upper hull diameter (D₂).

8. The structure (10) of claim 7 wherein:

said hull neck diameter (D₃) is between 80 and 85 percent of said upper hull diameter (D₂); and

said lower hull diameter (D₁) is between 120 and 125 percent of said upper hull diameter (D₂).

9. The structure (10) of claim 1 further comprising:

a moveable hawser connection including an arcuate rail mounted to an upper outer wall of the hull (12); and

a trolley captured by and movably disposed on said rail;

whereby said trolley defines a hard point for mooring a vessel thereto.

10. The structure (10) of claim 1 further comprising:

a central moon pool (26) formed in said hull (12) extending from said keel (12f) to said main deck (12a).

11. The structure (10) of claim 1 further comprising:

a fin (84) fixed to said lower cylindrical portion (12e) of said hull (12) near said keel (12f), said fin extending radially outwardly from said hull (12).

12. The structure (10) of claim 11 wherein:

said fin comprises at least first and second discrete fin sections intervaled about the circumference of the hull; and

said first and second discrete fin sections are spaced apart to define a gap therebetween.

13. The structure (10) of claim 1 wherein:

said structure (10) defines a center of gravity and a center of buoyancy; and

said center of gravity is located below said center of buoyancy.

14. The structure (10) of claim 1 further comprising:

one or more compartments forming a ring shape disposed in a lowermost outermost portion of said hull (12); and

ballast disposed in said one or more compartments.

15. The structure (10) of claim 1 further comprising:

a multifunctional center frame (92) connected to said keel (12f) and protruding below the elevation of said keel (12f);

whereby

said multifunctional center frame (92) is operable to act as a riser landing porch for accommodating a vertical riser (91).

16. A buoyant structure (10) for petroleum drilling, production, storage and offloading, comprising:

a hull (12) symmetric about a vertical axis (100) and having a vertical profile including

an upper vertical wall section (12b),

an upper tapered wall section (12c) having a gentle inward slope,

a lower tapered wall section (12d) having a steep outward slope, and

a lower vertical wall section (12e),

said hull including a planar horizontal keel (12f) of a lower hull diameter D₁, and a generally horizontal main deck (12a).

17. The structure (10) of claim 16 wherein:

said upper tapered wall section (12c) slopes at a first angle (α

) with respect to said vertical axis (100) between 10 and 15 degrees; and

said lower tapered wall section (12d) slopes at a second angle (γ

) with respect to said vertical axis (100) between 55 and 65 degrees.

18. The structure (10) of claim 16 wherein:

said hull (12) has a polygonal planform.

19. The structure (10) of claim 16 wherein:

said hull has a circular planform.

20. The structure (10) of claim 16 wherein:

said upper vertical wall section (12b) abuts said upper tapered wall section (12c);

said lower vertical wall section (12e) abuts said lower tapered all section (12d); and

said upper tapered wall section (12c) abuts said lower tapered wall section (12d) at a diameter (D₃).

21. The structure (10) of claim 16 wherein:

the height (h) of said hull (12), defined from said keel (12f) to said main deck (12a), is less than the largest diameter (D₁) of said hull.

22. The structure (10) of claim 16 wherein:

the height (h) of said hull (12), defined from said keel (12f) to said main deck (12a), is less than the smallest diameter (D₃) of said hull.

23. The structure (10) of claim 16 wherein:

said upper vertical wall section (12b) defines an upper hull diameter (D₂);

the bottom of said upper tapered wall section (12c) defines a hull neck diameter (D₃);

said hull neck diameter (D₃) is between 75 and 90 percent of said upper hull diameter (D₂); and

said lower hull diameter (D₁ is between 115 and 130 percent of said upper hull diameter (D₂).

24. The structure (10) of claim 23 wherein:

said hull neck diameter (D₃) is between 80 and 85 percent of said upper hull diameter (D₂); and

said lower hull diameter (D₁) is between 120 and 125 percent of said upper hull diameter (D₂).

25. The structure (10) of claim 16 wherein:

said structure (10) defines a center of gravity and a center of buoyancy; and

said center of gravity is located below said center of buoyancy.

26. The structure (10) of claim 16 further comprising:

one or more compartments forming a ring shape disposed in a lowermost outermost portion of said hull (12); and

ballast disposed in said one or more compartments.

27. A buoyant structure (10) for hydrocarbon drilling, production, storage and offloading, comprising:

a hull (12) symmetric about a vertical axis (100); and

a first moveable hawser connection (40) including a first arcuate rail (42) mounted to an upper outer wall of the hull (12) and a first trolley (46) captured by and movably disposed on said first arcuate rail (42), said first trolley (46) defining a first movable hard point (48) for mooring a vessel (T) thereto.

28. The structure of claim 27 wherein:

said first arcuate rail (42) is circular and disposed 360 degrees about said hull (12).

29. The structure of claim 27 further comprising:

a second moveable hawser connection (60) including a second arcuate rail mounted to an upper outer wall of the hull (12) opposite said first arcuate rail and a second trolley captured by and movably disposed on said second rail, said second trolley defining a second movable hard point for mooring a vessel thereto.

30. The structure of claim 29 wherein:

said first arcuate rail defines a first center point located on said vertical axis;

said second arcuate rail defines a second center point located on said vertical axis;

said first arcuate rail defines a first arc extending approximately 90 degrees about said first center point;

said second arcuate rail defines a second arc extending approximately 90 degrees about said second center point and approximately 180 degrees opposite said first arcuate rail;

whereby

each of said first and second movable hawser connections allows a vessel moored thereto to weathervane approximately 270 degrees about said structure.

31. A method for ballasting an offshore structure comprising the steps of:

forming a non-curing slurry including a heavy material, and

adding said non-curing slurry into a compartment in said structure.

32. The method of claim 31 further comprising the steps of:

combining a water with at least one from a group consisting of hematite, barite, limonite, and magnetite to form said non-curing slurry.

33. The method of claim 32 wherein:

said slurry consists of about three parts water to one part hematite.

34. A buoyant structure (10) for petrolitic drilling, production, storage and offloading, comprising:

a hull (12) symmetric about a vertical axis (100), the height (h) of said hull (12), defined from a keel (12f) to a main deck (12a) of said hull (12), being less than a largest horizontal dimension of (D₁) of said hull;

a superstructure (13) carried by said hull and disposed above said main deck (12a);

wherein

said structure (10) defines a center of gravity and a center of buoyancy; and

said center of gravity is located below said center of buoyancy.

35. The structure (10) of claim 34 wherein:

said hull (12) has a polygonal planform.

36. The structure (10) of claim 34 wherein:

said hull has a circular planform.