Floating offshore structure containing apertures

• US 6,230,645 B1
• Filed: 10/13/1999
• Issued: 05/15/2001
• Est. Priority Date: 09/03/1998
• Status: Expired due to Fees

• Current Assignee: Texaco Development Corporation (Chevron Corp.), Texaco Incorporated (Chevron Corp.)
• Original Assignee: Texaco Incorporated (Chevron Corp.)
• Inventors: Chow, Fred I.
• Primary Examiner(s): AVILA, STEPHEN P
• Application Number:
  US09/417,689
• Time in Patent Office: 580 Days
• Field of Search: 114/121, 114/122, 114/125, 114/264, 114/265, 114/266, 114/124
• US Class Current: 114/264
• CPC Class Codes: B63B 2035/442 Spar-type semi-submersible structures, i.e. shaped as single slender, e.g. substantially cylindrical or trussed vertical bodies
• 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

A floating offshore structure for use in oil or gas drilling or production operations, having apertures in its sides in order to reduce the movement of the structure as a result of undersea currents is disclosed herein. The structure contains a production platform extending above the ocean'"'"'s surface, a series of buoyancy tanks providing the structure with the ability to float, apertures, surrounded by coamings, located around the structure such that ocean currents are allowed to flow laterally through the center of the structure and such that oil and gas can dissipate from the center of the structure if a rupture occurs, a fluid retention tank and ballast in order to lower the center of gravity of the structure and make it more stable, and a centerwell running through the longitudinal center of the structure which allows one or more risers to run from the ocean floor to the operating platform. The structure can then be moored to the sea floor through the use of a catenary or other mooring system.

Claims

1. An offshore floating structure comprising:

an outer wall, said wall defining a centerwell through the longitudinal central portion of said structure;

an operating platform, said platform being attachable to said wall;

buoyancy tanks connected to the inner sides of said structure, said buoyancy tanks being sufficient to maintain the operating platform a predetermined distance above the surface of a body of water after said operating platform has been attached to said wall;

a first portion of said wall having a plurality of apertures, the total surface area of said apertures being less than or equal to the one third of the total surface area of said first portion of said wall, said first portion of said wall further including a coaming surrounding one or more of said apertures, each of said coamings protruding outwardly from said wall;

a second portion of said wall including a fluid retention tank connected to the inner sides of said wall, said tanks being characterized by the ability to retain variable volumes of fluid;

a ballast located beneath said fluid retention tank; and

a means for releasably mooring said structure.

6. The offshore floating structure of claim 1 or 5, each said coaming completely surrounding the area of each said aperture.

2. An offshore floating structure comprising:

an outer wall, said wall defining a centerwell through the longitudinal central portion of said structure;

buoyancy tanks connected to said wall, said buoyancy tanks sufficient to maintain the buoyancy of said structure such that a portion of said wall is maintained a predetermined distance above the surface of a body of water;

a plurality of apertures in the sides of a first portion of said wall, the first portion of said wall containing no solid inner wall;

a means for lowering the center of gravity of said structure; and

a means of mooring said structure to the floor of a body of water.

3. The offshore floating structure of claim 2, further comprising an operating platform being attachable to said structure, and able to be maintained a predetermined distance above the surface of a body of water.

4. The offshore floating structure of claim 2, said buoyancy tanks being located inside of said outer wall.

5. The offshore floating structure of claim 2, further comprising a coaming surrounding one or more of said apertures.

7. The offshore floating structure of claim 2, said means for lowering the center of gravity of said structure comprising a fluid retention tank.

8. The offshore floating structure of claim 7, said fluid retention tank being connected to the inside of said outer wall, and defining a centerwell running longitudinally through a central portion of said fluid retention tank.

9. The offshore floating structure of claim 2, said means for lowering the center of gravity of said structure comprising a ballast located at the bottom of said structure.

10. The offshore floating structure of claim 2, said means for lowering the center of gravity of said structure comprising a fluid retention tank and a ballast, both of said fluid retention tank and ballast defining a centerwell through a longitudinally central portion of said fluid retention tank and ballast.

11. The offshore floating structure of claim 2, said means of mooring said structure to the floor of a body of water comprising a catenary mooring system.

12. The offshore floating structure of claim 2, said means of mooring said structure to the floor of a body of water comprising a plurality of high tension mooring wires.

13. An offshore floating structure comprising:

an outer wall, said wall defining a centerwell through the longitudinal central portion of said structure;

buoyancy tanks connected to said wall, said buoyancy tanks sufficient to maintain the buoyancy of said structure such that a portion of said wall is maintained a predetermined distance above the surface of a body of water;

a plurality of apertures in the sides of a first portion of said wall, with a coaming completely surrounding one or more of said apertures;

a means for lowering the center of gravity of said structure; and

a means of mooring said structure to the floor of a body of water.