Claims
- 1. A floating offshore platform comprising:an inner structure, including at least one riser and a support buoy, wherein said support buoy is tethered to a sea floor tether point by a tether with a tether connection connected along a longitudinal center line of said support buoy and said support buoy supports said at least one riser generally in a vertical orientation; an outer hull structure, circumferentially surrounding said support buoy and moored with respect to the sea floor independently of said inner structure; a connection mechanism disposed between said inner structure and said outer structure, wherein said connection mechanism substantially decouples heave, pitch and roll motions acting on said outer hull structure from acting on said inner structure, and said tether and tether connection allows said inner structure to incline to accommodate relative angles between said inner structure and said sea floor tether point induced by hull, surge, or sway excursions thereby minimizing riser bending at said support buoy.
- 2. The floating offshore platform of claim 1, wherein,at least one buoyant device is coupled to said at least one riser, and a slidable coupling is positioned between said at least one riser and said support buoy, whereby heaving, pitching and rolling motions acting on said outer hull structure are substantially decoupled from said riser.
- 3. The offshore platform of claim 2, wherein said buoyancy device is completely submerged when said offshore platform is in operation.
- 4. The floating offshore platform of claim 1, wherein said inner structure includes a drilling draw works mounted on said support buoy.
- 5. The floating offshore platform of claim 4, wherein said drilling draw works includes a derrick for drilling equipment.
- 6. An offshore platform comprising:an inner structure tethered to the sea floor comprising a riser structure including at least one riser arranged and designed for connection to a sea floor and a buoyant device creating tension on said riser, and a support buoy structure slidably coupled to said riser structure by a slidable coupling; an outer hull structure moored to the sea floor independently of said inner structure and which circumferentially surrounds said inner structure, and a passive, non-disconnectable connection mechanism between said outer hull structure and said support buoy structure which substantially decouples heave, pitch and roll forces which act on said outer hull structure from being transferred to said inner structure.
- 7. The offshore platform of claim 6, further comprisinga deck coupled to said outer hull structure.
- 8. The offshore platform of claim 6, whereinsaid connection mechanism includes link arms connected between said support buoy and said outer hull structure by pivot connections and spherical bushings.
- 9. The offshore platform of claim 6, whereinsaid connection mechanism includes sliding bearings.
- 10. The offshore platform of claim 6, whereinsaid slidable coupling includes a sliding shoe which is positioned between said at least one buoyant device and said support buoy structure.
- 11. The offshore platform of claim 6 wherein,said support buoy structure is tethered to said sea floor by a tether connected along a longitudinal center line of said support buoy whereby said inner structure is capable of inclining to accommodate relative angles between said inner structure and said sea floor tether point induced by hull, surge or sway excursions thereby minimizing bending of said at least one riser at said support buoy structure.
- 12. A method of decoupling motions acting on a riser structure, comprising the steps of:centering a floating inner structure which is tethered to the sea floor inside an outer hull structure, wherein said inner structure includes said riser structure, and wherein said riser structure includes at least one riser and at least one buoyant device; and providing a passive, permanent coupling between said outer hull structure and to said inner structure in a manner which decouples heave, pitch and roll motions acting on said outer hull structure from acting on said inner structure wherein, said coupling step is achieved by coupling link arms between said floating inner structure and said outer hull structure via spherical bushings and pivot connections.
- 13. The method of claim 12 further comprising the step oftethering said floating inner structure to said sea floor by connecting a tether from said sea floor to a point along a longitudinal center line of said buoyant device.
- 14. A floating offshore platform comprising,an inner structure including at least one riser and a support buoy, wherein said support buoy is tethered to a sea floor tether point and supports said at least one riser generally in a vertical condition; wherein, at least one buoyant device is coupled to said at least one riser, and a slidable coupling is positioned between said at least one riser and said support buoy, an outer hull structure which circumferentially completely surrounds said support buoy and is moored with respect to the sea floor independently of said inner structure, whereby said inner structure is substantially isolated from wave and wind forces of the sea by the outer hull structure; and a passive linking mechanism permanently connected between said inner structure and said outer structure, said linking mechanism being designed and arranged to substantially decouple heave, pitch and roll motions acting on said outer hull structure from acting on said inner structure.
- 15. The offshore platform of claim 14 whereina tether is attached at said sea floor tether point and at a point along a longitudinal center line of said support buoy to allow said inner structure to incline to accommodate relative angles between said inner structure and said sea floor tether point induced by hull, surge, or sway excursions.
- 16. The offshore platform of claim 15 wherein,said linking mechanism is a mechanical assembly including link arms connected between said support buoy and said outer hull structure.
- 17. A floating offshore platform comprising,an inner structure, including at least one riser and a support buoy, with said support buoy tethered to a sea floor tether point by a tether with a tether connection provided along a longitudinal center line of said support buoy, and with said support buoy supporting said at least one riser generally in a vertical orientation, an outer hull structure, circumferentially surrounding said support buoy and moored with respect to the sea floor independently of said inner structure, and a connection mechanism permanently connected between said inner structure and said outer structure, wherein said connection mechanism substantially decouples heave, pitch and roll motions acting on said outer hull from acting on said inner structure, and said tether connection allows said inner structure to incline to accommodate relative angles between said inner structure and said sea floor tether point induced by hull, surge or sway excursions, and a drilling rig mounted on said support buoy, whereby said drilling rig is substantially isolated from heave, pitch and roll motions of said outer structure.
- 18. The floating offshore platform of claim 17 wherein,said connection mechanism includes link arms connected between said support buoy and said outer hull structure by pivot connections and spherical bushings.
- 19. The floating offshore platform of claim 17 wherein,said outer structure includes a frustro conically shaped interior which surrounds said support buoy.
CROSS REFERENCE TO RELATED APPLICATION
This is a Continuation-in-Part Application which claims priority from U.S. patent application Ser. No. 10/017,175 filed on Dec. 7, 2001, which claims priority from U.S. Provisional Application Serial No. 60/251,938, filed on Dec. 7, 2000.
US Referenced Citations (16)
Foreign Referenced Citations (4)
Number |
Date |
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2 574 367 |
Dec 1984 |
FR |
2147549 |
May 1985 |
GB |
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GB |
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Provisional Applications (1)
|
Number |
Date |
Country |
|
60/251938 |
Dec 2000 |
US |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
10/017175 |
Dec 2001 |
US |
Child |
10/068013 |
|
US |