초록 ▼

This invention relates to a marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel (1) on the surface of the sea. The riser system comprises a submerged buoy (2), a plurality of risers suspended from the buoy (2) to the location on t

This invention relates to a marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel (1) on the surface of the sea. The riser system comprises a submerged buoy (2), a plurality of risers suspended from the buoy (2) to the location on the sea bed and a plurality of flexible conduits (8) extending from the vessel to the submerged buoy (2). Connectors (7) carried by the submerged buoy (2) connect the flexible conduits (8) to the risers (6), each connector being remotely operable to disconnect all the flexible conduits from the risera. A central tether (5) may be provided during an installation phase only, until the risers ( 6) are in place and hold the buoy (2) by their own tension. Alternatively, the tether (5) may remain in place, and tensioned to limit vertical motion of the buoy.

대표청구항 ▼

The invention claimed is: 1. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) submerged buoy, (b) a like plurality of risers each suspended from the buoy a

The invention claimed is: 1. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) submerged buoy, (b) a like plurality of risers each suspended from the buoy and extending from the buoy in mutually different directions to a respective one of the locations on the sea bed whereby differently acting directions of riser-weight-applied pull on the buoy tend to keep the buoy horizontally between the locations, the vessel floating substantially above the submerged buoy, (c) a like plurality of flexible conduits extending from the vessel to the submerged buoy, (d) a respective connector carried by the submerged buoy and connecting the lower end of the respective flexible conduit to the upper end of one of the risers; and (e) wherein the risers are each suspended from the buoy by means of a respective flexible link. 2. A marine riser system as claimed in claim 1 wherein each connector is remotely operable to disconnect all the flexible conduits from the risers. 3. A marine riser system as claimed in claim 1, wherein the vessel in use is stationed above the buoy such that the buoy is substantially directly below the center of yaw of the vessel. 4. A marine riser system as claimed in claim 1, wherein the submerged buoy is tethered substantially vertically to an anchor in the sea bed. 5. A marine riser system as claimed in claim 1, wherein the submerged buoy is held submerged by the weight of said risers without a central anchor. 6. A marine riser system as claimed in claim 1, wherein the buoy is submerged to a depth below the depth to which wave disturbances can normally penetrate. 7. A marine riser system as claimed in claim 1, wherein the sea bed locations are disposed substantially symmetrically about a central point that is substantially directly beneath the buoy. 8. A marine riser system as claimed in claim 1, wherein the suspension of the risers from the buoy is disposed to minimize the transfer of bending moment from the buoy to the risers. 9. A marine riser system as claimed in claim 6, wherein the buoy is fitted with roll motion damping means. 10. A marine riser system as claimed in claim 1, wherein each flexible link comprises a respective chain whose length is substantially less than the length of the riser suspended by that length of chain. 11. A marine riser system as claimed in claim 1, wherein at least one riser comprises steel pipe disposed in a catenary. 12. A marine riser system as claimed in claim 1, wherein at least one riser comprises a flexible pipe or hose. 13. A marine riser system as claimed in claim 1, wherein at least one riser comprises a bundle of fluid transporting conduits. 14. A marine riser system as claimed in claim 1, wherein the end of at least one riser adjacent the sea bed is disposed in a wave formation. 15. A marine riser system as claimed in claim 1, wherein the plurality of flexible conduits extending from the vessel each to a respective connector are collectively disposed in an array resembling a "Chinese lantern". 16. A method of installing a marine riser system as claimed in claim 1, the method comprising the steps of: (a) tethering the buoy to an anchor at a location which is horizontally intermediate the sea bed locations and which is vertically beneath the sea surface, (b) suspending each of the plurality of risers on the buoy to extend therefrom to a respective one of the sea bed locations, (c) providing a respective connector on the upper end of each riser, subsequently stationing the vessel to have its center of yaw substantially directly above the buoy, (d) extending an appropriate plurality of flexible conduits from the vessel each to a respective one of the connectors, and (e) connecting the flexible conduits to the respective connector. 17. A method as claimed in claim 16, characterized by the further step of subsequently removing the tether of the buoy whereby the buoy is thereafter kept stationed by tension in the risers. 18. A method as claimed in claim 16, wherein after the risers are installed, the tether of the buoy is tensioned at least to an extent that substantially eliminates vertical movement of the buoy whereby substantially to avoid positional disturbances of the riser system induced by variations of the densities of fluids carried by the risers in use of the riser system. 19. A method as claimed in claim 16, wherein the plurality of flexible conduits extended from the vessel each to a respective connector are collectively disposed in an array resembling a "Chinese lantern". 20. A method as claimed in claim 16, wherein the buoy is submerged to a depth below the depth to which substantial wave disturbances normally penetrate. 21. A method as claimed in claim 16, characterized that the sea bed locations are disposed substantially symmetrically around a central point that is substantially directly beneath the buoy. 22. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) a submerged buoy, (b) a like plurality of risers each suspended from the buoy and extending from the buoy in mutually different directions to a respective one of the locations on the sea bed whereby differently acting directions of riser-weight-applied pull on the buoy tend to keep the buoy horizontally between the locations, the vessel floating substantially above the submerged buoy, (c) a like plurality of flexible conduits extending from the vessel to the submerged buoy, (d) a respective connector carried by the submerged buoy and connecting the lower end of the respective flexible conduit to the upper end of one of the risers; and (e) wherein the vessel in use is stationed above the buoy such that the buoy is substantially directly below the center of yaw of the vessel. 23. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) a submerged buoy, (b) a like plurality of risers each suspended from the buoy and extending from the buoy in mutually different directions to a respective one of the locations on the sea bed whereby differently acting directions of riser-weight-applied pull on the buoy tend to keep the buoy horizontally between the locations, the vessel floating substantially above the submerged buoy, (c) a like plurality of flexible conduits extending from the vessel to the submerged buoy, (d) a respective connector carried by the submerged buoy and connecting the lower end of the respective flexible conduit to the upper end of one of the risers; and (e) wherein the submerged buoy is tethered substantially vertically to an anchor in the sea bed. 24. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) a submerged buoy, (b) a like plurality of risers each suspended from the buoy and extending from the buoy in mutually different directions to a respective one of the locations on the sea bed whereby differently acting directions of riser-weight-applied pull on the buoy tend to keep the buoy horizontally between the locations, the vessel floating substantially above the submerged buoy, (c) a like plurality of flexible conduits extending from the vessel to the submerged buoy, (d) a respective connector carried by the submerged buoy and connecting the lower end of the respective flexible conduit to the upper end of one of the risers; and (e) wherein the buoy is fitted with roll motion damping means. 25. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) a submerged buoy, (b) a like plurality of risers each suspended from the buoy and extending from the buoy in mutually different directions to a respective one of the locations on the sea bed whereby differently acting directions of riser-weight-applied pull on the buoy tend to keep the buoy horizontally between the locations, the vessel floating substantially above the submerged buoy, (c) a like plurality of flexible conduits extending from the vessel to the submerged buoy, (d) a respective connector carried by the submerged buoy and connecting the lower end of the respective flexible conduit to the upper end of one of the risers; and (e) wherein at least one riser comprises steel pipe disposed in a catenary. 26. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) a submerged buoy, (b) a like plurality of risers each suspended from the buoy and extending from the buoy in mutually different directions to a respective one of the locations on the sea bed whereby differently acting directions of riser-weight-applied pull on the buoy tend to keep the buoy horizontally between the locations, the vessel floating substantially above the submerged buoy, (c) a like plurality of flexible conduits extending from the vessel to the submerged buoy, (d) a respective connector carried by the submerged buoy and connecting the lower end of the respective flexible conduit to the upper end of one of the risers; and (e) wherein the end of at least one riser adjacent the sea bed is disposed in a wave formation. 27. A marine riser system for transferring fluid between a plurality of mutually separated locations on the seabed and a vessel floating on the surface of the sea, the riser system comprising: (a) a submerged buoy, (b) a like plurality of risers each suspended from the buoy and extending from the buoy in mutually different directions to a respective one of the locations on the sea bed whereby differently acting directions of riser-weight-applied pull on the buoy tend to keep the buoy horizontally between the locations, the vessel floating substantially above the submerged buoy, (c) a like plurality of flexible conduits extending from the vessel to the submerged buoy, (d) a respective connector carried by the submerged buoy and connecting the lower end of the respective flexible conduit to the upper end of one of the risers; and (e) wherein the plurality of flexible conduits extending from the vessel each to a respective connector are collectively disposed in an array resembling a "Chinese lantern").