초록 ▼

A system is described for offloading LNG (liquified natural gas) from a tanker for eventual delivery to an onshore gas distribution station. The system includes a floating structure that floats at the sea surface and that is connected to the tanker so they weathervane together. The floating structur

A system is described for offloading LNG (liquified natural gas) from a tanker for eventual delivery to an onshore gas distribution station. The system includes a floating structure that floats at the sea surface and that is connected to the tanker so they weathervane together. The floating structure carries a regas unit that heats the LNG to produce gas, and delivers the gas through a riser to an underground cavern that stores the gas. Gas from the cavern is delivered through a seafloor pipeline to an onshore gas distribution station. The regas unit includes water pumps and other equipment that is powered by electricity. The electricity can be obtained from an electric generator on the floating structure, with surplus electricity delivered through a sea floor electric power line that extends along the sea floor to an onshore electricity distribution facility. The electricity can instead be obtained by delivery from an onshore facility though a sea floor electric power line that extends up to the floating structure and to the regas unit.

대표청구항 ▼

1. An offshore gas unloading system that lies in a sea having a sea surface and a sea floor, wherein a tanker unloads liquified cold hydrocarbons that are gaseous at room temperature, comprising:a floating structure that lies at the sea surface and that is moored so it weathervanes;a regas unit on s

1. An offshore gas unloading system that lies in a sea having a sea surface and a sea floor, wherein a tanker unloads liquified cold hydrocarbons that are gaseous at room temperature, comprising:a floating structure that lies at the sea surface and that is moored so it weathervanes;a regas unit on said floating structure, that heats at least some of the cold hydrocarbons that were received from the tanker;a sea floor platform that lies at the sea floor;a riser that extends from said floating structure to said sea floor platform to carry hydrocarbons from one to the other;said floating structure being connected to said tanker to form a combination of said floating structure and said tanker that weathervane together;at least one mooring line that extends from the sea floor to said combination to moor the combination and allow it to weathervane;an underground cavern and a pipe that is coupled to said cavern and to said riser, to thereby store at least some of the gas in the cavern.2. The system described in claim 1 including:an onshore gas distribution station;a seafloor pipeline that is coupled to said cavern and that extends primarily along the sea floor from said cavern to said onshore station to carry said gas from said cavern to said onshore station.3. The system described in claim 1 including:an onshore gas distribution station;a second riser extending from said floating structure to sea floor;a sea floor pipeline that extends primarily along the sea floor from a lower end of said second riser to said onshore station, whereby to enable the passage of gas into said cavern or directly to said onshore station without passing through said cavern.4. The system described in claim 1 including:an onshore gas distribution station;said riser comprises a cryogenic hose, and including a connection that carries some of the cold hydrocarbons received by the floating structure, directly to the cavern without passing through said regas unit so liquid cold hydrocarbons pass down through said cryogenic hose;said cavern has upper and lower portions, and including a sea floor gas pipeline that has a proximal end coupled to said cavern upper portion to receive gas therefrom, said pipeline extending to said onshore station.5. The system described in claim 1 wherein:said regas unit is electrically energized; and includingan electric generator apparatus mounted on said floating structure, which is fueled by gas from said regas unit and that generates electricity to energize said regas unit.6. The system described in claim 5 including:an onshore electric power distributing facility;an electric current-carrying power line extending from said electric generator apparatus to the sea floor and along the sea floor to said onshore facility for carrying power to said onshore facility when such power is not required at the floating structure.7. The system described in claim 1 wherein:said regas unit is electrically energized; and includingan onshore power distributing facility;an electric current-carrying power line that extends along the sea floor from said onshore facility to a location under said floating structure and up through the sea to said floating structure to carry electric power to said regas unit.8. An offshore gas unloading system that lies in a sea that has a sea floor and a sea surface, and that lies within about fifty kilometers of a shore, for unloading cold hydrocarbons from a tanker, comprising:a floating structure that lies at the sea surface and that has a fluid coupling for receiving said liquid cold hydrocarbons from said tanker;a cavern that stores gas;a sea floor platform and at least one pipe that extends from said sea floor platform to said storage facility;at least one riser that extends from said floating structure to said sea floor platform and that is coupled to said pipe to carry hydrocarbons between said sea-surface structure and said cavern;said floating structure carrying an electrically powered equipment including a regas unit;an electric power facility that lies on the shore;a current carrying power line that extends between said sea-surface structure and said electric power facility on the shore, to carry electricity between them.9. The system described in claim 8 including:an electricity generator mounted on said floating structure that supplies electricity to said equipment, and an electric switch arrangement that delivers electricity from said generator to said power line when much of the electricity is not required for said equipment.10. The system described in claim 8 wherein:said electric power facility that lies on the shore is constructed to deliver electrical power to said power line, to provide electrical power to energize said equipment.11. The system described in claim 8 wherein:said storage facility comprises an underground cavern that is connected to an end of said pipe that is opposite said riser; and includinga gas-powered electricity generator on said floating structure;a valve arrangement that is operable to pass said gas from said regas unit through said riser and pipe to said cavern, and to pass gas from said cavern through said pipe and said riser to said electricity generator, whereby the cavern stores gas to power the electricity generator.12. A gas offloading system that lies off shore in a sea, for receiving cold liquified gaseous hydrocarbons from a tanker, comprising:an offshore structure that lies at the sea surface and that has a coupling for receiving said liquified hydrocarbons from the tanker;a regas unit mounted on said offshore structure to heat said cold hydrocarbons to produce gas;an electric power-generating facility on said offshore structure that is powered by said gas and that produces electricity;an onshore power facility that distributes electric power;a current carrying power line that extends between said electric power-generating facility and said onshore power facility to carry electricity from said power-generating facility to said onshore power facility.13. The system described in claim 12 wherein:said regas unit consumes electric power in the heating of said cold gas, and including a switch arrangement that directs electricity from said electric power-generating facility to said regas unit to heat cold gas when such cold gas is received from a tanker, said switch arrangement being switchable to direct electricity from said electric power-generating facility to said power line when the regas unit is not operated to heat cold gas.14. A method for operating an offshore facility that lies off shore, and that unloads cold hydrocarbons from a tanker, for delivery of the hydrocarbons after warming, to a shore station on the shore, comprising:offloading cold hydrocarbons from the tanker to a floating structure that has a regas unit, and passing said cold hydrocarbons through said regas unit to produce warmed gaseous hydrocarbons;flowing at least some of said warmed gaseous hydrocarbons down along a riser to an underground cavern and storing said warmed hydrocarbons in the cavern;flowing gaseous hydrocarbons through a sea floor pipeline from said cavern to an onshore gas distribution station.15. The method described in claim 14 including:flowing a second portion of said warmed gas down along a riser directly to said sea floor pipeline so said second portion of the gas flows to the onshore station without having first passed into said cavern.16. The method described in claim 14 including:energizing said regas unit with electricity, including using some of said warmed gaseous hydrocarbons to fuel an electrical generator apparatus on said floating structure to generate electric power to energize said regas unit;delivering electricity from said electrical generator apparatus along a sea floor electric power line to an onshore facility when excess electric power is available from said electric generator apparatus.17. The method described in claim 14 including:energizing said regas unit with electricity;delivering electricity from an onshore facility along a sea floor electric power line to said floating structure to energize said regas unit with electric power from the onshore facility.18. A method for operating an offshore facility that lies off shore, and that unloads liquid cold hydrocarbons from a tanker, for delivery of the hydrocarbons as gas after warming, to a shore station on the shore, comprising:offloading cold liquid hydrocarbons from the tanker to a floating structure that has a regas unit, energizing said regas unit and passing said cold hydrocarbons through said regas unit to produce warmed gaseous hydrocarbons;flowing at least some of said warmed gaseous hydrocarbons down along a riser, and flowing warmed gaseous hydrocarbons through a sea floor pipeline to an onshore gas distribution station;said step of energizing said regas unit includes using some of said warmed gaseous hydrocarbons as fuel to energize an electricity generating apparatus on said floating structure that generates electricity, and supplying at least some of said electricity from said electricity generating apparatus to said regas unit to energize it;passing some of said electricity from said electric generating apparatus through an electric power line that extends along the sea floor, to an onshore power distribution station.19. A method for operating an offshore facility that lies off shore, and that unloads cold liquid hydrocarbons from a tanker, for delivery of the hydrocarbons after warming, to a shore station on the shore, comprising:offloading cold hydrocarbons from the tanker to a floating structure that has a regas unit, energizing said regas unit and passing said cold hydrocarbons through said regas unit to produce warmed gaseous hydrocarbons;flowing at least some of said warmed gaseous hydrocarbons down along a riser, and flowing warmed gaseous hydrocarbons through a sea floor pipeline to an onshore gas distribution station;said step of energizing said regas unit includes carrying electric power from an onshore facility and along an electric power line that extends along the sea floor and up to said floating structure to said regas unit to energize said regas unit with electric power from the shore.