Hydraulic and earth engineering – Marine structure or fabrication thereof – Floatable to site and supported by marine floor
Patent
1992-10-28
1994-10-11
Reese, Randolph A.
Hydraulic and earth engineering
Marine structure or fabrication thereof
Floatable to site and supported by marine floor
405210, 405211, 4052243, E02D 2302, E02D 2738
Patent
active
053541510
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a system for loading at sea, more specifically for arctic and subarctic regions.
BACKGROUND OF THE INVENTION
Systems of this kind comprise a conveying structure for underwater production which makes it possible to bring the contents of an underwater reservoir or pipeline to a vessel to take it away, such as an oil tanker. All of the elements of this system must have structures that are resistant to icebergs and ice floes due to the layer of ice that covers certain areas periodically, or must be removed from the surface when the weather conditions at sea become too rough.
Usually, oil tankers are loaded at sea using a permanent anchorage consisting of a buoy anchored by chains or any combination of chains and cables. Loading is accomplished through a flexible pipe connecting the underwater reservoir, or the pipeline, to the buoy or directly to the ship being loaded. All of these loading stations are characterized by the permanent presence of an object located at the surface or in the immediately adjacent subsurface area (about 10 m beneath the surface of the ocean).
In oceans that are exposed to ice or to floes, such anchorages are destroyed immediately when they encounter an ice floe, or even when they are trapped in surface ice. Even if the buoy is designed to withstand the pressure of the ice locally, the total forces of interaction resulting from the drifting of ice floes at the anchorage are of such intensity that the mooring lines cannot resist it. It is therefore necessary to remove from the surface and from the subsurface all parts of the mooring system when there is a threat of ice or an encounter with an iceberg.
U.S. Pat. No. 4,650,431 describes a system allowing rapid disconnection of a ship being loaded from the transfer structure, with the pipes or tubes permitting the transfer of the output to the loading vessel being immersed at a level beneath the zone of turbulence or ice formation on the sea, yet at a certain height relative to the ocean bottom so that the flexible lines are not damaged by resting on the ocean bottom. This system has the disadvantage of leaving the flexible lines within the reach of icebergs, and the latter can have a considerable draft.
The document entitled "Sols for Floating Production Systems" issued during the conference entitled "Floating Production Systems" held in London on Dec. 11-12, 1989 describes a system which does not require any object at the surface to transfer production to a vessel, but which suffers from two serious disadvantages: it requires tankers with dynamic positioning and special equipment, said vessels having to be equipped with a specific system for loading, which requires these vessels to be dedicated to this operation. The multiplicity of loading systems on each vessel thus makes the economic feasibility of the system doubtful.
SUMMARY OF THE INVENTION
The goal of our invention is to remedy the disadvantages associated with previous systems and to suggest a less expensive system which does not leave any object exposed to any disturbing elements such as icebergs, violent storms, or any other weather event at sea that could damage one of the elements constituting a loading system.
This goal is achieved by virtue of the fact that the system for loading at sea, described in the present application, comprises a conveying structure such as a buoy, means for anchoring the conveying structure characterized by the conveying structure being submersible and by the system comprising a bottom structure itself comprising a receptacle for the conveying structure and by comprising means for maneuvering the conveying structure, said maneuvering means or guiding means being designed to move the conveying structure so as to insert it into the receptacle.
The above bottom structure can be composed of at least one underwater reservoir.
The system can comprise means for conveying the liquid cargo contained in said reservoir to a floating loading structure, such as a vessel.
The conveying means can comprise a c
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Institut Francais du Pe'trole
McBee J. Russell
Reese Randolph A.
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