Ships – Mooring device – Line type
Patent
1999-04-09
2000-07-04
Sotelo, Jesus D.
Ships
Mooring device
Line type
441 3, B63B 2100
Patent
active
06082283&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to improved methods and apparatus for the mooring of marine vessels. The invention is particularly, but not exclusively, concerned with offshore mooring systems for use in recovering fluid products (particularly hydrocarbon products such as oil and gas) from an offshore, subsea product source. The subsea product source is typically a subsea pipeline terminal, but could be a subsea wellhead, storage facility or the like. The invention might also find application in other situations where a tanker or the like is required to be moored reliably away from conventional mooring facilities, for handling other types of fluids such as water, liquid or gaseous chemicals, or for management of power supplies directed to or from the seabed, or simply for mooring large vessels.
In accordance with a first aspect of the invention, there is provided apparatus for mooring a marine vessel comprising: a subsea mooring assembly including anchor means for anchoring the assembly directly or indirectly to the seabed and including swivel means adapted for rotation about a substantially vertical axis; and at least one mooring line having a first end connected to said swivel and having a second end adapted to be connected, in use, to a marine vessel.
Preferably, the apparatus includes sensor means adapted to monitor tension applied to said mooring line. The apparatus preferably further includes transmitter means for transmitting signals from said sensor means and receiver means adapted to be located on the vessel, in use, for receiving said signals.
Preferably, said anchor means comprises an anchor pile, said swivel being secured to an upper end of said pile. Alternatively, said anchoring means comprises a subsea installation which is itself adapted to be anchored to the seabed. In a further alternative embodiment, said swivel is mounted on a buoyant body and said anchor means is secured to said buoyant body and adapted to maintain said buoyant body in a submerged condition at a predetermined height above the seabed, in use.
Preferably, the second end of said mooring line is connected to buoyancy means.
The apparatus preferably further includes a flexible riser conduit having a first end adapted to be connected a subsea source of a fluid product. Preferably also, said riser is coupled to said mooring line at at least two points between the first and second ends of said mooring line, and may be provided with buoyancy means between said two points.
Preferably, said riser has a second end adapted to be connected to a floating hose assembly.
In accordance with a second aspect of the invention, there is provided a method for mooring a marine vessel using apparatus in accordance with the first aspect of the invention, comprising securing the second end of said mooring line to the bow of said vessel and applying reverse thrust to said vessel so as to place said mooring line under tension.
Preferably also, the method includes monitoring the tension applied to the mooring line and varying the thrust applied to the vessel in order to maintain a substantially constant, predetermined tension on said mooring line.
Preferably, the method further comprises connecting said riser to a fluid manifold of fluid storage means located on the vessel, via said floating hose assembly.
The invention enables the use of a standard tanker vessel which is connected to the mooring line by means of its standard bow mooring equipment, or with minimal modification or upgrading of its bow mooring equipment. In applications involving the recovery of a fluid from a subsea source, this may be done via the standard midships manifold of the vessel. The floating hose assembly employed for this purpose may also be of standard type. The apparatus of the invention is relatively simple compared with existing mooring systems of equivalent functionality, and the present system avoids the need for specially adapted vessels, requiring, at most, minimal modification of standard vessels.
Embodiments of the invention will now be described, by way of examp
REFERENCES:
patent: 3248937 (1966-05-01), Vincent
patent: 3880105 (1975-04-01), Bryant
patent: 5284452 (1994-02-01), Corona
Coflexip Stena Offshore Limited
Sotelo Jesus D.
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