Claims
- 1. A method for permanently mooring a floating storage vessel (10A, having a turret (20A) in the sea with anchor legs (26A) for remaining on station at all times without any quick disconnection of the turret from the anchor legs and any quick reconnection of the turret to the anchor legs for temporary removal of the vessel and with the vessel capable of maintaining a heading toward environmental forces; said method comprising the steps of:
- mounting said turret (20A, ) in a well at a position forward of a vertical center line of said vessel (10A) on a bearing assembly (46A) so that relative rotation of said turret and said vessel tends to occur when a longitudinal center line of said vessel is not aligned with environmental forces of the sea;
- mooring said vessel to said sea bed solely with said anchor legs by disposing a plurality of anchor legs (26A) between the sea bed and said turret (20A) with each of said anchor legs being fixedly secured to said turret without any quick disconnection of said legs from said turret or any quick reconnection of the legs to said turret to permit temporary removal of the vessel;
- extending a plurality of risers (22A) from the turret (20A) downwardly from said turret to the sea bed to receive oil or gas from production units on the sea bed;
- fixedly securing a plurality of support buoys (28A) to each of said anchor legs (26A) at predetermined positions in each anchor leg between the sea bed (16A) and said turret (20A);
- forming each anchor leg (26A) with long length flexible anchor leg lines connected to said turret and said plurality of support buoys for dividing each anchor leg into at least a turret-to-buoy section, a buoy to buoy section, and a buoy to-sea section, each section forming a uniform curved catenary sufficient to space each anchor leg from said risers at all times and sufficient to direct a large portion of the axial forces along each anchor leg into a horizontal component to provide a large torque force to assist in rotation of said turret (20A); and
- providing each of said support buoys (28A) with a buoyancy sufficient to submerge each support (28A) buoy to a predetermined depth while connected to said anchor leg, the buoyancy of each of said support buoys being commensurate with a size of said vessel and said turret to provide enhanced horizontal components of forces on said turret between said turret and said support buoys (28A), such that when said environmental forces tend to cause said vessel to weathervane about said turret, said horizontal components of force on said turret through said anchor legs are sufficiently high such that torque on said turret causes said vessel to weathervane about said turret on said bearing assembly to maintain a heading of said vessel into said prevailing environmental forces.
- 2. A permanently moored floating storage vessel (10A) for remaining on station at all times including a turret (20A) mounted in a well at a position forward of a vertical center line of said vessel on a bearing assembly (46A) so that rotation of said turret tends to occur where a longitudinal center line of said vessel is not aligned with environmental forces of the sea, said vessel being moored solely by a plurality of anchor legs (26A) each fixedly secured to the turret at one end without any quick disconnection or reconnection thereto to permit temporary removal of the vessel and connected to the sea bed at the other end, and risers (22A) extending downwardly from the turret to the sea bed for receiving hydrocarbons from production units, wherein said vessel includes an improvement comprising:
- a plurality of submerged support buoys (28A) fixedly secured at predetermined depths below sea level in each anchor leg for dividing each anchor leg into at least a turret-to-buoy section, a buoy to buoy section, and a buoy to-sea section, each section forming a uniform curved catenary sufficient to space each anchor leg (26A) from the risers at all times and sufficient to direct a large portion of the axial forces for each anchor leg into a horizontal component to provide a large torque force to assist in rotation of said turret (20), the horizontal component of the weight of each anchor leg adjacent each buoy being greater than the vertical component of such anchor leg adjacent each buoy, each anchor leg fixedly connected to said turret without any quick disconnection from said turret and any quick reconnection to said turret for temporary removal of the vessel, said support buoys (28A) being designed and arranged to have a buoyancy commensurate with a size of said vessel and said turret to provide enhanced horizontal components of forces on said turret from each anchor leg, such that when said environmental forces tend to cause said vessel to weathervane about said turret, said horizontal components of forces on said turret through each anchor leg are sufficient to provide torque great enough on said turret to cause said vessel to weathervane about said turret on said bearing assembly to maintain a heading of said vessel into said prevailing environmental forces.
- 3. A method for permanently mooring a floating mooring buoy (25B) in the sea with anchor legs (26B) without any quick disconnection of the mooring buoy from the anchor legs and any quick reconnection of the mooring buoy to the anchor legs for temporary removal of the mooring buoy; said method comprising the steps of:
- mooring said mooring buoy (25B) to said sea bed solely with said anchor legs (26B) by disposing a plurality of anchor legs between the sea bed and said mooring buoy (25B) with each of said anchor legs being fixedly secured to said mooring buoy without any quick disconnection of said legs from said mooring buoy or any quick reconnection of the legs to said mooring buoy to permit temporary removal of the mooring buoy;
- extending a plurality of risers (22B) supported from the mooring buoy downwardly from said mooring buoy to the sea bed to receive oil or gas from production units on the sea bed;
- securing a plurality of support buoys (28B) to each of said anchor legs (26B) at predetermined positions in each anchor leg between the sea bed and said mooring buoy;
- forming each anchor leg with a long length flexible anchor leg line between said mooring buoy (25B) and said sea bed for dividing each anchor leg line into at least a mooring buoy to support buoy section, a support buoy to support buoy section, and a support buoy to sea-floor section, each section having a length and direction forming a uniform curved catenary sufficient to space said anchor leg line from said risers at all times and sufficient to direct a large portion of the axial forces along each anchor leg into a horizontal component to provide a large torque force to assist in rotation of said mooring buoy (25B); and
- providing each support buoy (28B) with a buoyancy sufficient to submerge said buoy at a predetermined depth while connected to said anchor leg line, the buoyancy being sufficient to provide enhanced horizontal components of forces on said mooring buoy along those portions of said anchor leg lines between said mooring buoy and said buoy.
- 4. The method of claim 3 including the steps of:
- permanently connecting said mooring buoy (25B) to a floating storage vessel (10B) to permit said vessel to weathervane about said mooring buoy (25B) with the horizontal forces on said mooring buoy through said anchor leg lines sufficiently high so that environmental forces tend to cause said vessel to weathervane about said mooring buoy without the need for powered drives on said vessel to maintain a head of the vessel toward environmental forces.
- 5. The method of claim 4 including the steps of:
- providing said support buoy (25B) with a displacement of at least about twenty (20) tons; and
- submerging said support buoy (25B) at a depth below sea level at least about thirty-five (35) meters.
- 6. A method of mooring a vessel floating on a body of water above a sea floor including a turret and vertical bearings for relative rotation of said vessel about said turret, said vessel being moored solely by laterally and downwardly extending anchor legs securing said turret to said sea floor without any quick connection or any quick disconnection between said anchor legs and said turret, the method including the steps of:
- establishing only anchor legs between said turret and said sea floor as the sole means for mooring said vessel;
- placing a plurality of buoys at predetermined lateral distances away from said turret in each of said anchor legs, whereby each anchor leg is divided into at least a turret-to-buoy section, a buoy-to-buoy section and a buoy-to-sea floor section; and
- establishing each buoy at a sufficient distance from said turret and with a predetermined amount of buoyancy for forming a uniform curved catenary in each section and whereby weight of said buoy-to-sea floor section and of said buoy-to-buoy section of said anchor leg is not transferred to said turret and about fifty (50) percent of the weight of said turret-to-buoy section is transferred to said turret with the result that vertical load of said anchor legs on said turret is reduced and horizontal restoring forces are increased by said predetermined amount of buoyancy in each buoy relative to non-disconnectable mooring systems having no submerged buoys in anchor legs.
- 7. A mooring method for a mooring buoy floating on a body of water above a sea floor where said mooring buoy includes a rotatable part which is rotatable about a stationary part, said stationary part being moored solely by laterally and downwardly extending anchor legs for securing said stationary part to said sea floor without any quick connection or any quick disconnection between said anchor legs and said stationary part, the method including the steps of:
- establishing only anchor legs between said stationary part and said sea floor as the sole means for mooring said mooring buoy with said stationary part of said mooring buoy being substantially non-rotative with respect to the sea floor;
- placing a plurality of support buoys at predetermined lateral distances away from said turret in each of said anchor legs, whereby each anchor leg is divided into at least a stationary part-to-buoy section, a buoy-to-buoy section and a buoy-to-sea floor section; and
- establishing each support buoy at a sufficient distance from said stationary part and with a predetermined amount of buoyancy for forming a uniform curved catenary in each section and whereby weight of said buoy-to-sea floor section and of said buoy-to-buoy section of said anchor leg is not transferred to said stationary part and about fifty (50) percent of the weight of said stationary part-to-buoy section is transferred to said stationary part with the result that vertical load of said anchor legs on said stationary part is reduced and horizontal restoring forces are increased by said predetermined amount of buoyancy in each buoy relative to non-disconnectable mooring systems having no submerged buoys in anchor legs.
REFERENCE TO RELATED APPLICATIONS
This application is a continuation in part of application Ser. No. 08/905,854 filed Aug. 4, 1997; which is a continuation of application Ser. No. 08/599,859 filed Feb. 13, 1996; now U.S. Pat. No. 5,678,503 dated Oct. 21, 1997; which is a continuation of Ser. No. 08/339,924 filed Nov. 15, 1994 and abandoned; which is a continuation of Ser. No. 08/162,496 filed Dec. 3, 1993 and abandoned.
US Referenced Citations (6)
Foreign Referenced Citations (1)
Number |
Date |
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8802980 |
Jan 1990 |
NLX |
Continuations (3)
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599859 |
Feb 1996 |
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339924 |
Nov 1994 |
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162496 |
Dec 1993 |
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Continuation in Parts (1)
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905854 |
Aug 1997 |
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