Offshore anchoring systems and associated methods

Abstract

A system for anchoring an offshore vessel to a seabed includes a foundation including a longitudinal axis, a first end, and a second end opposite the first end along the longitudinal axis of the foundation, a keying-flap assembly including a plurality of flaps coupled to the foundation whereby the plurality of flaps are configured to pivot relative to the foundation about a plurality of rotational axes associated with the plurality of flaps, the keying-flap assembly having a run-in configuration in which each of the plurality of flaps occupies a first position, and a set configuration in which the plurality of flaps are pivoted from their first to occupy a plurality of second positions, and a follower configured to apply an extraction force to the foundation to transition the keying-flap assembly from the run-in configuration to the set configuration.

What is claimed is: 
     
         1 . A system for anchoring an offshore vessel to a seabed positioned beneath a column of water, the system comprising:
 a foundation comprising a longitudinal axis, a first end, and a second end opposite the first end along the longitudinal axis of the foundation;   a keying-flap assembly comprising a plurality of flaps coupled to the foundation whereby the plurality of flaps are configured to pivot relative to the foundation about a plurality of rotational axes associated with the plurality of flaps, the keying-flap assembly having a run-in configuration in which each of the plurality of flaps occupies a first position, and a set configuration in which the plurality of flaps are pivoted from their first positions in alternating rotational directions about their respective rotational axes to occupy a plurality of second positions angularly spaced from their first positions; and   a follower extending between a first end and a second end opposite the first end of the follower, the follower configured to apply an extraction force to the foundation to transition the keying-flap assembly from the run-in configuration to the set configuration.   
     
     
         2 . The system of  claim 1 , wherein the first positions of the plurality of flaps correspond to vertical positions of the plurality of flaps and the second positions of the plurality of flaps correspond to inclined positions of the plurality of flaps. 
     
     
         3 . The system of  claim 1 , wherein the plurality of flaps of the keying-flap assembly are grouped into one or more flap pairs each rotating in opposing rotational directions between their first positions and their inclined positions. 
     
     
         4 . The system of  claim 1 , wherein the plurality of flaps of the keying-flap assembly are grouped into one or more flap pairs each having a Y-shaped profile when the plurality of flaps are in their second positions. 
     
     
         5 . The system of  claim 1 , wherein the plurality of flaps of the keying-flap assembly are grouped into one or more flap pairs spaced at an angle that is equal to or less than 180 degrees when the plurality of flaps are in their second positions. 
     
     
         6 . The system of  claim 1 , wherein:
 the system further comprises a plurality of support members coupled to the foundation; and   the plurality of flaps of the keying-flap assembly are grouped into one or more flap pairs each coupled to a separate support member of the plurality of support members.   
     
     
         7 . The system of  claim 1 , wherein:
 the keying-flap assembly comprises one or more collars each defining a pair of opposed stop surfaces; and   the plurality of flaps are angularly spaced from the pair of stop surfaces of the one or more collars when the plurality of flaps are in their first positions, and the plurality of flaps contact the pair of stop surfaces of the one or more collars when the plurality of flaps are in their second positions.   
     
     
         8 . A system for anchoring an offshore vessel to a seabed positioned beneath a column of water, the system comprising:
 a foundation comprising a longitudinal axis, a first end, and a second end opposite the first end along the longitudinal axis of the foundation;   a keying-flap assembly comprising a plurality of flaps coupled to the foundation whereby the plurality of flaps are configured to pivot relative to the foundation about a plurality of rotational axes associated with the plurality of flaps, the keying-flap assembly having a run-in configuration in which each of the plurality of flaps occupies a first position, and a set configuration in which the plurality of flaps are pivoted from their first positions about their respective rotational axes to occupy a plurality of inclined positions angularly spaced from their first positions; and   a follower extending between a first end and a second end opposite the first end of the follower, the follower configured to apply an extraction force to the foundation to transition the keying-flap assembly from the run-in configuration to the set configuration whereby a first flap of the plurality of flaps applies a first torque to the foundation in a first rotational direction and a second flap of the plurality of flaps applies a second torque to the foundation in a second rotational direction that is opposite the first rotational direction.   
     
     
         9 . The system of  claim 8 , wherein the first torque cancels out the second torque resulting in a zero net torque applied to the foundation in response to the application of the extraction force to the foundation by the follower. 
     
     
         10 . The system of  claim 8 , wherein the first positions of the plurality of flaps correspond to vertical positions of the plurality of flaps and the second positions of the plurality of flaps correspond to inclined positions of the plurality of flaps. 
     
     
         11 . The system of  claim 8 , wherein at least some of the plurality of flaps rotate in opposed rotational directions between their respective first positions and their respective second positions. 
     
     
         12 . The system of  claim 8 , wherein, from a perspective located along the longitudinal axis of the foundation, at least some of the plurality of flaps pivot in a clockwise direction between their respective first positions and their respective second positions and at least some of the plurality of flaps pivot in an opposing counterclockwise direction. 
     
     
         13 . The system of  claim 8 , wherein the plurality of flaps of the keying-flap assembly are grouped into one or more flap pairs each rotating in opposing rotational directions between their first positions and their inclined positions. 
     
     
         14 . The system of  claim 8 , wherein:
 the keying-flap assembly comprises one or more collars each defining a pair of opposed stop surfaces; and   the plurality of flaps are angularly spaced from the pair of stop surfaces of the one or more collars when the plurality of flaps are in their first positions, and the plurality of flaps contact the pair of stop surfaces of the one or more collars when the plurality of flaps are in their second positions.   
     
     
         15 . An offshore vessel, comprising:
 a deck; and   a winch assembly supported on the deck and connected to the system of  claim 8  by one or more tension cables extending between the winch assembly and the foundation of the system of  claim 8 , the winch assembly comprising one or more winches and a surface controller configured to automatically confirm the transitioning of the keying-flap assembly into the set configuration in response to monitoring a magnitude of the extraction force applied to the foundation by the follower.   
     
     
         16 . A method for anchoring an offshore vessel to a seabed positioned beneath a column of water, the method comprising:
 (a) penetrating an anchoring system comprising a foundation and a follower through the seabed to an installation depth located beneath the seabed;   (b) applying an extraction force to the follower whereby the extraction force is transmitted to the foundation;   (c) transitioning a keying-flap assembly comprising a plurality of flaps pivotably coupled to the foundation from a run-in configuration in which each of the flaps occupies a first position to a set configuration in which each of the flaps occupies a second position pivoted from their first position in response to transmitting the extraction force to the foundation; and   (d) monitoring by a surface controller spaced from the foundation a magnitude of the extraction force as the keying-flap assembly is transitioned from the run-in configuration to the set configuration to automatically confirm that the keying-flap assembly has successfully transitioned to the set configuration.   
     
     
         17 . The method of  claim 16 , wherein the surface controller is configured to identify one or more transition points in the magnitude of the extraction force to automatically confirm that the keying-flap assembly has successfully transitioned to the set configuration. 
     
     
         18 . The method of  claim 17 , wherein each of the one or more transition points corresponds to a change in a slope of the magnitude of the extraction force over time. 
     
     
         19 . The method of  claim 16 , wherein transitioning the keying-flap assembly from the run-in configuration to the set configuration comprises pivoting the plurality of flaps in alternating rotational directions relative to the foundation to occupy their respective second positions. 
     
     
         20 . The method of  claim 16 , wherein (c) comprises applying by a first flap of the plurality of flaps a first torque to the foundation in a first rotational direction and applying by a second flap of the plurality of flaps a second torque to the foundation in a second rotational direction that is opposite the first rotational direction.