Spar

Abstract

The invention relates to floating offshore facilities, columnar in form, often referred to as spars comprising a body having an upper column, a main compartment and a lower leg joined together to define the spar, wherein the spar further comprises an articulation for connecting an end of the lower leg to the seabed, wherein the lower leg geometry has been configured as having a particular geometry that in combination with a particular residual buoyancy of the spar, and for any particular geometry of the upper column and main compartment and in any specific water depth, the spar provides a particular dynamic response to wind, wave and forces applied by sea currents. The invention also relates to methods for varying the dynamic response to wind, wave and forces applied by sea currents of the spar and to methods for transferring materials and personnel between a production facility such as the spar and at least one transportation apparatus such as a dynamically positioned vessel.

1 . A spar comprising a body having an upper column, a main compartment and a lower leg joined together to define the spar, wherein the spar further comprises an articulation for connecting an end of the lower leg to the seabed, wherein the lower leg geometry has been configured as having a particular geometry that in combination with a particular residual buoyancy of the spar, and for any particular geometry of the upper column and main compartment and in any specific water depth, the spar provides a particular dynamic response to wind, wave and forces applied by sea currents. 
     
     
         2 . The spar in accordance with  claim 1 , wherein the particular dynamic response of the spar is varied to achieve near steady state behaviour for specific sea states. 
     
     
         3 . The spar in accordance with  claim 1  or  2 , wherein the particular dynamic response of the spar is varied for the spar to be sufficiently steady, to function as a reference object for station keeping devices normally employed for close-in positioning of dynamically positioned vessels. 
     
     
         4 . The spar in accordance with  claim 1 , wherein the particular dynamic response of the spar is varied so that the motion of the spar is compatible with the motion of a dynamically positioned vessel thereby enabling the deployment of a gangway between the vessel and the spar, and the use of that gangway to transfer of personnel and materials to or from the vessel or spar. 
     
     
         5 . The spar in accordance with any one of the preceding claims, wherein the particular dynamic response of the spar is varied to achieve accelerations within acceptable ranges to mitigate free surface effects in liquid containing process equipment located within the spar. 
     
     
         6 . A spar in accordance with any one of  claims 1  to  5  wherein the spar is adapted to provide a facility for a plug and play connection of flow lines and cables from the spar to subsea features served by the spar. 
     
     
         7 . A spar in accordance with any one of the preceding claims further comprising moorings means extending from a location above the lower leg to the seabed for further modifying the dynamic response of the spar. 
     
     
         8 . A spar which is continuous surface to seabed, and with articulation connection at the seabed, has dynamic responses to wind, wave and current forces, which may be varied by manipulation of the lower leg geometry, in combination with residual buoyancy, for any particular upper body geometry, in any specific water depth. 
     
     
         9 . A spar in accordance with  claim 8 , wherein the dynamic response of the spar is varied to achieve near steady state behaviour for specific sea states. 
     
     
         10 . A spar in accordance with  claim 8  wherein the dynamic response of the spar is varied to be sufficiently steady, to function as a reference object for station keeping devices normally employed for close-in positioning of dynamically positioned vessels. 
     
     
         11 . A spar in accordance  claim 8  wherein the dynamic response of the spar is varied to create a motion form at surface, compatible with the motion form of a dynamically positioned vessel thereby enabling the deployment of a gangway between the two, and the use of that gangway to transfer of personnel and materials to or from each. 
     
     
         12 . A spar in accordance any one of  claims 8  to  11  wherein the dynamic response of the spar may be varied to achieve accelerations within acceptable ranges to mitigate of free surface effects, in liquid containing process equipment, located within the spar. 
     
     
         13 . A spar in accordance with any one of  claims 8  to  12  having an articulation for connection at the seabed, the spar being adapted for a single plug and play connection of flow lines and cables from spar to subsea features the spar serves. 
     
     
         14 . A spar in accordance with any one of  claims 8  to  13  wherein the dynamic response of the spar may be further modified by the addition of catenary cable or chain moorings from the buoy to the seafloor. 
     
     
         15 . A method for transferring materials and personnel between a production facility and at least one transportation apparatus, the method for transferring materials and personnel comprising the steps of:
 adjusting the movement of the production facility in such a manner that the transportation apparatus moves in synchronism with the movement of the production facility;   joining the production facility and transportation apparatus to allow transfer of materials and personnel; and   conducting the transfer;   wherein the step of adjusting the movement of the production facility comprises incorporating the production facility onto a spar as described in any of the  claims 1  to  14 .   
     
     
         16 . A method in accordance with  claim 15  wherein the production facility comprises at least one transportation apparatus comprises a dynamically positioned vessel. 
     
     
         17 . A method in accordance with  claim 15  or  16  wherein the steps of adjusting the movement of the production facility such as the spar comprises the steps of configuring the lower leg geometry of the spar to have a particular geometry that in combination with a particular residual buoyancy of the spar, and for any particular geometry of the upper column and main compartment and in any specific water depth, the spar provides a particular dynamic response to wind, wave and forces applied by sea currents that permits the production facility to move in synchronism with the movement of the transportation apparatus. 
     
     
         18 . A method for varying the dynamic response to wind, wave and forces applied by sea currents of a spar comprising a body having an upper column, a main compartment and a lower leg joined together to define the spar, wherein the spar further comprises an articulation for connecting an end of the lower leg to the seabed, wherein the method comprises the step of configuring the lower leg geometry to a particular geometry that in combination with a particular residual buoyancy of the spar, and for any particular geometry of the upper column and main compartment and in any specific water depth, the spar provides a particular dynamic response to wind, wave and forces applied by sea currents.