Riser assembly and method

Abstract

A riser assembly and method of producing a riser assembly are disclosed. The riser assembly includes a riser having a plurality of buoyancy elements provided at predetermined intervals along the length of the riser for supporting the riser, and at least one further buoyancy element arranged to support the riser in a configuration for accommodating tension changes in the riser due to vessel movement.

1 . A riser assembly for transporting fluids from a location deep under water, comprising:
 a riser having a plurality of buoyancy elements provided at predetermined intervals along the length of the riser for supporting the riser, and at least one further buoyancy element arranged to support the riser in a configuration for accommodating tension changes in the riser due to vessel movement.   
     
     
         2 . A riser assembly according to  claim 1 , wherein the at least one further buoyancy element is provided to form a sag bend, in use. 
     
     
         3 . A riser assembly according to  claim 1 , wherein the at least one further buoyancy element is provided to form a waved configuration, in use. 
     
     
         4 . A riser assembly according to  claim 1 , wherein the riser comprises a first section, a second section and a third section provided in series, and wherein the first section is for attachment to a vessel on a sea surface, the second section comprises the at least one further buoyancy element, and the third section comprises the plurality of buoyancy elements. 
     
     
         5 . A riser assembly according to  claim 4 , wherein the first section is relatively shorter than the third section. 
     
     
         6 . A riser assembly according to  claim 3 , wherein the waved configuration comprises a sag bend and a hog bend, and in use the portion of riser at the hog bend lies between 5 and 500 metres from a base of the vessel. 
     
     
         7 . A riser assembly according to  claim 6 , wherein in use the portion of riser at the hog bend lies between 5 and 300 metres from a base of the vessel. 
     
     
         8 . A riser assembly according to  claim 7 , wherein in use the portion of riser at the hog bend lies between 5 and 150 metres from a base of the vessel. 
     
     
         9 . A method of providing a riser assembly for transporting fluids from a location deep under water, comprising:
 providing a riser having a plurality of buoyancy elements provided at predetermined intervals along the length of the riser for supporting the riser, and at least one further buoyancy element arranged to support the riser in a configuration for accommodating tension changes in the riser due to vessel movement.   
     
     
         10 . A method according to  claim 9 , further comprising providing the at least one further buoyancy element to form a sag bend, in use. 
     
     
         11 . A method according to  claim 9 , further comprising providing the at least one further buoyancy element to form a waved configuration, in use. 
     
     
         12 . A method according to  claim 11 , wherein the riser comprises a first section, a second section and a third section provided in series, and wherein the first section is for attachment to a vessel on a sea surface, the second section comprises the at least one further buoyancy element, and the third section comprises the plurality of buoyancy elements. 
     
     
         13 . A method according to  claim 12 , wherein the first section is relatively shorter than the third section. 
     
     
         14 . A method according to  claim 11 , wherein the waved configuration comprises a sag bend and a hog bend, and in use the portion of riser at the hog bend lies between 5 and 500 metres from a base of the vessel. 
     
     
         15 . A method according to  claim 14 , wherein in use the portion of riser at the hog bend lies between 5 and 300 metres from a base of the vessel. 
     
     
         16 . A method according to  claim 15 , wherein in use the portion of riser at the hog bend lies between 5 and 150 metres from a base of the vessel. 
     
     
         17 . (canceled) 
     
     
         18 . (canceled)