Riser assembly and method

Abstract

A riser assembly and method of supporting a flexible pipe are disclosed. The assembly includes a riser; at least one buoyancy compensating element attached to the riser for providing positive, negative or neutral buoyancy to the riser; and a tethering element connecting a first point of the riser with a further point of the riser so as to form a hog bend or a sag bend in the riser.

1 . A riser assembly for transporting fluids from a sub-sea location, comprising:
 a riser;   at least one buoyancy compensating element attached to the riser for providing positive, negative or neutral buoyancy to the riser; and   a tethering element connecting a first point of the riser with a further point of the riser so as to form a hog bend or a sag bend in the riser.   
     
     
         2 . A riser assembly as claimed in  claim 1 , wherein the tethering element comprises a chain, rope, filament, cord, cable, or the like, or a combination thereof. 
     
     
         3 . A riser assembly as claimed in  claim 1 , wherein the tethering element is at least partly flexible. 
     
     
         4 . A riser assembly as claimed in  claim 1 , wherein the tethering element is connected to the first point of the riser via a one of the at least one buoyancy compensating elements. 
     
     
         5 . A riser assembly as claimed in  claim 4  wherein the riser assembly comprises two or more buoyancy compensating elements and the tethering element is connected to the second point of the riser via a further buoyancy compensating element. 
     
     
         6 . A riser assembly as claimed in  claim 1  where the tethering element is joined to the first and/or second point of the riser via at least one connector ring or clamp. 
     
     
         7 . A riser assembly as claimed in  claim 1  wherein the tethering element comprises a plurality of sub-elements and the sub-elements comprise a chain, rope, filament, cord, cable, or the like. 
     
     
         8 . A riser assembly as claimed in  claim 7  wherein the sub-elements are each connected to the riser, directly or via a buoyancy compensating element. 
     
     
         9 . A riser assembly as claimed in  claim 7  wherein sub-elements are linked together at a common point. 
     
     
         10 . A riser assembly as claimed in  claim 9  further comprising a weighting element extending from the common point to a seabed region in use. 
     
     
         11 . A riser assembly as claimed in  claim 7  further comprising a connector element, and wherein the plurality of sub-elements are joined to the connector element. 
     
     
         12 . A riser assembly as claimed in  claim 11  wherein the connector element has a positive or negative buoyancy. 
     
     
         13 . A riser assembly as claimed in  claim 11  wherein the connector element is tethered to an anchoring element on a platform or the seabed in use. 
     
     
         14 . A riser assembly as claimed in  claim 11  wherein the connector element is a cylinder beam. 
     
     
         15 . A riser assembly as claimed in  claim 1 , wherein the tethering element has a length (L te ) extending from the first point to the second point of the riser, and the riser has a length extending from the first point to the second point (L r ), and the length of the tethering element (L te ) is shorter than the length of the riser between the first point and the second point (L r ). 
     
     
         16 . A method of supporting a flexible pipe, the method comprising the steps of:
 providing a riser;   providing at least one buoyancy compensating element attached to the riser for providing positive, negative or neutral buoyancy to the riser; and   providing at least one tethering element for joining a first point of the riser to a further point of the riser so as to form a hog bend or a sag bend in the riser.   
     
     
         17 . A method as claimed in  claim 16  wherein the tether element is provided with predetermined dimensions and joined to the first point and second point of the riser so as to provide a riser assembly with a predetermined shape in use. 
     
     
         18 . (canceled) 
     
     
         19 . (canceled)