Marine riser

Abstract

A marine riser has couplings with screw-threads for securing marine riser sections together, and a carousel mechanism for coupling auxiliary lines to the marine riser sections at various locations along the sections to permit the lines to rotate freely relative to the marine riser sections as the sections are rotatably assembled. The marine riser also has a buoyancy module which houses choke and kill lines in buoyancy module fairing portions.

What is claimed is:  
     
         1 . A fairing for use with a marine riser, the fairing comprising a first generally cylindrical portion for coupling to the riser and a second tapered portion coupled to the first portion, the fairing including buoyant material.  
     
     
         2 . A fairing as claimed in  claim 1  wherein the first and second portions are moulded from buoyant material.  
     
     
         3 . A fairing as claimed in  claim 1  wherein only the second portion is moulded from buoyant material.  
     
     
         4 . A fairing as claimed in  claim 1  wherein the second portion has an insert made of buoyant material.  
     
     
         5 . A fairing as claimed in  claim 2  wherein the second portion has an insert made of buoyant material.  
     
     
         6 . A fairing as claimed in  claim 3  wherein the second portion has an insert made of buoyant material.  
     
     
         7 . A fairing as claimed in  claim 1  wherein the buoyant material is non-absorbent syntactic foam.  
     
     
         8 . A fairing as claimed in  claim 2  wherein the buoyant material is non-absorbent syntactic foam.  
     
     
         9 . A fairing as claimed in  claim 3  wherein the buoyant material is non-absorbent syntactic foam.  
     
     
         10 . A fairing as claimed in  claim 4  wherein the buoyant material is non-absorbent syntactic foam.  
     
     
         11 . A fairing-shaped buoyancy module for use with a marine riser, said buoyancy module having carousel coupling means for coupling the buoyancy module to a carousel mechanism mounted on said riser, said buoyancy module being rotatable relative to said riser, said buoyancy module having a tapering fairing portion coupled to the carousel coupling means, the tapering portion being formed of a buoyant material and defining within the boundary of the tapering portion at least one passageway for an auxiliary line.  
     
     
         12 . A buoyancy module as claimed in  claim 11  wherein the tapering portion includes a plurality of passageways for a respective plurality of auxiliary lines.  
     
     
         13 . A buoyancy module as claimed in  claim 12  wherein said buoyancy module includes a nose portion coupled to said carousel mechanism, said nose portion being formed of a buoyant material and being disposed, when on said marine riser, in a substantially diametrically opposed position to said tapering fairing, said nose portion defining at least one passageway for an auxiliary line.  
     
     
         14 . A buoyancy module as claimed in  claim 11  wherein said buoyancy module is moulded into said carousel mechanism.  
     
     
         15 . A buoyancy module as claimed in  claim 12  wherein said buoyancy module is moulded into said carousel mechanism.  
     
     
         16 . A buoyancy module as claimed in  claim 13  wherein said buoyancy module is moulded into said carousel mechanism.  
     
     
         17 . A buoyancy module as claimed in  claim 11  wherein said buoyant material is syntactic foam.  
     
     
         18 . A buoyancy module as claimed in  claim 12  wherein said buoyant material is syntactic foam.  
     
     
         19 . A buoyancy module as claimed in  claim 13  wherein said buoyant material is syntactic foam.  
     
     
         20 . A buoyancy module formed of a buoyant material and being moulded to have a fairing portion, said buoyancy module being adapted to be disposed on a marine riser and to rotate relative to said marine riser, said buoyancy module, when disposed on said riser, produces a minimal increase in effective riser diameter and said fairing in at least one passageway for an auxiliary line.  
     
     
         21 . A buoyancy module as claimed in  claim 18  wherein said module includes a nose portion of buoyant material, said nose portion defining at least one passageway for an auxiliary line.