Riser tensioner with shrouded rods

Abstract

A surface assembly that communicates with subsea structures and includes a working deck on a floating structure. The working deck has an aperture extending axially therethrough. A riser extends from a subsea location to the working deck and through the aperture. The surface assembly includes a frame extending circumferentially around the riser so that the frame moves axially with the riser. The assembly also includes a tensioner assembly connected between the working deck and the frame. The tensioner assembly includes a piston slidably carried in a piston chamber, a piston rod extending from the piston and away from the piston chamber, and a shroud enclosing the piston rod. The shroud has a plurality of segments with at least one of the shroud segments being movable in unison with the piston rod.

1 . A surface assembly for subsea wells, comprising 
 a working deck on a floating structure, the working deck having an aperture extending axially therethrough;    a riser extending from a subsea location to the working deck and through the aperture;    a frame extending circumferentially around the riser, the frame being connected to the riser so that the frame moves axially with the riser; and    a tensioner assembly connected between the working deck and the frame comprising a piston slidably carried in a piston chamber, a piston rod extending from the piston and away from the piston chamber, and a shroud enclosing the piston rod, the shroud having a plurality of telescoping segments with at least one of the shroud segments being movable in unison with the piston rod.    
   
   
       2 . The surface assembly of  claim 1 , wherein the plurality of segments comprises an inner shroud segment being stationary relative to the piston rod.  
   
   
       3 . The surface assembly of  claim 1 , wherein the plurality of segments comprises an inner shroud segment and an outer shroud segment, the outer shroud segment telescoping over the inner shroud segment when the tensioner assembly is in a contracted position.  
   
   
       4 . The surface assembly of  claim 1 , wherein the plurality of segments comprises an inner shroud segment and an outer shroud segment, a substantial portion of the inner shroud segment is uncovered when the tensioner assembly is in an extended position.  
   
   
       5 . The surface assembly of  claim 1 , wherein the plurality of segments comprises an outer shroud segment and an inner shroud segment that is fixedly connected to an end portion of the piston chamber that receives the piston rod.  
   
   
       6 . The surface assembly of  claim 1 , wherein the plurality of segments comprises an inner shroud segment and an outer shroud segment that is fixedly connected to an end portion of the piston chamber that receives the piston rod.  
   
   
       7 . The surface assembly of  claim 1 , wherein the plurality of segments comprises an inner shroud segment, an intermediate shroud segment, and an outer shroud segment, the intermediate shroud segment telescoping over the inner shroud segment when the tensioner assembly is in a contracted position, and the outer shroud segment telescoping over the intermediate and inner shroud segments when the tensioner assembly is in a contracted position.  
   
   
       8 . The surface assembly of  claim 1 , wherein the piston chamber is sealed from the shroud.  
   
   
       9 . The surface assembly of  claim 1 , wherein the interior surface of the shroud is substantially at atmospheric pressure.  
   
   
       10 . A surface assembly for subsea wells, comprising: 
 a working deck on a floating structure, the working deck having an aperture extending axially therethrough;    a riser extending from a subsea location to the working deck and through the aperture;    a frame extending circumferentially around the riser, the frame being connected to the riser so that the frame moves axially with the riser; and    a tensioner assembly connected between the working deck and the frame, the tensioner assembly having a contracted position and an extended position, the tensioner assembly comprising a piston slidably carried in a piston chamber, a piston rod extending from the piston chamber, and a shroud surrounding at least part of the piston rod while in the contracted and extended positions, the piston chamber containing a pressurized fluid on an end of the piston opposite from the piston rod, the shroud having a plurality of shroud segments with at least one of the shroud segments being movable in unison with the piston rod and at least one of the shroud segments being fixedly connected to an end portion of the piston chamber that receives the piston rod.    
   
   
       11 . The surface assembly of  claim 10 , wherein the plurality of shroud segments comprise an inner shroud segment and an outer shroud segment, and the outer shroud segment telescoping over the inner shroud segment in the contracted position.  
   
   
       12 . The surface assembly of  claim 10 , wherein the plurality of shroud segments comprise an inner shroud segment and an outer shroud segment; and 
 the piston chamber being positioned above the piston rod and the outer shroud segment is the at least one of the shroud segments being fixedly connected to an end portion of the piston chamber that receives the piston rod.    
   
   
       13 . The surface assembly of  claim 10 , wherein the plurality of shroud segments comprise an inner shroud segment and an outer shroud segment; and 
 the piston chamber being positioned below the piston rod and the inner shroud segment is the at least one of the shroud segments being fixedly connected to an end portion of the piston chamber that receives the piston rod.    
   
   
       14 . The surface assembly of  claim 10 , wherein the plurality of shroud segments comprise an inner shroud segment and an outer shroud segment; and 
 the piston chamber being positioned above the piston rod;    the outer shroud segment is the at least one of the shroud segments being fixedly connected to an end portion of the piston chamber that receives the piston rod; and    the inner shroud segment is the at least one of the shroud segments being movable in unison with the piston rod.    
   
   
       15 . The surface assembly of  claim 10 , wherein the plurality of shroud segments comprise an inner shroud segment and an outer shroud segment; and 
 the piston chamber being positioned below the piston rod;    the inner shroud segment is the at least one of the shroud segments being fixedly connected to an end portion of the piston chamber that receives the piston rod; and    the outer shroud segment is the at least one of the shroud segments being movable in unison with the piston rod.    
   
   
       16 . The surface assembly of  claim 10 , wherein: 
 the plurality of segments comprises an inner shroud segment, an intermediate shroud segment, and an outer shroud segment, the intermediate shroud segment telescoping over the inner shroud segment when the tensioner assembly is in a contracted position, and the outer shroud segment telescoping over the intermediate and inner shroud segments when the tensioner assembly is in a contracted position; and    the at least one of the shroud segments being movable in unison with the piston rod is one of either the inner shroud segment and the outer shroud segment.    
   
   
       17 . A riser tensioner assembly for maintaining tension in a riser extending from a subsea well through an aperture in a working deck of a floating structure, comprising: 
 a piston slidably carried in a piston chamber;    a piston rod extending from the piston chamber, the piston rod and piston being movable between a contracted position and an extended position of the tensioner assembly; and    a shroud surrounding at least part of the piston rod while in the contracted and extended positions, the shroud having a plurality of shroud segments with at least one of the shroud segments being movable in unison with the piston rod and at least one of the shroud segments being fixedly connected to an end portion of the piston chamber that receives the piston rod    
   
   
       18 . The riser tensioner assembly of  claim 17 , wherein the plurality of shroud segments comprises an inner shroud segment and an outer shroud segment; 
 the inner shroud segment having a flange end connected to either the piston chamber or the piston rod and a telescoping end having an outer lip, and the outer shroud having a flange end connected to the other of the piston chamber or the piston rod and a telescoping end having an inner lip; and when the tensioner assembly is in the extended position:    the outer lip of the inner shroud engaging another shroud segment telescoping over the inner shroud and the inner lip of the outer shroud engaging another shroud segment telescoping within the outer shroud.    
   
   
       19 . The riser tensioner assembly of  claim 18 , wherein the plurality of shroud segments further comprises an intermediate shroud segment, the intermediate shroud segment telescoping over the inner shroud segment when the tensioner assembly is in a contracted position, and the outer shroud segment telescoping over the intermediate and inner shroud segments when the tensioner assembly is in a contracted position.  
   
   
       20 . The riser tensioner assembly of  claim 19 , wherein each intermediate shroud segment has an extension end and a contraction end, the extension end having an outer lip and the contraction end having an inner lip; and when the tensioner assembly is in the extended position: 
 the outer lip of the intermediate shroud segment engages an interior lip of either another intermediate shroud segment or the outer shroud segment, and the inner lip of the intermediate shroud segment engages an outer lip of either another intermediate shroud segment or the inner shroud segment.