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 has a piston, a piston chamber, and a piston rod extending from the piston and away from the piston chamber. A shroud encloses and moves 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 and movable in unison with the piston rod.    
   
   
       2 . The surface assembly of  claim 1 , wherein the piston chamber is sealed from the shroud.  
   
   
       3 . The surface assembly of  claim 1 , wherein the interior surface of the shroud is substantially at atmospheric pressure.  
   
   
       4 . The surface assembly of  claim 1 , wherein the frame is located above the working deck and the tensioner assembly inclines radially inward from the working deck to the frame.  
   
   
       5 . The surface assembly of  claim 1 , wherein the shroud telescopes over the piston chamber while the tensioner assembly moves between contracted and extended positions.  
   
   
       6 . The surface assembly of  claim 1 , further comprising upper and lower sets of guide rollers engaging the riser at axially spaced apart locations below the frame.  
   
   
       7 . The surface assembly of  claim 1 , further comprising an upper set of guide rollers engaging the riser at an axial location above the frame, and a lower set of guide rollers engaging the riser at an axial location below the frame.  
   
   
       8 . The surface assembly of  claim 1 , wherein the tensioner assembly inclines radially inward from the working deck to connect with the frame.  
   
   
       9 . The surface assembly of  claim 1 , wherein an annular clearance exists between the piston rod and the shroud.  
   
   
       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 and inclining radially inward 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 position, the shroud having at least one end open to atmospheric pressure and being movable in unison with the piston, the piston chamber containing a pressurized fluid on an end of the piston opposite from the piston rod.    
   
   
       11 . The surface assembly of  claim 10 , further comprising upper and lower sets of guide rollers engaging the riser at axially spaced apart locations below the frame.  
   
   
       12 . The surface assembly of  claim 10 , further comprising an upper set of guide rollers engaging the riser at an axial location above the frame, and a lower set of guide rollers engaging the riser at an axial location below the frame.  
   
   
       13 . The surface assembly of  claim 11 , further comprising: 
 a secondary deck on the floating structure, the secondary deck being spaced apart from the working deck and having a secondary aperture for the riser to extend therethrough; and    wherein the lower set of guide rollers extend from the working deck, and the upper set of guide rollers extend from the secondary deck and engage the riser at an elevation spaced apart from and above the lower roller assemblies extending from the working deck.    
   
   
       14 . 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 above the working deck, the frame being connected to the riser so that the frame moves axially with the riser;    a hydraulic tensioner assembly having an end connected to the working deck and another end connected to the frame, the hydraulic tensioner assembly inclining radially inward from the deck to the frame.    
   
   
       15 . The surface assembly of  claim 14 , wherein the hydraulic tensioner assembly comprises a piston, a piston chamber, a piston rod extending from the piston out of the piston chamber, and a pressurized fluid carried in the piston chamber on an end of the piston opposite the piston rod.  
   
   
       16 . The surface assembly of  claim 14 , wherein the hydraulic tensioner assembly comprises a piston, a piston chamber, a piston rod extending downward from the piston and out of the piston chamber, and a pressurized fluid carried in the piston chamber on an end of the piston opposite the piston rod.  
   
   
       17 . The surface assembly of  claim 14 , wherein the hydraulic tensioner assembly comprises a piston, a piston chamber, a piston rod extending upward from the piston and out of the piston chamber, and a pressurized fluid carried in the piston chamber on an end of the piston opposite the piston rod.  
   
   
       18 . 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 above the working deck, the frame being connected to the riser so that the frame moves axially with the riser;    a tensioner assembly having an end connected to the working deck and another end connected to the frame with the tensioner assembly inclining radially inward from the deck to the frame, the tensioner comprising a piston, a piston chamber, and a piston rod extending upward from the piston and out of the piston chamber, the piston chamber containing a pressurized fluid on a lower side of the piston, and a shroud having at least one end open to atmospheric pressure enclosing and moving in unison with the piston rod and at least the sealing portion of the piston assembly; and    upper and lower sets of guide rollers engaging the riser at axially spaced apart locations below the frame.