Long Stroke Riser Tensioner System and Wellbay Structure for a Floating Unit

Abstract

A riser tensioner system and a wellbay structure for a floating unit or platform for deep/ultra-deep water field development. The riser tensioner system includes a first cassette, a second cassette, a tension joint, one or more centralizers, and a plurality of cylinders. The one or more centralizers provide lateral support to the tension joint. Each of the plurality of cylinders comprises a first end, a second end, and an intermediate portion. The first end of each of the plurality of cylinders is secured to the first cassette, and an intermediate portion of each of the plurality of cylinders is secured to the second cassette. The wellbay structure includes a plurality of transverse girders and a plurality of longitudinal girders. The girders form a grid comprising a plurality of slots. Each of the plurality of slots is configured for receiving and supporting a first cassette of each a riser tensioner assembly.

What is claimed is: 
     
         1 . A riser tensioner system comprising:
 a first cassette;   a second cassette;   a tension joint disposed through the first cassette and the second cassette;   one or more centralizers providing lateral support to the tension joint; and   a plurality of cylinders, each comprising a first end, a second end, and an intermediate portion, wherein the first end of each of the plurality of cylinders is secured to the first cassette and the intermediate portion of each of the plurality of cylinders is secured to the second cassette.   
     
     
         2 . The riser tensioner system of  claim 1 , wherein the one or more centralizers comprise one or more first centralizers and one or more second centralizers, the one or more first centralizers secured to the first cassette, the one or more second centralizers secured to the second cassette, wherein the one or more first centralizers and the one or more second centralizers provide lateral support to the tension joint. 
     
     
         3 . The riser tensioner system of  claim 1 , further comprising a load ring attached to a top of the tension joint, wherein the plurality of cylinders are coupled to the load ring to apply tension thereto to apply tension to the tension joint. 
     
     
         4 . The riser tensioner system of  claim 3 , wherein each of the plurality of cylinders comprises a cylinder rod, a top of which is coupled to the load ring to apply the tension thereto to apply the tension to the tension joint. 
     
     
         5 . The riser tensioner system of  claim 4 , further comprising a first plurality of impact buckets or loading cups secured to the load ring and a second plurality of impact buckets or stoppers secured to the first cassette. 
     
     
         6 . The riser tensioner system of  claim 5 , wherein the top of the cylinder rod of each of the plurality of cylinders is secured to a respective one of the first plurality of impact buckets. 
     
     
         7 . The riser tensioner system of  claim 5 , wherein the cylinder rod of each of the plurality of cylinders is slidably disposed along a cylinder axis through to a respective one of the second plurality of impact buckets, and slidably slipped perpendicular to the cylinder axis within a respective one of the first plurality of loading cups 
     
     
         8 . The riser tensioner system of  claim 5 , wherein the first plurality of impact buckets and the second plurality of impact buckets are positioned to impact one another during a bottom-out condition of the riser tensioner system. 
     
     
         9 . The riser tensioner system of  claim 1 , wherein each of the plurality of cylinders comprises an interior shock absorber for absorbing an impact load resulting from a top-up condition of the riser tensioner system. 
     
     
         10 . The riser tensioner system of  claim 1 , wherein the first cassette comprise a top surface and a bottom surface, and wherein the first cassette is sized to be disposed within an opening in a wellbay so that the top surface of the first cassette is flush with a top surface of a structural support foundation of the wellbay. 
     
     
         11 . The riser tensioner system of  claim 10 , wherein the second cassette is securable to a lower support structure of the wellbay. 
     
     
         12 . The riser tensioner system of  claim 1 , further comprising a stabilization system comprising:
 at least one vertical support; and   at least one horizontal support, a first portion of which is disposed around the riser and a second portion of which is slidably connected to the at least one vertical support.   
     
     
         13 . The riser tensioner system of  claim 12 , wherein the at least one horizontal support comprises at least one respective tensioner ring that is disposed around the riser. 
     
     
         14 . The riser tensioner system of  claim 1 , further comprising a stabilization system comprising:
 at least one vertical support;   a platform disposed around the riser; and   at least one horizontal support, a first portion of which is connected to the platform and a second portion of which is slidably connected to the at least one vertical support.   
     
     
         15 . A wellbay structure for use in an offshore platform, the wellbay structure comprising:
 a plurality of transverse girders; and   a plurality of longitudinal girders,   wherein the plurality of transverse girders and the plurality of longitudinal girders form a grid comprising a plurality of slots, and   wherein each of the plurality of slots is configured for receiving and supporting a first cassette of each of a respective one of a plurality of riser tensioner assemblies.   
     
     
         16 . The wellbay structure of  claim 15 , wherein each of the plurality of transverse girders and each of the plurality of longitudinal girders are box girders. 
     
     
         17 . The wellbay structure of  claim 15 , wherein the grid comprises a top and a bottom, and wherein the bottom of the grid is flush with a bottom of a lower level deck of the offshore platform. 
     
     
         18 . The wellbay structure of  claim 15 , wherein the grid comprises a top and a bottom, and wherein the wellbay structure further comprises a drop-down structure attached to the bottom of the grid. 
     
     
         19 . The wellbay structure of  claim 18 , wherein the drop-down structure is configured for supporting a second cassette of each of the plurality of riser tensioner assemblies. 
     
     
         20 . The wellbay structure of  claim 15 , wherein each of plurality of slots comprises a ledge for supporting the first cassette of a respective one of the plurality of riser tensioner assemblies. 
     
     
         21 . The wellbay structure of  claim 20 , wherein the ledge in each of the plurality of slots is recessed from a top surface of the grid. 
     
     
         22 . The wellbay structure of  claim 20 , wherein the ledge in each of the plurality of slots comprises at least two or more horizontal members disposed on adjacent ones of the plurality of the plurality of transverse girders or adjacent ones of the plurality of longitudinal girders. 
     
     
         23 . An offshore floating platform comprising:
 an upper deck;   a lower deck; and   a wellbay structure comprising:
 a plurality of transverse girders; and 
 a plurality of longitudinal girders, 
   a plurality of riser tensioner assemblies, each comprising:
 a first cassette; 
 a second cassette; 
 a tension joint slidably disposed through the first cassette and the second cassette; 
 one or more centralizers providing lateral support to the tension joint; and 
 a plurality of cylinders, each comprising a first end, a second end, and an intermediate portion, wherein the first end of each of the plurality of cylinders is secured to the first cassette and the intermediate portion of each of the plurality of cylinders is secured to the second cassette, 
   wherein the plurality of transverse girders and the plurality of longitudinal girders of the wellbay structure form a grid comprising a plurality of slots, and   wherein each of the plurality of slots is configured for receiving and supporting the first cassette of a respective one of the plurality of riser tensioner assemblies.   
     
     
         24 . The offshore floating platform of  claim 23 , wherein each of the plurality of transverse girders and each of the plurality of longitudinal girders of the wellbay structure are box girders. 
     
     
         25 . The offshore floating platform of  claim 23 , wherein the grid of the wellbay structure comprises a top and a bottom, and wherein the bottom of the grid is flush with a bottom of the lower deck. 
     
     
         26 . The offshore floating platform of  claim 23 , wherein the grid of the wellbay structure comprises a top and a bottom, and wherein the wellbay structure further comprises a drop-down structure attached to the bottom of the grid. 
     
     
         27 . The offshore floating platform of  claim 26 , wherein the drop-down structure is configured with limited deformation for supporting a second cassette of each of the plurality of riser tensioner assemblies. 
     
     
         28 . The offshore floating platform of  claim 23 , wherein each of plurality of slots comprises a ledge for supporting the first cassette of a respective one of the plurality of riser tensioner assemblies. 
     
     
         29 . The offshore floating platform of  claim 28 , wherein the ledge in each of the plurality of slots is recessed from a top surface of the grid. 
     
     
         30 . The offshore floating platform of  claim 28 , wherein the ledge in each of the plurality of slots comprises at least two or more horizontal members disposed on adjacent ones of the plurality of the plurality of transverse girders or adjacent ones of the plurality of longitudinal girders. 
     
     
         31 . The offshore floating platform of  claim 23 , wherein the platform is capable to apply to dry tree production and/or drilling operations in deep or ultra-deep water field development.