Offshore Riser Retrofitting Method and Apparatus

Abstract

The invention relates to a method, apparatus and components for adding a riser to an offshore platform. The method may include positioning an L-shaped conduit in the water near the seabed and connecting an upward leg of the conduit to a riser located within the platform jacket through the use of a remotely-operated vehicle (ROV). A standard deepwater connector is used so the ROV can remotely connect the riser to the L-shaped conduit. A horizontal leg of the L-shaped conduit is connected to a pipeline located on the outside of the jacket. The method maybe performed without ceasing production operations of the platform, thereby resulting in significant cost savings. The riser maybe located in a column of conductor guides on the platform jacket. The riser maybe stabilized within the guides, and/or electrically isolated from the platform jacket, through the use of generally semi-circular shaped segmented centralizers or by positioning a bladder between the riser and each guide and then filling the bladder with a material, such as grout or epoxy. The L-shaped conduit may be attached to a skid having one or more inflatable balloons for use in positioning the upward leg of the conduit beneath the riser. Various video, sonar and lighting equipment is disclosed to facilitate the remote connection of the L-shaped conduit to the riser. An assembly station is disclosed on the platform deck for constructing the riser in sections. The riser sections may be welded together in a positive-pressure welding habitat.

1 . A method of establishing a fluid flow path from a deck of an offshore platform supported by a jacket to a pipeline located in a body of water beneath the deck, comprising:
 positioning a conduit in the body of water below the deck, the conduit having a first end located within the jacket and a second end located outside of the jacket;   constructing a riser having an upper end and a lower end;   positioning the riser within the jacket with the upper end located at the deck; and   connecting the lower end of the riser to the first end of the conduit.   
   
   
       2 . The method of  claim 1 , further including performing each of the steps without ceasing production operations of the platform. 
   
   
       3 . The method of  claim 1 , further including connecting the second end of the conduit to the pipeline. 
   
   
       4 . The method of  claim 1 , further including establishing fluid communication between the upper end of the riser and a source of hydrocarbons below the body of water. 
   
   
       5 . The method of  claim 1 , further including positioning the riser within a plurality of conductor guides on the jacket. 
   
   
       6 . The method of  claim 5 , further including stabilizing the riser within the conductor guides. 
   
   
       7 . The method of  claim 5 , further including positioning a pair of generally semi-circular shaped centralizer members in an annulus formed between the riser and each conductor guide. 
   
   
       8 . The method of  claim 5 , further including filling an annulus between the riser and each conductor guide with a material and allowing the material to set. 
   
   
       9 . The method of  claim 8 , wherein the material is at least one of a grout and an epoxy. 
   
   
       10 . The method of  claim 1 , further including electrically isolating the riser from the jacket. 
   
   
       11 . The method of  claim 1 , wherein connecting the lower end of the riser to the first end of the conduit is performed without the use of a diver. 
   
   
       12 . The method of  claim 1 , wherein connecting the lower end of the riser to the first end of the conduit is performed with a remotely operated vehicle. 
   
   
       13 . The method of  claim 1 , further including connecting at least one inflatable bladder to the conduit and remotely controlling the pressure in the bladder to assist in positioning the first end of the conduit adjacent the lower end of the riser conduit. 
   
   
       14 . The method of  claim 13 , further including an enclosure containing the inflatable bladder. 
   
   
       15 . The method of  claim 1 , further including using a diverless connector to connect the lower end of the riser to the first end of the conduit. 
   
   
       16 . The method of  claim 1 , further including using a light source to align the lower end of the riser with the first end of the conduit. 
   
   
       17 . An apparatus for connecting a generally vertical riser within a jacket of an offshore platform to a pipeline located outside of the jacket, comprising:
 a frame; and   a generally L-shaped conduit attached to the frame, the L-shaped conduit having a first end adapted for connection to a lower end of the riser conduit and a second end adapted for connection to the pipeline.   
   
   
       18 . The apparatus of  claim 17 , further including at least one remotely-controllable inflatable bladder adapted to assist in positioning the first end of the conduit adjacent the lower end of the riser. 
   
   
       19 . The apparatus of  claim 17 , further including a diverless connector connected to the first end of the L-shaped conduit and a mating connector connected to the lower end of the riser. 
   
   
       20 . An apparatus for constructing a riser comprising:
 a support base;   a tower rotatably attached to the base and moveable between a lower position and an upper position;   a top clamp movably attached to the tower;   a bottom clamp attached to the support base, and aligned with the top clamp when the tower is in its upper position; and   an enclosure having an open position and closed position, the enclosure being positioned between the bottom clamp and the top clamp when the enclosure is in its closed position.