Improved subsea riser system

Abstract

An improved riser system which comprises a connector for connecting conduits and a mooring system for mooring the connector to the floor of a body of water. The connector may include a pivoting device. The improved riser system also comprises a buoy system for supporting the connector. The buoy system is configured to provide a fixed buoyancy for the connector, the mooring system and at least a portion of the conduits and for providing variable buoyancy for placement of the connector at a predetermined water depth. The improved riser system may also include a flexible conduit made of titanium.

1 - 27 . (canceled) 
     
     
         28 . An improved riser system for use in a body of water, said system comprising:
 a first conduit having a first and second end, said first end interfacing the floor of the body of water;   a connector connected to said second end of said first conduit;   a mooring system for mooring said connector to the floor of the body of water;   a second conduit having a first and second end, wherein said second conduit's wall comprises titanium, said connector connected to the first end of said second conduit, said first and second conduits being coupled together and in fluid communication with each other; and   a buoy system for providing buoyancy support in said riser system.   
     
     
         29 . The system of  claim 28  wherein said buoy system is configured to provide a fixed buoyancy force for said connector, said mooring system and at least a portion of said first and second conduits, and for providing a variable buoyancy force for placement of said connector at a predetermined water depth. 
     
     
         30 . The system of  claim 28  wherein said second conduit comprises at least one section of titanium and at least one section of steel. 
     
     
         31 . The system of  claim 28  wherein said second conduit and said first conduit have the same internal diameter. 
     
     
         32 . The system of  claim 28  wherein said second conduit and said first conduit have substantially the same internal diameter such that said first and second conduits may be pigged by a pig designed for changing diameters. 
     
     
         33 . The system of  claim 28  wherein said connector comprises a pivoting device. 
     
     
         34 . The system of  claim 33  wherein said pivoting device comprises a hinge. 
     
     
         35 . A method of installing a riser system in a body of water, said method comprising the steps of:
 assembling a foundation system, wherein said assembling comprises:
 attaching a first portion of a connector to a mooring system above said body of water, said mooring system comprising a fastening device and a tendon; 
 attaching said mooring system to the floor of the body of water, and 
 suspending said connector in said body of water using a buoyancy device; 
   assembling a riser structure above said body of water, wherein said assembling comprises:
 connecting a first conduit to a second portion of said connector, said second portion of said connector configured to be coupled with said first portion of said connector; 
 connecting a second conduit to said first connector so that said first and second conduits are in fluid communication; and 
 connecting a buoyancy apparatus to said second portion of said connector; 
   after said assembling of said foundation system and said riser structure, deploying said riser structure in said body of water; and   connecting said foundation system to said riser structure by connecting said first portion of said connector to said second portion of said connector.   
     
     
         36 . The method of  claim 35  further comprising:
 guiding said second portion of said connector with a guide cone prior to connection of said second portion of said second connector to said first portion of said second connector. 
 
     
     
         37 . A system for pigging a riser system in a body of water, said system comprising:
 a pig launching station connected to a first conduit, wherein at least a portion of said first conduit is located on a floor of said body of water; and   a pig receiving station connected to said first conduit, said pig receiving station configured to receive a pig and liquid displaced from said first conduit by said pig, wherein said first conduit is connected to a second conduit, said second conduit having an internal diameter different from said first conduit.   
     
     
         38 . The system of  claim 37  wherein said pig launching station and said pig receiving station are located on the floor of said body of water. 
     
     
         39 . The system of  claim 37  further comprising:
 a connector that connects said first conduit to said second conduit, wherein said pig launching station is located on said connector and said pig receiving station is located on the floor of said body of water. 
 
     
     
         40 . The system of  claim 37  further comprising:
 a connector that connects said first conduit to said second conduit, wherein said pig receiving station is located on said connector and said pig launching station is located on the floor of said body of water. 
 
     
     
         41 . A method for pigging a riser system in a body of water, said method comprising:
 launching a pig from a pig launching station connected to a first conduit of said riser system, wherein at least a portion of said first conduit is located on the floor of said body of water and said first conduit is connected to a second conduit, said second conduit having an internal diameter different from said first conduit; and   receiving, at a pig receiving station, said pig and liquid displaced from said first conduit by said pig, wherein said pig receiving station is connected to said first conduit.   
     
     
         42 . The method of  claim 41  wherein said pig launching station and said pig receiving station are located on the floor of said body of water. 
     
     
         43 . The method of  claim 41  wherein said pig launching station is located on a connector that connects said first conduit to said second conduit and wherein said pig receiving station is located on the floor of said body of water. 
     
     
         44 . The method of  claim 41  wherein said pig receiving station is located on a connector that connects said first conduit to said second conduit and wherein said pig launching station is located on the floor of said body of water. 
     
     
         45 . An improved riser system for use in a body of water, said system comprising:
 a first conduit having a first and second end, said first end interfacing the floor of the body of water;   a connector that comprises a pivoting device, said connector connected to said second end of said first conduit;   a second conduit having a first and second end, said second conduit connected to said connector, said connector connected to the first end of said second conduit, said first and second conduits being coupled together and in fluid communication with each other; and   a mooring system for mooring said connector to a floor of the body of water, said mooring system comprising a tendon connected to said pivoting device, said pivoting device adapted to allow any one of or a combination of said first conduit and said second conduit to pivot about said pivoting device when a load is applied to any one of said tendon, said first conduit and said second conduit.   
     
     
         46 . The system of  claim 45  further comprising:
 a buoy system for supporting said connector, said buoy system configured to provide a fixed buoyancy force for said connector, said mooring system and at least a portion of said first and second conduits, and for providing a variable buoyancy force for placement of said connector at a predetermined water depth. 
 
     
     
         47 . The system of  claim 45  further comprising:
 a triangular support connecting said hinge to said second conduit, said triangular support adapted for reducing a bending load on said second conduit. 
 
     
     
         48 . The system of  claim 45  wherein said pivoting device comprises a hinge. 
     
     
         49 . The system of  claim 45  wherein said pivoting device comprises a trunnion. 
     
     
         50 . The system of  claim 45  wherein said second conduit passes through said trunnion. 
     
     
         51 . The system of  claim 45  wherein said second conduit comprises titanium. 
     
     
         52 . A method of installing a riser system, said riser system having a system structure including a first conduit connected to a frame having a pivoting device and a buoy having a tubular configuration with a lumen and a lift line passing through said lumen, said method comprising the steps of:
 connecting at least one mooring tendon to said frame;   deploying said riser system structure in a body of water;   connecting the at least one mooring tendon to a floor of said body of water;   positioning a second conduit via said lift line passing through said buoy's lumen; and   connecting said second conduit to said first conduit so that said second and said first conduit are in fluid communication.