Self-Standing Riser System Having Multiple Buoyancy Chambers

Abstract

A multi-tiered self-standing riser system includes one or more intermediate buoyancy chambers configured to provide an upward lifting force on strings of associated riser assemblies. The intermediate chambers have either an open-bottomed or closed container design. The chambers can further include an auxiliary buoyant material designed to either mix with or contain pressurized fluids injected into the chambers. The self-standing riser system further includes a lower riser assembly affixed to a primary well-drilling fixture. The system also includes an upper riser assembly and one or more additional buoyancy chambers disposed in either direct or indirect communication with one another, as well as with drilling, production and exploration equipment as required by associated operations.

1 . A self-standing riser system suitable for deepwater oil and gas exploration and production, said system comprising:
 a lower riser assembly disposed in communication with a primary well-drilling fixture;   one or more intermediate buoyancy chambers disposed in communication with said lower riser assembly and one or more portions of intermediate riser assembly, wherein one or more of said buoyancy chambers further comprises an open-bottomed portion; and   an upper riser assembly disposed in communication with one or more upper buoyancy chambers, wherein one or more of said upper buoyancy chambers further comprises an open-bottomed portion.   
     
     
         2 . The self-standing riser of  claim 1 , wherein each of said open-bottomed intermediate buoyancy chambers further comprises a fluid ballast. 
     
     
         3 . The self-standing riser system of  claim 2 , wherein said fluid ballast further comprises a gas ballast. 
     
     
         4 . The self-standing riser system of  claim 2 , wherein said fluid ballast further comprises a liquid ballast. 
     
     
         5 . The self-standing riser system of  claim 2 , wherein said fluid ballast further comprises a ballast including both a liquid and a gas. 
     
     
         6 . The self-standing riser system of  claim 2 , wherein said fluid ballast further comprises an auxiliary ballast that lends additional pressure and density to said fluid. 
     
     
         7 . The self-standing riser system of  claim 6 , wherein said auxiliary ballast retards the escape of fluid from within said open-bottomed intermediate buoyancy chambers in the event said chambers tilt beyond a critical angle relative to its vertical axis. 
     
     
         8 . The self-standing riser system of  claim 1 , wherein one or more of said intermediate buoyancy chambers further comprises a closed bottom portion. 
     
     
         9 . The self-standing riser system of  claim 1 , wherein one or more of said upper buoyancy chambers further comprises a closed bottom portion. 
     
     
         10 . The self standing riser system of  claim 1 , wherein each of said open-bottomed upper buoyancy chambers further comprises a fluid ballast. 
     
     
         11 . The self-standing riser system of  claim 10 , wherein said fluid ballast further comprises a gas ballast. 
     
     
         12 . The self-standing riser system of  claim 10 , wherein said fluid ballast further comprises a liquid ballast. 
     
     
         13 . The self-standing riser system of  claim 10 , wherein said fluid ballast further comprises a ballast including both a liquid and a gas. 
     
     
         14 . The self-standing riser system of  claim 10 , wherein said fluid ballast further comprises an auxiliary ballast that lends additional pressure and density to said fluid. 
     
     
         15 . The self-standing riser system of  claim 14 , wherein said auxiliary ballast retards the escape of fluid from within said open-bottomed intermediate buoyancy chambers in the event said chambers tilt beyond a critical angle relative to its vertical axis. 
     
     
         16 . The self-standing riser system of  claim 1 , wherein one or more lengths of said lower riser assembly and said upper riser assembly further comprises one or more stress joints for absorbing stress accumulated within said lengths of said assemblies.