Production Riser

Abstract

The present invention is directed to a system including a self supporting riser (SSR) which is connected to a well to produce fossil hydrocarbon reservoirs deep below the seafloor. The SSR is constructed of a plurality of joints comprising regular joints and specialty joints that define the SSR and are selected to optimize the SSR for a well in a specific location. A unique aspect of the SSR of the present invention is that while capable of connecting to the wellhead, or tree on the seafloor, it can also be secured to an anchor during operations. The invention is further directed to a small vessel moored to the SSR by a line such as a hawser, the riser providing an anchor to the vessel, and the SSR carrying fluids from the well to the vessel and from the vessel to the well. The vessel has provisions for processing the fluids from the wellhead.

1 . A riser system comprising:
 a single self supporting riser (SSR) which comprises a plurality of joints comprising regular joints and specialty joints that define said SSR and selected to optimize said SSR for a particular location; at least one specialty joint comprising a buoyancy module, said one is the uppermost buoyancy module near but below the sea surface and another specialty joint having provisions at the lower end of said SSR to prevent excessive bending moment in the riser; said riser providing fluid communication between said SSR and a well having a wellhead on the seafloor; and   a specialty joint in the SSR providing fluid communication between said SSR and a vessel subject to high vessel motions of heave, pitch and roll.   
     
     
         2 . A riser system according to  claim 1  wherein said specialty joint in the SSR providing fluid communication between said SSR and a vessel includes a swivel. 
     
     
         3 . A riser system according to  claim 1  wherein said SSR is secured to an element of a subsea infrastructure. 
     
     
         4 . A riser system according to  claim 1  wherein said specialty joint having provisions at the lower end of said SSR to prevent excessive bending moment in the riser is a flexible connector. 
     
     
         5 . A riser system according to  claim 4  wherein said flexible connector is connected to an anchor on the seafloor. 
     
     
         6 . A riser system according to  claim 4  wherein said flexible connector is a section of flexible pipe. 
     
     
         7 . A riser system according to  claim 4  wherein said flexible connector is links of chain. 
     
     
         8 . A riser system according to  claim 2  wherein said swivel is above said buoyancy module. 
     
     
         9 . A production system comprising:
 a self supporting riser (SSR) which comprises a plurality of joints comprising regular joints and specialty joints that define said SSR and selected to optimize said SSR for a particular location; at least one specialty joint comprising a buoyancy module, said one is the uppermost buoyancy module near but below the sea surface; said riser in fluid communication with a hydrocarbon producing well having a wellhead on the seafloor; and   a vessel subject to high vessel motions of heave, pitch and roll; said riser providing an anchor to said vessel and providing fluid communication between said well and said vessel.   
     
     
         10 . A small sea vessel subject to high vessel motion of heave, pitch and roll having on deck a hydrocarbon processing system comprising:
 a stabilized frame on which said hydrocarbon processing equipment is held; and   a stabilization system consisting of paired cylinders to maintain said frame essentially level.   
     
     
         11 . A small sea vessel according to  claim 10  wherein each cylinder is mounted on said deck and each cylinder rod extends upward to a compliant connection to support said frame. 
     
     
         12 . A small sea vessel according to  claim 10  wherein there are at least two pair of cylinders. 
     
     
         13 . A small sea vessel according to  claim 10  wherein each pair of cylinders is controlled by accelerometers or inclinometers. 
     
     
         14 . A small sea vessel according to  claim 10  wherein each pair of cylinders has a hydraulic control system consisting of a fluid line between the load bearing chambers and a second line between the non-load bearing chambers; and
 a reversible pump in one of said lines. 
 
     
     
         15 . A small sea vessel according to  claim 14  wherein said pump is in said non-load bearing line. 
     
     
         16 . A small sea vessel according to  claim 14  wherein said pump is controlled by accelerometers or inclinometers. 
     
     
         17 . A small sea vessel according to  claim 10  including mooring lines to a self supporting riser having a flexible connection at the lower end permitting said SSR to be pulled off vertical without introducing a high bending moment to said SSR. 
     
     
         18 . A small sea vessel according to  claim 10  including:
 lines and a surface buoy securing and mooring said vessel to a self supporting riser through which said hydrocarbons are carried from the seafloor to said hydrocarbon processing equipment. 
 
     
     
         19 . A self supporting riser (SSR) comprising:
 a plurality of joints comprising regular joints and specialty joints that define said SSR and selected to optimize said SSR for a particular location;   at least one specialty joint comprising a buoyancy module, said one is the uppermost buoyancy module near but below the sea surface; and   a lowermost specialty joint that is a flexible connector.   
     
     
         20 . A self supporting riser (SSR) according to  claim 19  further including:
 a specialty joint that is a seafloor shutoff device above said connector; and 
 a specialty joint that has blow-out preventer functions below said buoyancy module. 
 
     
     
         21 . A self supporting riser (SSR) according to  claim 20  wherein said riser is multiple tubular. 
     
     
         22 . A self supporting riser (SSR) according to  claim 19  wherein said flexible connector is connected to a subsea infrastructure. 
     
     
         23 . A self supporting riser (SSR) according to  claim 22  wherein said subsea infrastructure is an anchor. 
     
     
         24 . A self supporting riser (SSR) according to  claim 19  wherein said flexible connector is a section of flexible pipe. 
     
     
         25 . A self supporting riser (SSR) according to  claim 19  wherein said flexible connector is links of chain. 
     
     
         26 . A self supporting riser (SSR) according to  claim 19  further comprising:
 a swivel located at the top end of the SSR for connection of a line to carry hydrocarbons from said SSR to processing equipment on a stabilized platform on a vessel. 
 
     
     
         27 . A self supporting riser (SSR) according to  claim 26  wherein said swivel is above said buoyancy module. 
     
     
         28 . A hydrocarbon production system comprising:
 a self supporting riser (SSR) which comprises a plurality of joints comprising regular joints and specialty joints that define said SSR and selected to optimize said SSR for a particular location; at least one specialty joint comprising a buoyancy module, said one is the uppermost buoyancy module near but below the sea surface; said riser in fluid communication with a hydrocarbon producing well having a wellhead on the seafloor, and   a vessel moored to said SSR;   said riser having a specialty joint at the lower end of said SSR to prevent excessive bending moment in the riser to provide an anchor to said vessel and providing fluid communication between said well to said vessel.   
     
     
         29 . A hydrocarbon production system according to  claim 28  wherein said SSR further includes:
 a specialty joint that is a seafloor shutoff device near said specialty joint at the lower end to prevent excessive bending moment in the riser; and 
 a specialty joint that has blow-out preventer functions below said buoyancy module. 
 
     
     
         30 . A hydrocarbon production system according to  claim 28  wherein said riser is multiple tubular.